PDCD1LG2 and viral infectious disease: Having correlated gene-specific viral integration with elevated PD-L1 and PD-L2 expression in HPV-positive HNSC, we next correlated any viral infection with PD-L1, PD-L2, PD-1, CD80, CD86, CTLA-4, Tim-3, LAG3, and 4-1BB expressions.