Adjuvant skewing of host immune response to vaccination and subsequent infection with influenza virus

Abstract Despite being a vaccine-preventable disease, seasonal influenza is responsible for thousands of hospitalizations and deaths yearly. Currently licensed quadrivalent inactivated influenza virus vaccines (QIV) aim to induce neutralizing antibodies but are poor inducers of T-cell responses, which could be potentially overcome with adjuvants. We evaluated adjuvant skewing of host-immune responses after vaccination and its persistence after infection. Hereto, we compared two squalene-based adjuvants (AddaVax, and AddaS03) and IMDQ-PC, a lymph node-draining TLR7/8 agonist. All adjuvants resulted in enhanced antibody titers and protection against challenge with H1N1 influenza virus. Lung cytokine/chemokine profiling at 5 days post-infection showed that AddaVax results in higher levels of type 2 immunity-stimulating cytokines IL-4, -5, and -13 in the lungs, which is also reflected by a higher IgG1:IgG2a ratio. Meanwhile, IMDQ-PC showed higher serological IgG2a titers after vaccination and higher levels of IFNγ in the lungs after challenge. To investigate the role of the myeloid compartment in adjuvant skewing of host responses, we examined adjuvant-mediated skewing of bone-derived macrophages in-vitro using Arginase I and iNOS as M2 or M1 markers, respectively. We also pre-licensed macrophages with IL-4 and IFNγ to evaluate adjuvant-intrinsic skewing effects. Licensing was required to induce M1 or M2 phenotypes by squalene-based adjuvants, whereas IMDQ-PC skewed towards M1 phenotype irrespective of licensing. Correlating with the observed type I immune host response, IMDQ-PC induced iNOS more robustly with IFNγ than the other adjuvants. And, AddaS03 induced the highest levels of Arginase I in the IL-4 group. This study was also partly funded by CRIPT (Center for Research on Inuenza Pathogenesis and Transmission), a NIH NIAID funded Center of Excellence for Influenza Research and Response (CEIRR, contract number 75N93021C00014), by the NIAID funded SEM-CIVIC consortium to improve inuenza vaccines (contract number 75N93019C00051), to AG-S. By NIH/NIAID HHSN272201400008C (L.C.), and NIH/NIAID R21AI151229 and R01AI160706 (M.S.). B.G.D.G. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant N 817938).