[Correlation between structure and pathogenicity of myxoviruses (author's transl)]

Myxoviruses (ortho- and paramyxoviruses) possess on their surface two virus-specific glycoproteins, the functions of which are largely understood; These glycoproteins are synthesized on the rought endoplasmic reticulum, and during their transport to the plasma membrane on smooth intracellular membranes, they undergo modification through proteolytic cleavage. In this way, the orthomyxovirus hemagllutinin is converted from a high-molecular weight form (HA) into two smaller cleavage products (HA1 and HA2). With the paramyxoviruses, the glycoprotein F, which is responsible for fusion and hemolysis, is derived from proteolytic cleavage of a precursor, F0. Furthermore, with a few strains of avirulent NDV, a precursor of the hemagglutinin-neuraminidase complex, (HN0), has been identified which again, as a result of proteolysis, undergoes cleavage to HN. Whether cleavage takes place is as much dependent on the structure of the glycoprotein as on the host cell type. Proteolytic cleavage is indeed not necessary for virus particle production but is required for infectivity. Virus particles which possess the uncleaved glycoproteins may be activated by in vitro treatment with trypsin. As evidenced by experiments with orthomyxovirus recombinants, the glycoproteins alone do not determine the pathogenicity of the viruses. With paramyxoviruses, the pathogenic and apathogenic strains show clear differences in their host range spectrum which is directly related to the sensitivity of their glycoproteins twoard proteases. These observations provide an initial sketch for the molecular basis of infectivity and pathogenicity with myxoviruses.