T-LYMPHOCYTE MEDIATED PROTECTION AGAINST FACULTATIVE INTRACELLULAR BACTERIA

Acquired immunity against intracellular bacteria is T cell dependent. T cells play a major role in protection against intracellular bacteria , but bacterial antigens recognized by T cells have been studied less extensively than bacterial antigens recognized by B cells. Using T lym phocytes from animals immunized against Brucella abortus, we have scre ened a bacterial genomic library for genes encoding antigens recognize d by T cells. Lymphocytes that proliferated to B. abortus proteins wer e characterized for phenotype and cytokine activity. Bovine and murine lymphocytes recognized common bacterial antigens and possessed simila r cytokine profiles, suggesting an analogous immune response in these two animal species. In vivo protection afforded by a particular cell t ype is dependent on the bacterial antigens presented and mechanisms of antigen presentation. MHC class I and class II gene knockout animals infected with B. abortus have demonstrated that protection to B. abort us is especially dependent on CD8(+) T cells. Knowing the cells requir ed for protection, vaccines can be designed to elicit the protective s ubset of lymphocytes. Currently, we are testing several recombinant B. abortus proteins using different immunization strategies. Finally, ba cterial genes activated following intracellular phagocytosis are being examined using a novel, reporter system adapted to B. abortus.