Fusion membrane proteins derived subunit vaccine candidates effectively protect against Mycoplasma bovis challenge in mice

Mycoplasma bovis (M. bovis) is the causative agent of bovine mycoplasmosis, a disease that can lead to respiratory issues, otitis media, mastitis, and arthritis in cattle and causes huge economic losses to the cattle breeding industry. Although vaccination represents the most effective method for the prevention of M. bovis, there is a lack of commercially available subunit vaccines that are effective against this disease. Here, we developed several subunit vaccine candidates using different combinations of membrane proteins M27, M32, M498, and M663 derived from a M. bovis strain isolated in Guizhou Province, China. Subsequently, the immune efficacy of the subunit vaccine candidates was evaluated in mice through immunization and challenge experiments. The results showed that the M. bovis subunit vaccines constructed from different protein fusions (M27-32, M27-498, M27-663, M27-32-498, M27-32-663, M27-498-663, and M27-32-498-663) were capable of eliciting the secretion of specific antibodies in mice. Furthermore, these candidates also induced robust TNF-α, IFN-γ, IL-4, IL-5, and IL-6 in the serum of mice, suggesting the induction of Th1- and Th2-type immune responses. Microscopically, these M. bovis subunit vaccine candidates were also effective in reducing lung tissue damage caused by M. bovis infection, suggesting that they provide good protection against challenge with virulent M. bovis. Among the tested vaccine candidates, the M27-498-663 and the M27-32-498-663 subunit vaccine candidates demonstrated the most robust immune efficacy, laying the foundation for the effective control of M. bovis.