A combined use of autolysin p60 and listeriolysin O antigens induces high protective immune responses against Listeria monocytogenes infection.

Listeria monocytogenes is an intracellular bacterium responsible for listeriosis in both humans and animals. Infected livestock is believed to be one source of this pathogen. Vaccination is an optimal approach to control the occurrence of this disease in livestock. However, inactivated vaccines have been reported to be insufficient to offer immune protection against L. monocytogenes. Here we evaluated the immune protection capacity of a combination of recombinant p60 and LLO. Mice immunized with p60 and LLO generated a high level of anti-L. monocytogenes antibodies. In addition, the elevated levels of IFN-γ and the decreased levels of IL-4 were also observed in these treated mice. Consistent with the colonization of L. monocytogenes post infection, all mice in the control group died within 5 days after infection of L. monocytogenes, while 40, 40, 80, and 100 % of animals immunized with inactivated L. monocytogenes vaccine (ILMV), LLO + ILMV, p60 + ILMV, and p60 + LLO + ILMV, respectively, survived for 2 weeks. Collectively, the results presented in this study demonstrate the capacity of a combination of LLO and p60 to elicit high protective immune responses against L. monocytogenes infection.