In Vivo Evaluation of purD Gene Deleted Brucella abortus in Mice as Potential Vaccine Candidate for Control of Brucellosis

Brucella abortus ( B. abortus ) RB51 is a globally recognized and widely practiced vaccinal strain for the control of bovine brucellosis but has several reported drawbacks including pathogenic potential for humans and excreted in body fluids of vaccinated animals. In the present study, we constructed a more attenuated B. abortus Delta purD mutant by deleting the purD gene from the RB51 strain through sitedirected mutagenesis. For virulence attenuation comparison with the parent RB51 strain, the constructed mutant was evaluated for attenuation estimation and clearance in BALB/c mice. The B. abortus Delta purD mutant exhibited significant attenuation of virulence and cleared from the mice spleen after 20 th DPI when inoculated at the dose of 10 8 CFU per mice. In contrast to this, the parent RB51 strain induces splenomegaly and showed higher persistence with significantly higher splenic CFUs in the mice group at 10 th and 20 th DPI as compared to B. abortus Delta purD mutant. The histopathological comparison of spleens from both groups also revealed much infiltration of giant macrophages in the B. abortus Delta purD mice group as compared to the parent RB51 mice group indicating superior immune response generation. The findings of this study revealed that the highly attenuated B. abortus Delta purD mutant can be used effectively as a potential live attenuated vaccine candidate for the control of bovine brucellosis both in local and international settings.