A surface antigen influenza vaccine. 1. Purification of haemagglutinin and neuraminidase proteins.

Influenza virus was centrifuged in a KII rotor through a sucrose gradient containing Triton N101, a non-ionic surfactant. The micelles of surfactant formed a band in the gradient. As virus particles passed through the surfactant, the haemagglutinin and neuraminidase proteins were stripped from the surface and remained near the surfactant micelles. The residual virus particles sedimented into a denser region of the gradient and were thus separated from the haemagglutinin and neuraminidase antigens. Fractions containing the surface antigens were pooled and Triton was removed by phase-separation at the cloud point.