ARS | Publication request: Improvements to the BOVIGAM Interferon Gamma (IFN-gamma) Assay for use with Alternative Antigens as Stimulants of Whole Blood Cultures

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 2, 2009
Publication Date: September 2, 2009
Citation: Hardegger, R., Purro, M., Schroder, B., Moyen, J.L., Gormley, E., Waters, W.R., Palmer, M.V., Thacker, T.C., Whelan, A., Vordermeier, H.M., Raeber, A.J. 2009. Improvements to the BOVIGAM Interferon Gamma (IFN-gamma) Assay for use with Alternative Antigens as Stimulants of Whole Blood Cultures [abstract].

Technical Abstract: The success of bovine tuberculosis eradication programs in many countries have relied on antemortem diagnostic tests measuring cell-mediated immune (CMI) responses such as the tuberculin skin test or the interferon gamma test. The BOVIGAM® interferon gamma (IFN-gamma) test system constitutes a laboratory-based tuberculosis test and is widely used complementary to the tuberculin skin test. Traditional use of Bovigam is based on measuring the difference in IFN-gamma production between stimulation with bovine tuberculin and avian tuberculin. Recent advances in the use of Bovigam include the application of defined antigens such as ESAT-6 and CFP-10 derived from the M.Bovis genome for stimulation of whole blood cultures. In addition to providing increased diagnostic specificity in the Bovigam assay, specific antigens provide an important tool for differential diagnosis because they are absent form the vaccine strain M.bovis BCG. If the Bovigam test is used with alternative antigens, absolute levels of IFN-gamma are measured after stimulation with an antigen cocktail. We found that for the incorporation of the use with alternative antigens, the test can benefit from a higher range of the IFN-gamma detection part of the assay. In this study, we present several improvements of the BOVIGAM resulting in a lower detection limit for IFN-gamma, more flexibility with regard to incorporation of different reagents for stimulation (PPDs, alternative antigens, superantigens) and improved ease-of-use. Inter- and intraplate variances could be reduced to < 5%. In combination with alternative antigen cocktails to be used for stimulation of the cell mediated immune response, a significant higher specificity and equivalent sensitivity in comparison with PPDs could be achieved. Furthermore, the second generation BOVIGAM assay uses a one component substrate and less washing steps and thus reduces time and cost and allows full automation for high throughput testing needs. In conclusion, the new IFN-gamma assay can be used as in improved tool for the detection of TB infected cattle.