Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 17, 1995
Publication Date: N/A
Interpretive Summary: Brucellosis is a bacterial infection which kills fetuses and causes abortion in pregnant cows. The bacterium can also infect humans and cause undulant fever. The purpose of this study was to evaluate the safety of a new brucellosis vaccine in calves. Calves were immunized with vaccine candidate SRB51 or with the standard S19 vaccine. The lymph nodes draining the site of vaccination were examined for evidence of white blood cell, specifically T-lymphocyte, changes by using a computerized microscope assembly There were subtle changes in the lymph nodes of vaccinated cattle which were indicative of a beneficial immune response, but these changes were not statistically significant. There was no evidence of detrimental effects due to vaccination with either vaccine. The results of this study support the conclusion of that the use of SRB51 vaccine in cattle is safe. In addition, this new procedure for examining lymph nodes of cattle will allow us to pinpoint the white blood cells which are responsible for immunity against disease.
Technical Abstract: T-lymphocyte subpopulations were examined in vivo by computer-assisted morphometry of superficial cervical lymph nodes of cattle vaccinated with Brucella abortus. Twenty-four eight-month-old Hereford heifers were injected subcutaneously in the axillary area with 1 x 10*10 live B. abortus strain RB51 (SRB51, n=12) or strain 19 (S19, n=6) suspended in two ml of saline. Six control heifers were injected with sterile saline. Lymph nodes were collected at 1, 2, 4, 6, 10, and 12 weeks post vaccination (PV). Both SRB51 and S19 were cultured from lymph nodes, but SRB51 persisted for a longer period after vaccination (10 weeks) than S19 (6 weeks). Cryostat sections were incubated with Mab to CD4 (IL-A11), CD8 (IL-A51), or gamma/delta (IL-A29) bovine T-cell surface antigen and processed for immunoperoxidase staining. Numbers of stained lymphocytes in randomly selected fields were calculated using image-analysis software. There were no significant differences in the number (p=0.07) or relative proportions (p=0.22) of CD4+, CD8+, and gamma/delta lymphocytes in SRB51, S19, and control lymph nodes. There was a nonsignificant trend of increased proportion of CD4+ and decreased proportion of CD8+ cells in both vaccine groups There was a statistically significant difference in the distribution of the three T-cell subsets. The CD4+ cells were most closely grouped and the gamma/delta cells had the most widely scattered distribution, regardless of vaccination status. The results support other studies indicating lymphocyte depletion is not a sequela of infection with B. abortus vaccine strains given to conventionally-reared cattle.