[Influenza virus neuraminidase and its role in anti-influenzal immunity]

The direct relationship between immunogenicity of H3N2 formolvaccine and neuraminidase activity was established. A single intranasal immunization of mice with the vaccine having a titer of hemagglutinin 1:20,000-1:40,000 in 0.5 ml with active neuraminidase increased the resistance of the animals to the challenge with mouse-adapted influenza A/USSR/053/74 (H3N2) virus almost 5-fold. A vaccine with the same hemagglutinin titer but with neuraminidase inactivated by physico-chemical factors or blocked by specific antibody exerted a protective effect 2.5-3 fold weaker than the vaccine with the active enzyme.