Loss of Vpr-driven TRAIL-R2 expression protects HIV-infected cells from non-canonical NK cell TRAIL attack.

HIV escapes sterilizing immunity through a variety of mechanisms, including the downregulation of MHC-I expression by HIV Nef and Vpu to counteract CD8 + T cell responses. While reduced MHC-I expression would be expected to support targeting by NK cells, a subpopulation of infected CD4 + T cells consistently resists multiple rounds of NK cell natural and antibody-dependent cytotoxicity. Studies further reveal that the HIV accessory protein Vpr induces expression of TNFRSF10B (TRAIL-R2) in CD4 + T cells, with 'survivors' of NK cell targeting exhibiting relatively higher MHC-I and weaker expression of TRAIL-R2. In fact, reverse TRAIL signaling in NK cells leads to the release of perforin and granzymes, a pathway limited when TRAIL-R2 expression is diminished. Thus, independent of canonical death receptor signaling, TRAIL-R2 serves as an activating ligand that augments NK cell killing. These observations demonstrate that through Vpr, HIV can regulate the TRAIL/TRAIL-R2 axis to control NK cell functionality.