Antigenic characterization of the nucleoprotein and matrix protein of influenza C virus with monoclonal antibodies.

Monoclonal antibodies against the nucleoprotein (NP) and matrix (M) protein of influenza C virus were prepared and characterized. At least two non-overlapping or partially overlapping antigenic sites were delineated on each of the proteins by competitive binding assays. Western blot analysis showed that two antigenic sites on the M protein were highly resistant to conformational changes whereas two sites on NP were sensitive. No antigenic variation was seen in either the NP or the M protein when the reactivity of monoclonal antibodies with 23 different influenza C strains isolated over a 41 year period was studied by radioimmunoprecipitation and enzyme-linked immunosorbent assay. Immunofluorescence analysis with the monoclonal antibodies revealed that both the NP and M proteins migrated to the cell nucleus during the replication cycle of influenza C virus.