Abstract
Three newly established monoclonal hybridoma antibodies to the haemagglutinin molecule of HVJ, designated A7, B3 and F11, recognize operationally non-overlapping antigenic determinants and have neutralizing activity. Using these antibodies, the frequencies of occurrence of neutralization-resistant antigenic variants were analysed in virus populations released from four cell lines persistently infected with HVJ, namely GM2-HVJ, LLCMK2-HVJ, Vero-HVJ and GEsl-HVJ at various passage stages. Antigenic variants were selected from culture fluids of these HVJ carrier cells at a total frequency of 10-3.3, 10-3.8 and 10-3.6 by monoclonal antibodies A7, B3 and F11, respectively. These values were considerably higher than those of 10-4.7 to 10-5.2 detected in a stock preparation of wild-type virus with these antibodies. All the variant viruses isolated as above were negative in neutralization, haemagglutination inhibition and immunofluorescent staining tests with each monoclonal antibody used for their isolation, but were positive with the other antibodies.