Viral and Cellular factors leading to the Loss of CD4 Homeostasis in HIV-1 Viremic Nonprogressors.

HIV-1 viremic nonprogressors (VNPs) represent a very rare HIV-1 extreme phenotype. VNPs are characterized by persistent high plasma viremia and maintenance of CD4+ T cell counts in the absence of treatment. However, the causes of nonpathogenic HIV-1 infection in VNPs remain elusive. Here, we identified for the first time two VNPs who experienced the Loss of CD4+ Homeostasis (LoH) after more than 13 years. We characterized in deep detail viral and host factors associated with the LoH and compared with standard VNPs and healthy controls. Viral factors determined included HIV-1 coreceptor usage and replicative capacity. Changes in CD4+ and CD8+ T cell activation, maturational phenotype and expression of CCR5 and CXCR6 in CD4+ T cells were also evaluated as host-related factors. Consistently, we determined a switch in HIV-1 coreceptor use to CXCR4 concomitant with an increase in replicative capacity at the LoH for the two VNPs. Moreover, we delineated an increase in the frequency of HLA-DR+CD38+ CD4+ and CD8+ T-cells, and trace the augment of naive T cells upon polyclonal activation with LoH. Remarkably, very low and stable levels of CCR5 and CXCR6 expression in CD4+ T cells were measured over time. Overall, our results demonstrated HIV-1 evolution towards highly pathogenic CXCR4 strains in the context of very limited and stable expression of CCR5 and CXCR6 in CD4+ T-cells as potential drivers of LoH in VNPs. These data bring novel insights into the correlates of nonpathogenic HIV-1 infection. IMPORTANCE: The mechanism behind nonpathogenic HIV-1 infection remains poorly understood mainly due to the very low frequency of viremic non-progressors (VNPs). Here, we report two cases of VNPs who experienced the loss of CD4+ T-cell homeostasis (LoH) after more than 13 years of HIV-1 infection. The deep characterization of viral and host factors supports the contribution of viral and host factors to the LoH in VNPs. Thus, HIV-1 evolution towards highly replicative CXCR4 strains together with changes in T cell activation and maturational phenotypes were found. Moreover, we measured very low and stable levels of CCR5 and CXCR6 in CD4+ T cells over time. These findings support viral evolution towards X4 strains limited by coreceptor expression to control HIV-1 pathogenesis, and demonstrate the potential of host-dependent factors, yet to be fully elucidated in VNPs, to control HIV-1 pathogenesis.