Maximal immune response and cross protection by influenza virus nucleoprotein derived from E. coli using an optimized formulation

- The nucleoprotein is a promising antigen to develop a universal influenza A virus vaccine.
- Maximal cross protection by E. coli-derived NP was observed with the formulation of Alum plus CpG.
- 10 µg of NP combined with Alum and CpG induced higher protection than 90 µg of NP without any adjuvant.
- A combination of Al(OH)3 and CpG may be an efficient adjuvant in the NP formulation.

The highly conserved internal nucleoprotein (NP) is a promising antigen to develop a universal influenza A virus vaccine. In this study, mice were injected intramuscularly with Escherichia coli-derived NP protein alone or in combination with adjuvant alum (Al(OH)3), CpG or both. The results showed that the NP protein formulated with adjuvant was effective in inducing a protective immune response. Additionally, the adjuvant efficacy of Al(OH)3 was stronger than that of CpG. Optimal immune responses were observed in BALB/c mice immunized with a combination of NP protein plus Al(OH)3 and CpG. These mice also showed maximal resistance following challenge with influenza A virus PR8 strain. Most importantly, 10 µg NP formulated with Al(OH)3 and CpG induced higher protection than did 90 µg NP. These findings indicated that a combination of Al(OH)3 and CpG may be an efficient adjuvant in the NP formulation.

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