@ARTICLE{10.3389/fimmu.2019.00646, AUTHOR={Bhide, Yoshita and Dong, Wei and Gribonika, Inta and Voshart, Daniëlle and Meijerhof, Tjarko and de Vries-Idema, Jacqueline and Norley, Stephen and Guilfoyle, Kate and Skeldon, Sarah and Engelhardt, Othmar G. and Boon, Louis and Christensen, Dennis and Lycke, Nils and Huckriede, Anke}, TITLE={Cross-Protective Potential and Protection-Relevant Immune Mechanisms of Whole Inactivated Influenza Virus Vaccines Are Determined by Adjuvants and Route of Immunization}, JOURNAL={Frontiers in Immunology}, VOLUME={10}, YEAR={2019}, URL={https://www.frontiersin.org/articles/10.3389/fimmu.2019.00646}, DOI={10.3389/fimmu.2019.00646}, ISSN={1664-3224}, ABSTRACT={Adjuvanted whole inactivated virus (WIV) influenza vaccines show promise as broadly protective influenza vaccine candidates. Using WIV as basis we assessed the relative efficacy of different adjuvants by carrying out a head-to-head comparison of the liposome-based adjuvants CAF01 and CAF09 and the protein-based adjuvants CTA1-DD and CTA1-3M2e-DD and evaluated whether one or more of the adjuvants could induce broadly protective immunity. Mice were immunized with WIV prepared from A/Puerto Rico/8/34 (H1N1) virus intramuscularly with or without CAF01 or intranasally with or without CAF09, CTA1-DD, or CTA1-3M2e-DD, followed by challenge with homologous, heterologous or heterosubtypic virus. In general, intranasal immunizations were significantly more effective than intramuscular immunizations in inducing virus-specific serum-IgG, mucosal-IgA, and splenic IFNγ-producing CD4 T cells. Intranasal immunizations with adjuvanted vaccines afforded strong cross-protection with milder clinical symptoms and better control of virus load in lungs. Mechanistic studies indicated that non-neutralizing IgG antibodies and CD4 T cells were responsible for the improved cross-protection while IgA antibodies were dispensable. The role of CD4 T cells was particularly pronounced for CTA1-3M2e-DD adjuvanted vaccine as evidenced by CD4 T cell-dependent reduction of lung virus titers and clinical symptoms. Thus, intranasally administered WIV in combination with effective mucosal adjuvants appears to be a promising broadly protective influenza vaccine candidate.} }