Preparation and evaluation of genetically engineered recombinant subunit vaccines containing serine metalloprotease, anchor M domain-containing protein, and pyolysin against Trueperella pyogenes infection in a mouse model.

Trueperella pyogenes (T. pyogenes) is an important opportunistic bacterial pathogen that causes infections in livestock and wildlife. The increasing antimicrobial resistance of this bacterium poses significant challenges to the prevention and control of T. pyogenes-related diseases. Vaccines are widely used to control infectious diseases. Therefore, the development of vaccines against T. pyogenes would be valuable for the prevention of these diseases. In the current study, the genes encoding the predicted T. pyogenes serine metalloprotease (SMP) and anchor M domain-containing protein (AMD) were cloned. Recombinant SMP (rSMP), AMD fragments (rAMD-1 and rAMD-2), and rPLO D123 (a truncated form of pyolysin containing domains 1, 2, and 3, but not domain 4) were expressed in Escherichia coli cells and purified. The purified recombinant proteins were formulated into genetic engineering subunit vaccines with aluminum hydroxide adjuvant and administered subcutaneously to mice. The vaccines induced high levels of anti-rPLO D123, anti-rSMP, and anti-rAMD antibodies. These antibodies could agglutinate T. pyogenes cells and/or inhibit PLO-induced hemolysis. Mice were challenged intraperitoneally or subcutaneously. The results showed that vaccines containing rSMP provided better immunoprotection than the others. Since the mice receiving rSMP-containing vaccines exhibited attenuated tissue damage, faster resolution of infectious inflammation, and higher survival rate compared to those in other groups. In contrast, the incorporation of rAMD-1/rAMD-2 did not significantly improve the immunoprotective effect of the vaccines. Our findings confirm the potential of SMP as a promising protective antigen for the development of vaccines against T. pyogenes.