Immune preservation in HIV+ Viremic Non-Progressors is associated with downregulation of type-I IFN pathway and reduced activation of cytotoxic compartments


BACKGROUND: Extreme phenotypes of infection eluding HIV-1 pathogenesis could allow the identification of novel therapeutic targets. Viremic Non-Progressors (VNPs) maintain high CD4+ counts despite high-level viremia in absence of antiretroviral treatment (ART) by unknown mechanisms. We aim to generate a comprehensive understanding of the lack of pathogenicity in VNPs.
METHODS: We retrospectively selected 16 VNPs and 29 HIV progressors (control group) showing similar viral load (median logVL>4), but different CD4+ decay rate (median annual CD4+ count loss <10% and >10%, respectively). 43/45 total individuals are male. Patients are followed-up at Germans-Trias-Pujol University Hospital (Badalona, Spain). Experiments were conducted between 2019-2021 using cryopreserved PBMCs. Statistical differences were assessed by Wilcoxon test. Total and intact HIV-DNA and cell-associated HIV-RNA were quantified on sorted CD4+ T-cell subsets by droplet digital PCR at pre-ART and on-ART timepoints. CD4+ and CD8+ T-cell immunophenotype was characterized by flow cytometry. Fourteen individuals (seven matched pairs) were selected for comparative PBMCs transcriptome analysis by single-cell RNA-sequencing (scRNAseq).
RESULTS: VNPs showed lower levels of total and intact HIV-DNA and cell-associated HIV-RNA in CD4+ T-cells before ART initiation, especially among Effector Memory cells (640 vs 1928 total HIV-DNA copies/106cells, p<0.05). However, viral reservoir size and composition were equivalent on-ART. Pre-ART CD4+ T-cell subset composition and activation was similar in both groups. CD8+ T-cells in untreated VNPs showed higher percentage of naive cells (24.2% vs 11.7%, p<0.001), lower levels of activation (HLA-DR+/CD38+) among memory compartments (15.5% vs 21.8%, p<0.01), and scRNAseq revealed lower expression of cytotoxic markers in CD8+ T and NK cells. Expression of Interferon-Stimulated Genes was significantly lower in VNPs across multiple cell types. We also found lower expression of TGFB1 in CD4+ T-cells, possibly involved in lymphoid tissue fibrosis.
CONCLUSIONS: Before ART initiation, VNPs showed lower levels of infected CD4+ T-cells and lower expression of CD8+ T and NK cell activation/cytotoxicity markers than HIV progressors in periphery. However, the preservation of the CD4+ compartment could be driven by downregulation of the chronic type-I IFN response and reduced damage at lymphoid tissues. These pathways might be potential therapeutic targets for HIV+ immunological non-responders that do not recover CD4+ counts despite suppressive ART.

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