mRNA-LNPs encoding Ornithodoros moubata antigens induces humoral and cellular immune responses and tick resistance in rabbits

Ornithodoros moubata and Ornithodoros erraticus are important vectors of African swine fever virus and relapsing fever Borrelia spp., highlighting the need for effective and sustainable control strategies. In this study, six previously identified O. moubata vaccine candidates, including salivary and/or midgut antigens cyclophilin (OmCPH), peroxiredoxin (OmPXR), hypothetical protein 275 (OmH275), aquaporin 23 (OmAQP23), subolesin (OmSUB) and Om85, were evaluated as messenger RNA-lipid nanoparticle (mRNA-LNP) vaccines. Rabbits received three intradermal immunisations with individual mRNA-LNP formulations, and humoral, cellular, and protective immune responses were assessed. All mRNA-LNP constructs induced antigen-specific IgM and IgG responses and generated antibodies capable of recognising native proteins in tick salivary glands and/or midgut tissues. Antigen stimulation of peripheral blood mononuclear cells revealed antigen-specific cellular responses characterised by increased expression of IFN-γ, TNF-α, IL-8, CXCL10, IL-2, and IL-4, although the extent of these responses varied among antigens. OmCPH induced the strongest IL-8 response, OmSUB markedly increased CXCL10, IL-2 and IL-4 expression, and OmH275 elicited consistent IFN-γ and TNF-α responses. Vaccination adversely affected tick feeding, reproduction, development, and survival, with the most pronounced effects observed on female oviposition and fertility. Vaccine efficacies against O. moubata reached 19.8% (OmCPH), 3.7% (OmPXR), 25.6% (OmH275), 10.1% (OmAQP23), 25.2% (OmSUB), and 38.5% (Om85), while efficacies against O. erraticus reached 0%, 26.5%, 6.2%, 11.7%, 10.6%, and 18.5%, respectively. These findings demonstrate that mRNA-LNP vaccination induces both humoral and cellular immune responses against Ornithodoros antigens and provides measurable protection against tick infestations, supporting the application of mRNA technology for the development of multivalent anti-tick vaccines.