THE ROLE OF PROTEOLYTIC CLEAVAGE OF VIRAL GLYCOPROTEINS IN THE PATHOGENESIS OF INFLUENZA-VIRUS INFECTIONS

Infectivity, tropism, spread, and pathogenicity of influenza viruses a re based on the interplay between the fusogenic glycoproteins and appr opriate host endoproteases. The hemagglutinin (HA) of influenza A and B viruses and the HEF (hemagglutinating; esterase, fusion) glycoprotei n of influenza C virus receive their full biological activity by prote olytic cleavage of a precursor molecule at a definite cleavage site. T he amino acid motifs at the cleavage site and the availability of suit able proteases are critical for the clinical manifestation of the infe ction. Prototype cleavage proteases, including bacterial enzymes, are described.