DURATION OF STRAIN-2308 INFECTION AND IMMUNOGENICITY OF BRUCELLA-ABORTUS LIPOPOLYSACCHARIDE IN 5 STRAINS OF MICE

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Abstract
A study was conducted to compare immunogenicity of a Brucella abortus lipopolysaccharide (LPS) and the duration of infection in 5 strains of mice. Mice of strains CBA/NJ, BALB/c, CD-1, C3H/HeN and C3H/HeJ were allotted into 2 large groups (vaccinated with proteinase K-treated LPS or nonvaccinated) and 6 subgroups based on the intervals between challenge exposure to B. abortus strain 2308 and the week the response data were obtained. Criteria used in comparing responses between the various strain of mice as well as between vaccinated and nonvaccinated mice were splenomegaly, colony-forming units (CFU) from spleens, and antibody titers. Responses were evaluated at 1, 2, 3, 5, 8 and 12 weeks after challenge exposure. Results indicated that all strains of mice became infected and maintained infection throughout the 12-week period, the percentages of mice infected were significantly (P < 0.05) less in vaccinated mice for the first 5 weeks after challenge exposure, and there were no direct correlations between increased immunoglobulins (IgM and IgG titers) and reduction in CFU. Vaccinated mice of strains BALB/c, CD-1, C3H/HeN and C3H/HeJ had increased titers when challenge exposed and also had significantly (P < 0.05) smaller spleens and lower CFU. Vaccinated CBA/NJ mice did not have marked antibody titers. The overall results indicated the vaccination with LPS offers some initial protection against B. abortus strain 2308 infection, but this protection disappears gradually and in various degrees in the 5 strains of mice studied.