Use of Mucosally Administered Outer Membrane Vesicles Derived fromBordetella pertussisto Diminish Nasal Bacterial Colonization

Background We previously identified Bordetella pertussis -derived outer membrane vesicles (OMVs) as a promising immunogen for improving pertussis vaccines. In this study, we evaluated the efficacy of our vaccine prototype in immunization strategies aimed at reducing disease transmission by targeting colonization in the upper airways while maintaining protection against severe disease by reducing colonization in the lower respiratory tract. Methods We assessed different mucosal administration strategies in a murine model, including homologous 2-dose schedules and heterologous prime-boost strategies combining intramuscular (IM) systemic immunization with mucosal routes (intranasal (IN) or sublingual (SL)). We utilized mucosal c-di-AMP and/or systemic alum adjuvants to formulate the OMV vaccine prototype. A homologous IM immunization schedule and commercial vaccines were used for comparison. Results All tested heterologous schemes induced higher levels of specific IgG with significant avidity, as well as high levels of IgG1 and IgG2 compared, to corresponding homologous 2-dose schemes via mucosal routes (OMV IN-IN or OMV SL-SL ). High IgA levels were observed post- B. pertussis challenge following OMV IN-IN treatments and heterologous treatments where the second dose was administered via a mucosal route. Furthermore, schemes involving the intranasal route, whether in a homologous or heterologous scheme, induced the highest levels of IL-17 and IFN-γ. Accordingly, these schemes showed superior efficacy against nasal colonization than the commercial vaccines. Specifically, homologous intranasal immunization exhibited the highest protective capacity against nasal colonization while maintaining an excellent level of protection in the lower respiratory tract. To enhance the protective capacity against nasal colonization further, we conducted a comparative analysis of formulations containing different adjuvants (c-di-AMP, alum, or a combination of both) administered via homologous intranasal routes. These assays revealed that the use of alum, either alone or in combination with c-di-AMP, did not enhance the immune protective capacity. Conclusions All the experiments presented here highlight that the use of OMVs, regardless of the scheme utilized, with the exception of OMV SL-SL , outperformed acellular pertussis (aP) vaccines, achieving a greater reduction in bacterial colonization in the upper respiratory tract (p<0.001).