PROTECTION OF BALB C MICE AGAINST HOMOLOGOUS AND HETEROLOGOUS SPECIESOF BRUCELLA BY ROUGH STRAIN VACCINES DERIVED FROM BRUCELLA-MELITENSISAND BRUCELLA-SUIS BIOVAR-4/

Objective-To evaluate stable rough mutants derived from Brucella melit ensis 16M and B suis 2579 (biovar 4) as vaccines against homologous an d heterologous Brucella spp in the BALB/c mouse model. Design, Animals , and Procedure-Rough mutants VTRM1 and VTRS1 were obtained from B mel itensis 16M and B suis 2579, respectively, by allelic exchange of the rfbU gene encoding mannosyltransferase with a Tn5-disrupted rfbU gene. Mice were vaccinated with VTRM1 or VTRS1 and challenge exposed 8 week s later. Results-VTRM1 and VTRS1 replicated extensively in the spleen during the first 3 weeks of infection, then decreased rapidly. Antibod ies specific for the O polysaccharide were not detected in sera of mic e inoculated with either rough strain. Vaccination with VTRM1 or VTRS1 induced protection against virulent strains of B abortus (2308), B me litensis (16M), B suis biovar 1 (750), and B suis biovar 4 (2579). VTR M1 also protected against B ovis (PA) and against 4 field isolates of B abortus from bison or elk. VTRS1 conferred protection against 4 fiel d isolates of B suis biovar 4 from reindeer. Vaccines prepared from li ve VTRM1 or VTRS1 provided significantly greater protection than that afforded by vaccines of killed cells in QS-21 adjuvant. Vaccination wi th VTRM1 containing VTRS1 gave minimal protection against the antigeni cally unrelated Listeria monocytogenes, thus demonstrating the immunol ogic specificity of protection against Brucella spp. Conclusions and C linical Relevance-Results encourage evaluation, in primary host specie s, of VTRM1 and VTRS1, along with RB51, as alternative vaccines to str ain 19, Rev 1, or other smooth phase vaccines.