Safety and efficacy of a Bordetella bronchiseptica outer membrane proteins (OMPs) subunit vaccine in a murine model.

Importance: Bordetella bronchiseptica is a major pathogen responsible for respiratory infections in dogs, posing significant challenges to companion animal health. The whole-cell vaccine currently available has various adverse effects, and concerns persist regarding the efficacy of acellular vaccines. Therefore, developing a safer and more effective vaccine is critical for addressing these issues.

Objective: This study evaluated the safety and efficacy of B. bronchiseptica outer membrane proteins (OMPs) and dermonecrotic toxin (DNT) as subunit vaccine candidates, individually and in combination, compared to conventional vaccine formulations in murine models.

Methods: The immune responses and side effects were assessed after vaccination with OMPs and DNT as subunit vaccine candidates, individually and in combination. The safety evaluations included monitoring the body temperature, weight, and vitality scores, while the efficacy was measured using immunoglobulin quantification, hemagglutination-inhibition (HI) assays, and challenge tests. The vaccine candidates were compared with conventional vaccine formulations.

Results: The OMP-based vaccine induced a T helper 1-biased immune response, providing robust protection against B. bronchiseptica with minimal adverse effects. More than 90% disease protection was achieved at OMP concentrations of 25-50 µg/mL, with immunoglobulin G levels exceeding 2¹³ (8,192) and HI titers surpassing 2^7.5 (181). In contrast, commercially available Bordetella vaccine formulations, which contain cellular wall components and toxins, showed reduced efficacy and heightened side effects.

Conclusions and relevance: OMPs are a promising, cost-effective component for B. bronchiseptica vaccine development, providing a balance between safety and efficacy. These insights could promote the development of improved Bordetella vaccines for dogs and potentially humans, addressing the longstanding trade-offs in current vaccine formulations and contributing to better animal health.