Variations in immunoglobulin isotype produced during the antibody response to Brucella abortus and Staphylococcus aureus vaccines in sheep.

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 IgG 1 and IgG 2 antibody than did killed B abortus. Live B abortus stimulated a more protracted synthesis of IgG 2 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 lgG 2 anti-brucella antibody. The results suggested that the enhanced production of lgG 2 antibody induced by live vaccines does not depend solely on a pyogenic lesion at the vaccination site.