Immunization with recombinant PlpE of ovine Mannheimia haemolytica isolate provides protection against lethal challenge in mice

Background: Mannheimia haemolytica primarily causes pneumonia leading to heavy morbidity and mortality in domestic livestock world-wide. Recently, outer membrane lipoproteins have emerged as targets for inducing protective immunity against the Pasteurella infection. Aims: This study aimed to evaluate recombinant outer membrane lipoprotein E (PlpE) from the ovine M. haemolytica isolate, as a potential vaccine candidate. Methods: Recombinant PlpE was constructed using pET26 (b) expression vector in Escherichia coli. Expressed recombinant PlpE was purified and injected subcutaneously to mice. The protection index of the vaccine was evaluated by challenge of mice intraperitoneally. Results: Anti-PlpE antibody responses in the immunized mice was significantly increased in comparison with the control group which in turn, provided effective protection when challenged with strain of virulent M. haemolytica. Conclusion: Recombinant PlpE from ovine M. haemolytica isolate had the potential to be used as a vaccine candidate against M. haemolytica infection in sheep flocks.