Abstract
Measles virus matrix (M) proteins were compared by competitive monoclonal antibody-binding studies. Three strains of measles and of subacute sclerosing panencephalitis viruses were found to be identical in this way. The matrix protein formed by Edmonston strain virus during a persistent infection could be distinguished from that made in the lytic virus infection. It is concluded that structural alterations in the M peptide can occur during persistence.