Study of serum bactericidal and splenic activity of Total-OMP-CagA combination from Brucella abortus and Helicobacter pylori in BALB/c mouse model

Background: Brucella is a Gram-negative and facultative intracellular organism that causes brucellosis, a common zoonotic disease. Over 500,000 people are annually affected by brucellosis. Brucella is highly infectious through inhalation route; for this reason it is used for biological warfare aims. This study aimed to study the serum bactericidal and splenic activity of Total-OMP-r CagA immunogens from Brucella abortus and Helicobacter pylori in a BALB/c mouse model. Methods: Immunization of BALB/c mice was performed with immunogenic proteins three times subcutaneously (S.C.) at 14-day intervals. The protective effects of two component vaccines with CpG adjuvant were evaluated after mice were challenged with H. pylori ss1 and Brucella abortus strain 544. The specific IgG1 and IgG2a antibodies in sera were assessed using ELISA test. For measuring the antigen-specific IL-4, IL-12 and IFN-gamma responses in sera of immunized mice after challenge, RT-PCR technique was applied. Twenty days after the challenge, mice were killed then gastric, splenic and serum samples were assessed and bacterial colony count was measured based on the pour plate count agar. Results: The results indicated that rCagA + OMP decreased bacterial colonization in these tissues, and significant difference was observed between test and control groups (p value<0.001). Conclusion: Our results showed that the combination vaccine was effective against an oral exposure and the bacterial burden in the spleen, serum and gastric tissues were reduced in mice immunized with the Total-OMP-CagA.