Comparison Between Protective Immunity Induced by gamma-Irradiated Brucella abortus Field Strain and Commercial Brucella abortus Strain 19 in Mice

Brucellosis is an important zoonotic disease of nearly worldwide distribution. Despite the availability of live vaccine strains for bovine (S19 and RB51) and (Rev-1) for small ruminants but they have several drawbacks including residual virulence. So, in this study, gamma irradiated Brucella abortus vaccine prepared from an Egyptian field isolate was evaluated as a safe, stable and protective vaccine for protection of mice against challenge infection with virulent B. abortus 2308 in comparison with live attenuated B. abortus strain 19. The irradiated Brucella vaccine prevented splenomegaly when injected in mice in a dose of 1 x 10 CFU while 8 those given S19 suffered from mild degree of splenomegaly. Also it was immunogenic as antibody titre in sera of vaccinated mice monitored with slide agglutination tests was parallel to those titres produced by B. abortus strain 19. By indirect enzyme linked immunosorbent assay, antibody titres for irradiated vaccine in pooled serum samples of vaccinated mice at 2 week post vaccination showed non-significant increase as 1.338 when nd compared with those given S19 as 1.423 but significant shooting registered by the 4 week post vaccination th and two weeks from booster dose as 1.445 to come in parallel level with that titre achieved by mice group given strain 19 as 1.447 and the ELISA antibody titres began to decrease by 6 week post vaccination in sera of both th mice groups. On challenge test for both vaccinated groups, irradiated B. abortus vaccine was potent as it succeeded in a reduction of challenge virulent strain 2308. Colonization of spleens of vaccinated mice as 5.33 CFU /gm at 2 week post challenge and 3.82 CFU/gm at 4 week post challenge while those inoculated with S19 nd th cleared challenge strain 5.33 CFU /gm at 2 week post challenge and 4.91 CFU /gm at 4 week post challenge. nd th So, gamma irradiated B. abortus vaccine prepared from field isolate is considered as a promising safe and protective vaccine against brucellosis in mice and further investigation in cattle is needed.