Attenuated Salmonella enteritidis E23 as a vehicle for the rectal delivery of DNA vaccine coding for HIV-1 polyepitope CTL immunogen.

This study is focusing on elucidation of the capacity of attenuated Salmonella enteritidis E23 (cya, crp) to serve as a vehicle for the rectal delivery of the DNA vaccine. Earlier for creation HIV-1 candidate DNA vaccine we have designed the polyepitope protein TCI (T-cell immunogen), which comprises over 80 CTL epitopes from subtype A, B and C HIV-1 proteins. The gene coding for TCI protein was used to construct the eukaryotic expression plasmid pcDNA-TCI. The attenuated S. enteritidis E23 was transformed by electroporation with recombinant plasmid pcDNA-TCI and the expression of the TCI gene was determined in vitro and in vivo. BALB/c mice were rectally immunized with S. enteritidis E23/pcDNA-TCI (10⁸ cfu) twice at 4 week interval. Bacteria were not pathogenic for mice and spontaneously eliminated from mice spleen and liver to 60 days post the immunization. Detectable antibodies were generated in 2 weeks after immunization and their level increased after second immunization. The results of INF-γ ELISpot show that mice immunized with S. enteritidis E23/pcDNA-TCI elicited HIV-specific cellular immune response. This study demonstrates that attenuated S. enteritidis E23 is an effective live vector for rectal delivery of the DNA vaccine pcDNA-TCI to generate humoral and T-cellular responses against HIV-1.