Activation of PD-1/PD-L1 immune checkpoint by Zika virus.

Zika virus (ZIKV) has emerged as a rising concern in global health in recent years. The role of PD-1/PD-L1 immune checkpoint in acute ZIKV infection remains to be understood. In this study we demonstrated the activation of PD-1/PD-L1 immune checkpoint by ZIKV. mRNA and protein expression of PD-L1 was boosted by ZIKV not only in SF268 and JEG3 cell lines but also in human dendritic cells. PD-1 expression was more abundant on CD8+ T cells in ZIKV-infected mice. Elevated PD-L1 expression was also observed in the brain, testis and spleen of ZIKV-infected A129 mice. Blocking PD-L1 effectively inhibited ZIKV infection, reducing viral loads in all tissues. In addition, anti-PD-L1 antibody treatment further increased virus-specific CD8+ T cells, KLRG+ CD8+ T cells, and effector memory CD8+ T cells. PD-L1 blockade also induced interferon γ, granzyme B, and interleukin 2 expression in antigen-specific CD8+ T cells, consistent with activation of these cells. Mechanistically, the induction of PD-L1 expression might be ascribed to viral NS4B protein and its interaction with GRP78. Our findings suggest that targeting the PD-1/PD-L1 pathway could have antiviral effect against ZIKV.