A Novel Attenuated and Marker M. bovis-BoHV-1 Combined Vaccine Provides Broad Protection Against Diverse Bovine Herpesvirus Type 1 Genotypes

Bovine herpesvirus 1 (BoHV-1) and Mycoplasma bovis are major pathogens causing significant respiratory disease and reproductive issues in cattle. In our previous study, we prepared a M. bovis-BoHV-1 combined vaccine and evaluated its safety and efficacy. In the current study, the combined vaccine was then compared to an inactivated BoHV-1 vaccine in protecting cattle against BoHV-1 challenge. Cattle were divided into three groups: the M. bovis-BoHV-1 combined vaccine, the inactivated vaccine, and a non-immune challenge group. The groups were challenged with either the BoHV-1 1.1a or 1.2b strains, and virus shedding was measured using RT-PCR. The results showed that the combined vaccine group was able to induce a higher level of humoral immune response compared to the inactivated vaccine group, and it induced a high degree of expression of cytokines, B cells and T cell-associated signaling pathways. Both the combined vaccine group and the inactivated vaccine group had significantly lower titers and shorter duration of virus shedding compared to the non-immune challenge group, for both BoHV-1 strain challenges. Specifically, the combined vaccine group had about 2 titers reduction in peak virus titers and a 6-8 day earlier clearance of virus shedding compared to the non-immune challenge group. Notably, the combined vaccine group demonstrated slightly better performance in limiting virus shedding of the different BoHV-1 subtypes compared to the inactivated vaccine group, indicating the combined vaccine may provide better cross-protection. These findings highlight the protective efficacy of these vaccines and provide important insights for effective disease control strategies in cattle herds.