Characterization of specific immune responses of mice inoculated with recombinant vaccinia virus expressing an 18-kilodalton outer membrane protein of Brucella abortus

Using the shuttle vector pMCO2 and the vaccinia virus wild-type WR strain, we constructed a recombinant virus expressing an 18-kDa outer membrane prot ein of Brucella abortus. BALB/c mice inoculated with this virus produced 18 -kDa protein-specific antibodies, mostly of immunoglobulin G2a isotype, and in vitro stimulation of splenocytes from these mice with purified maltose binding protein-18-kDa protein fusion resulted in lymphocyte proliferation and gamma interferon production. However, these mice were not protected aga inst a challenge with the virulent strain B. abortus 2308. Disruption of th e 18-kDa protein's gene in vaccine strain B. abortus RB51 did not affect ei ther the strain's protective capabilities or its in vivo attenuation charac teristics. These observations suggest that the 18-kDa protein plays no role in protective immunity.