Studies of some biological and molecular characteristics of avian influenza A/H7 (Hav1) subtypes.

Current isolates of the subtypes H7N3 and H7N7 from 1979 to 1981 were examined and compared with the reference strains with regard to their antigenic variability and to their pathogenicity for birds and mammals in order to establish the potentiality of influenza A/H7 virus (Hav1) transmission from birds to mammals. The analysis of the electrophoretic mobility of virus-induced polypeptides and of the double-stranded RNA segments after hybridization revealed equal, similar and deviating patterns. A substantial drift was determined in the surface antigens, especially in the neuraminidase. The avian strains replicated also in mammalian cells and were pathogenic for mammals. All strains examined were reisolated from the infected mammals; they caused more pronounced inflammatory changes in the trachea and lungs of infected mammals than in those of birds.