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Background: Although combination antiretroviral therapy has increased life expectancy in people living with HIV, it has led to a marked increase in the prevalence of hypertension, the cause of which is unknown. Despite combination antiretroviral therapy, HIV-derived proteins remain expressed and produced by CD4 + T lymphocytes in people living with HIV. However, their contribution to HIV-associated hypertension and impaired endothelium-dependent relaxation remains ill defined., Methods: Here, we tested the hypothesis that CD4 + T cells expressing viral proteins contribute to endothelial dysfunction and hypertension using the Tg26 mouse model of HIV that expresses 7 of the 9 HIV proteins under the long terminal repeat promoter. We used male and female mice, bone marrow transplantation (BMT), adoptive transfer of CD4 + T cells, and aorta specimen discarded from people living with HIV., Results: We reported that intact Tg26 mice and mice receiving BMT (Tg26→WT) or CD4 + T cells from Tg26 mice display impaired endothelium-dependent relaxation and hypertension. Conversely, BMT from WT mice into Tg26 mice, inhibition of T cell activation, and CD4 + T cell depletion restored endothelial function and blood pressure in Tg26 mice. Cytokine profiling revealed that Tg26 mice, Tg26→WT, and Tg26 CD4 + T cells consistently exhibit high interleukin 1α (IL-1α) levels with no significant increase in other cytokines, whereas BMT from WT mice into Tg26 mice reduced IL-1α levels. IL-1α neutralization reduced blood pressure and restored endothelial function in Tg26 mice. To investigate the role of CD4 + T cells and IL-1α in endothelial dysfunction, we developed an aorta-immune cell coculture system. Exposure of WT aortas to Tg26 CD4 + T cells impaired endothelium-dependent relaxation, which was blocked by IL-1α-neutralizing antibody. While investigating the mechanisms of endothelial dysfunction, we reported that Tg26 mice, Tg26→WT aorta exhibit high NADPH oxidase (NOX) 1 expression. IL-1α exposure increased NOX1 in human microvascular endothelial cells, and NOX1 blockade restored endothelial function in Tg26 and Tg26→WT arteries, whereas NOX1 deficiency protected against Tg26 BMT-induced impaired endothelium-dependent relaxation and hypertension. Aortas from people living with HIV exhibit high NOX1 levels, and exposure of human aorta to Tg26 T cells increased NOX1 expression., Conclusions: We provide the first evidence that CD4 + T cells expressing HIV viral proteins induced hypertension through IL-1α-mediated increases in vascular NOX1, which impairs endothelial function in males and females.