Back in October 2009, Bob Siliciano’s laboratory at Johns Hopkins described a new in vitro system for screening drugs with the potential to reverse HIV latency. At the time of that publication, only one such compound had been identified using the screen, 5HN, which was too toxic to be considered for clinical evaluation. In a new paper just published online by the Journal of Virology, the researchers report the identification of another drug, disulfiram, which is already FDA approved as a treatment for alcoholism. At concentrations that are known to be achieved in vivo, disulfiram induced HIV gene expression in latently infected CD4 T cells without causing cellular activation or cytokine release. However, in the case of resting CD4 T cells isolated directly from HIV positive individuals on ART, an effect of disulfiram treatment on virus production could not be clearly demonstrated. The authors therefore stress that it is uncertain whether the drug can deplete HIV reservoirs in vivo. To try and address this question, the research group of Steve Deeks at UCSF is now conducting a pilot clinical trial. The collaboration between Deeks and Siliciano has been facilitated and supported by the recently launched amfAR Research Consortium on HIV Eradication (ARCHE).
In another paper from Siliciano’s lab published a few weeks ago, the same in vitro model of latent HIV infection of CD4 T cells is used to probe how viral latency is established. One theory posits that latency ensues when HIV integrates into inactive parts of the CD4 T-cell’s genetic code--essentially the genetic equivalent of driving down a one-way street and not being able to hit reverse. The new study finds little evidence to support this theory, but rather shows that the virus preferentially integrates into genes that are active and busily going about their protein-making business. This result supports an alternate theory that latency results from something called transcriptional interference. In this scenario, the machinery used to make proteins from the gene sort of sticks a wheel clamp on the virus and, while there’s plenty of genetic traffic, HIV’s genes are immobilized in the midst of it.
JVI Accepts, published online ahead of print on 6 April 2011
J. Virol. doi:10.1128/JVI.02033-10
Sifei Xing, Cynthia K. Bullen, Neeta S. Shroff, Liang Shan, Hung-Chih Yang, Jordyn L. Manucci, Shridhar Bhat, Thomas C. Quinn, David M. Margolis, Janet D. Siliciano, and Robert F. Siliciano
Department of Medicine, and Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Howard Hughes Medical Institute, Baltimore, Maryland, USA; Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA; University of North Carolina, Chapel Hill, North Carolina, USA
Highly active antiretroviral therapy (HAART) can reduce plasma HIV-1 levels to below the detection limit. However, due to the latent reservoir in resting CD4+ cells, HAART is not curative. Elimination of this reservoir is critical to curing HIV-1 infection. Agents that reactivate latent HIV-1 through nonspecific T cell activation are toxic. Here we demonstrate in a primary CD4+ T cell model that the FDA-approved drug disulfiram reactivates latent HIV-1 without global T cell activation. The extent to which disulfiram reactivates latent HIV-1 in patient cells is unclear, but the drug alone or in combination may be useful in future eradication strategies.
JVI Accepts, published online ahead of print on 23 March 2011
J. Virol. doi:10.1128/JVI.02536-10
Liang Shan, Hung-Chih Yang, S. Alireza Rabi, Hector C. Bravo, Rafael A. Irizarry, Hao Zhang, Joseph B. Margolick, Janet D. Siliciano, and Robert F. Siliciano*
Departments of Medicine and Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Department of Biostatistics and Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Howard Hughes Medical Institute, Baltimore, Maryland 21205, USA
Human Immunodeficiency Virus Type 1 (HIV-1) establishes a latent reservoir in resting memory CD4+ T cells. This latent reservoir is a major barrier to the eradication of HIV-1 in infected individuals and is not affected by highly active antiretroviral therapy (HAART). Reactivation of latent HIV-1 is a possible strategy for elimination of this reservoir. The mechanisms with which latency is maintained are unclear. In the analysis of the regulation of HIV-1 gene expression, it is important to consider the nature of HIV-1 integration sites. In this study, we analyzed the integration and transcription of latent HIV-1 in a primary CD4+ T cell model of latency. The majority of integration sites in latently infected cells were in introns of transcription units. Serial analysis of gene expression (SAGE) demonstrated that more than 90% of those host genes harboring a latent integrated provirus were transcriptionally active, mostly at high level. For latent, we observed a modest preference for integration in the same transcriptional orientation as the host gene (63.8% vs. 36.2%). In contrast, this orientation preference was not observed in acutely infected or persistently infected cells. These results suggest that transcriptional interference may be one of the important factors in the establishment and maintenance of HIV-1 latency. Our findings suggest that disrupting the negative control of HIV-1 transcription by upstream host promoters could facilitate the reactivation of latent HIV-1 in some resting CD4+ T cells.