• Vaccine Name: B. melitensis strain VTRM1
• Target Pathogen: Brucella spp.
• Target Disease: Brucellosis
• Vaccine Ontology ID: VO_0000300
• Type: attenuated live vaccine
• Preparation: VTRM1 was obtained from B. melitensis 16M by allelic exchange of the rfbU gene encoding mannosyltransferase with a Tn5-disrupted rfbU gene (Winter et al., 1996).
• Virulence: VTRM1, like RB51, is a stable rough form of B. melitensis that does not revert during passage in mice (Winter et al., 1996).
• Description: Vaccination with the rough strain VTRM1 induces protection against virulent strains of B. abortus (2308), B melitensis (16M), B. suis biovar 1 (750), B. suis biovar 4 (2579), and B. ovis (Winter et al., 1996).

Mouse Response

• Host Strain: VTRM1
• Vaccination Protocol: Five groups of mice, (eight to nine weeks old), were vaccinated with the following live organism vaccines. These included: VTRM1, VTRS1, and Rev 1 (5 x 10^4 CFU); strain 19 (S19) (5 x 10^3 CFU); and RB51 (3 x 10^8 CFU). Each vaccine was delivered intravenously except RB51 which was administered intraperitoneally. All vaccines except RB51 were obtained directly from frozen stock cultures. Large doses of RB51 were required, therefore stock cultures were inoculated onto plates. After three days of culture and growth after 3 days was diluted to the appropriate concentration (Winter et al., 1996).
• Challenge Protocol: Eight weeks after the initial vaccination, mice were injected IV with 5x10^4 CFU of Brucella. The time interval between IV injection and euthanasia was two weeks for all Brucella strains with the exception of B abortus 8-954 and 2-1230; for these strains, a one-week time interval was chosen. Mice were euthanized by CO2 asphyxiation. Individual spleens were homogenized, the homogenate diluted serially, and plated on Schaedler blood agar. B abortus, B melitensis, or B suis colonies were counted after three days of incubation; B. ovis colonies were counted after four to five days of incubation at 37 C under 10% CO2 (Winter et al., 1996).
• Efficacy: Strains VTRM1 and VTRS1 were effective in inducing protection against virulent strains of heterologous, and homologous, Brucella spp. Vaccination with either strain conferred substantial protection against exposure to virulent laboratory strains of B melitensis, B abortus, and B suis of biovars 1 and 4. VTRM1 provided protection against B. ovis (Winter et al., 1996).