Comparative immunogenicity of live influenza viruses and their solubilized neuraminidases: results of mouse protection experiments.

Antigenicity and immunogenicity of three influenza virus strains A/PR/8/34 (H1N1). A/Hong Kong/1/68 (H3N2) and A/Port Chalmers/1/73 (H-3H2) were assayed comparatively with their corresponding neuraminidase isolated by proteolysis, and with the recombinant virus X-42 (Heq1 N2). It was concluded that intranasal immunization of mice with live virus induced heterologous immunity. Except in homologous neuraminidase-vaccinated mice, the subunit always was shown less effective and demonstrated a significantly lower antibody response than the corresponding whole virus.