Characterization of Four Parainfluenza Virus Type 3 Proteins by Use of Monoclonal Antibodies

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Abstract
Monoclonal antibodies directed against four structural components of the ATCC strain C243 of parainfluenza virus type 3 were produced. The specific reaction of the antibodies with individual structural components were determined by radioimmune precipitation assay. In the collection of monoclonal antibodies, 21 reacted with haemagglutinin-neuraminidase (HN) glycoprotein (mol. wt 72000), eight with the fusion (F) glycoprotein (mol. wt 64000), 27 with the nucleocapsid (NP) protein (mol. wt. 69000) and 24 with the matrix (M) protein (mol. wt. 40000). The F-specific monoclonal antibodies precipitated two proteins which were interpreted to represent intact F protein and the large cleavage product F1 (mol. wt. 52000). The numbers of epitopes were determined in a competition of ELISA with the monoclonal antibodies. The epitopes found were six for the HN, two for the F, six for the NP and six for the M protein. The six groups of antibodies reacting with different epitopes on the HN molecule showed varying capacities to inhibit biological activities. Two exhibited high neutralization (NT), haemagglutination inhibition (HI) and haemolysis inhibition (HLI) activity. Three groups had some what lower NT, lower HI and no detectable HLI activity. One group showed no activity in these tests. Of the eight monoclonal antibodies directed to the F protein two had demonstrable HLI activity.