PVR exposure influences the activation, adhesion, and protein expression of human CD8+ T cells, including the CD96-mediated transfer of PVR.

Abstract

Poliovirus receptor (PVR) ligands have gained attention as immunotherapy targets, yet their regulation remains unclear. Here, we examine the impact of PVR exposure on primary human CD8+ T cells. We used flow cytometry and Western blot analysis to quantify expression of PVR and its ligands in naïve and effector T cells and used adhesion assays and enzyme-linked immunosorbent assay (ELISA) to assess the impact of PVR on T cell adhesion and cytokine production. Stimulation with phytohemagglutinin P strongly increased DNAM-1 expression and caused a less robust and more variable increase in TIGIT expression. Exposure to PVR-Fc enhanced the CD8+ T cell adhesion to ICAM-1-coated plates in a dose-dependent manner, while exposure to PVR-expressing K32 cells mildly decreased CD8+ T cell interferon γ release. However, PVR exposure strongly decreased the expression of DNAM-1, TIGIT, and CD96. The reduction of DNAM-1, TIGIT, and CD96 induced by PVR was dominant to the increase caused by T cell receptor signaling. The impact of PVR on their expression was completely abolished by the Q63R and F128R point mutations of PVR, while DNAM-1 was partially rescued by inhibitors of Src and protein kinase C. Additionally, PVR exposure along with T cell receptor signaling promoted the transfer of surface proteins including PVR from K32 cells to CD8+ T cells. This PVR transfer was mediated by the IgV domain of PVR and CD96 on CD8+ T cells and required cellular contact. Our findings collectively demonstrate that PVR engagement has a mild antagonistic effect on interferon γ production but strongly impacts CD8+ T cell adhesion and protein expression.