HIV persistence in tissue reservoirs is a major barrier to HIV cure. While antiretrovirals (ARVs) suppress viral replication, antiretroviral therapy (ART) interruption results in rapid rebound viremia that may originate from lymphoid tissues. To understand the relationship between anatomic distribution of ARV exposure and viral expression in lymph nodes, we performed mass spectrometry imaging (MSI) of 6 ARVs, RNAscope in situ hybridization for viral RNA, and immunohistochemistry of collagen in mesenteric lymph nodes from 8 uninfected and 10 reverse transcriptase-simian/human immunodeficiency virus (RT-SHIV) infected rhesus macaque nonhuman primates (NHPs) dosed to steady-state with combination ART. MATLAB-based quantitative imaging analysis was used to evaluate spatial and pharmacologic relationships between these ARVs, viral RNA (both vRNA+ cells and FDC-bound virions) and collagen deposition. Using MSI, 31% of mesenteric lymph node tissue area was not covered by any ARV. Additionally, 28% of FDC-trapped virions and 21% of infected cells were not exposed to any detected ARV. Of the 69% of tissue area that was covered by cumulative ART exposure, nearly 100% of concentrations were greater than in vitro IC50 values; however, 52% of total tissue coverage was from only one ARV, primarily maraviroc. Collagen covered ∼35% of tissue area, but did not influence ARV distribution heterogeneity. Our findings are consistent with our hypothesis that ARV distribution, in addition to total-tissue drug concentration, must be considered when evaluating viral persistence in lymph nodes and other reservoir tissues.
Despite advances in treatment, finding a cure for HIV remains a top priority. Chronic HIV infection is associated with increased risk of comorbidities, such as diabetes and cardiovascular disease. Additionally, people living with HIV must remain adherent to daily antiretroviral therapy, because lapses in medication adherence can lead to viral rebound and disease progression. Viral recrudescence occurs from cellular reservoirs in lymphoid tissues. In particular, lymph nodes are central to the pathology of HIV due to their unique architecture and compartmentalization of immune cells. Understanding how antiretrovirals (ARVs) penetrate lymph nodes may explain why these tissues are maintained as HIV reservoirs, and how they contribute to viral rebound upon treatment interruption. In this report, we review (i) the physiology of the lymph nodes and their function as part of the immune and lymphatic systems, (ii) the pathogenesis and outcomes of HIV infection in lymph nodes, and (iii) ARV concentrations and distribution in lymph nodes, and the relationship between ARVs and HIV in this important reservoir.
Background Investigating antiretroviral (ARV) penetration and pharmacology in lymph nodes is crucial to understanding mechanisms of HIV persistence in tissue, but sampling these tissues in humans is invasive and costly. Physiologically based pharmacokinetic (PBPK) modelling is a non-invasive solution for understanding lymph node penetration of ARVs across multiple species. Objectives To develop customized PBPK models with a novel lymph node compartment, and use these models to describe the distribution of three ARVs—tenofovir, emtricitabine and efavirenz—into the plasma and lymph nodes of non-human primates (NHPs) and humans. Materials and methods In this analysis, we utilized standard monkey and human PBPK models in PK-Sim, and added a novel lymph node compartment using MoBi. We used these models to describe the distribution of tenofovir, emtricitabine and efavirenz into NHP and human plasma and lymph nodes, and compared model-predicted versus observed AUC and Cmax. Results For all three ARVs, population simulations using the base and final models reasonably characterized observed plasma and tissue data in NHPs and humans, with predicted/observed AUC and Cmax ratios within 0.7–2.0. Conclusions Overall, our novel PBPK model provides a framework for understanding lymph node penetration of ARVs or future HIV cure therapies.
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