Alterations in expression of measles virus polypeptides by antibody: molecular events in antibody-induced antigenic modulation.

Six hours after measles virus antibodies bind to the surface of HeLa cells acutely infected with measles virus, the expression of an external polypeptide F1, as well as internal polypeptides P and M are altered. The loss of F1 molecules during antibody-induced antigenic modulation explains the lack of cell-cell fusion and giant cell formation of infected cells cultured in the presence of antibody. The decrease in F1, P, and M viral polypeptides is specific, since the effect is only seen with antibodies directed against measles virus antigens expressed on the cell's surface and not with antibodies directed against nonviral antigens expressed on the surfaces of virus-infected cells. Since the P protein or its analog in other viral systems appears to be associated with transcriptive complex whereas the M protein is associated with nucleocapsid recognition and alignment at the plasma membrane, the alterations in these polypeptides might lead to aberrations in measles virus synthesis and maturation that are hallmarks of persistent measles virus infection.