Impairment of the M-Protein and Unmasking of a Superficial Type-Specific Antigen by Proteolytic Treatment of Influenza A Virions with Preservation of Host-Specific Antigenicity

Abstract

Influenza PR8 particles resulting from strong treatment with caseinase C are spikeless, devoid of neuraminidase and hemagglutinin 1 and 2 glycopeptides, and contain a Schiff-negative polypeptide of about 13,000 molecular weight which exists as traces in intact virions. Their M-protein polypeptide content is reduced to 50% of its original value, but there is no evidence of particle disruption nor of lipid release. They fix complement in the presence of both anti-M-protein antiserum and antiserum raised against a host polysaccharide. During exposure to caseinase C, an antigen is unmasked. It is type-specific and its identity with the M-protein is discussed.