Complexities in human herpesvirus-6A and -6B binding to host cells

Human herpesvirus-6A and -6B uses the cellular receptor CD46 for fusion and infection of the host cell. The viral glycoprotein complex gH–gL from HHV-6A binds to the short consensus repeat 2 and 3 in CD46. Although all the major isoforms of CD46 bind the virus, certain isoforms may have higher affinity than others for the virus. Within recent years, elucidation of the viral complex has identified additional HHV-6A and -6B specific glycoproteins. Thus, gH–gL associates with a gQ1–gQ2 dimer to form a heterotetrameric complex. In addition, a novel complex consisting of gH–gL–gO has been described that does not bind CD46. Accumulating evidence suggests that an additional HHV-6A and -6B receptor exists. The previous simple picture of HHV-6A/B-host cell contact therefore includes more layers of complexities on both the viral and the host cell side of the interaction.