Cellular Localization of Five Structural Proteins of Sendai Virus Studied with Peroxidase-labelled Fab Fragments of Monoclonal Antibodies

By the use of horseradish peroxidase-labelled Fab fragments of monoclonal antibodies, five major structural components of Sendai virus, namely the nucleocapsid (NP), polymerase (P), matrix (M), fusion (F), and haemagglutinin-neuraminidase (HN) proteins were localized in infected Vero cells. The P and NP proteins were found in association with large clusters of ribosome-like particles and nucleocapsids in the cell cytoplasm. They were not concentrated at the cytoplasmic membrane, except in nucleocapsids within budding viral particles. F and HN proteins, on the other hand, were found in connection with ribosomes and endoplasmic reticulum in the cell cytoplasm, but not in nucleocapsids. Both proteins were evenly distributed on the outer cytoplasmic membrane and appeared on the surface clearly before budding of viral particles. The M protein was seen in connection with both nucleocapsids and ribosomes. It was not found at the cell surface except in budding viral particles.