Anti-Brucella cell-mediated immunity in mice vaccinated with a cell-wall fraction

Immunity against Brucella, a facultative intracellular bacteria, can be induced in mice by live or by killed-whole-cell or fraction vaccine. This immunity can be adoptively transferred from live vaccinated donor to recipient mice, or passively with immune serum raised against bacterial fractions. A protein-bound peptidoglycan fraction (PG) was used to immunize DBA/2 donor mice intravenously or subcutaneously in the hind footpads. Splenic or popliteal lymph nodes cells were transferred to recipients that were intravenously challenged with a B abortus virulent strain. Brucella spleen counts, and in some cases liver counts, were done 15 days later or at successive times. Spleen cells depleted from macrophages and lymph nodes cells conferred immunity to recipients. This immunity increased after transfer for about 21 days. Lymph nodes cells were more efficient to transfer immunity than spleen cells. This immunity was abated but not abrogated by treatment of cells by anti-Thy serum and was transferred by both nylon wool non adherent (T enriched) or adherent (B enriched) cells. Comparative transfer experiments with DBA/2 versus CBA mice, live vaccine versus PG fraction vaccine, virulent versus avirulent (vaccinal) challenge evidenced that the three factors were involved in induction and/or expression of immunity. DBA/2 mice responded better to fraction vaccine and virulent challenge whereas CBA responded better to live vaccine and to avirulent challenge strain. In contrast DBA/2 X CBA F1 responded equally well against the virulent challenge to transfer of cells from live vaccine or PG fraction vaccinated donor mice. Two cell-mediated immune mechanisms may thus be involved in transferred immunity the expression of which may be genetically determined.