Induction of Specific Cytotoxic Lymphocytes in Mice Vaccinated withBrucella abortusRB51

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Abstract
A safe, more sensitive, nonradioactive, neutral red uptake assay was adopted to replace the traditional51Cr release assay for detection ofBrucella-specific cytotoxic T lymphocyte (CTL) activity. Our studies indicated thatBrucella abortusstrain RB51 vaccination of mice induced specific CTLs against both strain RB51- and strain 2308-infected J774.A1 macrophages but not againstListeria monocytogenes-infected J774.A1 cells. The antigen-specific cytotoxic activity was exerted by T lymphocytes but not by NK cells. CD3+CD4+T cells secreted the highest level of gamma interferon (IFN-γ) and were able to exert a low but significant level of specific lysis ofBrucella-infected macrophages. They also exerted a low level of nonspecific lysis of noninfected macrophages. In contrast, CD3+CD8+T cells secreted low levels of IFN-γ but demonstrated high levels of specific lysis ofBrucella-infected macrophages with no nonspecific lysis. These findings indicate thatB. abortusstrain RB51 vaccination of mice induces specific CTLs and suggest that CD3+CD4+and CD3+CD8+T cells play a synergistic role in the anti-Brucellaactivity.