The antigenic relationship of the neuraminidase of Hong Kong virus to that of other human strains of influenza A virus.

Segregation of the haemagglutinin and neuraminidase antigens of 6 representative influenza A2 viruses and the Hong Kong virus by genetic recombination permitted a precise analysis of the antigenic constitution of each virus. Although cross-reactivity of the Hong Kong influenza virus and all 6 influenza A2 strains was demonstrated, the cross-reactivity was shown to be entirely dependent upon and mediated through the viral neuraminidase and not the haemagglutinin. The neuraminidase of the Hong Kong virus is slightly reactive with the neuraminidase of older A2 strains but is apparently identical to the enzyme of the recent (1967-68) variants.