ARS | Publication request: Interferon Gamma Assay for the Diagnosis of Bovine Tuberculosis

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 16, 2008
Publication Date: October 16, 2008
Citation: Schiller, I., Marg-Haufe, B., Vordermeier, M., Waters, W.R., Whelan, A., Welsh, M., Keck, N., Moyen, J.L., Palmer, M.V., Thacker, T.C., Raeber, A., Oesch, B. 2008. Interferon Gamma Assay for the Diagnosis of Bovine Tuberculosis [abstract]. Paper No. 25.

Technical Abstract: Contact Irene Schiller Prionics AG Wagistrasse 27A CH-8952 Schlieren Switzerland irene.schiller@prionics.com Introduction Bovine tuberculosis (bTB), a zoonotic disease with a major economic impact, continues to be a significant problem with a global perspective and increasing prevalence in various countries. Control and eradication of bTB are based on a test and slaughter strategy. The BOVIGAM® interferon gamma (IFN-gamma) assay (Prionics, Switzerland) constitutes a laboratory-based test detecting the hosts's cell-mediated immune response (CMI). It is widely used complementary to the tuberculin skin test. The principle of this test has been adapted for TB diagnosis in humans (QuantiFERON®-TB). Aim Environmental conditions before and during the culturing of the leucocytes influence the efficacy of in vitro IFN-gamma production. We have analyzed various parameters of the IFN-gamma test in view of optimal conditions and potential simplifications in order to streamline the assay procedure. Results We show that the culture temperature needs to be 33°C or higher and that there is no need to use incubation in the presence of CO2. Furthermore, various plate formats are shown to be feasible. The produced IFN-gamma was stable at 4°C for 28 days as well as after repeated freeze-thaw cycles. The CMI is known to be impacted negatively by stress. We have stimulated fresh blood from animals with or without stress with mitogens resulting in significantly lower IFN-' production in stressed animals and therefore potentially leading to false negative results. Tuberculosis-specific stimulation is currently done with tuberculins. We have analyzed tuberculins at different concentrations from different sources and will report on the optimal standardized tuberculin activity. As an alternative, a cocktail of recombinant antigens for stimulation resulted in improved diagnostic sensitivity and specificity. Conclusion Simplified culture conditions in combination with the high stability of natural IFN-gamma and optimized stimulation antigens will simplify the assay as well as the logistics for blood samples considerably. These recent developments in measuring the CMI represent excellent tools for control and eradication of bTB.