Characteristics of fresh isolates of wild measles virus.

Characteristics of fresh isolates of wild measles virus were studied by immunofluorescence using monoclonal antibodies, SDS-polyacrylamide gel electrophoresis, and electron microscopy. By the immunofluorescence test, hemagglutinin, nucleocapsid-associated phosphorylated, and fusion proteins were found only in the cytoplasm of cells infected with the virus at a low passage level. Nucleocapsid (NP) and membrane (M) proteins were found in both the cytoplasm and nuclei. Since the M protein is present only in the cytoplasm of cells infected with the laboratory strain of measles virus, this intranuclear M protein may be specific to the wild virus. At an increased passage level, the intranuclear M protein became undetectable, but the NP protein was still present in the nuclei. SDS-polyacrylamide and electron microscopy showed that wild measles viruses were shown to have characteristics similar to those of laboratory strains.