Evaluating Bacillus Calmette–Guérin Polysaccharide Nucleic Acid as an Adjuvant for Influenza Vaccines in Mice

Background

To enhance influenza vaccine efficacy, it is essential to investigate new adjuvants that are both safe and effective. In a recent study utilizing a mouse model, Bacillus Calmette–Guérin polysaccharide nucleic acid (BCG-PSN) emerged as a promising candidate vaccine adjuvant.

Methods

This study evaluated the immunomodulatory effects of BCG-PSN on influenza vaccines hemagglutinin antigen and aluminum adjuvant as controls. Mice were immunized with H1N1 antigen and adjuvants, and serum antibody levels were measured using hemagglutination inhibition, enzyme-linked immunosorbent assay, and microneutralization assays. Flow cytometry and enzyme-linked immunospot assays assessed T cell phenotypes and cytokine expression. The protective effects were tested through challenge experiments, and the adjuvants were further evaluated in a quadrivalent seasonal influenza vaccine.

Results

BCG-PSN adjuvant exhibited favorable safety profiles and demonstrated an ability to elevate total antibody titers, particularly enhancing neutralizing antibody production when co-administered with the H1N1 antigen. BCG-PSN increased cytokine levels and the proportion of CD8+ T lymphocytes, indicating its capacity to enhance cellular immunity. Upon viral challenge in mice, BCG-PSN mitigated the production of inflammatory factors and reduced lung pathology, effectively protecting the mice. Furthermore, BCG-PSN displayed heightened immunogenicity against a mixture of four antigens.

Conclusions

BCG-PSN is a reliable and efficient adjuvant for influenza vaccines, holding promise for enhancing vaccine efficacy and increasing immune responses.