Submitted to: Sensors
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/15/2014
Publication Date: 5/20/2014
Publication URL: http://handle.nal.usda.gov/10113/58876
Citation: Rasooly, R., Hernlem, B.J. 2014. Quantitative analysis of Staphylococcus enterotoxin A by differential expression of IFN-gamma in splenocyte and CD4+ T-cells. Sensors. 14:8869-8876 DOI:10.3390/s140508869. Interpretive Summary: Staphylococcus aureus is a bacteria that is a major cause of hospital infections and food sickness. It produces a group of toxins which include Staphylococcal Enterotoxin A (SEA) that has been associated with three quarters of food-poisonings caused by this bacteria. Fast tests are needed for the harmful active form of toxins to protect the public health and food supply. Some tests only respond to SEA whether or not it is active and poses a threat or inactive which poses no threat. We showed that certain cells taken from mice make, in a dose dependent manner, a protein chemical called interferon-gamma (IFN-gamma) in response to SEA and that this can be used to quickly sense the presence and amount of active SEA.
Technical Abstract: Staphylococcus aureus is an important bacterial pathogen that produces a range of Staphylococcal Enterotoxins (SEs) which cause gastroenteritis and superantigen activation of T cells, the mechanism of which is not well understood. The ability to rapidly detect and quantify SEs is very important in order to learn the causes of staphylococcal outbreaks and to stop similar outbreaks in the future. Enzyme-linked immunosorbent assays (ELISA) have been developed for detection of several SEs. However, these immunological methods cannot distinguish between active and inactive toxin. It is known that interferon-gamma (IFN-gamma) expressed in response to stimulation by SEs contributes significantly to the pathogenesis of S. aureus infection. Nonetheless, the cellular source of IFN-gamma is still unclear and the contributions of the specific splenocyte types. In our effort to understand the immunologic response to Staphylococcal Enterotoxin A (SEA) exposure, we studied IFN-gamma production in mouse splenocytes. We demonstrated that short term ex vivo exposure of splenocytes or primary naïve CD4+ T-cells to biologically active SEA induces differential expression of IFN-gamma mRNA in a time and dose dependent manner and the expression levels reflect the levels of IFN-gamma secreted protein. Positive isolated CD4+ T-cells accounted for only 10% of IFN-gamma production. We also demonstrate that expression of IFN-gamma can be used for rapid quantitative analysis of active SEA with a detection limit of 1 ng/mL.