Effect of Suberoylanilide Hydroxamic Acid (SAHA) Administration on the Residual Virus Pool in a Model of Combination Antiretroviral Therapy-Mediated Suppression in SIVmac239-Infected Indian Rhesus Macaques

Abstract

Nonhuman primate models are needed for evaluations of proposed strategies targeting residual virus that persists in HIV-1-infected individuals receiving suppressive combination antiretroviral therapy (cART). However, relevant nonhuman primate (NHP) models of cART-mediated suppression have proven challenging to develop. We used a novel three-class, six-drug cART regimen to achieve durable 4.0-to 5.5-log reductions in plasma viremia levels and declines in cell-associated viral RNA and DNA in blood and tissues of simian immunodeficiency virus SIVmac239-infected Indian-origin rhesus macaques, then evaluated the impact of treatment with the histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA; Vorinostat) on the residual virus pool. Ex vivo SAHA treatment of CD4 ؉ T cells obtained from cART-suppressed animals increased histone acetylation and viral RNA levels in culture supernatants. cART-suppressed animals each received 84 total doses of oral SAHA. We observed SAHA dose-dependent increases in acetylated histones with evidence for sustained modulation as well as refractoriness following prolonged administration. In vivo virologic activity was demonstrated based on the ratio of viral RNA to viral DNA in peripheral blood mononuclear cells, a presumptive measure of viral transcription, which significantly increased in SAHAtreated animals. However, residual virus was readily detected at the end of treatment, suggesting that SAHA alone may be insufficient for viral eradication in the setting of suppressive cART. The effects observed were similar to emerging data for repeat-dose SAHA treatment of HIV-infected individuals on cART, demonstrating the feasibility, utility, and relevance of NHP models of cART-mediated suppression for in vivo assessments of AIDS virus functional cure/eradication approaches.

Defining total-body AIDS-virus burden with implications for curative strategies

“…The remaining five SIVmac251 infected animals were euthanized and necropsied after 20-22 weeks of treatment with raltegravir, darunavir, ritonavir, emtricitabine, and tenofovir started at 56 dpi (Supplementary Figure 1A). We also analyzed LN from 11 SIVmac239 infected RM housed at the National Institutes of Health (NIH) on suppressive ART regimens (described in the methods section and previous publications 22,24,25 , Supplementary Figure 1B, C); and tissues from four untreated RT-SHIV infected juvenile RM housed at the California National Primate Research Center (CNPRC) euthanized and necropsied at 19, 24, 41 or 69 weeks after infection and tissues from 4 RT-SHIV-infected juvenile RM from CNPRC after a minimum of 26 weeks of ART with a combination of efavirenz, emtricitabine, and tenofovir 26 (Supplementary Figure 1D). Collectively, we assessed the tissue viral burden in 27 RMs infected with three distinct simian AIDS viruses.…”

“…The experimental conditions and ART regimens employed for the 11 rhesus macaques housed at the National Cancer Institute were previously described for 5 RM (DCCN, DCHV, DCT3, DCEG, and DCJB) which received 26-32 weeks of ART beginning at 4 weeks post-infection and 6 RM (DCLJ, DCT2, DCEA, DC1G, DCCP and DCEW) which received a different regimen and also begun at 4 weeks post-infection, for 31-32 weeks 22,24,25 Lymph nodes were collected by surgical extraction before (4 wpi) and 26-32 weeks after the initiation of ART (30-40 wpi) and immediately fixed in freshly prepared neutral buffered 4% paraformaldehyde (PFA) for 24 h at room temperature. After fixation for 24 h, fixative was replaced with 80% ethanol and tissues were paraffin embedded as previously described 25 .…”

“…After fixation for 24 h, fixative was replaced with 80% ethanol and tissues were paraffin embedded as previously described 25 .…”

“…Viral RNA load in the lysed samples was quantitated using Real-time NASBA assay as described elsewhere 35 . Plasma SIVmac239/251 viral loads were determined as described, with an assay threshold of 30 copies/mL 24,25 Plasma isolated from the blood of RT-SHIV infected challenged macaques was analyzed using previously described methods 26 where the lower limit of detection was 5 copies/ml.…”

Animal models to achieve an HIV cure

“…Agents designed to reactivate latent virus (latency reversing agents, LRA), including histone de-acetylase inhibitors (HDACi) such as Vorinostat, Panobinastat, and Romidepsin, and a drug used to treat alcohol addiction Disulfiram, have been used safely in HIV-infected individuals in several pilot studies, although with limited impact on virus reactivation and virtually no effect on the size of the virus reservoirs (67–71). Ling et al and Del Prete et al tested Vorinostat in suppressed SIV infection of Chinese and Indian RM, respectively, and obtained results similar to those of the above mentioned human clinical trials (72,73). Del Prete et al have also recently used a pan HDACi, Romidepsin, to reactivate SIV infection in ART-treated RMs (74).…”