Abstract

Purpose: To investigate the efficacy of a double DNA vaccine encoding of Brucella melitensis omp31 gene and of Escherichia coli eae gene in inducing protective immune response in a mouse model. Methods: After performing PCR assays and cloning both the eae and omp31 genes, the generated DNA vaccines were intramuscularly injected into BALB/c mice. Purified proteins and transformed cell lysates were identified by western blot and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and analyzed by enzyme-linked immunosorbent assay (ELISA). Results: pcDNA3-omp31-eae provokes a significant, high level of protection in BALB/c mice against challenges with E. coli and B. melitensis. Titers ranging from 90: 160 to 2,570: 5,110 were detected 60 days after vaccination. Notably, rOmp31 and rEae proteins significantly induced the production of IFN-gamma in cells from pcDNA3-omp31-eae-immunized mice (p < 0.05 in both groups) and only low levels of IL-10 were found in all groups. The lymphocytes from mice immunized with pcDNA3-omp31-eae had an apparent T cell proliferative response to rOmp31 and rEae proteins (p < 0.01) with a stimulation index of 14.90. Conclusion: The novel pcDNA3-omp31-eae construct can be used as a DNA vaccine to prevent E. coli and B. melitensis infections in future studies.