Vitamins as influenza vaccine adjuvant components.

A number of adjuvant formulations were assayed in mice immunized with 3.75 µg of A/California/7/2009 (H1N1) pdm09 influenza vaccine with vitamins A, D and/or E in emulsions or B2 and/or B9 combined with Bordetella pertussis MPLA and/or alum as adjuvants. Squalene was used as positive control, as well as MPLA with alum. The immune response was evaluated by a panel of tests, including a hemagglutination inhibition (HAI) test, ELISA for IgG, IgG1, and IgG2a and IFN-γ, IL-2, IL-6 and IL-10 quantification in splenocyte culture supernatant after stimulus with influenza antigen. Immunological memory was evaluated using a 1/10 dose booster 60 days after the first immunization followed by assessment of the response by HAI, IgG ELISA, and determination of the antibody affinity index. The highest increases in HAI, IgG1 and IgG2a titers were obtained with the adjuvant combinations containing vitamin E, or the hydrophilic combinations containing MPLA and alum or B2 and alum. The IgG1/IgG2a ratio indicates that the response to the combination of B2 with alum would have more Th2 character than the combination of MPLA with alum. In an assay to investigate the memory response, a significant increase in HAI titer was observed with a booster vaccine dose at 60 days after immunization with vaccines containing MPLA with alum or B2 with alum. Overall, of the 27 adjuvant combinations, MPLA with alum and B2 with alum were the most promising adjuvants to be evaluated in humans.