Effects of exogenous recombinant interleukin-12 on immune responses and protection against Brucella abortus in a murine model

This study determined if murine interleukin-12 (IL-12) would influence immu nity in mice vaccinated with live or killed Brucella abortus strain RB51 (S RB51). Mice received live or gamma -irradiated SRB51 bacteria alone, or wit h IL-12 (0.5 or 1.0 mug, 2x or 3x), whereas other mice received saline or I L-12 alone. Post-vaccination antibody responses to live or killed SRB51 and clearance of live SRB51 from splenic tissue were not influenced by IL-12 t reatments. Mice were challenged at 12 weeks with 4 X 10(4) cfu of B. abortu s strain 2308 (S2308) and were euthanized 2 weeks later. The highest IL-12 treatment increased (P < 0.05) post-challenge antibody responses when co-ad ministered with killed SRB51. Co-administration of 1.0 mug of IL-12 with li ve SRB51, but not killed SRB51, reduced (P < 0.05) 52308 colonization of sp lenic tissues. Our data suggest that although IL-12 may augment protective immunity induced by live SRB51, it does not influence protection induced by vaccination with killed SRB51.