Elevated Plasma Viral Loads in Romidepsin-Treated Simian Immunodeficiency Virus-Infected Rhesus Macaques on Suppressive Combination Antiretroviral Therapy

Abstract

dReplication-competent human immunodeficiency virus (HIV) persists in infected people despite suppressive combination antiretroviral therapy (cART), and it represents a major obstacle to HIV functional cure or eradication. We have developed a model of cART-mediated viral suppression in simian human immunodeficiency virus (SIV) mac239-infected Indian rhesus macaques and evaluated the impact of the histone deacetylase inhibitor (HDACi) romidepsin (RMD) on viremia in vivo. Eight macaques virologically suppressed to clinically relevant levels (<30 viral RNA copies/ml of plasma), using a three-class five-drug cART regimen, received multiple intravenous infusions of either RMD (n ‫؍‬ 5) or saline (n ‫؍‬ 3) starting 31 to 54 weeks after cART initiation. In vivo RMD treatment resulted in significant transient increases in acetylated histone levels in CD4 ؉ T cells. RMD-treated animals demonstrated plasma viral load measurements for each 2-week treatment cycle that were significantly higher than those in saline control-treated animals during periods of treatment, suggestive of RMD-induced viral reactivation. However, plasma virus rebound was indistinguishable between RMD-treated and control-treated animals for a subset of animals released from cART. These findings suggest that HDACi drugs, such as RMD, can reactivate residual virus in the presence of suppressive antiviral therapy and may be a valuable component of a comprehensive HIV functional cure/eradication strategy.A lthough combination antiretroviral therapy (cART) can suppress viral replication in human immunodeficiency virus type 1 (HIV-1)-infected patients to levels below the limits of quantification for standard clinical assays, recrudescent virus emerges upon treatment interruption in virtually all patients who initiate therapy during the chronic phase of infection, even after many years of treatment and virologic suppression (1, 2). A long-lived residual virus pool persists despite apparently effective treatment (3-7). For this reason, current cART does not represent a definitive treatment for HIV infection, and lifelong treatment is required in the vast majority of infected patients. Despite the fact that cART can substantially improve the life expectancy of HIV-1-infected individuals, there are concerns about the development of viral drug resistance and drug-related toxicities in patients with such long-term treatment. In addition, the financial burden of lifelong cART is considerable (8), and recent studies have indicated that well-suppressed patients still have elevated levels of immune activation with increased non-AIDS morbidities and reduced life expectancies compared with those of uninfected people (9-21). These considerations have motivated a substantial scientific research effort to identify treatments that will result in either the eradication of residual virus or in the durable control of viral replication in the absence of cART.A number of different potential in vivo sources of replicationcompetent virus that can reemerge upon treatment cessation...

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 .…”

“…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.…”

The potential role for romidepsin as a component in early HIV-1 curative efforts

“…In a non-human primate model (ART-suppressed simian immunodeficiency virus (SIV)mac239-infected Indian-origin rhesus macaques), romidepsin 2.5 mg/m 2 and 3.75 mg/m 2 induced a cyclic appearance of histone acetylation in CD4+ T cells and increased plasma SIV-RNA levels [13]. The authors note that plasma SIV-RNA was not contaminated with SIV-DNA (due to cell toxicity), and time to viral rebound was unaffected during ART interruption.…”

“…Moreover, large interpersonal differences in reservoir size and response to LRA treatment may complicate the interpretation of study results [10,29]. Addressing these temporal (order and duration) and spatial (compartments) administration issues is a key to advancing the HIV-1 cure field [13]. Finally, it should be noted that the current knowledge about romidepsin among HIV-1-infected individuals is still sparse and more data are needed to confirm its safety and effect on HIV-1 latency.…”