Quadrivalent hemagglutinin and adhesion expressed on Saccharomyces cerevisiae induce protective immunity against Mycoplasma gallisepticum infection and improve gut microbiota

Mycoplasma gallisepticum (MG) infection causes infectious respiratory diseases in poultry, causing economic losses to the poultry industry. Therefore, this study aims to develop a safe, convenient, and effective multivalent recombinant Saccharomyces cerevisiae vaccine candidate and to explore its potential for oral immunization as a subunit vaccine. Mycoplasma gallisepticum Cytadhesin (MGC) and variable lipoprotein and hemagglutinin (vlhA) are associated with the pathogenesis of MG. In this study, a quadrivalent recombinant Saccharomyces cerevisiae (ST1814G-MG) displaying on MGC2, MGC3, VLH5, and VLH3, proteins was innovatively constructed, and its protective efficiency was evaluated in birds. The results showed that oral immunization with ST1814G-MG stimulates specific antibodies in chickens, reshapes the composition of the gut microbiota, reduces the Mycoplasma loading and pulmonary disease injury in the lungs. In addition, we found that oral ST1814G-MG had better protection against MG infection than an inactivated vaccine, and co -administration with the inactivated vaccine was even more effective. The results suggest that ST1814G-MG is a potentially safer and effective agent for controlling MG infection.