Humoral and cellular immune responses in cattle upon Clostridium chauvoei vaccination and challenge

Andrea RossiJulio GuarnaschelliAnalía RialMaría MorenoMariana Rivera-PatronAndres IriarteJose Alejandro Chabalgoity^*

• Unidad Académica de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay, Montevideo, Uruguay

Clostridium chauvoei is the causative agent of blackleg, a severe disease in cattle. Vaccination reduces disease incidence but the immune mechanisms that underlie vaccine-induced protection remain poorly understood, particularly the role of cellular immunity. In this study we characterized the humoral and cellular immune responses induced by a polyclostridial vaccine and assessed their correlation with protection against a C. chauvoei challenge. Antibody titers, cytokine gene expression and lymphocyte proliferation were evaluated pre-and post-challenge in vaccinated and control cattle. While vaccination protected cattle upon challenge and all animals survived, unvaccinated controls developed severe disease and died. Vaccination induced a strong specific antibody response although with inter-individual variation as well as a specific cytokine profile characterized by increased expression of IFN-γ, TGF-β1, and IL-4. Post-challenge, IFN-γ and IL-12B expression declined in vaccinated animals, but TGF-β1 persisted. High pre-challenge IgG, IFN-γ, and TGF-β1 were associated with protection, whereas increased IL-12B post-challenge was associated with disease severity. These findings demonstrate a coordinated interplay between humoral and cellular immune responses in vaccine-induced protection, with IFN-γ emerging as a potential biomarker in conjunction with antibody titre. The study provides a deeper further understanding on the immune mechanisms underlying vaccine-mediated protection against C. chauvoei and shall be relevant for the development of more effective vaccines.