Effects of Gamma Interferon on Intestinal Epithelial Cells Stimulated with Salmonella Enterica serovar Typhimurium and Candida albicans

Aims: The objective of this study was to determine the level of secretion of gamma-interferon by interferon-primed and unprimed Caco-2 intestinal epithelial cells and their survival or growth following infection with Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 14028), Salmonella enterica subsp. enterica serovar Typhimurium DT104 (ATCC 700408), and Candida albicans (Robin) Berkhout, anamorph (ATCC 10231) as well as the survival of the test microorganisms following infection.
Study Design: Controlled laboratory experiments were performed using two different species of Salmonella and adenocarcinoma Caco-2 cells. Untreated/ unprimed Caco-2 cells served as control; Caco-2 cells’ growth and interferon production were then determined using, Enzyme Linked Immunosorbent Assay (ELISA) and flow cytometry.
Place and Duration of Study: Department of Biological & Environmental Sciences Alabama A& M University and Center for Excellence in Post-Harvest Technologies, North Carolina A&T University USA April 2008 and February 2010.
Methodology: Cell culture supernatants of Caco-2 intestinal epithelial cells, primed and unprimed with IFN-γ were infected with either wild-type Salmonella Typhimurium 14028, Candida albicans10231 or multi-drug resistant Salmonella Typhimurium DT104 were collected and analyzed. ELISA and flow cytometry were used to determine apoptosis, cell growth and interferon production. The Bioscreen-C Automated Growth Curve Analysis System was used under controlled environment to determine the growth of the microorganisms in the presence of different concentrations of IFN-γ.
Results: Secretion of IFN-γ from Caco-2 cells that were previously treated with 50μg/ml, 20μg/ml, 10μg/ml, 5μg/ml, and 2.5 μg/ml of IFN-γ were not concentration dependent. However, the amount of IFN-γ released from Caco-2 cells was dependent on microbial stimulus type. Cells that were pretreated with 5 μg/ml and 2.5 μg/ml of IFN-γ and then infected with Salmonella Typhimurium DT104 showed an increase in the amount of IFN-γ in the culture medium after 5 minutes. IFN-y induced CaCo-2 cell death was dose-dependent for S.Typhimurium DT104 and Candida albicans. Results are reported as mean ± SEM fortriplicate values from three independent experiments at each time point and IFN-γ dose.
Conclusion: These findings indicate that IFN-γ may serve as alternative antimicrobial compounds to reduce the persistence of multi-drug resistant microorganisms such as S. Typhimurium DT104. Induction of interferon-gamma production may be related to microbial virulence/pathogenicity. The potential of IFN-γ as a natural therapeutic for persistent infections in the immune-compromised populations still needs to be further investigated.