• Vaccine Name: B. melitensis WR201 (16MΔpurEK)
• Target Pathogen: Brucella spp.
• Target Disease: Brucellosis
• Vaccine Ontology ID: VO_0000345
• Type: Live, attenuated vaccine
• Antigen: This vaccine is an live, attenuated purine-auxotrophic mutant strain of Brucella meletensis, WR201 (Hoover et al., 1999).
• purK gene engineering:
  • Type: Recombinant protein preparation
  • Description: The B. melitensis strain WR201 (or called delta purE201) was created through the deletion of the gene purE and the deletion of the first seven bases of purK (Drazek et al., 1995; Hoover et al., 1999). Specifically, B. melitensis 16M was electroporated with suicide plasmids containing a kanamycin resistance cassette that replaced 226 bp at the carboxyl end of purE, the intergenic region, and 18 bases of the purK open reading frame. Recombinant B. melitensis delta purE201 required exogenous purines for growth on minimal media. This mutant failed to grow in human monocyte-derived macrophages, while the growth of wild-type 16M and the complemented strain, delta purE201 (pSD5), increased by nearly two logs (Drazek et al., 1995).
  • Detailed Gene Information: Click Here.
• purE gene engineering:
  • Type: Gene mutation
  • Description: This purE mutant is from Brucella melitensis (Crawford et al., 1996).
  • Detailed Gene Information: Click Here.
• Preparation: The WR201 strain was procured and the bacterial cells were killed by treatment for 16 h with 0.5% phenol. These cells were then washed and pelleted several times, eventually leading to a product containing approximately 3.0 mg of protein per ml (Hoover et al., 1999).
• Virulence: The antigens for this vaccine were severely attenuated. The strain WR201 fails to replicate in cultured human monocyte-derived macrophages (Hoover et al., 1999).

Mouse Response

• Host Strain: BALB/c
• Vaccination Protocol: The mice were immunized by intraperitoneal administration of vaccine. Each vaccine contained approximately 10^5 WR201 cells Nonimmunized, control mice received 0.9% NaCl intraperitoneally (Hoover et al., 1999).
• Immune Response: After mice were innoculated, they were found to have made serum antibody to non-O-polysaccharide and lipopolysaccharideantigens. The splenocytes from the immunized animals were found to have released interleukin-2, gamma interferon, and IL-10 when cultured with Brucella antigens (Hoover et al., 1999).
• Challenge Protocol: Nine weeks post immunization, animals were innoculated intranasally with 10^4 CFU of B. melitensis 16M in 30 μl of 0.9% NaCl. The vaccine was administered dropwise into the external nares with a micropipette (Hoover et al., 1999).
• Efficacy: Immunization of the mice led to protection from disseminated infection. Immunization had only a slight effect on the clearance of the challenge inoculum from the lungs (Hoover et al., 1999).
• Description: This study suggests that WR201 may be a good vaccine candidate for the prevention of human brucellosis (Hoover et al., 1999).
• Host Ifng (Interferon gamma) response
  • Description: Spleen cells obtained 9 weeks after inoculation of mice with WR201 produced more IFN-gamma than non-immunized, non-infected control mice. These results were significant (Hoover et al., 1999).
  • Detailed Gene Information: Click Here.
• Host IgG response
  • Description: Sera obtained from immunized animals from 1 to 8 weeks after intraperitoneal administration of WR201 showed a rise in anti-protein IgG by week 4 (Hoover et al., 1999).
  • Detailed Gene Information: Click Here.
• Host Il10 (interleukin 10) response
  • Description: Spleen cells obtained 9 weeks after inoculation of mice with WR201 produced more IL-10 than non-immunized, non-infected control mice. These results were significant (Hoover et al., 1999).
  • Detailed Gene Information: Click Here.
• Host Il2 response
  • Description: Spleen cells obtained 9 weeks after inoculation of mice with WR201 produced more IL-2 than non-immunized, non-infected control mice. These results were significant (Hoover et al., 1999).
  • Detailed Gene Information: Click Here.

Mouse Response

• Host Strain: BALB/c
• Vaccination Protocol: Mice were first orally administered 0.2 ml of sterile 2.5% sodium bicarbonate, then they were administered 0.2 ml of the bacterial suspension which had been standardized to 5 × 10^11 cells/ml. In designated experiments, bacteria were further diluted to provide an inoculum of 1010 or 109 CFU, then administered. In another experiment, strain WR201 was killed by treatment overnight at room temperature with 0.8% (vol/vol) formaldehyde prior to administration to mice (Izadjoo et al., 2004).
• Persistence: No bacteria were recovered from the spleens of 54 mice eight weeks post-vaccination, while no bacteria were recovered from the iguinal lymph nodes of 15 mice at this time either. Strain WR201 was progressively lost from the feces following oral administration (Izadjoo et al., 2004).
• Immune Response: When grown in cultures with Brucella antigens, splenocytes from immunized animals released interleukin-2 and gamma interferon. Immunized mice made serum antibody to lipopolysaccharide and non-O-polysaccharide antigens (Izadjoo et al., 2004).
• Challenge Protocol: For virulent strain 16M i.n. challenge, 30 μl of bacterial suspension adjusted to contain 104 CFU of bacteria. This was administered with a micropipette into the external nares of mice (Izadjoo et al., 2004).
• Efficacy: The mice that were immunized had protection from infection and better clearance of the challenge inoculum from the lungs. The best protection was found with the administration of live bacteria with the inclusion of a booster dose. The results suggest that strain WR201 may be a candidate for a vaccine to prevent human brucellosis (Izadjoo et al., 2004).