Development of a new live attenuated Leishmania major p27 gene knockout: Safety and immunogenicity evaluation in BALB/c mice

Genetically modifying Leishmania major by eliminating essential virulence genes have been proposed as potential vaccine candidates. p27 is a COX component that is responsible for ATP synthesis. In this study a new mutant of Leishmania major (L. major) (MRHO/IR/75/ER) lacking the p27 gene (Lmp27(-/-)) was produced via homologous recombination, marking the first time such a strain has been developed. In vitro macrophage infectivity and In vivo safety, and overall immunogenicity were evaluated at various time periods following inoculation into BALB/ c mice. Skin lesion development, parasite burden in the liver and spleen, cytokine and antibody levels, splenocyte proliferation, and delayed type hypersensitivity (DTH) were the measured variables. Results demonstrated that the Lmp27(-/-) mutant caused no skin lesion, had low parasitic burdens in the liver and spleen, and had a significantly increased Th1 response. These results suggest that the Lmp27(-/- )mutant has the potential to be evaluated as a vaccine candidate.