Comparison of Brucella Cu,Zn SOD-specific IgG, IgG1, and IgG2a responses in sera of mice vaccinated with O. anthropi strain 49237SOD (⧫) and Brucella RB51SOD (▪). Groups of five mice either were immunized i.p. with either O. anthropi strain 49237, O. anthropi strain 49237SOD, B. abortus strain RB51, or B. abortus strain RB51SOD or were inoculated with saline alone. Mice were bled individually at 6 weeks after immunization, and their serum samples were used for detection of IgG, IgG1, and IgG2a antibodies specific to purified Brucella Cu,Zn SOD by indirect ELISA. Each serum sample was tested in duplicate. Neither saline, O. anthropi strain 49237, nor Brucella RB51 induced detectable antibody responses to purified Brucella Cu,Zn SOD (data not shown)