Potentiation of the immune response to influenza virus subunit vaccines.

Influenza subunit vaccines are poorly immunogenic in unprimed lower animals and man and methods were sought to potentiate the humoral response. Influenza B intact virus vaccines potentiated the antibody response of hamsters to purified vaccines containing influenza A hemagglutinin and neuraminidase subunits. The levels of anitbody induced were at least as high as those induced by equivalent doses of whole virus. Similarly, intact heterologous influenza A virus vaccine (A/Victoria/3/75 [H3N2]) potentiated the antibody response of hamsters to A/NJ/76 [Hswl NI] subunit vaccines but large doses of intact virus were required. Considerably lower doses of homologous intact A/NJ/76 [Hswl NI] potentiated the antibody response of hamsters and sero-negative people to subunit vaccines. This suggests that future influenza subunit vaccines for use in seronegative people should contain a minimal dose of whole virus vaccine sufficient to potentiate the immune response to the subunits but insufficient to be reactogenic. A synthetic water soluble adjuvant (N-acetyl-muramyl-L-alanyl-D-isoglutamine) was also shown to potentiate the immune response of hamsters to A/NJ/76 [Hswl NI] influenza virus subunit vaccines.