Antigenic Competition and Nonspecific Immunity after a Rickettsial Infection in Mice: Restoration of Antibacterial Immunity by Phenyl-Imidothiazole Treatment

A prior Coxiella burneti infection renders mice nonspecifically resistant to a Brucella abortus challenge but depresses the specific activities of either dead vaccine (in incomplete adjuvant) or of live Brucella vaccine and inhibits Brucella antibody formation that usually follows the use of live vaccine. Thus, a first antigenic stimulus interferes with responses to a second unrelated antigen to cover both nonspecific immunity and antigenic competition. Phenylimidothiazole treatment 2 days after anti-Brucella vaccinations restores most of the specific activities of these vaccines which were reduced by C. burneti priming, but leaves as impaired as they were Brucella antibodies titrated through three serologic tests. This finding suggests that phenylimidothiazole stimulates above all cell-mediated immunity.