An oral recombinant Salmonella enterica serovar Typhimurium mutant elicits systemic antigen-specific CD8+ T cell cytokine responses in mice.
BACKGROUND
The induction of antigen-specific CD8+ T cell cytokine responses against an attenuated, oral recombinant Salmonella enterica serovar Typhimurium vaccine expressing a green fluorescent protein (GFP) model antigen was investigated. A GFP expression plasmid was constructed in which the gfp gene was fused in-frame with the 5' domain of the Escherichia coli beta-galactosidase alpha-gene fragment with expression under the lac promoter. Groups of mice were orally immunized three times with the bacteria and systemic CD8+ T cell cytokine responses were evaluated.


RESULTS
High level of the GFP model antigen was expressed by the recombinant Salmonella vaccine vector. Systemic GFP-specific CD8+ T cell cytokine (IFN-gamma and IL-4) immune responses were detected after mice were orally vaccinated with the bacteria. It was shown that 226 net IFN-gamma and 132 net IL-4 GFP-specific SFUs/10e6 splenocytes were formed in an ELISPOT assay. The level of IFN-gamma produced by GFP peptide-stimulated cells was 65.2-fold above background (p < 0.05). The level of IL-4 produced by the cells was 10.4-fold above background (p < 0.05).


CONCLUSIONS
These results suggested that a high expressing recombinant Salmonella vaccine given orally to mice would elicit antigen-specific CD8+ T cell responses in the spleen. Salmonella bacteria may, therefore, be used as potential mucosal vaccine vectors.
Chin'ombe
Nyasha
N
Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Rd, Observatory 7925, Cape Town, South Africa. Nyasha.Chinombe@uct.ac.za
Bourn
William R
WR
Williamson
Anna-Lise
AL
Shephard
Enid G
EG