Caratterizzazione antigenica dell'emoagglutinina e della neuraminidasi dei ceppi di virus influenzale di tipo B isolati in Italia nel 1962, 1967 e 1971.

The hemagglutinin and neuraminidase antigens of 3 influenza type B viruses isolated in Italy during the epidemics of 1962, 1967 and 1971 were characterized. As reference strains, the prototypes B/Lee/40, B/Bon/43, B/Johannesburg/58, B/Taiwan/62 and B/Hong Kong/8/73 were chosen. The data obtained with specific chicken antisera show that the hemagglutinins of the Italian strains have an immunological relation between themselves and with the hemagglutinating antigen of the B/Johannesburg and B/Taiwan viruses. Only in the case of B/Hong Kong/8/73 strain no cross reactivity with the earlier viruses was found. However the B/Hong Kong immune serum inhibited at low titer hemagglutinin of B/Taiwan virus. The neuraminidases of the Italian strains appear very similar and highly correlated with the enzymes of the B/Johannesburg and B/Taiwan viruses. Also the neuraminidase of B/Hong Kong is strictly related to that of previously prevalent viruses with the exception of the B/Lee and B/Bon. The behaviour of homologous and heterologous hemagglutination and neuraminidase inhibition antibody in the sera of patients (age over 10 years) involved in the three epidemics was studied. At the hemagglutination inhibition and neuraminidase inhibition tests the majority of the patient sera reacted also with the heterologous strains. It is concluded that the B influenza viruses belong to the same antigenic spectrum.