Impact of Pre-ART Blood CD4+ T Cell Level on the Rectal Reservoir in Long-term HIV-1 Treated Men

Overview

Although combined antiretroviral therapy (cART) has dramatically improved quality of life and lifespan of HIV infected individuals, it still fails to eliminate viral reservoirs. The Gut Associated Lymphoid Tissue (GALT) is the largest reservoir of HIV-1, as it harbors most of HIV target cells as activated memory Cluster of differentiation (CD)4+/CCR5+ T cells. Intestinal T and B cells express α4β7 integrin, a gut mucosal homing receptor which binds to gp120 HIV-1 envelope facilitating the infection of intestinal T cells and the early establishment of the gut HIV reservoir. Intensive viral replication in the GALT leads to an early impairment of mucosal immunity, due to the severe CD4+ T cells depletion, that could be also explained by a lack of recruitment in the gut. Among T cells, interleukin-(IL-)17 secreting CD4+ T cells (Th17) are particularly depleted during HIV infection. This depletion could be associated with HIV progression since these cells play a crucial role in the maintenance of mucosal immunity. A dysbalance of the Th17/Treg ratio may reflect the loss of the intestinal epithelial barrier integrity. These damages are responsible for an increase in microbial translocation, which is associated with immune activation and progression to AIDS. Several recent studies have shown that cART initiation during acute or early HIV-1 infection reduces HIV DNA reservoir size and improves immune reconstitution in blood. Post-treatment controllers, who started long-term cART early after HIV infection, have very low levels of HIV DNA in peripheral blood mononuclear cells, similarly to elite controllers. Unlike most HIV-infected individuals, they maintain an undetectable plasmatic viral load after several years of cART interruption, suggesting that a weak reservoir is a prerequisite to achieve a functional cure. By extrapolation, it could be hypothesized that the gut viral reservoir is also decreased and that mucosal immunity is restored when cART is initiated during primary phase of infection. The gut viral reservoir begins to form within the first days after HIV exposure, and grows during acute HIV infection. Similarly, intestinal T cells are depleted very early after infection, due to high viral replication, host immune response and bystander effects. Most studies also concluded that long-term and optimal treatment can't fully restore mucosal immunity. These observations led us to study the impact of time of cART start on the size of viral reservoir and on immune reconstitution in the gut. For this, we analyzed the virological and immunological characteristics of the rectal HIV reservoir of long-term treated patients regarding their blood CD4+ T cells count at the time of cART initiation.