Thymic HIV-2 Infection Uncovers Posttranscriptional Control of Viral Replication in Human Thymocytes

Abstract

A unique HIV-host equilibrium exists in untreated HIV-2-infected individuals. This equilibrium is characterized by low to undetectable levels of viremia throughout the disease course, despite the establishment of disseminated HIV-2 reservoirs at levels comparable to those observed in untreated HIV-1 infection. Although the clinical spectrum is similar in the two infections, HIV-2 infection is associated with a much lower rate of CD4 T-cell decline and has a limited impact on the mortality of infected adults. Here we investigated HIV-2 infection of the human thymus, the primary organ for T-cell production. Human thymic tissue and suspensions of total or purified CD4 single-positive thymocytes were infected with HIV-2 or HIV-1 primary isolates using either CCR5 or CXCR4 coreceptors. We found that HIV-2 infected both thymic organ cultures and thymocyte suspensions, as attested to by the total HIV DNA and cell-associated viral mRNA levels. Nevertheless, thymocytes featured reduced levels of intracellular Gag viral protein, irrespective of HIV-2 coreceptor tropism and cell differentiation stage, in agreement with the low viral load in culture supernatants. Our data show that HIV-2 is able to infect the human thymus, but the HIV-2 replication cycle in thymocytes is impaired, providing a new model to identify therapeutic targets for viral replication control. IMPORTANCE HIV-1 infects the thymus, leading to a decrease in CD4 T-cell production that contributes to the characteristic CD4 T-cell loss.HIV-2 infection is associated with a very low rate of progression to AIDS and is therefore considered a unique naturally occurring model of attenuated HIV disease. HIV-2-infected individuals feature low to undetectable plasma viral loads, in spite of the numbers of circulating infected T cells being similar to those found in patients infected with HIV-1. We assessed, for the first time, the direct impact of HIV-2 infection on the human thymus. We show that HIV-2 is able to infect the thymus but that the HIV-2 replication cycle in thymocytes is impaired. We propose that this system will be important to devise immunotherapies that target viral production, aiding the design of future therapeutic strategies for HIV control.

miRNA profiling of human naive CD4 T cells links miR‐34c‐5p to cell activation and HIV replication

“…The amount of virus in cell-free culture supernatants was quantified in terms mass of active reverse transcriptase (ng RT) using the Cavidi Lenti RT Activity kit (Cavidi Tech AB), a non-radioactive ELISA method that measures RT-dependent DNA synthesis in the extract normalized to a standard curve of recombinant HIV-1 RT protein. This test was shown to have similar efficacy for both viruses (Soares et al, 2011a;Nunes-Cabaço et al, 2015). Viral stocks were concentrated by ultracentrifugation (30 min/50,000 g/4°C; Beckmann L8-60M) before resuspension in culture medium supplemented with polybrene (3 lg/ml; Sigma) and used to infect unstimulated and TCRstimulated primary cells or stably transfected cell lines, at a dose of 0.853 ng RT/10 6 cells, during 3 h culture under standard conditions (37°C/5% CO 2 ).…”

Preservation of Lymphopoietic Potential and Virus Suppressive Capacity by CD8+ T Cells in HIV-2–Infected Controllers

“…We and others previously reported that thymic function is preserved in HIV-2-infected individuals with low viral load (25). It was also recently shown that HIV-2 infection in thymocytes is impaired (26,27), which may contribute to the maintenance of high CD4 + T cell counts in HIV-2-infected patients. In this study, we measured sjTREC levels in total PBMC to estimate thymic function in HIC2.…”

HIV-2 infection is associated with preserved GALT homeostasis and epithelial integrity despite ongoing mucosal viral replication

“…Of note, cell-associated DNA levels were significantly higher in sigmoid than in peripheral blood mononuclear cells (PBMC) (P ¼ 0.04). We further confirmed HIV-2 mucosal replication via immunohistochemistry using a previously validated anti-HIV-2 Gag-specific antibody, 22 using one biopsy per patient. Cells positive for HIV-2 Gag protein were detected in both sigmoid and ileum biopsies irrespective of antiretroviral treatment (sigmoid: 2/6 untreated and 3/7 ART patients; ileum: 1/5 untreated and 3/7 ART patients, Figure 1b).…”

“…Standard curves were generated from serial dilutions of a plasmid containing both amplicons. 22 Cell-associated HIV-2 DNA was quantified in 50 ng of total DNA purified from PBMCs or from digested gut biopsies. The first step of the PCR was carried out in a 50 ml reaction mix containing the ''outer'' primers, dNTPs, MgCl2, Taq DNA Polymerase (GoTaq Flexi, Promega, Madison, WI), buffer, and 5 ml of DNA or of serial dilutions of the plasmid.…”

“…19,20 Importantly, HIV-2 targets the same cell populations as HIV-1, and is able to establish a disseminated infection with evidence of persistent ongoing viral replication despite the low to undetectable viremia observed even in the absence of ART. 21,22 The mechanisms underlying this relatively benign course are incompletely understood, but are unlikely to result from intrinsic viral properties, 23 and may be in part due to the host-specific immune responses. 24 As yet, no direct studies of gut mucosa in HIV-2-infected individuals have been reported.…”