Antigenic modulation of measles subacute sclerosing panencephalitis virus in a persistently infected rat glioma cell line by monoclonal anti-haemagglutinin antibodies.

Rat glioma C6 cells persistently infected with measles subacute sclerosing panencephalitis (SSPE) virus (C6/SSPE) express the viral membrane proteins haemagglutinin (HA) and F on their cell surface as well as the intracellular proteins N, P and M. Previously we have shown that the addition of a polyclonal antibody against the HA antigen to the growth medium of C6/SSPE cells led to a gradual loss of all viral antigens. Here we show that the addition of a monoclonal antibody (MAb K83) leads only to a transient decrease in viral antigens during the first three passages. After the third passage viral antigens start to increase and after five passages they produce more antigens than at the premodulation level. At this point of the MAb treatment, MAb K83 no longer recognized the HA antigen on the surface of the cells and in virus particles produced by these cells in contrast with polyclonal antibodies or other MAbs against the HA antigen. The results suggest that specific variants of the SSPE virus with an altered HA antigen were selected by the MAb treatment.