The major obstacle to maximizing HIV elimination from the
body is the existence of latently infected cells (for an excellent introduction to the topic, see this free access minireview from J. Virology). These cells harbor HIV DNA
that has integrated into the chomosomal DNA, and virus particles are typically not
produced unless the cell is stimulated in some way. Latently infected cells are
thus invisible to the immune system, and while antiretrovirals can prevent
any virus they produce from infecting other cells, the drugs cannot excise
the integrated HIV DNA. This has led researchers to pursue new approaches to
awakening dormant HIV, but the pursuit has been slowed by a reliance on
cell lines, due to the lack of a physiologically relevant system for generating
latently infected primary CD4 T cells.
In a new paper in the Journal of Clinical Investigation,
Hung-Chih Yang and colleagues from Bob Siliciano’s laboratory at Johns Hopkins
report the development of a new screening system for identifying
latency-reversing drugs. The researchers introduced the survival gene Bcl-2
into CD4 T cells in vitro and this facilitated the generation of large numbers
of long-lived latently infected cells. As a proof of concept, one compound (named
5HN) that potently reactivated latent HIV without activating the CD4 T cells was
identified from a screen of several thousand drugs. The researchers note,
however, that 5HN is likely too toxic for human use. Screens of other compounds
are ongoing and the researchers hope to eventually identify candidates suitable
for clinical testing.
J. Clin. Invest. doi:10.1172/JCI39199.
Technical Advance
Small-molecule screening using a human primary cell model of
HIV latency identifies compounds that reverse latency without cellular
activation (free access to full text)
Hung-Chih Yang1, Sifei Xing1,2, Liang Shan1,2, Karen
O’Connell1, Jason Dinoso1,2, Anding Shen3, Yan Zhou1, Cynthia K. Shrum1, Yefei
Han1, Jun O. Liu2, Hao Zhang4, Joseph B. Margolick4 and Robert F. Siliciano1,5
1 Department of Medicine and 2 Department of Pharmacology and Molecular Sciences, Johns
Hopkins University School of Medicine, Baltimore, Maryland, USA. 3 Department of Biology, Calvin College, Grand Rapids,
Michigan, USA. 4 Department of Molecular Microbiology and Immunology, Johns
Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA. 5 Howard Hughes Medical Institute, Baltimore, Maryland, USA.
Published October 1, 2009
Received for publication March 16, 2009, and accepted in
revised form July 29, 2009.
The development of highly active antiretroviral therapy
(HAART) to treat individuals infected with HIV-1 has dramatically improved
patient outcomes, but HAART still fails to cure the infection. The latent viral
reservoir in resting CD4+ T cells is a major barrier to virus eradication.
Elimination of this reservoir requires reactivation of the latent virus.
However, strategies for reactivating HIV-1 through nonspecific T cell
activation have clinically unacceptable toxicities. We describe here the
development of what we believe to be a novel in vitro model of HIV-1 latency
that we used to search for compounds that can reverse latency. Human primary
CD4+ T cells were transduced with the prosurvival molecule Bcl-2, and the
resulting cells were shown to recapitulate the quiescent state of resting CD4+
T cells in vivo. Using this model system, we screened small-molecule libraries
and identified a compound that reactivated latent HIV-1 without inducing global
T cell activation, 5-hydroxynaphthalene-1,4-dione (5HN). Unlike previously
described latency-reversing agents, 5HN activated latent HIV-1 through ROS and
NF-κB without affecting nuclear factor of activated T cells (NFAT) and PKC,
demonstrating that TCR pathways can be dissected and utilized to purge latent
virus. Our study expands the number of classes of latency-reversing
therapeutics and demonstrates the utility of this in vitro model for finding
strategies to eradicate HIV-1 infection.
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