Immunogenicity in mice and non-human primates of an Advax-CpG55.2-adjuvanted recombinant hemagglutinin seasonal quadrivalent influenza vaccine.

There is a need to improve the effectiveness of seasonal influenza vaccines. Influenza vaccines based on recombinant hemagglutinin offer advantages over traditional approaches. We asked whether Advax-CpG55.2 or alum-CpG55.2 adjuvants could enhance the immunogenicity of a quadrivalent influenza vaccine (QIV) comprising recombinant full-length native hemagglutinins (HA0) produced in Sf9 insect cells. Adult C57BL/6 mice were immunized intramuscularly twice 10 days apart with 4 μg of QIV alone or with adjuvant. QIV induced only modest levels of anti-influenza IgG1 whereas the adjuvanted formulations induced significantly higher levels of IgG1 plus IgG2c. When challenged with the H1N1pdm strain, A/South Australia/348/2023, adjuvanted QIV immunized mice showed minimal illness, whereas QIV alone immunized mice all succumbed to infection. Advax-CpG55.2 adjuvanted QIV similarly increased influenza-specific IgG against all four vaccine strains in Cynomolgus macaques. Adjuvanted recombinant hemagglutinin approaches offer a promising alternative to existing seasonal influenza vaccine platforms.