Das, S.; Tenaglia, B. M.; Riley, D.; Speed, S.; Baracco, L.; Gardner, F. M.; Varisco, D. J.; Yang, H.; Nijhuis, H.; Kerstetter, L.; Krammer, F.; Sun, W.; Frieman, M. B.; Ernst, R. K.

Seasonal influenza viruses continue to pose a significant threat, causing substantial morbidity and mortality in the US and worldwide despite the availability of vaccines and antivirals. These challenges may be addressed by improving vaccine immunogenicity through the inclusion of adjuvants that enhance immune responses against key antigens including influenza hemagglutinin (HA). BECC (Bacterial Enzymatic Combinatorial Chemistry) adjuvants are novel Toll-like Receptor 4 (TLR4) ligands created by modifying enzymes from lipid A synthesis pathways in Gram-negative bacteria. This study compares the ability of the biological and synthetic versions of these adjuvants to enhance the efficacy of recombinant HA (rHA) antigens in mouse influenza virus challenge. Mice immunized with rHA adjuvanted with BECCs stimulate the humoral and cell-mediated arms of the immune system without exhibiting cytotoxicity/pyrogenicity. A robust HA-specific immunoglobulin subtype, especially IgG2a, response was observed in mice adjuvanted with BECCs as compared to control adjuvants, MPL, and PHAD Further, animals adjuvanted with BECC470 cleared infection seven days post-infection, demonstrating their potential for further translational development. Vaccination adjuvanted with BECCs were also able to increase immune recognition of linear B and T cell epitopes when compared to control adjuvants, as well as induce durable immune response eighteen months post-vaccination. Together, these findings indicate that BECCs may serve as highly effective adjuvants in influenza vaccination.