Simian Immunodeficiency Virus Persistence in Cellular and Anatomic Reservoirs in Antiretroviral Therapy-Suppressed Infant Rhesus Macaques

Abstract

Worldwide, nearly two million children are infected with human immunodeficiency virus (HIV), with breastfeeding accounting for the majority of contemporary HIV transmissions. Antiretroviral therapy (ART) has reduced HIV-related morbidity and mortality but is not curative. The main barrier to a cure is persistence of latent HIV in long-lived reservoirs. However, our understanding of the cellular and anatomic sources of the HIV reservoir during infancy and childhood is limited. Here, we developed a pediatric model of ART suppression in orally simian immunodeficiency virus (SIV)-infected rhesus macaque (RM) infants, with measurement of virus persistence in blood and tissues after 6 to 9 months of ART. Cross-sectional analyses were conducted to compare SIV RNA and DNA levels in adult and infant RMs naive to treatment and on ART. We demonstrate efficient viral suppression following ART initiation in SIV-infected RM infants with sustained undetectable plasma viral loads in the setting of heterogeneous penetration of ART into lymphoid and gastrointestinal tissues and low drug levels in the brain. We further show reduction in SIV RNA and DNA on ART in lymphoid tissues of both infant and adult RMs but stable (albeit low) levels of SIV RNA and DNA in the brains of viremic and ART-suppressed infants. Finally, we report a large contribution of naive CD4 T cells to the total CD4 reservoir of SIV in blood and lymph nodes of ART-suppressed RM infants that differs from what we show in adults. These results reveal important aspects of HIV/SIV persistence in infants and provide insight into strategic targets for cure interventions in a pediatric population. While antiretroviral therapy (ART) can reduce HIV replication, the virus cannot be eradicated from an infected individual, and our incomplete understanding of HIV persistence in reservoirs greatly complicates the generation of a cure for HIV infection. Given the immaturity of the infant immune system, it is critically important to study HIV reservoirs specifically in this population. Here, we established a pediatric animal model to simulate breastfeeding transmission and study SIV reservoirs in rhesus macaque (RM) infants. Our study demonstrates that ART can be safely administered to infant RMs for prolonged periods and that it efficiently controls viral replication in this model. SIV persistence was shown in blood and tissues, with similar anatomic distributions of SIV reservoirs in infant and adult RMs. However, in the peripheral blood and lymph nodes, a greater contribution of the naive CD4 T cells to the SIV reservoir was observed in infants than in adults.

Analytical treatment interruption after short-term anti-retroviral therapy in a postnatally SHIV infected infant rhesus macaque model

“…In this study, the infant and adult RMs were infected with a clade C SHIV variant, SHIV.CH505.375H.dCT, due to the predominance of clade C viruses in sub-Saharan Africa, where most pediatric HIV infections occur (36). In both infant and adult models, this SHIV variant achieved a peak viral load comparable to previously described SIV/SHIV models (21, 37), yet did not achieve a viral “set point” in most of the monkeys (Figure 1B and 3B). Additionally, a few monkeys from our cohort achieved natural virologic control, which is not uncommon in previously described SHIV infection models (38, 39).…”

“…While pediatric ATI models of SIV-infected RMs are not new to the HIV field (34), clinically translatable RM models of ATI using SHIVs have been advancing (35). Thus, we have sought to establish an oral SHIV-infected infant ATI model with a previously validated ART regimen (21).…”

“…SHIV DNA/million CD4+ T cells was estimated after normalizing SHIV gag copy numbers with input CD4+ counts. Quantification of SHIV DNA in peripheral lymph node-associated naïve, memory and Tfh CD4+ T cell population was performed by qPCR as described in (21), using primers and probes described in Table S3.…”

“…Thus, pediatric rhesus macaque (RM) models of HIV infection and treatment can be instrumental (19). Building on pediatric RM models of breast milk transmission (20) and persistence (21) with simian immunodeficiency viruses (SIVs), here we have developed a pediatric RM model of ART and viral rebound using infant RMs experimentally infected with a next generation chimeric simian-human immunodeficiency virus, SHIV.CH505.375H.dCT (22), that would permit an assessment of interventions directed against the HIV-Env. This virus carries a mutation in the CD4 binding site that facilitates entry via rhesus CD4 molecule that has been previously demonstrated to replicate efficiently in adult RMs (22), recapitulating the viral replication dynamics and immunopathogenesis of HIV infection in humans (23).…”

Despite early antiretroviral therapy effector memory and follicular helper CD4 T cells are major reservoirs in visceral lymphoid tissues of SIV-infected macaques

“…Interestingly, in ART-suppressed infant SIV-infected RMs, treated at week 3 after infection, 75 or here in RMs treated at week 6 post infection, the levels of cell-associated viral DNA were similar in CD4 T cells isolated from the different tissues such as blood, peripheral LNs, and the spleen. In contrast, the administration of early ART, a situation not often occurring in HIV-infected individuals, resulted in limited viral seeding in the spleen and mesenteric LNs as well as in the absence of viral DNA detection in blood and peripheral LNs.…”