Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 9, 1996
Publication Date: N/A
Interpretive Summary: Vaccinating cattle with Brucella abortus strain 19 and removing animals with brucellosis from vaccinated herds has been used for over 5 years as a program to eradicate brucellosis from cattle in the United States. However, the program has failed to eradicate brucellosis and has cost $4-5 billion during the past 30 years. Tests have revealed that a new vaccine, B. abortus strain RB51, is better than the strain 19 vaccine because cattle vaccinated with strain RB51 do not produce antibodies which are detected in diagnostic tests for brucellosis. Therefore, cattle having brucellosis can be more easily identified and the eradication of brucellosis from cattle can be more rapidly achieved by using the strain RB51 vaccine. Bison and elk in Yellowstone National Park and the surrounding area have a high incidence of brucellosis and they are potential sources of infection for neighboring cattle herds. Preventing brucellosis in bison and elk could be most easily achieved by development of an oral RB51 vaccine. Results from this study indicate that oral RB51 vaccination is effective in preventing brucellosis in laboratory mice. These findings are an important first step in developing an oral RB51 vaccine for preventing brucellosis in bison and elk and other wild animals which may transmit the disease to cattle.
Immune responses and resistance to infection with Brucella abortus strain 2308 (S2308) were measured in mice following oral or intraperitoneal (IP) vaccination with strain RB51 (SRB51). Increased resistance to S2308 infection occurred at 12-20 weeks in mice vaccinated IP with SRB51 (5 x 10*8 or 5 x 10*6 CFU) but occurred at 12 weeks only in mice vaccinated orally with SRB51 (5 x 10*8 CFU). Oral SRB51 vaccination induced lower levels of SRB51 antibodies than did IP vaccination. Mice vaccinated orally with SRB51 and challenged with S2308 at 12-20 weeks had lower and less persistent spleen cell proliferation and production of IFN-gamma in response to S2308 than did mice vaccinated IP with SRB51. However, mice vaccinated orally or IP with SRB51 and challenged with S2308 had similar spleen cell TNF-alpha production. These results indicate that oral vaccination of mice with SRB51 was effective in inducing protective immunity to S2308 infection, although the immunity was lower and less persistent than that induced by IP vaccination. The lower protective immunity induced by oral vaccination may have resulted from lower and less persistent cell-mediated immunity and IFN-gamma production in response to S2308.