What is "immunoevasin"

Immunoevasins are proteins expressed by some viruses that enable the virus to evade immune recognition by preventing the appearance of peptide on MHC I complexes on the infected cell. Some viral immunoevasins block peptide entry into the endoplasmic reticulum (ER) by targeting the TAP transporters.

For example, the Herpes simplex virus, produces a protein, ICP47, that binds to cytosolic surface of TAP, preventing peptides from ever entering the ER, which would prevent the cascade reaction that would lead the cell from presenting the MHC complex from reaching the surface.