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Deciphering the mechanisms underlying viral persistence is critical to achieving a cure for human immunodeficiency virus (HIV) infection. Here, we implement a systems approach to discover molecular signatures of HIV latently infected CD4+ T cells, identifying the immunosuppressive, adenosine-producing ectonucleotidase CD73 as a key surface marker of latent cells. Hypoxic conditioning, reflecting the lymphoid tissue microenvironment, increases the frequency of CD73+ CD4+ T cells and promotes HIV latency. Transcriptomic profiles of CD73+ CD4+ T cells favor viral quiescence, immune evasion, and cell survival. CD73+ CD4+ T cells are capable of harboring a functional HIV reservoir and reinitiating productive infection ex vivo. CD73 or adenosine receptor blockade facilitates latent HIV reactivation in vitro, mechanistically linking adenosine signaling to viral quiescence. Finally, tissue imaging of lymph nodes from HIV-infected individuals on antiretroviral therapy reveals spatial association between CD73 expression and HIV persistence in vivo. Our findings warrant development of HIV-cure strategies targeting the hypoxia-CD73-adenosine axis.

During acute viral infections, innate immune cells invade inflamed tissues and face hypoxic areas. Hypoxia-inducible factors (HIFs) adapt cellular responses towards these conditions. We wanted to investigate the effects of a loss of HIF-2 α in macrophages during acute Friend murine leukemia retrovirus (FV) infection in C57BL/6 mice using a Cre/loxP system. Remarkably, micewith floxed Hif-2a (Hif-2afl; Hif-2a is also known as Epas1) did not show any signs of FV infection independent of Cre activity. This prevented a detailed analysis of the role of macrophage HIF-2 α for FV infection but allowed us to study a model of unexpected FV resistance. Hif-2afl mice showed a significant decrease in the expression of the Atp6v1e2 gene encoding for the E2 subunit of the vacuolar H+-ATPase, which resulted in a decreased acidification of lysosomes and limited virus entry into the cell. These findings highlight that the insertion of loxP sites is not always without functional consequences and has established a phenotype in the floxed Hif-2a mouse, which is not only unexpected, but unwanted and is of relevance for the use of this mouse strain in (at least virus) experiments. [ABSTRACT FROM AUTHOR]

During acute viral infections, innate immune cells invade inflamed tissues and face hypoxic areas. Hypoxia-inducible factors (HIFs) adapt cellular responses towards these conditions. We wanted to investigate the effects of a loss of HIF-2α in macrophages during acute Friend murine leukemia retrovirus (FV) infection in C57BL/6 mice using a Cre/loxP system. Remarkably, mice with floxed Hif-2a (Hif-2afl; Hif-2a is also known as Epas1) did not show any signs of FV infection independent of Cre activity. This prevented a detailed analysis of the role of macrophage HIF-2α for FV infection but allowed us to study a model of unexpected FV resistance. Hif-2afl mice showed a significant decrease in the expression of the Atp6v1e2 gene encoding for the E2 subunit of the vacuolar H+-ATPase, which resulted in a decreased acidification of lysosomes and limited virus entry into the cell. These findings highlight that the insertion of loxP sites is not always without functional consequences and has established a phenotype in the floxed Hif-2a mouse, which is not only unexpected, but unwanted and is of relevance for the use of this mouse strain in (at least virus) experiments., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Background: Because the nuclear factor-κB (NF-κB) coupled pathway is believed to amplify inflammation prevailing in sepsis, the authors tested the hypotheses that the insertion-deletion polymorphism (-94ins/delATTG) (1) alters nuclear translocation of nuclear factor-κB and activator protein-1 (NF-κB1) in monocytes after lipopolysaccharide stimulation; (2) affects lipopolysaccharide-induced NF-κB1 messenger RNA expression, tumor necrosis factor α concentrations, and tissue factor activity; and (3) may be associated with increased 30-day mortality in patients with sepsis., Methods: Nuclear translocation of NF-κB1 in monocytes after lipopolysaccharide stimulation from healthy blood donors was performed with immunofluorescence staining (n = 5 each). Lipopolysaccharide-induced NF-κB1 messenger RNA expression was measured with real-time polymerase chain reaction (PCR; n = 60), tumor necrosis factor α concentrations with a multiplexing system kit (n = 60), and tissue factor activity with thromboelastometry (n = 105). In a prospective study, multivariate proportional hazard analysis tested 30-day mortality in patients with sepsis (n = 143)., Methods and Results: The homozygous deletion genotype compared with the homozygous insertion genotype was associated with a nearly twofold increase in nuclear translocation of NF-κB1 (P = 0.001), a threefold difference in NF-κB1 messenger RNA expression (P = 0.001), and a twofold increase in tissue factor expression (P = 0.021). The deletion allele in adults with severe sepsis was tested as an independent prognostic factor for 30-day mortality (hazard ratio, 2.3; 95% CI, 1.13-4.8; P = 0.022). Mortality was 25% for homozygous insertion genotypes but 41% for combined heterozygous deletion/homozygous deletion genotypes (P = 0.034)., Conclusion: The deletion allele of the NFκB1 insertion-deletion (-94ins/delATTG) polymorphism is associated with increased 30-day mortality in patients with severe sepsis and increased reaction of the innate immune system.

Myeloid cells recruited to sites of bacterial inflammation are exposed to low oxygen tension, hypoxia, and high concentrations of inflammatory cytokines that significantly affect myeloid cell function. Therefore, we analyzed the direct consequences of acute and severe hypoxia on monocytic adhesion to the endothelium in coculture experiments. Marked upregulation of monocytic ICAM-1, but no other monocytic adhesion molecule, was responsible for an approximately 50-fold increase in adhesion of the monocytic cells THP-1 to human and rat endothelial cells. ICAM-1 expression was rapidly induced after the onset of severe hypoxia, but it decreased after 4 h. Knockdown of ICAM-1 by siRNA in endothelial and monocytic cells abolished the adhesion, indicating that ICAM-1 expression on both cell types was indispensable for hypoxia-induced adhesion of monocytes to the endothelium. siRNA-mediated knockdown of hypoxia inducible factor (HIF)-1alpha, HIF-2alpha, and the NF-kappaB family member p65 revealed that hypoxic upregulation of ICAM-1 resulted from hypoxic NF-kappaB induction but not from activation of HIFs. Within the leukocyte-adhesion cascade, our results provide evidence for prolyl hydroxylase-dependent but HIF-independent activation of hypoxia-induced monocyte-endothelial adhesion and assign a new function to monocytic ICAM-1 under acute hypoxic conditions.