Intranasal and Intramuscular Immunization with Outer Membrane Vesicles from Serogroup C Meningococci Induced Functional Antibodies and Immunologic Memory

ABSTRACT

Background

Immunization is the key to prevent invasive meningococcal disease (IMD), caused by Neisseria meningitidis. Outer membrane vesicles (OMVs) can be used as meningococcal antigens.

Methods

Isogenic mice A/Sn (H2^a) were immunized with low antigenic doses of OMVs of an N. meningitidis C:2a:P1.5 strain, via intranasal/intramuscular route, adjuvanted by cholera toxin subunit B (CTB) or via intramuscular route only, adjuvanted by aluminium hydroxide (AH). Mice were followed until old age and humoral and cellular responses were assessed by ELISA, Immunoblotting, Dot-blot, Serum-bactericidal assay, Immunohistochemistry and ELISpot.

Results

OMV+CTB and OMV+AH groups presented statistically higher antibodies titers, which persisted until middle and old ages. IgG isotypes point to a Th2 type of response. Avidity indexes were considered high, regardless of adjuvant use, but only groups immunized with OMVs and adjuvants (OMV+CTB and OMV+AH) presented bactericidal activity. The antibodies recognized antigens of molecular weights attributed to porin and cross-reactivity proteins. Although the spleen of old mice did not present differences in immunohistochemistry marking of CD68+, CD4+, CD79+ and CD25+ cells, splenocytes of immune groups secreted IL-4 and IL-17 when stimulated with OMVs and meningococcal C polysaccharide.

Conclusion

We concluded that both adjuvants, CTB and AH, improved the immunogenicity of low doses of OMVs and contributed to a persistent immune response. Even though AH is well established in the vaccinology area, CTB seems to be a promising adjuvant candidate for meningococcal vaccines: it is suitable for mucosal delivery and supports a Th2 type of response. Therefore, OMVs are still a relevant vaccine platform.

KEYWORDS:

• Aluminium hydroxide
• cholera toxin subunit B
• Neisseria meningitidis
• outer membrane vesicles
• prime-booster immunization

Acknowledgments

The authors would like to thank Dr Ana Paula Lemos (Bacteriology Center, Adolfo Lutz Institute) for providing the bacteria strains used in this study; the Bromatology Center (Adolfo Lutz Institute) for support in the LAL Gel-Clot Endosafe analysis; the Microorganisms Culture Collection (Adolfo Lutz Institute) for reactivating the bacterium strain; the staff from Bacteriology Center (Adolfo Lutz Institute) from support in Serum Bactericidal Assay and Aline Rodrigues da Silva and Fernanda Alencar Rodrigues (Pathology Center, Adolfo Lutz Institute), for support in the Immunohistochemistry assay.

Authors’ contribution

All authors contributed with discussions of the results, reviewed the final manuscript and agreed with its submission. AIP: Investigation, methodology, data curation and analysis, writing original manuscript. VAC: Investigation, methodology, data analysis. CSC: Investigation, methodology, data analysis. EDG: Conceptualization, investigation, methodology, data curation and analysis, funding acquision, supervision.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

Data are available upon reasonable request to the correspondent author (Elizabeth De Gaspari).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08820139.2022.2107931

Additional information

Funding

This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) under grants numbers [12/15568–0; 18/04202-0 and 19/02042-9] and by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under grant number [131412/2019-1].