Cell-mediated immune response after Brucella abortus S19 vaccination

Area of Science:

• Veterinary Immunology
• Bacteriology
• Vaccinology

Background:

• Brucella abortus S19 is a live vaccine used to control brucellosis in cattle.
• Assessing cell-mediated immunity (CMI) is crucial for understanding vaccine efficacy.
• Existing methods for CMI assessment in cattle can be challenging.

Purpose of the Study:

• To evaluate cell-mediated immunity in heifers following vaccination with Brucella abortus S19.
• To compare the efficacy of two distinct assays for measuring CMI: the stimulation of protein synthesis (SPS) microassay and the delayed hypersensitivity skin test.
• To investigate the correlation between CMI responses and residual antibody titers post-vaccination.

Main Methods:

• Cell-mediated immunity was measured in young heifers using the microassay for stimulation of protein synthesis (SPS) with [3H]leucine.
• A delayed hypersensitivity skin test was also employed to assess CMI.
• Brucella melitensis protein allergen and a crude Brucella abortus S19-soluble antigen were compared in the SPS test.

Main Results:

• The SPS test was negative in unvaccinated heifers and strongly positive in twice-vaccinated steers.
• In S19-vaccinated heifers, the SPS test was positive in 13 of 30, and the delayed hypersensitivity skin test was positive in 9 of 29.
• The two tests for CMI showed good agreement, and vaccination-induced antibody titers showed partial correlation with CMI outcomes.

Conclusions:

• The study demonstrated variable cell-mediated immunity responses to Brucella abortus S19 vaccination in heifers.
• Both the SPS microassay and the skin test are viable methods for assessing CMI in cattle, showing good concordance.
• Residual antibody titers may offer some predictive value for cell-mediated immunity status post-vaccination.