The major goal of this project is to characterize virus antigens and other components expressed on the surface of infected cells which are the targets of the immune response. Monoclonal antibodies against the five structural proteins of measles virus have been produced and are used to characterize and purify these viral components. Focus has been placed on the two components, the hemagglutinin (HA) and the fusion (F) protein, expressed on the membrane surface. The HA protein is being studied in the Edmonston and hampster neurotropic strains of measles. Immune cells recognize viral antigen(s) in association with components of major histocompatibility complex (MHC). The relationship between human MHC molecules and measles HA and F proteins is being examined.