PRF1 and viral infectious disease: In a mouse polyomavirus encephalitis model and in mouse cytomegalovirus, HSV, and WNV infection mouse models, CD8+ TRM cells play an important role in controlling viral infections by secreting effector molecules such as granzymes, perforin, and IFN‐γ, which persist in the central nervous system (CNS) parenchyma after the clearance of viral infections.145, 146, 147