[Antigenic anachronism of influenza viruses A(H2N2) in Leningrad in 1980. II. The laboratory characteristics of influenza A/Leningrad/80 viruses].

As indicated by the results of the hemagglutination inhibition (HAI) test, influenza viruses A/Leningrad/80 contain hemagglutinin (HA), similar to that of virus A/Singapore/1/57 (H2N2). Neuraminidase contained in viruses A/Leningrad/80 belongs to serological subtype N2 and is similar to that of virus A/Singapore/1/57 (H2N2). No differences in the polypeptide composition of the virus-induced proteins of viruses A/Leningrad/527/80, A/Leningrad/549/80, A/Leningrad/553/80 and virus A/Singapore/1/57 used as reference have been detected in the study of their electrophoretic mobility in polyacrylamide gel, as well as the mobility of duplexes obtained by the hybridization of the virion and complement RNA of viruses A/Leningrad/553/80 and A/Singapore/1/57.

[Differentiating markers of virulent and attenuated (cold-adapted) strains of influenza A virus].

A high sensitivity of influenza virus to replication at a high temperature and a reduction of the temperature optimum of the neuraminidase activity are important genetic markers correlating with the degree of attenuation for the man. Cold-adapted variants of influenza virus produced in the course of passages at a low (25-28 degrees C) temperature are thermo-sensitive. The passage of the viruses at the optimal temperature (32 degrees C) does not change the range of thermal sensitivity even in variants, harmless for adult persons.