| Abstract: | Experiments in sheep were carried out to examine factors modifying the immunoglobulin (Ig) isotype of the antibody response to Brucella abortus. Live B abortus (S19) stimulated higher titres of agglutinating antibody and IgG1 and IgG2 antibody than did killed B abortus. Live B abortus stimulated a more protracted synthesis of IgG2 antibody during the primary and secondary responses than did the killed S19 vaccine. In a second experiment, the capacity of live and killed Staphylococcus aureus to modify the antibody response to killed B abortus was examined. Both live and killed S aureus enhanced production of anti-brucella antibodies; this response was attributed to the adjuvant properties of S aureus. Killed S aureus enhanced production of anti-brucella antibody to a greater extent than live S aureus. Live S aureus did not preferentially enhance production of IgG2 anti-brucella antibody. The results suggested that the enhanced production of IgG2 antibody induced by live vaccines does not depend solely on a pyogenic lesion at the vaccination site. |
