Research

An oral recombinant Salmonella enterica serovar Typhimurium mutant elicits systemic antigen-specific CD8+ T cell cytokine responses in mice

Nyasha Chin'ombe¹ , William R Bourn² , Anna-Lise Williamson¹ and Enid G Shephard^1,3

¹  Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Rd, Observatory 7925, Cape Town, South Africa

²  Kapa Biosystems (Pty) Ltd, Observatory 7925, Cape Town, South Africa

³  MRC/UCT Liver Research Centre, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Rd, Observatory 7925, Cape Town, South Africa

author email corresponding author email

Gut Pathogens 2009, 1:9doi:10.1186/1757-4749-1-9

Published:	29 April 2009

Abstract

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 β-galactosidase α-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-γ and IL-4) immune responses were detected after mice were orally vaccinated with the bacteria. It was shown that 226 net IFN-γ and 132 net IL-4 GFP-specific SFUs/10e6 splenocytes were formed in an ELISPOT assay. The level of IFN-γ 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).

Conclusion

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.