Influenza vaccine based on AS03-adjuvanted chimeric HA induces long-lived stalk-specific plasma cells in bone marrow and lymph nodes of nonhuman primates

Current influenza vaccines face challenges due to antigenic evolution of the circulating virus and waning immunity in humans. Here we investigated the durability of humoral immunity induced by an influenza vaccine based on AS03-adjuvanted chimeric hemagglutinin (cHA) in nonhuman primates (NHPs). Two groups of NHPs received two doses of a seasonal quadrivalent influenza vaccine, followed by sequential immunization with split virus cHA vaccines cH8/1N1, and cH5/1N1. One group received cHA immunizations with AS03 adjuvant. We monitored serum antibodies and long-lived plasma cells in bone marrow for nearly 2 years after the final vaccination. cHA vaccines induced stalk-specific antibody responses. The addition of AS03 enhanced both the magnitude and durability of humoral immunity by establishing long-lived plasma cells in the bone marrow and lymph nodes for nearly 2 years. Passive transfer of NHP serum provided protection against challenge with heterologous influenza A virus strains in mice. This study highlights the potential of the AS03-adjuvanted chimeric HA vaccine strategy to provide durable and broadly protective humoral immunity. The authors report that an AS03-adjuvanted chimeric hemagglutinin-based influenza vaccine induces persistent stalk-specific serum antibody and bone marrow plasma cell responses in nonhuman primates, offering promise for broader and durable flu protection.