Vasopressins are evolutionarily conserved peptide hormones. Mammalian vasopressin functions systemically as an antidiuretic and regulator of blood and cardiac flow essential for adapting to terrestrial environments. Moreover, vasopressin acts centrally as a neurohormone involved in social and parental behavior and stress response. Vasopressin synthesis in several cell types, storage in intracellular vesicles, and release in response to physiological stimuli are highly regulated and mediated by three distinct G protein coupled receptors. Other receptors may bind or cross-bind vasopressin. Vasopressin is regulated spatially and temporally through transcriptional and post-transcriptional mechanisms, sex, tissue, and cell-specific receptor expression. Anomalies of vasopressin signaling have been observed in polycystic kidney disease, chronic heart failure, and neuropsychiatric conditions. Growing knowledge of the central biological roles of vasopressin has enabled pharmacological advances to treat these conditions by targeting defective systemic or central pathways utilizing specific agonists and antagonists.

HIV reservoirs persist in gut-homing CD4⁺ T cells of people living with HIV and receiving antiretroviral therapy, but the antigenic specificity of such reservoirs remains poorly documented. The imprinting for gut homing is mediated by retinoic acid (RA), a vitamin A–derived metabolite produced by dendritic cells (DCs) exhibiting RA-synthesizing (RALDH) activity. RALDH activity in DCs can be induced by TLR2 ligands, such as bacterial peptidoglycans and fungal zymosan. Thus, we hypothesized that bacterial/fungal pathogens triggering RALDH activity in DCs fuel HIV reservoir establishment/outgrowth in pathogen-reactive CD4⁺ T cells. Our results demonstrate that DCs derived from intermediate/nonclassical CD16⁺ compared with classical CD16⁻ monocytes exhibited superior RALDH activity and higher capacity to transmit HIV infection to autologous Staphylococcus aureus–reactive T cells. Exposure of total monocyte-derived DCs (MDDCs) to S. aureus lysates as well as TLR2 (zymosan and heat-killed preparation of Listeria monocytogenes) and TLR4 (LPS) agonists but not CMV lysates resulted in a robust upregulation of RALDH activity. MDDCs loaded with S. aureus or zymosan induced the proliferation of T cells with a CCR5⁺integrin β7⁺CCR6⁺ phenotype and efficiently transmitted HIV infection to these T cells via RALDH/RA–dependent mechanisms. Finally, S. aureus– and zymosan-reactive CD4⁺ T cells of antiretroviral therapy-treated people living with HIV carried replication-competent integrated HIV-DNA, as demonstrated by an MDDC-based viral outgrowth assay. Together, these results support a model in which bacterial/fungal pathogens in the gut promote RALDH activity in MDDCs, especially in CD16⁺ MDDCs, and subsequently imprint CD4⁺ T cells with gut-homing potential and HIV permissiveness. Thus, nonviral pathogens play key roles in fueling HIV reservoir establishment/outgrowth via RALDH/RA–dependent mechanisms that may be therapeutically targeted. Key Points CD16⁺ MDDCs exhibit high RALDH activity upon exposure to bacterial/fungal pathogens. CD16⁺ MDDCs promote HIV trans infection in S. aureus–reactive CD4⁺ T cells. MDDCs loaded in bacterial/fungal pathogens promote HIV outgrowth in CD4⁺ T cells.

Background: While the role of CD4 ⁺ T-cells in HIV-1 reservoir persistence during antiretroviral therapy (ART) is well-established, studies on tissue-resident macrophages (MΦ) in people with HIV-1 (PWH) are restricted by difficulties in accessing deep tissue samples. Investigations in myeloid-only humanized mouse models demonstrated the contribution of MΦ to viral rebound upon ART interruption. Two distinct MΦ subsets exist in mice and humans: one of embryonic origin and self-renewal capacity generating long-lived tissue-resident MΦ (LL-TRM), and another one of short-lived MΦ (SL-MΦ), constantly replenished by bone marrow monocytes. The relative contribution of LL-TRM versus SL-MΦ to tissue HIV-1 reservoir persistence during ART remains understudied. Here, we used a humanized BM-liver-thymus (hu-BLT) mouse model to quantify integrative HIV-1 infection in liver/lung MΦ versus CD4 ⁺ T-cells before/after ART and document their expression of LL-TRM/SL-MΦ markers. Results: Lung/liver immune cells were extracted from ART-naive (ART-) and ART-treated (ART+) HIV-infected (HIV+) hu-BLT mice, as well as HIV-uninfected mice (HIV-). MΦ were identified as cells expressing the myeloid markers CD33/HLA-DR and/or CD68 and flow-cytometry sorted based on their differential expression of CD14 and/or CCR2. Matched CD3 ⁺ CD4 ⁺ T-cells were sorted in parallel and used as controls. HIV-DNA integration was measured by nested real-time PCR. In contrast to CD4 ⁺ T-cells that carried the highest levels of proviral HIV-DNA before and after ART, integrative infection in liver/lung MΦ was detected before ART, but was drastically reduced in HIV+ART+ hu-BLT mice, regardless of CD14 or CCR2 expression on MΦ. Markers of LL-TRM (CD163/CX3CR1/Ki67/c-Kit) were expressed on a small fraction of liver but not lung MΦ, indicative of a deficient LL-TRM development in this hu-BLT model. Conclusions: Together our results demonstrate that lung/liver MΦ in hu-BLT mice support integrative HIV-1 infection in vivo , but their contribution to viral reservoir persistence during ART is minor when compared to CD4 ⁺ T-cells. This is consistent with the deficient development of LL-TRM we observed in hu-BLT mice. However, HIV-1 permissive MΦ present in this model likely contribute to viral rebound upon ART interruption. Therefore, HIV-1 cure interventions that are tested in such preclinical models should consider targeting HIV-1 replication in both MΦ and CD4 ⁺ T-cells.

Antiretroviral therapy (ART) controls HIV-1 replication in people with HIV-1 (PWH), but intestinal integrity impairment persists and fuels microbial translocation and chronic immune activation, thus heightening the cardiovascular disease (CVD) risk. Here, we sought to identify novel immunological correlates of the HIV and CVD status in ART-treated PWH (HIV⁺; n = 42) and uninfected participants (HIV⁻; n = 40) of the Canadian HIV and Aging Cohort Study (CHACS), with/without subclinical coronary atherosclerotic plaques, measured by Coronary Computed Tomography Angiography as total plaque volume (TPV, mm³). PBMCs were analyzed by flow cytometry for the expression of T-cell lineage (CD45, CD3, CD4, CD8αα, CD8αβ, TCRαβ, TCRγδ), epithelial cell (EpCAM/CD326), activation (HLA-DR), and gut-homing/residency markers (CD69, CD196/CCR6, CD199/CCR9, CD49d/Itgα4, CD103/ItgαE, Itgβ7). Alterations in the CD3⁺ T-cell pool, such as increased frequencies of CD8⁺TCRαβ⁺ and TCRγδ⁺ cells, to the detriment of CD4⁺TCRαβ⁺ subsets, were associated with the HIV status. Also, CD4⁺ T-cells with CD326⁺CD69⁺CCR6⁺ItgαE⁺ and CCR6⁺Itgβ7⁻ phenotypes were increased in frequency in HIV⁺ vs. HIV⁻ participants, together with a decreased frequency of CD8⁺ T-cells with an intraepithelial lymphocyte (IEL)-like CD3⁺CD4⁻TCRαβ⁺TCRγδ⁻CD8αα⁺CD8αβ⁻ phenotype. Finally, multivariate logistic regression identified the frequency of ItgαE⁺CD8⁺, ItgαE⁻CD8⁺, CCR6⁺CD4⁺, and CCR6⁺Itgβ7⁻CD4⁺ T-cells as strong positive correlates of HIV status and atherosclerotic plaque in ART-treated PWH.

Despite antiretroviral therapy, human immunodeficiency virus type 1 (HIV-1) persists in latently-infected cells through epigenetic and transcriptional mechanisms. Latency-reversing agents have failed clinically, partly due to incomplete understanding of HIV -1 latency reversal. Here, using DNA-affinity capture and mass spectrometry on the HIV -1 5’ long terminal repeat (5'LTR) enhancer-core promoter, we identify KLF16 (Krüppel-like Factor 16) as a novel regulator of HIV-1 gene expression. KLF16 binds to the HIV-1 5'LTR in vivo at Sp1 binding sites, and KLF16 depletion reactivates latent HIV-1 in T-lymphoid and monocytic cell models. Mechanistically, KLF16 represses HIV-1 transcription by competing with Sp1 for promoter binding and by recruiting the Sin3A/HDAC1 and HP1α/Suv39H1 repressive epigenetic complexes. KLF16 is also upregulated in CD4+ T cells from ART-treated people with HIV-1 upon T-cell activation. Additionally, All-Trans retinoic acid (ATRA)reactivates latent HIV-1 in myeloid cells, partly by downregulating KLF16. These findings establish KLF16 as a novel transcriptional repressor of HIV -1, identifying it as a potential promising therapeutic target for cure strategies.