Involvement of human leukocyte antigen class I molecules in human immunodeficiency virus infection of CD4-positive cells.

We have studied the putative roles of human immunodeficiency virus (HIV)-associated and cell surface-expressed major histocompatibility complex class I (MHC-I) molecules in the course of the HIV life cycle by the combined use of MHC-I molecule-positive and MHC-I molecule-negative virus particles and MHC-I molecule-positive and MHC-I molecule-negative CD4+ human cells. We found (i) that several anti-MHC-I monoclonal antibodies neutralize cell infection by direct interaction with HIV-associated MHC-I antigens, (ii) that these HIV-associated MHC-I antigens are however dispensable for cell infection, and (iii) that the cell surface-expressed MHC-I molecules are unnecessary for productive infection of CD4+ human cells. These results clarify further the functions of MHC-I molecules during the HIV life cycle.