• Vaccine Name: E. coli Escheriosome-mediated Cytosolic Delivery of recombinant Brucella rL7/L12 Protein
• Target Pathogen: Brucella spp.
• Target Disease: Brucellosis
• Vaccine Ontology ID: VO_0000423
• Type: Subunit vaccine
• Antigen: The vaccine antigen is Brucella L7/L12 protein, which was delivered by an E. coli lipid liposome (escheriosome)-mediated cytosolic delivery system (Mallick et al., 2007).
• Adjuvant:
  • Adjuvant name:
  • VO adjuvant ID: VO_0000139
• Preparation: The rL7/L12 proteins were purified and introduced into Escherischia coli lipid liposome, allowing for escheriosome-mediated cytosolic delivery of the antigen, recombinant rL7/L12 protein. Combinations containing rL7/L12 protein and different adjuvants were formed for vaccination (Mallick et al., 2007).

Mouse Response

• Host Strain: BALB/c
• Vaccination Protocol: Four-to-six-week-old female Balb/c mice were randomly distributed into eight experimental groups so that each group consisted of 20 animals. Each group consisted of 20 animals. Various groups of mice were injected separately through subcutaneous route, on days 0,21, and 28 with escheriosome entrapped rL7/L12 (E-Lip-L7), egg PC/Chol liposome entrapped rL7/L12 protein (P-Lip-L7), rL7/L12 protein with Complete Freund’s adjuvant (IFA-L7), rL7/L12 protein alone (free form; F-L7), E. coli lipid sham liposome and sham escheriosome mixed with free rL7/L12 protein, a physical mixture (EL + L7). The positive control in this study were mice vaccinated with about 5 x 10^6 cfu of Brucella S-19. The negative control for this study received only PBS. Each animal was immunized with a priming dose of 50 micrograms of rL7/L12 protein per animal (day 0) and boosted with 30 micrograms per animal (days 21 and 28) (Mallick et al., 2007).
• Immune Response: Analysis of the mouse sera revealed non-significant antibody titre up to day 14 post-immunization in various groups of immunized mice. Significantly higher titre of IgG was detected on day 21 post-immunization in sera of animals which were primed with E-Lip-L7 form of the antigen as compared with the P-Lip-L7. Antibody titre was significantly less in the animals immunized with S-19 or IFA-L7 combination. High antibody response was maintained in E-Lip-L7 immunized mice following each booster with maximum antibody level on seventh day after the last immunization as compared with P-Lip-L7 group which was unable to rise to that extent. The antibody response evoked by S-19 or IFA-L7 was significantly less as compared to E-Lip-L7 immunized group. It was observed that E-Lip-L7 maintained significantly higher titer of IgG1 and IgG2a as compared with P-Lip-L7-immunized group. Both S-19 as well as IFA-L7 combination failed to induce significant level of IgG1 and IgG2a titre in the serum after 42 days post-first immunization and the trend was maintained even after day 60 post-immunization (Mallick et al., 2007).
• Challenge Protocol: One week after the final immunization, the mice belonging to various groups were challenged with 2 x 10^5 cfu of a virulent culture of B. abortus 544 intraperitoneally in 0.2ml
  of saline solution. After 7, 15 and 30 days post-challenge, four mice from each group were euthanatized and their spleens were analyzed (Mallick et al., 2007).
• Efficacy: Escherischia coli escheriosome-mediated cytosolic delivery of recombinant rL7/L12 protein can elicit strong immunological responses in the Balb/c mice. However, egg PC/Chol liposome entrapped rL7/L12 was found to impart relatively poor immune response. Escheriosome-entrapped rL7/L12 protein elicited high IgG2a isotype response, suggestive of its relevance in imparting protection against brucellosis in mice(Mallick et al., 2007).