Infected cell protein 47

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ICP-47 (infected cell protein 47) is a viral protein made by herpes simplex virus and cytomegalovirus. It helps the virus hide from the immune system by stopping infected cells from showing viral pieces to CD8+ T cells. It blocks TAP, the transporter that moves viral peptides into the endoplasmic reticulum so they can be loaded onto MHC class I molecules for T-cell recognition. Without these peptide-MHC I complexes, CD8+ T cells can’t easily detect and kill the infected cell. The protein’s structure includes three helices. Its effects can vary between species; human TAP is inhibited by ICP-47, while some rodent TAPs differ, which helps explain why mice are less susceptible to HSV.