TAG HIV Basic Science, Vaccines, and Cure Project Blog

By Richard Jefferys, Project Director at Treatment Action Group (TAG).

recent posts

  • New Case of “Remission” Reported in a Perinatally Infected Teenager

    A new example of long-term post-treatment control of HIV viral load was reported this past Monday at the 8th IAS Conference on HIV Pathogenesis, Treatment and Prevention (IAS 2015) in Vancouver, attracting widespread media attention. Presented by Asier Sáez-Cirión from Institut Pasteur in France, the case involves a teenager who acquired HIV infection perinatally and was taken off ART at around the age of six, subsequently maintaining very strict control of viral load for over 12 years and counting (the slide presentation is now posted online). Sáez-Cirión is also the lead investigator for the well publicized VISCONTI cohort, a group of early-treated adults who are exhibiting long-term of HIV viral load after ART interruption (described in some detail in a paper in 2013, at which time the cohort had 14 members, and recently reported to now number 20 with an average time off ART of over nine years. Update 7/25/15: the status of several VISCONTI cohort participants has changed, see addendum below). 

    The new case was discovered as a result of an analysis of the French National Agency for AIDS Research (ANRS) pediatric cohort study, which has been following over 10,000 mother-child pairs sine 1986. A total of 100 infants were identified who had begun ART within six months of birth and, of those, 15 had interrupted treatment after an average of 33 months. Only two of the 15 showed evidence of control of viral load: one for around three years before viral load climbed above 500 copies, the other on an ongoing basis, making her the subject of further investigation.

    Records showed that the mother had advanced disease at the time of birth, with a viral load of 4.63 million copies and a CD4 count of 81. The baby received six weeks of AZT monotherapy in an unsuccessful attempt to prevent infection, after which HIV viral load became detectable and rose to 2.17 million copies leading to the initiation of ART consisting of AZT, ddI, 3TC and ritonavir (the AZT was later dropped from the regimen due to side effects). Viral load was suppressed but briefly rebounded during two periods of nonadherence, to 75,190 and 97,000 copies, respectively.

    In an echo of the Mississippi baby case, the child was lost to follow up between 5.8 and 6.8 years of age. On return to care, it was learned that ART had been stopped several months previously, but viral load remained below 50 copies. During continued follow up, viral load has stayed undetectable with the exception of two readings, one a little over 500 copies at age 11 and another of 48 copies at age 14 (close to the borderline of the more sensitive assay used at that time).  Recently, ultrasensitive tests capable of detecting as few as 4 copies of HIV RNA per milliliter of blood have been employed, with no positive results recorded. The CD4 percentage is reportedly within the normal range for a comparable HIV-negative person. The individual is now 18.5 years old. The researchers have tested for the presence of ART in plasma samples to formally rule out any possibility of undisclosed usage, and these tests were all negative.

    HIV reservoir measurements revealed that HIV DNA is present at around 125 – 316 copies per million CD4 T cells, and low levels of replication-competent virus were detected in samples of purified CD4 T cells after stimulation. HIV-specific CD8 T cells were detectable but were of a low magnitude, and no evidence of CD8 T cell-mediated suppression of HIV replication was observed in a laboratory assay. No data on HIV-specific CD4 T cell responses are available as yet—notably, a poster at IAS 2015 reported that VISCONTI cohort members have “robust” HIV-specific CD4 T cell responses, challenging the widely held view that anti-HIV immunity in these individuals is unusually weak (abstract appended below, an earlier version of the study was presented at CROI 2014)). No immune response genes known to be associated viral load control were present in the individual and they were homozygous for several HLA alleles, a phenomenon that has been associated with a greater risk of rapid progression in HIV in the absence of treatment. Analyses of inflammatory biomarkers have not been conducted yet (to the best of my knowledge, no data on inflammatory biomarkers in VISCONTI cohort members has been presented either).

    As with the published paper on the VISCONTI cohort, Sáez-Cirión and colleagues were careful to use the term “virological remission” to describe the outcome in their IAS 2015 abstract describing the case. Although the distinction may seem subtle, this is not necessarily synonymous with just “remission” (the term used in most of the news reports), which is generally interpreted as meaning remission from any increased risk of disease. At the current time, it is not actually known for sure if the low levels of HIV present in these post-treatment controllers are associated with a long-term health prognosis that is similar to, better, or worse than a comparable HIV-positive individual whose virus is suppressed by ART. As covered in a recent blog post, there are some reasons to be concerned that the HIV suppression in at least some of these cases may not have equivalent health benefits to that achieved by ART.  

    The researchers have also stressed that post-treatment control is an extremely rare phenomenon and that ART should not be interrupted outside of clinical trials at this time. There have been many published studies of ART interruptions in children and adolescents, some including quite large numbers of participants, but examples of even short-term post-treatment control are few and far between. Examples in the scientific literature include a teenager who maintained undetectable viral load for over five years after stopping ART; however there was no documented history of high viral load prior to treatment and they were found to be heterozygous for the CCR5-Δ32 mutation. Another paper mentions one participant whose viral load stayed below 400 copies for one year after ART interruption, but no further details are provided. The majority of children in these studies experienced viral load rebound and CD4 T cell loss as a result of treatment cessation.

    The new case adds to the evidence that early ART is beneficial and may, in rare instances, facilitate long-term control of viral load after treatment interruption. Ongoing and planned trials in both children and adults aim to carefully investigate the extent to which virologic remission might be achieved by this strategy. Researchers are also exploring early ART combined with additional interventions such as latency-reversing agents and immunotherapies with the aim of increasing the likelihood of virologic remission.

    Addendum 7/25/15, VISCONTI cohort update:  Asier Sáez-Cirión's slide presentation has now been posted on the International AIDS Society's Towards an HIV Cure Symposium website (along with the other materials from the meeting, which took place in Vancouver on July 18 & 19, immediately prior to IAS 2015). At the end, the slides include an important update on the current status of VISCONTI cohort participants. Of the 14 individuals described in the 2013 PLoS Pathogens paper, one has experienced a viral load rebound (reaching close to 100,000 copies) after six years off ART, necessitating reinstitution of treatment. Another has persistently detectable viral load (in the 100-1,000 copy range) and a declining CD4 T cell count that is now below 500 cells. A third is reported to have developed "ORL cancer" (which I believe refers to head and neck cancer), and resumed treatment. Lastly, a fourth member of the original 14 is lost to follow up. Of the remaining 10, nine continue to be followed with undetectable viral load while one had a viral load level of 211 copies at the time of the last measurement. 

    The last slide of the presentation notes that six additional post-treatment controllers have been added to the VISCONTI cohort (explaining the reference to a total of 20 individuals in Sáez-Cirión's latest published review from earlier this year), but no details on their viral loads and CD4 T cell counts are provided. A graph is shown for one of the new additions who, like several of the initial cohort members, possesses the HLA B*35 allele; the viral load in this individual appears to be well-controlled off ART but the CD4 T count is below 400. Hopefully these updated findings will be fully disclosed and discussed soon.

    8th IAS Conference on HIV Pathogenesis, Treatment and Prevention (IAS 2015), Vancouver, Canada, July 19-22, 2015

    MOAA0105LB Oral Abstract 

    HIV-1 virological remission for more than 11 years after interruption of early initiated antiretroviral therapy in a perinatally-infected child

    P. Frange1,2,3, A. Faye4,5, V. Avettand-Fenoel1,2, E. Bellaton6, D. Deschamps7,8, M. Angin9, S. Caillat-Zucman10,11, G. Peytavin12,13, J. Le Chenadec14,15, J. Warszawski14,15, C. Rouzioux1,2, A. Saez-Cirion9, ANRS EPF-CO10 Pediatric Cohort 

    1Assistance Publique – Hôpitaux de Paris (AP-HP), Hôpital Necker – Enfants malades, Laboratoire de Microbiologie clinique, Paris, France, 2EA7327, Université Paris Descartes, Paris, France, 3AP-HP, Hôpital Necker – Enfants malades, Unité d'Immunologie, Hématologie et Rhumatologie pédiatriques, Paris, France, 4AP-HP, Hôpital Robert Debré, Service de Pédiatrie générale, Paris, France, 5Université Paris 7 Denis Diderot, Paris, France, 6AP-HP, Hôpital Robert Debré, Service d'Hématologie pédiatrique, Paris, France, 7AP-HP, Hôpital Bichat – Claude Bernard, Laboratoire de Virologie, Paris, France, 8INSERM UMR1137 IAME Université Paris Diderot, Paris, France, 9Institut Pasteur, Unite de HIV inflammation et persistance, Paris, France, 10AP-HP, Hôpital Robert Debré, Laboratoire d'Immunologie, Paris, France, 11INSERM UMR1149, Université Paris Diderot, Paris, France, 12AP-HP, Hôpital Bichat, Laboratoire de Pharma-Toxicologie, Paris, France, 13IAME, INSERM UMR 1137, Université Paris Diderot, Paris, France, 14AP-HP, Hôpital Bicêtre, Service d'Epidémiologie et de Santé publique, Le Kremlin-Bicetre, France, 15INSERM U1018, Université Paris Sud, Le Kremlin-Bicetre, France

    Background: Durable HIV-1 remission after interruption of combined antiretroviral therapy (cART) has been reported in some adults who started cART during primary HIV-1 infection. The in utero HIV-1-infected «Mississippi child», exhibited transient viral control after interrupting very early-initiated cART. However viremia rebounded 27 months later, leaving unclear the possibility of obtaining long-term post-treatment remission in vertically-infected children. Here we report the case of a perinatally-HIV-1-infected adolescent who shows unprecedented virological remission more than 11 years after cART discontinuation.

    Methods: HIV-RNA and CD4+ T-cell counts have been monitored since birth. Ultrasensitive HIV-RNA, PBMC-associated HIV-DNA, flow-cytometry-assessed frequency of HIV-specific CD8+ T-cells, CD8+ T-cell mediated HIV-suppression, reactivation of the CD4+ T-cell reservoir were evaluated after 10 and 11 years of control off therapy. Plasma concentrations of antiretrovirals were determined by tandem mass spectrometry.

    Results: One infant born from a woman with uncontrolled HIV-1 viremia received zidovudine-based prophylaxis during 6 weeks. HIV-RNA and DNA were not detected 3 and 14 days after birth. HIV-DNA was detected at 4 weeks of age. HIV-RNA reached a peak of 2.1×106 copies/ml at 3 months of age when cART (zidovudine, lamivudine, didanosine, ritonavir) was initiated. HIV-RNA was undetectable one month later and remained below assay-detection limits while on cART, except at 15 and 21 months of age. Between 5.8 and 6.8 years of age cART was discontinued by the family. HIV-RNA was undetectable at 6.8 years of age and cART was not resumed. HIV-RNA has remained < 50 copies/ml through 18.3 years of age, except for one blip (515 copies/ml). CD4+ T-cell counts remained stable. After 11 years of control off therapy (confirmed by undetectable plasma concentrations of antiretrovirals), HIV-RNA was below 4 copies/ml and HIV-DNA was 2.2 Log copies/106 PBMC. Low levels of HIV-RNA and p24 were detected upon activation of CD4+ T-cells with PHA. HLA genotype showed homozygosity at several loci (A*2301-;B*1503/4101;C*0210/0802;DRB1*1101-;DQB1*0602-). HIV-specific CD8+ T-cell responses and T-cell activation were very weak. HIV-1 western blot was positive with absence of antibodies against gp110 and p18.

    Conclusions: This case provides first-time evidence that very long-term HIV-1 remission is possible in perinatally-infected-early-treated children, with similar characteristics as reported in adult post-treatment controllers.

    TUPEA093 – Poster Exhibition

    Robust HIV-specific T cells in post-treatment controllers from the VISCONTI cohort

    A. Samri1, V. Avettand-Fenoel2,3, L. Hocqueloux4, C. Bacchus-Souffan5, A. Cheret6, A. Emarre7, B. Descours8, A. Saez-Cirion9, C. Rouzioux2,3, B. Autran10,11, VISCONTI Study Group

    1Centre d'Immunologie et Maladies Infectieuses, UMR-S Inserm UPMCU 1135, Paris, France, 2Paris-Descartes University, Sorbonne Paris-Cité, Virology Laboratory, EA 3620, Paris, France, 3Necker Enfants-Malades Hospital, Virology Laboratory, Paris, France, 4Regional Hospital Center, Infectious and Tropical Diseases Department, Orléans, France, 5Université Pierre et Marie Curie, Sorbonne Universités, Centre d'Immunologie et Maladies Infectieuses, CIMI, UMR-S 1135, Paris, France, 6CHU Druon, Infectious Diseases Department, Tourcoing, France, 7Université Pierre et Marie Curie, Centre d'Immunologie et Maladies Infectieuses, CIMI, UMR-S 1135, Paris, France, 8Université Pierre et Marie Curie, Laboratoire Immunité et Infection UMR-S-945, Paris, France, 9Institut Pasteur, Unité de Régulation des Infections Rétrovirales, Paris, France, 10Université Pierre et Marie Curie, Sorbonne Universités, Centre d'Immunologie et Maladies Infectieuses, CIMI, Paris, France, 11Pitié-Salpétrière, C. Foix University Hospital, AP-HP, Immunology Department, Paris, France

    Background: Post-Treatment-Controllers (PTCs) represent models of functional HIV remission with an exceptional HIV control years after interruption of an early-initiated antiretroviral therapy. The enrichment in the HLA-B35 allele, associated with symptomatic primary-infection and poor prognosis, instead of the protective HLA alleles reported in Elite Controllers (ECs) questions the role mechanism of this HIV control and the role of anti-HIV T cell responses, particularly those driven by HLA-B35. We therefore compared the PTCs HIV-specific CD4 and CD8 T cells to those from continuously early-treated patients (CETs) and ECs.

    Methods: We included 12 PTCs from the VISCONTI study*, half HLA-B35+, 10 CETs under a cART initiated within 10 weeks post-infection and 8 ECs from the ANRS-Co15 cohort. Multiparametric flow-cytometry assessed HIV-specific IFNg, IL2, TNFα, MIP1β or CD40L producing CD4 and CD8 T cell stimulated with HIV-p24 protein and peptides. The cell-associated HIV-DNA was measured in PBMCs and naïve and memory sorted resting CD4 T cell subsets.

    Results: High frequencies of HIV-p24 specific CD4+ cellswere observed in PTCs and did not differ from the ECs or CETs ones. A third of these PTCs HIV-p24 specific CD4 cells were highly polyfunctional producing 2, 3 and 4 functions, similarly to from CETs and ECs. HLA-B35 did not influence these results. In contrast frequencies of PTCs CD8+ cells producing against HIV-p24 peptides IFNg (p=0.015) or MIP1b (p=0.001) were lower than ECs but equivalent to CETs ones, without differences in poly-functionality between the 3 groups. Among the functions tested here-in there were 20-fold less IFN-g producing HLA-B35+ CD8 T cells than HLA-B35- ones (0.006% versus 0.130%, p=0.041) against HIV-p24 peptides.

    Conclusions: The model of HIV remission represented by VISCONTI PTCs is characterized by robust polyfunctional HIV-specific CD4+ T cells similar to those from Elite Controllers and from continuously early-treated patients, independently from the HLA-B35 allele which negatively impacts IFN-g producing CD8 T cells. These results illustrate differences between ECs and PTCs linked to HLA background and suggest early initiation of treatment allows maintenance of robust HIV-p24 specific CD4 T cells in PTCs.

  • Interleukin-21 May Have Therapeutic Potential in HIV Infection

    Cytokines are a family of proteins that play important roles in immune cell communication. The best-known example is interleukin-2 (IL-2), which is FDA-approved as a therapy for kidney cancer. Many cytokines have been evaluated in HIV infection and one of the latest candidates being considered for human testing is IL-21. Laboratory and animal model research indicates IL-21 can enhance natural killer cell and CD8 T cell activity, and clinical trials are already underway in people with cancers.

    At several recent conferences, including the IAS Towards an HIV Cure Symposium in 2014, Mirko Paiardini has presented results from a study of IL-21 in SIV-infected macaques suggesting the cytokine may ameliorate immune activation and limit the size of the latent viral reservoir (see most recently the webcast of a talk by Luca Micci from Paiardini’s laboratory at CROI 2015). A newly published open access paper in Nature Communications describes an additional, novel mechanism of action against HIV: the researchers found that IL-21 enhances antiviral activity in CD4 T cells by inducing expression of microRNA-29. MicroRNAs are short sequences of RNA that do not encode proteins but can act to regulate cellular gene expression, and microRNA-29 has previously been reported to inhibit HIV replication in vitro. When administered to humanized mice challenged with HIV, IL-21 significantly lowered HIV replication levels.

    The new results further bolster the rationale for investigating recombinant IL-21 in the setting of HIV infection (preliminary evidence that IL-21 might have beneficial effects has been covered on the blog previously; see Interleukin-21 in Chronic Viral Infection and IL-21 in HIV Infection). Published findings from trials in cancer state that IL-21 is “generally well tolerated” but note a range of side effects, albeit considerably milder than those seen with IL-2. It's yet not clear if dosing in HIV would need to be similar to that studied in cancer.

    Nature Communications 6, Article number: 7562 doi:10.1038/ncomms8562

    IL-21 induces antiviral microRNA-29 in CD4 T cells to limit HIV-1 infection

    Stanley Adoro, Juan R. Cubillos-Ruiz, Xi Chen, Maud Deruaz, Vladimir D. Vrbanac, Minkyung Song, Suna Park, Thomas T. Murooka, Timothy E. Dudek, Andrew D. Luster, Andrew M. Tager, Hendrik Streeck, Brittany Bowman, Bruce D. Walker, Douglas S. Kwon, Vanja Lazarevic & Laurie H. Glimcher

    Abstract

    Initial events after exposure determine HIV-1 disease progression, underscoring a critical need to understand host mechanisms that interfere with initial viral replication. Although associated with chronic HIV-1 control, it is not known whether interleukin-21 (IL-21) contributes to early HIV-1 immunity. Here we take advantage of tractable primary human lymphoid organ aggregate cultures to show that IL-21 directly suppresses HIV-1 replication, and identify microRNA-29 (miR-29) as an antiviral factor induced by IL-21 in CD4 T cells. IL-21 promotes transcription of all miR-29 species through STAT3, whose binding to putative regulatory regions within the MIR29 gene is enriched by IL-21 signalling. Notably, exogenous IL-21 limits early HIV-1 infection in humanized mice, and lower viremia in vivo is associated with higher miR-29 expression. Together, these findings reveal a novel antiviral IL-21-miR-29 axis that promotes CD4 T-cell-intrinsic resistance to HIV-1 infection, and suggest a role for IL-21 in initial HIV-1 control in vivo.

  • Prime-Boost HIV Vaccine Approach Shows Promise in Macaques; Janssen Aims to Advance to Human Efficacy Trials

    A paper published earlier this month in Science augurs a major new effort to advance a prime-boost HIV vaccine strategy into human efficacy trials. The vaccine components are manufactured by Crucell Holland B.V, which is now one of the Janssen Pharmaceutical Companies of Johnson & Johnson, and—in a very welcome development for the HIV vaccine field—Janssen has recently outlined a comprehensive development plan that they hope will lead to a licensable HIV vaccine. Frank Tomaka, MD, Clinical Leader, HIV Vaccines, presented details on an AVAC webinar held May 18th (slides and audio are available online). Since the failure of Merck’s candidate in 2007, there has been a dearth of major pharmaceutical company involvement in HIV vaccine research, and planning for further efficacy trials was limited to one collaborative endeavor known as the Pox-Protein Public-Private Partnership (P5) (the work of P5 is also described on the AVAC webinar by Glenda Gray). The promising macaque results described in the new Science paper offer some insight into why Janssen has now entered the fray.

    The experiments involved a priming immunization with an adenovirus serotype 26 (Ad26) vector encoding SIV Env/Gag/Pol antigens followed by boost with either an SIV envelope trimer protein or an Ad35 vector also expressing Env/Gag/Pol. Twelve macaques received each of the vaccine regimens and eight served as controls. Six of the 12 recipients of the Ad26/Env trimer combination remained uninfected after six sequential challenges with the highly pathogenic SIVmac251, compared to two in the Ad26/Ad35 group. Two of the infected animals in the Ad26/Env trimer group controlled viral load to undetectable levels whereas the 10 infected recipients of Ad26/Ad35 displayed detectable viral loads typical of progressive disease. As expected, high viral loads were seen in all unimmunized controls.

    The researchers (led by Dan Barouch from Beth Israel Deaconess Medical Center) conducted several experiments to confirm that the apparently protected macaques were truly uninfected, including transfer of 60 million peripheral blood and lymph node mononuclear cells into naïve animals. While cells from the two macaques controlling viral load efficiently transferred SIV infection, this was not the case for any of the protected macaques. The results are impressive because the challenge virus SIVmac251 has historically been very difficult to protect against. The authors also note that in a separate experiment with a different challenge virus (the HIV/SIV hybrid SHIV162P3), protection was also observed in recipients of the Ad26/Env trimer regimen albeit at a slightly lower rate (8 of 20 animals or 40%).   

    In both sets of experiments, protection correlated with the presence of antibodies capable of exerting multiple Fc effector functions (referred to as polyfunctional antibody responses). Fc effector functions include induction of immunological mechanisms such as antibody-dependent cellular phagocytosis, which can mediate clearance of infected cells. Notably, the Env trimer protein boost was found to be essential for inducing a more polyfunctional antibody response. 

    Several human clinical trials are now evaluating the safety and immunogenicity of different components of the vaccine regimen. This ongoing work was highlighted in a press release about the macaque study issued by Johnson & Johnson. If all goes according to plan, efficacy trials may begin in 2017. 

    Science. 2015 Jul 2. pii: aab3886. [Epub ahead of print]

    Protective efficacy of adenovirus-protein vaccines against SIV challenges in rhesus monkeys.

    Barouch DH, Alter G, Broge T, Linde C, Ackerman ME, Brown EP, Borducchi EN, Smith KM, Nkolola JP, Liu J, Shields J, Parenteau L, Whitney JB, Abbink P, Ng'ang'a DM, Seaman MS, Lavine CL, Perry JR, Li W, Colantonio AD, Lewis MG, Chen B, Wenschuh H, Reimer U, Piatak M, Lifson JD, Handley SA, Virgin HW, Koutsoukos M, Lorin C, Voss G, Weijtens M, Pau MG, Schuitemaker H.

    Abstract

    Preclinical studies of viral vector-based HIV-1 vaccine candidates have previously shown partial protection against neutralization-resistant virus challenges in rhesus monkeys. In this study, we evaluated the protective efficacy of adenovirus serotype 26 (Ad26) vector priming followed by purified envelope (Env) glycoprotein boosting. Rhesus monkeys primed with Ad26 vectors expressing SIVsmE543 Env, Gag, and Pol and boosted with AS01B-adjuvanted SIVmac32H Env gp140 demonstrated complete protection in 50% of vaccinated animals against a series of repeated, heterologous, intrarectal SIVmac251 challenges that infected all controls. Protective efficacy correlated with the functionality of Env-specific antibody responses. Comparable protection was also observed with a similar Ad/Env vaccine against repeated, heterologous, intrarectal SHIV-SF162P3 challenges. These data demonstrate robust protection by Ad/Env vaccines against acquisition of neutralization-resistant virus challenges in rhesus monkeys.

  • Perspectives on Post-Treatment Control of HIV

    Several recent papers offer perspectives on the possibility of achieving post-treatment control of HIV replication by starting antiretroviral therapy (ART) during acute infection. Interest in this topic has been sharpened by reports about the VISCONTI cohort, a group of individuals in France who all started ART soon after HIV acquisition, maintained treatment for several years, then interrupted and are now controlling viral load to very low or undetectable levels. At the time of the last published update, the VISCONTI cohort included 20 individuals (identified from various trials) who have been off ART for an average of nine years.

    In a paper titled “How often does treatment of primary HIV lead to post-treatment control?” in Antiviral Therapy, Janine Maenza and colleagues identify 22 individuals who started ART during acute infection (within 12 weeks of acquisition), continued for at least 11 months, then interrupted. Out of this group, only one individual with a low viral load of 2,248 copies at the time of ART initiation maintained viral load below 500 copies for three years after interruption. The viral load then rose to levels similar to baseline for the following three years.  The researchers state: “given our single controller’s relatively low HIV-1 RNA levels during primary infection…we question whether he might have become a natural controller, regardless of initiation of early therapy.”

    A study led by Antoine Chéret, published in the Journal of Antimicrobial Chemotherapy, primarily set out to evaluate the size of the HIV reservoir in different CD4 T cell subsets in 11 participants from the OPTIPRIM clinical trial, who began ART an average of 36 days after becoming infected and maintained treatment for at least two years. But the authors note that two individuals in this study displayed control of viral load after ART interruption; in one case the level was consistently below 20 copies for 24 months, in the other there was a rebound followed by control to low but detectable levels (530 copies after 18 months off treatment). The case involving stricter containment of HIV replication showed traits similar to VISCONTI cohort members: high viral load and low CD4 T cell count prior to ART initiation, possession of the HLA B*35 allele that has been associated with faster disease progression in some studies, and low HIV DNA levels, particularly in naïve and central memory CD4 T cells. Also mirroring the VISCONTI cohort, HIV-specific CD8 T cell responses appeared weak and were not able to suppress viral replication in a laboratory assay. 

    A third paper by Jessica Conway and Alan Perelson attempts to mathematically model the parameters that might contribute to post-treatment control, and suggests that both the HIV reservoir size and the strength of the HIV-specific cytotoxic T-lymphocyte (CTL) response may be important. The authors explain that the model is relatively simple and that other types of immune responses weren’t considered but could play a role, such as natural killer (NK) cells, CD4 T cells and antibodies. A forthcoming AIDS Clinical Trials Group (ATCG) study is mentioned that plans to evaluate whether the size of the HIV reservoir correlates with time to viral load rebound after ART interruption, as the model predicts (ACTG A5345).

    An overarching and extremely important question relating to post-treatment control is not discussed in any of the papers: namely, whether the degree of HIV suppression in post-treatment controllers is equivalent to that achieved by ART when it comes to clinical outcomes. Conway and Perelson write that post-treatment control “corresponds to functional cure, sustained remission that does not require therapy,” but it isn't yet known if this is true. It has become apparent in recent years that elite controllers, who show similar suppression of viral load in the absence of treatment, can ultimately lose CD4 T cells and progress to AIDS (perhaps best documented in an analysis of a large cohort of HIV-positive individuals that was published in PLoS One last year).

    The majority of elite controllers also show elevated levels of immune activation, inflammatory biomarkers, and lymph node fibrosis compared to similar HIV-negative individuals. A study presented at CROI last year, and published in January in the Journal of Infectious Diseases, found that elite controllers have higher hospitalization rates compared to HIV-positive individuals on ART, primarily due to cardiovascular disease (although there are some concerns about the influence of confounding variables in this analysis, as described in an excellent AIDSMap article on the paper by Gus Cairns). Furthermore, there is evidence that ART may benefit at least some elite controllers, reviewed recently in the new open access Journal of Virus Eradication by Trevor Crowell and Hiroyu Hatano.

    The fact that some post-treatment controllers appear to have weaker HIV-specific T cell responses than elite controllers might suggest that immune activation and inflammation levels are likely to be lower, but there is a lack of data addressing this issue. The main published paper on the VISCONTI cohort only compares immune activation levels to individuals on ART, reporting that they are similar, and there is no comparison to HIV-negative individuals or elite controllers (there is a comparison to a group defined as "HIV controllers" with viral loads below 400 copies, as opposed to the threshold of 50 copies generally used to define elite control). To my knowledge, no data on inflammatory biomarker levels has been presented or published, even though this was one of the questions posed to the investigator Asier Sáez-Cirión when he first described the VISCONTI cohort at a conference several years ago.

    The point of raising this concern isn’t to be pessimistic about post-treatment control, but rather to highlight that there needs to be greater clarity about what the term means in relation to clinical outcomes.  In particular, post-treatment control should not be considered synonymous with “remission” or “functional cure;” these designations should refer to a state of health that is at least comparable to, if not superior to, that obtained by ART. At the current time, how the long-term health of post-treatment controllers compares to individuals whose viral loads are suppressed by ART is not known.

    The VISCONTI researchers do attempt to highlight this uncertainty by stating that cohort participants are examples of "long-term virological remission" (emphasis added); however, as the Conway and Perelson paper shows, this distinction is not always appreciated by other scientists and is certainly lost in much of the media coverage (the BBC headline on the VISCONTI cohort was: "Early HIV drugs 'functionally cure about one in 10'"). 

    There are reasons for optimism: anecdotally, the health of VISCONTI cohort members has been described to be good, and it is possible that they will not face the long-term risks seen in some elite controllers. Additionally, reports indicate there is a subset of elite controllers with extremely low HIV DNA levels from whom infectious HIV cannot be recovered, and gene expression analyses suggest these individuals have similar profiles to HIV-negative individuals (see abstract below from the recent Keystone Symposia on HIV cure research; several similar cases were reported in 2012 by the research group of Stephen Migueles at NIAID).  While further studies are needed, this subset of elite controllers might turn out to represent a model of strict HIV control that lacks inflammatory and health consequences, thereby offering clues as to the degree of post-treatment control that equates to clinical remission.

    Antivir Ther. 2015 Apr 23. doi: 10.3851/IMP2963. [Epub ahead of print]

    How often does treatment of primary HIV lead to post-treatment control?

    Maenza J1, Tapia K, Holte S, Stekler JD, Stevens CE, Mullins JI, Collier AC.

    Abstract

    BACKGROUND: Post-treatment control of viremia after discontinuation of antiretroviral therapy begun during primary HIV-1 infection is considered a potential path toward a sustained remission of infection.

    METHODS: Subjects enrolled in an observational primary infection cohort who received at least 11 months of highly active antiretroviral therapy beginning within the first 12 weeks of HIV-1 infection and who subsequently discontinued therapy were evaluated for post-treatment control.

    RESULTS: Within a cohort of 389 subjects with primary HIV-1 infection enrolled over 22 years, only 22 met criteria for evaluation of post-treatment control. Among these subjects, twenty-one (95%) had loss of viral control (HIV-1 RNA> 500 copies/mL) within 18 months after treatment discontinuation, and only 1 (4.5%, 95% CI (0.32%, 18.9%)) controlled viral load to levels <500 copies/mL for at least 24 months. The median time to virologic failure was 2.17 (IQR 1.18 – 3.39) months.

    CONCLUSIONS: Our data suggest a low likelihood of post-treatment control even when highly active antiretroviral therapy is started within 12 weeks of HIV-1 infection.

    J Antimicrob Chemother. 2015 Apr 21. pii: dkv084. [Epub ahead of print]

    Combined ART started during acute HIV infection protects central memory CD4+ T cells and can induce remission.

    Chéret A, Bacchus-Souffan C, Avettand-Fenoël V, Mélard A, Nembot G, Blanc C, Samri A, Sáez-Cirión A, Hocqueloux L, Lascoux-Combe C, Allavena C, Goujard C, Valantin MA, Leplatois A, Meyer L, Rouzioux C, Autran B; OPTIPRIM ANRS-147 Study Group.

    Abstract

    BACKGROUND: Therapeutic control of HIV replication reduces the size of the viral reservoir, particularly among central memory CD4+ T cells, and this effect might be accentuated by early treatment.

    METHODS: We examined the effect of ART initiated at the time of the primary HIV infection (early ART), lasting 2 and 6 years in 11 and 10 patients, respectively, on the HIV reservoir in peripheral resting CD4+ T cells, sorted into naive (TN), central memory (TCM), transitional memory (TTM) and effector memory (TEM) cells, by comparison with 11 post-treatment controllers (PTCs).

    RESULTS: Between baseline and 2 years, CD4+ T cell subset numbers increased markedly (P < 0.004) and HIV DNA levels decreased in all subsets (P < 0.009). TTM cells represented the majority of reservoir cells at both timepoints, T cell activation status normalized and viral diversity remained stable over time. The HIV reservoir was smaller after 6 years of early ART than after 2 years (P < 0.019), and did not differ between PTCs and patients treated for 6 years. One patient, who had low reservoir levels in all T cell subsets after 2 years of treatment similar to the levels in PTCs, spontaneously controlled viral replication during 18 months off treatment.

    CONCLUSIONS: Early prolonged ART thus limits the size of the HIV reservoir, protects long-lived cells from persistent infection and may enhance post-treatment control.

    Proc Natl Acad Sci U S A. 2015 Apr 28;112(17):5467-72. doi: 10.1073/pnas.1419162112. Epub 2015 Apr 13.

    Post-treatment control of HIV infection.

    Conway JM, Perelson AS.

    Abstract

    Antiretroviral therapy (ART) for HIV is not a cure. However, recent studies suggest that ART, initiated early during primary infection, may induce post-treatment control (PTC) of HIV infection with HIV RNA maintained at <50 copies per mL. We investigate the hypothesis that ART initiated early during primary infection permits PTC by limiting the size of the latent reservoir, which, if small enough at treatment termination, may allow the adaptive immune response to prevent viral rebound (VR) and control infection. We use a mathematical model of within host HIV dynamics to capture interactions among target cells, productively infected cells, latently infected cells, virus, and cytotoxic T lymphocytes (CTLs). Analysis of our model reveals a range in CTL response strengths where a patient may show either VR or PTC, depending on the size of the latent reservoir at treatment termination. Below this range, patients will always rebound, whereas above this range, patients are predicted to behave like elite controllers. Using data on latent reservoir sizes in patients treated during primary infection, we also predict population-level VR times for noncontrollers consistent with observations.

    Keystone Symposia: Mechanisms of HIV Persistence: Implications for a Cure (E1), Abstract #2012

    A subset of HIV elite controllers lacking evidence of ongoing viral replication

    Katja Kleinsteuber1,2, Nzuekoh Nchinda1,2, Selena Vigano1, Maria J. Buzon1, Megan E. Curtis1, Anne-Sophie Dugast1, Christine D. Palmer1, R. Brad Jones1, Sean Harrington1, Marisol Romero-Tejeda1, Alicja Piechocka-Trocha1,2, Mathias Lichterfeld1 and Bruce D. Walker1,2

    1Ragon Institute of MGH, MIT and Harvard, USA; 2 Howard Hughes Medical Institute (HHMI), USA

    Elite controllers are individuals who control HIV infection in the absence of therapy. However, most of these individuals still show signs of ongoing viral replication, such as generalized immune activation, intermittent blips in viral load, persistent antibody responses, effector memory T cell responses, and some experience progressive CD4 T cell decline. Here, we identify a subgroup of stable elite controllers characterized by an incomplete Western blot for virus-specific antibodies and the absence of viral blips. Plasma of these individuals mediated diminished HIV-specific antibody-dependent cell-mediated cytotoxicity (ADCC) as compared to other elite controllers, providing additional evidence of decreased antibody levels. We also detected diminished effector and increased central memory HIV-specific CD8 T-cell populations by tetramer staining, as well as decreased HIV-specific responses by intracellular cytokine staining. Analysis of the HIV reservoir showed low but detectable HIV genome in CD4 T cells from those patients. In line with these results, previously performed principal component analysis of transcriptional data from two of these patients revealed grouping with uninfected persons rather than with other elite controllers. Moreover, preliminary studies have failed to recover infectious virus thus far. Together these results suggest sustained absence of replicating virus in a subset of elite controllers, with implications for functional cure studies.

  • Enlisting Mice in the Search for Residual HIV

    One of the challenges in HIV cure research is developing methods for finding extremely low levels of replication-competent virus. For example, there have been three cases where individuals were considered possibly cured of HIV because the virus could not be detected even though ART had been stopped (the Mississippi baby and two Boston patients), but all ultimately experienced viral load rebounds. The research group of Joel Blankson at Johns Hopkins University is working on an approach to this problem involving mice, and recently published preliminary results in the Journal of Infectious Diseases. 

    The technique is described as a murine viral outgrowth assay (MVOA) and involves the transfer of human CD4 T cells into immune deficient mice (these mice are more commonly reconstituted with human immune cells to create humanized mice for research purposes). The researchers show that transfer of CD4 T cells from HIV-positive individuals on ART or elite controllers led to the outgrowth of replication-competent HIV in the mice; importantly, virus was detected in the case of one elite controller from whom HIV could not be cultured by normal laboratory methods. The results are in accordance with a previous report involving a post-treatment controller from whom HIV could not be detected using laboratory culture methods but was evident when CD4 T cells were transferred into immune deficient mice; this case has not yet been published, but was presented as a poster at the 7th IAS Conference on HIV Pathogenesis, Treatment and Prevention in 2013 by Jan van Lunzen and colleagues.

    The MVOA can only give binary results—replication-competent HIV is either detected or not—but nevertheless could offer a useful additional means of analysis when cases similar to the Mississippi baby and the Boston patients occur in the future.

    J Infect Dis. 2015 Apr 15. pii: jiv230. [Epub ahead of print]

    A murine viral outgrowth assay to detect residual HIV-1 in patients with undetectable viral loads.

    Metcalf Pate KA, Pohlmeyer CW, Walker-Sperling VE, Foote JB, Najarro KM, Cryer CG, Salgado M, Gama L, Engle EL, Shirk EN, Queen SE, Chioma S, Vermillion MS, Bullock B, Li M, Lyons CE, Adams RJ, Zink MC, Clements JE, Mankowski JL, Blankson JN.

    Abstract

    BACKGROUND: Sensitive assays are needed for detection of residual HIV in patients with undetectable plasma viral loads to determine if eradication strategies are effective. The gold standard quantitative viral outgrowth assay (QVOA) underestimates the magnitude of the viral reservoir. We sought to determine whether xenograft of leukocytes from HIV-1 infected patients with undetectable plasma viral loads into immunocompromised mice would result in viral amplification.

    METHODS: Peripheral blood mononuclear cells (PBMCs) or purified CD4+ T cells from HIV/SIV infected subjects with undetectable plasma viral loads were adoptively transferred into NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice. The mice were monitored for viremia following depletion of human CD8+ T cells to minimize antiviral activity. In some cases humanized mice were also treated with activating anti-CD3 antibody.

    RESULTS: With this murine viral outgrowth assay (MVOA), we successfully amplified replication-competent HIV-1/SIV from all subjects tested including 5 HIV+ patients on suppressive antiretroviral therapy (ART) and 6 elite controllers or suppressors (ES) who maintain undetectable viral loads without ART, including an ES from whom we were unable to recover virus by QVOA.

    CONCLUSIONS: Our results suggest that the MVOA has the potential to serve as a powerful tool to identify residual HIV in patients with undetectable viral loads.

  • Mapping the HIV Integration Landscape: “Cancer Genes” and the Persistence of the Latent Reservoir

    Several presentations at last year’s CROI offered evidence that the proliferation and persistence of latently infected CD4 T cells is associated with HIV integration into certain genes that have also been implicated in the development of cancers. The results prompted the investigators to hypothesize that HIV integration into cancer-associated genes plays a causative role in sustaining the reservoir of latently infected CD4 T cells by promoting their survival. Some of the scientists involved in the research went so far as to suggest that the findings might somehow contribute to explaining the elevated risk of cancer in HIV-positive people (see the CROI 2014 summary on the blog). The studies were eventually published in Science last July, along with a commentary by David Margolis and Frederic Bushman pointing out that “most HIV-related malignancies are not T cell cancers, and even most HIV-related lymphomas are of B cell origin” and gently noting: “alternative interpretations of the data are possible." 

    Recently, in the journal Cell, a comprehensive analysis of HIV integration sites was published and the data argues against the idea that HIV targets cancer-associated genes as a means to persist; rather, integration into these genes is shown to be consistent with HIV’s well-documented preference for integrating into genes that are active in the cell it has infected. A separate but complementary paper in Nature provides a topological explanation for HIV’s integration preferences.

    To start with the study published in Cell (led by Lillian B. Cohn from the laboratory of Michel Nussenzweig at Rockefeller University), it identified a staggering 6,719 unique HIV integration sites in CD4 T cells from 13 individuals. Three participants provided samples before and after starting ART, two were already on ART, four were untreated and the remaining four were viremic controllers (viral loads less than 2000 copies in the absence of ART). In all cases, there was evidence of proliferation of CD4 T cells containing integrated HIV DNA. Termed “clonal expansions,” these cells are identifiable because the HIV DNA they contain is integrated into the same exact location in the genome.

    Consistent with previous studies, clonal expansions of CD4 T cells containing integrated HIV DNA were more common in participants in whom HIV replication was suppressed by ART compared to those with ongoing virus replication (perhaps because homeostatic proliferation of CD4 T cells contributes to immune reconstitution after ART initiation). There was also a bias for clonal expansions to involve HIV integrated into genes with lower expression levels compared to single, non-expanded HIV integrations, which more often occurred in highly expressed genes.

    Based on this finding, the authors suggest that the latent HIV in clonally expanded CD4 T cells is less likely to be capable of expression and may not contribute substantially to the replication-competent HIV reservoir.  In additional support for this argument, they note that all 75 of the clonally expanded HIV genomes they tested were defective, consistent with two previously published reports demonstrating homeostatic proliferation of CD4 T cells containing integrated HIV DNA; in both of those studies the viruses were also grossly defective (see Imamichi et al., 2014 and Josefsson et al., 2013). However they acknowledge: “we cannot rule out the possibility that a rare clone of cells contains an active virus,” and this proved a wise caveat because at CROI 2015 several presentations described examples of clonally expanded HIV DNA that appeared replication-competent (e.g. Sarah Palmer, who showed that in one participant in a clinical trial of panobinostat, a clonally expanded HIV contributed to viral load rebound after an ART interruption).  

    The Cell paper addresses the issue of HIV integration into cancer-associated genes in several ways. An analysis of all HIV integration sites confirms that these genes are overrepresented, but the authors explain: “this preference does not seem to be significant because it is similar to the overall preference for integration into highly expressed genes.” Importantly, there were no associations between HIV integrations into cancer-associated genes and persistence or clonal expansion, and a longitudinal study involving three participants who initiated ART demonstrated a significant decrease in integrations into these genes over time.

    A logical interpretation is that HIV’s preference for integrating into active genes causes the virus to frequently end up located in genes that are being expressed in the CD4 T cells it is infecting; these genes inevitably include those involved in the cell cycle and proliferation because HIV primarily replicates in activated CD4 T cells. And it is cell cycle and proliferation genes that commonly go awry in cancer, hence the association between HIV integration sites and cancer-associated genes.

    The paper in Nature, by Bruna Marini and colleagues, offers a relatively prosaic explanation for HIV’s integration site preferences, albeit one that required complex experiments to reveal. Essentially, it appears that the three-dimensional composition of a cell’s nucleus dictates the gene regions that are most rapidly reachable by HIV and, upon entry into the nucleus, the virus plumps for the nearest options. These areas are on the periphery of the nucleus, and there is a strong bias against integration into genes located more centrally. In addition to the location, the genes also need to be accessible for integration, and because genes that are not being expressed are cloaked in chromatin, this means the genes have to be active to some extent. The authors’ suggestion is: “the virus simply integrates into the first open chromatin regions it meets along its route into the nucleus.”

    While these recent papers offer some evidence contrary to the notion that HIV integrates into cancer-associated genes as a strategy to facilitate its persistence, it appears likely that the topic will continue to be the subject of debate, at least until more data become available. A senior author of one of the Science papers, Stephen Hughes from the National Cancer Institute (NCI), continued to argue the original hypothesis in a plenary presentation at CROI 2015. Hughes showed a slide with the following bullet point: “Data from several labs show that there are genes in which HIV integration can cause clonal expansion (MKL2 and BACH2).” But a causative relationship between HIV integration into these genes and clonal expansion of CD4 T cells is not established; the reported data only supports an association. Rather than reflecting cause, the association could be an effect of these genes being active in CD4 T cells differentiating into a long-lived memory phenotype (BACH2 is known to have a role in CD4 T cell differentiation).   

    Additionally, the last bullet point of Hughes’s presentation states: “There are reports of HIV integrations into human cancers, including a report of a tumor with an integration in BACH2 (Mack et al.).” Hughes’s Science paper includes a similar statement: “there are reports of a small number of lymphomas with HIV proviruses integrated at defined sites; one lymphoma had a provirus integrated in BACH2 (15, 29, 30).” The three numbered cites are all from the same laboratory (of Michael McGrath), and are dated 2003, 1994 and 1992 respectively. To the best of my knowledge, no other similar findings have been reported. The Mack et al citation is #15 (full text PDF is available free), and the problem is that it does not show that “one lymphoma had a provirus integrated in BACH2.” The paper clearly states: "The integration assay used had a relatively low sensitivity, indicating that identified integration sites were from multiple clonal cell populations. Some of these HIV-infected clonal cell populations may be associated with induction of pathogenesis in these tissues." Nowhere does it confirm that the HIV integration was in the lymphoma.

    Although it’s understandable that the low sensitivity of the assay used in the study might lead someone to assume that the integration must have been in the cancer cells (because those cells would be present at high frequency), that is not the only potential explanation. An alternative possibility is that the HIV integration was in the genome of a clonally expanded CD4 T cell population infiltrating the cancerous tissue. Coincidentally, a study reporting exactly that phenomenon was presented at CROI 2015 by Francesco Simonetti from NCI. Simonetti demonstrated the clonal expansion of a latently infected CD4 T cell in tumor tissue—perhaps due to the CD4 T cell specifically responding to a cancer antigen—in an HIV-positive individual with squamous cell carcinoma. 

    At this point, it appears that the specter of an additional cause of cancer in HIV-positive people has been raised with no compelling supporting evidence. And the most recent of the three papers that have been cited as offering inferential evidence was miscited. When you consider how many people are living with HIV and the amount of HIV integration events occurring in those individuals, contrasted with the relative rarity of T cell cancers, it never seemed a very plausible idea to begin with—as David Margolis and Frederic Bushman imply in their Science commentary. This issue is not only relevant to HIV-positive people, but also for gene therapy researchers using HIV-based vectors to modify T cell receptors as a means to target cancers for immune-mediated destruction (an approach that has had considerable success in clinical trials).

    For cure research, a central issue is whether latently infected memory CD4 T cells behave any differently from other memory CD4 T cells. Certainly, long-term persistence and homeostatic proliferation are completely normal facets of memory CD4 T cell biology; this is why, for example, smallpox-specific memory CD4 T cells remain detectable for decades after vaccination despite the absence of any exposure to smallpox antigens. Also, if HIV integration into specific genes exerts some kind of control over memory CD4 T cell behavior, it does not lead to notable growth of the latent HIV reservoir—longitudinal studies show that the reservoir decays slowly with a half-life of around 43-44 months. The latest longitudinal study was just published in the Journal of Infectious Diseases by David Margolis’s research group and, as is noted in an accompanying commentary by Bob and Janet Siliciano, the estimated half-life of 43 months matches previous data almost exactly (the prior estimate was 44 months).  

    Because the techniques that allow comprehensive analyses of HIV integration sites are new, it’s perhaps inevitable that there is some wrangling over how to interpret the data. The confusion is likely to resolve as more results become available, and there is clearly room for larger longitudinal studies to track clonally expanded latently infected CD4 T cells and their HIV integration sites over time, and better define what proportion of these expanded virus genomes are replication-competent. 

    Science. 2014 Jul 10. pii: 1256304. [Epub ahead of print]

    Proliferation of cells with HIV integrated into cancer genes contributes to persistent infection. (open access)

    Wagner TA, McLaughlin S, Garg K, Cheung CY, Larsen BB, Styrchak S, Huang HC, Edlefsen PT, Mullins JI, Frenkel LM.

    Abstract

    Antiretroviral treatment (ART) of HIV infection suppresses viral replication. Yet if ART is stopped, virus re-emerges due to the persistence of infected cells. We evaluated the contribution of infected-cell proliferation and sites of proviral integration to HIV persistence. 534 HIV integration sites (IS) and 63 adjacent HIV env sequences were derived from three study participants over 11.3 to 12.7 years of ART. Each participant had identical viral sequences integrated at the same position in multiple cells, demonstrating infected-cell proliferation. Integrations were overrepresented in genes associated with cancer and favored in 12 genes across multiple participants. Over time on ART, a greater proportion of persisting proviruses were in proliferating cells. HIV integration into specific genes may promote proliferation of HIV-infected cells, slowing viral decay during ART. 

    Science. 2014 Jul 11;345(6193):179-83. doi: 10.1126/science.1254194. Epub 2014 Jun 26.

    HIV latency. Specific HIV integration sites are linked to clonal expansion and persistence of infected cells. (open access)

    Maldarelli F, Wu X, Su L, Simonetti FR, Shao W, Hill S, Spindler J, Ferris AL, Mellors JW, Kearney MF, Coffin JM, Hughes SH.

    Abstract

    The persistence of HIV-infected cells in individuals on suppressive combination antiretroviral therapy (cART) presents a major barrier for curing HIV infections. HIV integrates its DNA into many sites in the host genome; we identified 2410 integration sites in peripheral blood lymphocytes of five infected individuals on cART. About 40% of the integrations were in clonally expanded cells. Approximately 50% of the infected cells in one patient were from a single clone, and some clones persisted for many years. There were multiple independent integrations in several genes, including MKL2 and BACH2; many of these integrations were in clonally expanded cells. Our findings show that HIV integration sites can play a critical role in expansion and persistence of HIV-infected cells.

    Science. 2014 Jul 11;345(6193):143-4. doi: 10.1126/science.1257426.

    HIV/AIDS. Persistence by proliferation? (open access)

    Margolis D, Bushman F.

    Cell. 2015 Jan 29;160(3):420-32. doi: 10.1016/j.cell.2015.01.020.

    HIV-1 Integration Landscape during Latent and Active Infection.

    Cohn LB, Silva IT, Oliveira TY, Rosales RA, Parrish EH, Learn GH, Hahn BH, Czartoski JL, McElrath MJ, Lehmann C, Klein F, Caskey M, Walker BD, Siliciano JD, Siliciano RF, Jankovic M, Nussenzweig MC.

    Abstract

    The barrier to curing HIV-1 is thought to reside primarily in CD4(+) T cells containing silent proviruses. To characterize these latently infected cells, we studied the integration profile of HIV-1 in viremic progressors, individuals receiving antiretroviral therapy, and viremic controllers. Clonally expanded T cells represented the majority of all integrations and increased during therapy. However, none of the 75 expanded T cell clones assayed contained intact virus. In contrast, the cells bearing single integration events decreased in frequency over time on therapy, and the surviving cells were enriched for HIV-1 integration in silent regions of the genome. Finally, there was a strong preference for integration into, or in close proximity to, Alu repeats, which were also enriched in local hotspots for integration. The data indicate that dividing clonally expanded T cells contain defective proviruses and that the replication-competent reservoir is primarily found in CD4(+) T cells that remain relatively quiescent.

    Nature (2015) doi:10.1038/nature14226

    Nuclear architecture dictates HIV-1 integration site selection

    Bruna Marini, Attila Kertesz-Farkas, Hashim Ali, Bojana Lucic, Kamil Lisek, Lara Manganaro, Sandor Pongor, Roberto Luzzati, Alessandra Recchia, Fulvio Mavilio, Mauro Giacca & Marina Lusic

    Abstract

    Long-standing evidence indicates that human immunodeficiency virus type 1 (HIV-1) preferentially integrates into a subset of transcriptionally active genes of the host cell genome1, 2, 3, 4. However, the reason why the virus selects only certain genes among all transcriptionally active regions in a target cell remains largely unknown. Here we show that HIV-1 integration occurs in the outer shell of the nucleus in close correspondence with the nuclear pore. This region contains a series of cellular genes, which are preferentially targeted by the virus, and characterized by the presence of active transcription chromatin marks before viral infection. In contrast, the virus strongly disfavours the heterochromatic regions in the nuclear lamin-associated domains5 and other transcriptionally active regions located centrally in the nucleus. Functional viral integrase and the presence of the cellular Nup153 and LEDGF/p75 integration cofactors are indispensable for the peripheral integration of the virus. Once integrated at the nuclear pore, the HIV-1 DNA makes contact with various nucleoporins; this association takes part in the transcriptional regulation of the viral genome. These results indicate that nuclear topography is an essential determinant of the HIV-1 life cycle.

    J Infect Dis. first published online April 15, 2015 doi: 10.1093/infdis/jiv218

    Precise Quantitation of the Latent HIV-1 Reservoir: Implications for Eradication Strategies (open access)

    A.M. Crooks, R. Bateson, A.B. Cope, N.P. Dahl, M.K. Griggs, J.D. Kuruc, C.L. Gay, J.J. Eron, D.M. Margolis, R.J. Bosch and N.M. Archin

    Abstract

    The quantitative viral outgrowth assay (QVOA) provides a precise minimal estimate of the reservoir of resting CD4+ T cell infection (RCI). However, the variability of RCI over time on ART, relevant to assess potential effects of latency-reversing agents or other interventions, has not been fully described. We performed QVOA on resting CD4+ T cells obtained via leukapheresis from 37 HIV+ patients, on stable suppressive ART over a period of 6 years. Patients who started ART in acute HIV infection (AHI, n=17) or in chronic infection (CHI, n=20) were studied once HIV RNA was <50 copies/mL for≥6 months. Using random effects analysis of 160 RCI measurements, we found that RCI declined significantly over time (p<0.001) with estimated mean half-life of 3.6 (95% CI: 2.3-8.1) years, remarkably consistent with prior studies. There was no evidence of more rapid decay for AHI vs. CHI (p=0.99) in patients suppressed for≥6 months. RCI was reliably estimated with longitudinal measurements generally showing <2-fold variation from the previous measure. When QVOA is performed in this format, RCI decreases >6 fold were rare. We suggest that a 6-fold decline is a relevant threshold to reliably identify effects of anti-latency therapeutics on RCI.

    J Infect Dis. first published online April 15, 2015 doi:10.1093/infdis/jiv219

    Editorial

    The remarkable stability of the latent reservoir for HIV-1 in resting memory CD4+ T cells (open access)

    Janet M. Siliciano and Robert F. Siliciano

  • Combining Latency-Reversing Agents, and Reviewing Methods of Measuring the Latent HIV Reservoir

    At CROI last year, Gregory Laird presented results from a laboratory study that tested the activity of several candidate HIV latency-reversing agents (LRAs) on latently infected CD4 T cells isolated from HIV-positive individuals on ART. The results were disappointing: only one LRA showed a very modest effect on HIV gene expression and none induced significant production of HIV virions (the study was later published in Nature Medicine). Laird concluded his CROI talk by offering a glimpse at more hopeful preliminary data suggesting that combinations of LRAs could perform better, and these experiments have since been completed and were published recently in the Journal of Clinical Investigation (the paper is open access).

    The nub of the results is that pairings of LRAs from different classes can show synergistic or additive effects, depending on the combination. In particular, HDAC inhibitors—several of which are undergoing evaluation in clinical trials—showed evidence of synergy with the PKC agonists bryostatin-1 and prostratin. The researchers used the extent of latency reversal achieved with maximal CD4 T cell activation as the benchmark for judging the activity of LRA combinations and, as an example, bryostatin-1 and the HDAC inhibitor panobinostat prompted an induction of HIV gene expression that averaged around 50% of that obtained with T cell activation. Although there are concerns about the potential toxicity of bryostatin-1, it is being evaluated in a small trial in Spain and other PKC agonists—most notably an extract from a tropical shrub named Ingenol B—are being considered for clinical testing. Laird’s study found that low doses of bryostatin-1 worked synergistically with the HDAC inhibitor romidepsin, suggesting a means to try and minimize the risk of adverse effects.

    The paper also presents data derived from mathematical models indicating that, in clinical trials, effective LRAs or LRA combinations should produce bursts of HIV production of sufficient magnitude to be detected with standard viral load assays. The authors note that so far evidence of this effect has only been reported for the HDAC inhibitor romidepsin (see the AIDS 2014 conference presentation by Dr. Ole Schmeltz Søgaard).

    The senior author of the study is latency expert Robert Siliciano from Johns Hopkins University. In a separate open access review just published in Trends in Microbiology, Siliciano and colleagues describe the current tools available to measure the latent HIV reservoir in vivo. The pros and cons of each are delineated, and the need for improved technologies highlighted in the concluding remarks: “Without a high-throughput, sensitive, and well-validated assay, it will remain difficult for researchers to identify novel LRAs, move forward with clinical trials, and develop strategies to eradicate HIV-1.”

    J Clin Invest. doi:10.1172/JCI80142.

    Research Article

    Ex vivo analysis identifies effective HIV-1 latency–reversing drug combinations

    Gregory M. Laird1, C. Korin Bullen1, Daniel I.S. Rosenbloom2, Alyssa R. Martin3,Alison L. Hill4, Christine M. Durand1, Janet D. Siliciano1 and Robert F. Siliciano1,5

    Authorship note: Gregory M. Laird and C. Korin Bullen contributed equally to this work. 

    Published March 30, 2015

    Submitted: November 21, 2014; Accepted: February 6, 2015.

    Reversal of HIV-1 latency by small molecules is a potential cure strategy. This approach will likely require effective drug combinations to achieve high levels of latency reversal. Using resting CD4+ T cells (rCD4s) from infected individuals, we developed an experimental and theoretical framework to identify effective latency-reversing agent (LRA) combinations. Utilizing ex vivo assays for intracellular HIV-1 mRNA and virion production, we compared 2-drug combinations of leading candidate LRAs and identified multiple combinations that effectively reverse latency. We showed that protein kinase C agonists in combination with bromodomain inhibitor JQ1 or histone deacetylase inhibitors robustly induce HIV-1 transcription and virus production when directly compared with maximum reactivation by T cell activation. Using the Bliss independence model to quantitate combined drug effects, we demonstrated that these combinations synergize to induce HIV-1 transcription. This robust latency reversal occurred without release of proinflammatory cytokines by rCD4s. To extend the clinical utility of our findings, we applied a mathematical model that estimates in vivo changes in plasma HIV-1 RNA from ex vivo measurements of virus production. Our study reconciles diverse findings from previous studies, establishes a quantitative experimental approach to evaluate combinatorial LRA efficacy, and presents a model to predict in vivo responses to LRAs.

    Trends Microbiol. 2015 Apr;23(4):192-203. doi: 10.1016/j.tim.2015.01.013. Epub 2015 Mar 5.

    Towards an HIV-1 cure: measuring the latent reservoir.

    Bruner KM, Hosmane NN, Siliciano RF.

    Abstract

    The latent reservoir (LR) of HIV-1 in resting memory CD4+ T cells serves as a major barrier to curing HIV-1 infection. While many PCR- and culture-based assays have been used to measure the size of the LR, correlation between results of different assays is poor and recent studies indicate that no available assay provides an accurate measurement of reservoir size. The discrepancies between assays are a hurdle to clinical trials that aim to measure the efficacy of HIV-1 eradication strategies. Here we describe the advantages and disadvantages of various approaches to measuring the LR.

  • Broadly Neutralizing Antibody Suppresses HIV in Clinical Trial

    The past decade has seen a boom in the identification of antibodies capable of potently neutralizing a broad array of different HIV isolates (broadly neutralizing antibodies or bNAbs). New technologies that allow antibodies to be fished from huge numbers of individual B cells and tested for activity have spurred this rapid acceleration of discovery. There is now intense interest in learning whether the blossoming array of bNAbs can be put to therapeutic and preventive use. A paper published yesterday in Nature describes encouraging results from a phase I trial involving the bNAb 3BNC117. Reflecting the level of interest in the topic, the paper has attracted extensive press coverage.

    Led by Marina Caskey from Rockefeller University, the study enrolled 12 HIV-negative and 17 HIV-positive individuals (including two on ART) who received a single infusion of 3BNC117 at various doses (1, 3, 10 or 30 mg kg−1). The infusions were well tolerated; there were no grade 3 or greater adverse events and no laboratory abnormalities. HIV-positive participants receiving the two highest doses showed significant declines in viral load, with the exception of one individual whose virus turned out to be resistant to 3BNC117 at baseline. The eight recipients of the 30 mg kg−1 dose experienced reductions in viral load ranging from 0.8 to 2.5 logs, with four remaining below baseline at the last reported follow-up (day 56 post-infusion). Evidence of HIV evolving resistance to 3BNC117 was documented, particularly in the lowest dose groups. Assessments of whether anti-3BNC117 immune responses were invoked in any participants are not yet complete, but will be reported in the near future. 

    The study confirms that bNAbs are active against HIV in humans, consistent with humanized mice and macaque experiments. A number of pathways toward the therapeutic and preventive use of bNAbs can now be explored, but could still prove challenging to navigate. As the authors of the paper note, bNAbs will likely need to be used in combination to maximize activity and prevent resistance; they may also benefit from additional modifications to enhance their potency and persistence in the body.

    On the therapeutic side, there is the potential to combine bNAbs with latency-reversing agents with the aim of promoting clearance of the viral reservoir via antibody-mediated cellular cytotoxicity (ADCC). Another approach is to test whether combination bNAbs could provide a long-acting alternative or supplement to daily ART. A trial involving the combination of the bNAb VRC01 plus ART is due to start later this year in individuals with acute HIV infection in Thailand (see Jintanat Ananworanich’s presentation at last year’s Forum for Collaborative HIV Research cure research meeting for background). Dan Barouch has plans to study the bNAb PGT121 in several different populations, as outlined in his talk at CROI 2015. 

    On the preventive side, there is interest in evaluating the efficacy of passive immunization (either intravenous or subcutaneous) with bNAbs in both high risk adults and infants exposed to HIV via breastfeeding (see the webcast of Barney Graham’s presentation at the 2014 R4P conference for additional information).

    While this research is likely to move forward, there are many lingering uncertainties regarding passive immunization: the need for repeated injections raises the concern of practicality (particularly in the prevention context), and another issue that has to be considered is the complexity and cost of bNAb manufacture (for an informative excursion into the industry of bNAb production, see Michael Dumiak’s 2014 IAVI Report article, “Making it to Manufacturing”). As has been covered previously on the blog, there is at least one alternative, potentially simpler method of bNAb delivery: gene transfer with adeno-associated virus (AAV), which is being tested in an ongoing phase I trial in the UK. But it is not yet known if AAV can deliver bNAb levels high enough to be efficacious.  

    To discuss the prospects for passive immunization against HIV, AVAC is hosting a webinar on Tuesday, April 21 at 11am EDT with Dr. Sarah Schlesinger from Rockefeller University (click here to register). 

    Nature (2015) doi:10.1038/nature14411

    Viraemia suppressed in HIV-1-infected humans by broadly neutralizing antibody 3BNC117

    Marina Caskey, Florian Klein, Julio C. C. Lorenzi, Michael S. Seaman, Anthony P. West Jr, Noreen Buckley, Gisela Kremer, Lilian Nogueira, Malte Braunschweig, Johannes F. Scheid, Joshua A. Horwitz, Irina Shimeliovich, Sivan Ben-Avraham, Maggi Witmer-Pack, Martin Platten, Clara Lehmann, Leah A. Burke, Thomas Hawthorne, Robert J. Gorelick, Bruce D. Walker, Tibor Keler, Roy M. Gulick, Gerd Fätkenheuer, Sarah J. Schlesinger & Michel C. Nussenzweig

    HIV-1 immunotherapy with a combination of first generation monoclonal antibodies was largely ineffective in pre-clinical and clinical settings and was therefore abandoned. However, recently developed single-cell-based antibody cloning methods have uncovered a new generation of far more potent broadly neutralizing antibodies to HIV-1. These antibodies can prevent infection and suppress viraemia in humanized mice and nonhuman primates, but their potential for human HIV-1 immunotherapy has not been evaluated. Here we report the results of a first-in-man dose escalation phase 1 clinical trial of 3BNC117, a potent human CD4 binding site antibody, in uninfected and HIV-1-infected individuals. 3BNC117 infusion was well tolerated and demonstrated favourable pharmacokinetics. A single 30 mg kg−1 infusion of 3BNC117 reduced the viral load in HIV-1-infected individuals by 0.8–2.5 log10 and viraemia remained significantly reduced for 28 days. Emergence of resistant viral strains was variable, with some individuals remaining sensitive to 3BNC117 for a period of 28 days. We conclude that, as a single agent, 3BNC117 is safe and effective in reducing HIV-1 viraemia, and that immunotherapy should be explored as a new modality for HIV-1 prevention, therapy and cure.

    Nature News

    doi:10.1038/nature.2015.17260

    Antibody shows promise as treatment for HIV

    Erika Check Hayden

  • Souped-Up IL-15 Sparks Natural Killer Cell Activity Against HIV

    The cytokine interleukin-15 (IL-15) can exert a range of effects on the immune system, but is particularly important for promoting the proliferation and function of natural killer (NK) cells and CD8 T cells. Some observational studies in HIV have suggested salutary effects of higher IL-15 levels, in one case finding an association with delayed viral load rebound after ART interruption. But attempts at therapeutic administration of the cytokine to SIV-infected macaques have generally produced deleterious effects, including CD4 T cell depletion. More recently, IL-15 has been reexamined in the context of cure research, with laboratory studies demonstrating it can induce latently infected CD4 T cells to produce HIV. There is also increasing interest in therapeutic manipulation of NK cell responses as a means to eliminate the HIV reservoir, a task for which IL-15 may be well suited. A paper published last week in the Journal of Virology reports that an optimized form of IL-15 promoted potent inhibition of HIV by NK cells in humanized mice.  

    The version of IL-15 used in the study is described as a superagonist, comprising the cytokine bound to part of the receptor with which it interacts. This modified IL-15 is being developed as a cancer therapeutic under the name ALT-803 and, in mice, it has been shown to have superior biological activity (~25-fold greater) and a much longer half-life (~25 hours vs. ~40 minutes) compared to the unaltered cytokine. The new Journal of Virology paper reports that in a humanized mouse model, administration of ALT-803 either one or three days after HIV challenge reduced subsequent virus levels by over 90% (measured up to 21 days later). However, there was no significant effect if the delay in ALT-803 administration was extended to five days after challenge. The researchers used cell transfer experiments to confirm that NK cells, and not CD8 T cells, mediated the inhibition of acute HIV infection in this model. Discussing the results, they state: “to our knowledge, this study is the first reported demonstration that in vivo activation of NK cells can inhibit acute HIV-1 infection.” They also note that the poor outcomes seen previously in the SIV model could be due to unmodified IL-15 producing less antiviral activity and more unwanted effects (e.g. CD4 T cell activation), or might reflect differential responsiveness in macaque compared to human cells. 

    A dose-escalation pilot trial of ALT-803 in HIV-positive individuals on ART is due to start soon at the University of Minnesota. The primary aim is to evaluate safety and tolerability, but the study will also measure HIV reservoir levels as a secondary endpoint. Due to evidence from animal studies that ALT-803 may be able to invoke NK cell activity against tumors, several phase I trials are already ongoing in people with cancers.

    J Virol. 2015 Apr 1. pii: JVI.00563-15. [Epub ahead of print]

    In Vivo Activation of Human NK cells by Treatment with an IL-15 Superagonist Potently Inhibits Acute In Vivo HIV-1 Infection in Humanized Mice.

    Seay K, Church C, Zheng JH, Deneroff K, Ochsenbauer C, Kappes JC, Liu B, Jeng EK, Wong HC, Goldstein H.

    Abstract

    Natural killer (NK) cells with anti-HIV-1 activity may inhibit HIV-1 replication and dissemination during acute HIV-1 infection. We hypothesized that the NK cell capacity to suppress acute in vivo HIV-1 infection would be augmented by activating them via treatment with an IL-15 superagonist, IL-15 bound to soluble IL-15Rα, an approach that potentiates human NK cell-mediated killing of tumor cells. In vitro stimulation of human NK cells with a recombinant IL-15 superagonist significantly induced their expression of cytotoxic effector molecules granzyme B and perforin, their degranulation upon exposure to K562 cells as indicated by cell-surface expression of CD107a and their capacity to lyse K562 cells and HIV-1-infected T cells. The impact of IL-15 superagonist-induced activation of human NK cells on acute in vivo HIV-1 infection was investigated using hu-spl-PBMC-NSG mice, NOD-SCID-IL2rγ-/- mice intrasplenically injected with human PBMCs, which develop productive in vivo infection after intrasplenic inoculation with HIV-1. IL-15 superagonist treatment potently inhibited acute HIV-1 infection in hu-spl-PBMC-NSG mice even when delayed until three days after intrasplenic HIV-1 inoculation. Removal of NK cells from the human PBMCs prior to intrasplenic injection into NSG mice completely abrogated IL-15 superagonist-mediated suppression of in vivo HIV-1 infection. Thus, the in vivo activation of NK cells, integral mediators of the innate immune response, by treatment with an IL-15 superagonist increases their anti-HIV activity and enables them to potently suppress acute in vivo HIV-1 infection. These results indicate that in vivo activation of NK cells may represent a new immunotherapeutic approach to suppress acute HIV-1 infection.

  • CROI 2015 Round Up

    The 2015 Conference on Retroviruses and Opportunistic Infections (CROI) took place in Seattle from February 23rd to the 26th. The major news that emerged from the meeting was the extremely high degree of protection from HIV infection obtained with pre-exposure prophylaxis in two studies, PROUD and IPERGAY. On the vaccine and cure fronts nothing was quite as headline grabbing, but there were a number of interesting presentations. Webcasts of all conference sessions are available on the CROI website along with the abstract book and, where available, PDFs of posters. Excellent coverage of CROI is available from several websites, including AIDSMap, i-Base and NATAP (whose reports often include slides from the talks).

    TAG (along with AIDS Treatment Activists Coalition, AVAC and Project Inform) co-sponsored a pre-conference community workshop on cure research on February 22nd, covered by Gus Cairns for AIDSMap and Siegfried Schwarze for EATG; the EATG CROI 2015 Facebook page also has photos of some of the slide presentations.

    Links to several CROI presentations and posters of possible interest are below.

    A Path to an HIV Vaccine

    Galit Alter, Ragon Institute of MIT, MGH and Harvard, Cambridge, MA, United States

    – A sprightly, enthusiastic and fairly optimistic review of the state of HIV vaccine science delivered by Galit Alter at the pre-conference workshop for young investigators.

    Treatment With a TLR7 Agonist Induces Transient Viremia in SIV-Infected ART-Suppressed Monkeys

    James B. Whitney, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

    – The most widely publicized of the cure-related presentations at CROI. A toll-like receptor 7 (TLR7) agonist being developed by Gilead induced SIV production from the latent reservoir in a small macaque study. A complementary poster presentation demonstrated activation of HIV production in latently infected cells isolated from individuals on ART. The compound in clinical development (GS-9620) has already been found safe in human trials for hepatitis B and C, and a small trial in HIV-positive individuals is underway and fully enrolled (although regrettably Gilead have not registered the trial in clinicaltrials.gov). 

    Broadly Neutralizing Antibodies for HIV-1 Eradication Strategies

    Dan H. Barouch, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

    – This presentation includes a description of a small study of the broadly neutralizing antibody (bNAb) PGT121 combined with ART in macaques chronically infected with SHIV162P3. Overall the combination led to reductions in the viral reservoir compared to ART alone (although this was not seen in all recipients) and was associated with a delayed viral load rebound after ART interruption. As an aside, Barouch also mentions that the reductions in viral load being seen in phase I trials of bNAbs in HIV-positive individuals appear comparable to those reported in SIV-infected macaques. These studies presage larger planned trials that will evaluate the effect of ART plus bNAbs on the HIV reservoir.

    Post-Treatment Controllers Have Particular NK Cells With High Anti-HIV Capacity: VISCONTI Study

    Daniel Scott-Algara, Institut Pasteur, Paris, France

    – Study results suggesting natural killer (NK) cell responses may be contributing to control of HIV viral load in the VISCONTI cohort participants. The analyses include a comparison of NK cell responses with an HIV-negative control group and it is worth noting that, so far, there has been no comparison between the VISCONTI cohort and HIV-negative controls when it comes to inflammatory and immune activation biomarkers. In the absence of this information, it is not yet clear if the long-term health of cohort members is likely to be comparable to uninfected individuals or if, like elite controllers, they have elevated inflammation levels that could lead to an increased risk of morbidity and mortality.

    Durable Control of Viral Rebound in Humanized Mice by ABX464 Targeting Rev Functions

    Jamal Tazi, University of Montpellier, Montpellier, France

    – Report on ABX464, a novel antiretroviral targeting the activity of HIV’s Rev protein that caused a prolonged reduction in viral load after a course of treatment in humanized mice. A phase I safety study in humans has already been completed, and a phase II clinical trial is underway.

    Aviremia 10-Year Post-ART Discontinuation Initiated at Seroconversion. Sabine Kinloch et al. Abstract Number: 377

    – Case report of prolonged post-treatment control of HIV viral load after ART interruption. Reported in detail by Simon Collins on i-Base. 

    In vivo effects of Panobinostat and Romidepsin on HIV-1-specific CD8 T Cell Immunity. Rikke Olesen et al. Abstract Number: 369.

    – An analysis of samples from two clinical trials indicating that HDAC inhibitors do not significantly suppress HIV-specific CD8 T cell responses in vivo, in contrast to the results of an in vitro study published last year.

    Selectively Eliminating HIV Latently Infected Cells Without Viral Reactivation. Grant Campbell et al. Abstract Number: 387

    – Laboratory study reporting latently infected cells may be distinguished from uninfected cells due to expression of X-linked inhibitor of apoptosis protein (XIAP), and that this may allow them to be selectively eliminated with an XIAP antagonist drug, GDC-0152. Sounds potentially exciting, but will need to be confirmed using primary latently infected CD4 T cells sampled from HIV-positive individuals on ART.

    Targeting HIV-1 Latency With a Potent Tat Inhibitor. Guillaume Mousseau et al. Abstract Number: 413

    – In the early 1990s clinical trials were conducted of a Tat inhibitor developed by Hoffman-LaRoche but it failed to show efficacy. This study describes a new candidate and suggests the idea should be revisited in the context of targeting HIV latency.

    Immunogenicity of AGS-004 Dendritic Cell Therapy in Patients Treated during Acute HIV Infection. Cynthia L. Gay et al. Abstract Number: 344

    – Small trial of a therapeutic HIV vaccine approach in acute HIV infection. Although HIV-specific immune responses were induced, this did not lead to sustained control of viral load after ART interruption in five out of the six participants, but one individual remains off ART after 268 days. The researchers plan to study AGS-004 in combination with a latency-reversing agent.

    Measuring HIV Latency Over Time: Reservoir Stability and Assessing Interventions. Nancie M. Archin et al. Abstract Number: 406

    – An assessment of the reproducibility of the quantitative viral outgrowth assay (QVOA) over time. Changes of >2.5 fold were fairly common, whereas changes >6 fold were rare, lead to the suggestion that the latter should be used as a threshold in evaluations of reservoir-depleting interventions.