Monoclonal antibodies reveal extensive antigenic differences between the hemagglutinin-neuraminidase glycoproteins of human and bovine parainfluenza 3 viruses.

A panel of twenty monoclonal antibodies to the hemagglutinin-neuraminidase (HN) glycoprotein of human parainfluenza 3 (PI3) virus has been obtained and tentatively classified into four different groups based on reactivity in hemagglutination inhibition (HI), neuraminidase inhibition (NI), and plaque neutralization (NT) tests. The antibodies were tested for cross-reactivity with bovine PI3 virus, Sendai virus, and simian virus 5 (SV5). Only two of these antibodies showed similar reactivities with human and bovine PI3 viruses in HI and NT tests; a few other antibodies showed low levels of reactivity with the heterologous viruses in HI tests. A competitive binding assay further suggested that the two cross-reactive antibodies are directed against the same domain of the HN molecule. Therefore, the HN glycoproteins of human and bovine PI3 viruses appear to be antigenically dissimilar, although they share at least one common epitope.