A human herpesvirus 7 glycoprotein, U21, diverts major histocompatibility complex class I molecules to lysosomes

All members of the herpesvirus family persist in their host throughout life . In doing so, herpesviruses exploit a surprising number of different strat egies to evade the immune system. Human herpesvirus 7 (HHV-7) is a relative ly recently discovered member of the herpesvirus family, and little is know n about how it escapes immune detection. Here we show that HHV-7 infection results in premature degradation of major histocompatibility complex class I molecules. We identify and characterize a protein from HHV-7, U21, that b inds to and diverts properly folded class I molecules to a lysosomal compar tment. Thus, U21 is likely to function in the normal course of HHV-7 infect ion to downregulate surface class I molecules and prevent recognition of in fected cells by cytotoxic T lymphocytes.