Abstract
The antigenic determinants of the haemagglutinin and haemolysin antigens of measles virus were located at the surface of HEp2 cells infected with measles virus and on measles virions released from these cells, using immunoelectron microscopy. Antisera specific for haemagglutinin or haemolysin antigen and peroxidase-conjugated antiglobulin were used. Treatment of the infected cells with trypsin removed the virus spikes and prevented binding by the anti-haemagglutinin serum, while the reaction with anti-haemolysin serum was unaltered. This suggests that the antigenic determinants for measles haemagglutinin reside on the spike, while the antigenic determinants for haemolysin reside on, or are close to, the virus membrane.