PREPARATION AND CHARACTERIZATION OF A PURIFIED INFLUENZA-VIRUS NEURAMINIDASE VACCINE

Influenza virus neuraminidase (NA) has been shown to induce protective but infection-permissive immunity in experimental animals. Challenge infection following such immunization is attended by decreased viral r eplication and disease manifestations but is sufficient to provide ant igenic stimulation and definitive immunity to the virus. The present r eport describes the preparation and characterization of a purified NA vaccine (NAV) used in Phase 1 (immunogenicity and toxicity) trials in humans. In essence, virion NA was isolated from detergent-disrupted vi rus by affinity chromatography on oxamic acid-agarose, treated with fo rmalin and tested for its enzymatic activity and for its immunogenicit y in Balb/c mice and New Zealand rabbits, The preparation was essentia lly free of viral hemagglutinin but contained residual NP and MI prote ins. Both dispersed and aggregated NA tetrameric heads were seen in el ectron micrographs. Enzymatic activity was preserved, and minimal immu nogenic doses in mice and rabbits, respectively, were 3.7 and 0.027 mu g per kg.