Chronic Morphine Administration Differentially Modulates Viral Reservoirs in a Simian Immunodeficiency Virus SIVmac251-Infected Rhesus Macaque Model

Human immunodeficiency virus (HIV) persists in cellular reservoirs despite effective combined antiretroviral therapy (cART), and there is viremia flare-up upon therapy interruption. Opioids modulate the immune system and suppress antiviral gene responses, which significantly impact people living with HIV (PLWH). However, the effect of opioids on viral reservoir dynamics remains elusive. Here, we developed a morphine-dependent simian immunodeficiency virus SIVmac251-infected rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. RMs on a morphine (or saline control) regimen were infected with SIVmac251. cART was initiated in approximately half the animals 5 weeks postinfection, and morphine/saline administration continued until the end of the study. Among the untreated RMs, we did not find any difference in plasma/cerebrospinal fluid (CSF) viral loads or in cell-associated DNA/RNA viral loads in anatomical tissues. On the other hand, within the cART-suppressed macaques, there was a reduction in cell-associated DNA load, intact proviral DNA levels, and in inducible SIV reservoirs in lymph nodes (LNs) of morphine-administered RMs. In distinction to those in LNs, in the central nervous system (CNS), the size of latent SIV reservoirs was larger in the CD11b(+) microglia/macrophages in morphine-dependent RMs. These results suggest that in the proposed model, morphine plays a differential role in SIV reservoirs by reducing the CD4(+) T-cell reservoir in lymphoid tissues while increasing the microglia/macrophage reservoir size in CNS tissue. The findings from this preclinical model will serve as a tool for screening therapeutic strategies to reduce/eliminate HIV reservoirs in opioid-dependent PLWH. IMPORTANCE Identification and clearance of human immunodeficiency virus (HIV) reservoirs is a major challenge in achieving a cure for HIV. This is further complicated by comorbidities that may alter the size of the reservoirs. There is an overlap between the risk factors for HIV and opioid abuse. Opiate abuse has been recognized as a prominent comorbidity in HIV-infected populations. People infected with HIV also abusing opioids have immune modulatory effects and more severe neurological disease. However, the impact of opioid abuse on HIV reservoirs remains unclear. In this study, we used a morphine-dependent simian immunodeficiency virus SIVmac251-infected rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. Our studies suggested that people with HIV who abuse opioids have higher reservoirs in central nervous system (CNS) than in the lymphoid system. Extrapolating the macaque findings to humans suggests that such differential modulation of HIV reservoirs among people living with HIV abusing opioids could be considered for future HIV cure research efforts.