Increased platelet–CD8+ T-cell aggregates displaying high activation, exhaustion, and tendency to death correlate with disease progression in people with HIV-1

Platelets engaged in HIV-1 infection by interacting with immune cells, which has been realized broadly. However, the potential interaction between platelets and CD8⁺ T cells remains unidentified. Here, treatment-naïve individuals with HIV-1 (TNs), complete immunological responders to antiretroviral therapy (CRs), and healthy controls (HCs) were enrolled. Firstly, we found that TNs had low platelet numbers and high CD8⁺ T cell counts when compared with CRs and HCs, leading to low platelet/CD8⁺ T cell ratio in peripheral blood which could effectively differentiate the status of HIV-1 infection. Moreover, cytokines that may be derived from platelets were higher in the plasma of people with HIV-1 despite viral suppression. Furthermore, we demonstrated that platelet-CD8⁺ T cell aggregates were elevated in TNs, which positively correlated with HIV-1 viral load, but negatively correlated with CD4⁺ T cell count and CD4/CD8 ratio. Finally, we revealed that platelet-CD8⁺ T cell aggregates with enhanced activation/exhaustion and pyroptosis/apoptosis than free CD8⁺ T cells. Moreover, platelets-induced caspase-1 activation of CD8⁺ T cells correlated with IL-1β and IL-18 plasma levels. In brief, we revealed the importance of platelets in HIV-1 infection, which might secrete more cytokines, and might mediate CD8⁺ T cell phenotypic characteristics by forming platelet-CD8⁺ T cell aggregates which were related to poor prognosis.