Since the pandemic (H1N1) 2009 virus has been a seasonal flu which still poses great human health concerns worldwide, vaccination would be considered as the most effective strategy to control the influenza virus spreading. Here, we assessed adjuvant efficacy of modified outer membrane vesicle (mOMV) towards the pandemic H1N1 split antigen.

For this study, mice were vaccinated twice with various amount of antigen (0.05, 0.1, and 0.5 µg/dose hemagglutinin [HA]) that were mixed with mOMV, aluminum hydroxide (alum), and MF59, as well as the combined adjuvant comprising the mOMV plus alum.

We found that all the adjuvanted vaccines of A/California/04/09 (CA04, H1N1) containing HA antigen more than 0.1 µg/dose protected effectively from lethal challenge (maCA04, H1N1) virus, compared to the antigen only group. Furthermore, vaccinated mice received as low as 0.05 µg/dose of the split vaccine containing the combined adjuvant (10 µg of mOMV plus alum) showed a full protection against lethal challenge with H1N1 virus. Taken together, these results suggest that mOMV can exert not only the self-adjuvanticity but also a synergy effect for the vaccine efficacy when combined with alum.

Our results indicate that mOMV could be a promising vaccine adjuvant by itself and it could be used as a vaccine platform for development of various vaccine formulations to prepare future influenza pandemic.