Immunopotentiation of humoral and cellular responses to inactivated influenza vaccines by two different adjuvants with potential for human use.

Two quite different adjuvants, currently under development for use in humans, have been examined for their effects on the magnitude and type of immunity elicited in response to inactivated influenza vaccine. Immunostimulating complexes (ISCOM adjuvant) contain the saponin ISCOPREP 703, and SPT is an oil-in-water emulsion of squalane, non-ionic block copolymer (L121) and Tween 80. Influenza virus vaccines formulated in either adjuvant were far superior to the non-adjuvanted aqueous vaccine in eliciting antibody and T-cell responses in mice, particularly at lower doses of antigen. In addition, the vaccines containing adjuvant were superior in eliciting protective immunity. One of the shortcomings of the unadjuvanted inactivated influenza vaccine was its inability to elicit a primary proliferative T-cell response. However, after one dose of either adjuvanted vaccine, strong proliferative responses were achieved. We also show that subcutaneous vaccination with inactivated vaccines is capable of modulating the isotype profile of antibody secreting cells generated in the lungs of mice in response to intranasal challenge with live virus. In this system, the isotype of antibody elicited after challenge of mice that had received ISCOM vaccine more closely mimicked that of animals vaccinated with live virus.