Comparison of recombinant MPB70 and SahH and a native 20-kDa protein for the detection of bovine tuberculosis by ELISA

Abstract

Background Bovine tuberculosis (bTB) is a zoonosis mainly caused by Mycobacterium bovis . Test-and-cull protocols and gross pathological examinations of abattoir animals as well as milk pasteurisation have been implemented for preventing the spread of tuberculosis from animals to humans worldwide, including in the Republic of Korea. Despite the importance of precise and rapid diagnostic tests, conventional methods, including intradermal skin tests and γ-interferon assays, are limited by the high rate of false negative results for cattle in the late infectious stage as well as laborious and time-consuming procedures. Therefore, antibody detection methods, such as enzyme-linked immunosorbent assay (ELISA), are urgently needed to supplement established approaches and to expand the diagnostic window. In this study, we developed a bTB ELISA by evaluating candidate recombinant and native proteins and various assay parameters.Results We produced recombinant MPB70 and SahH (rM70S) and a native 20-kDa protein (20K). The 20K ELISA showed 94.4% sensitivity and 98.2% specificity and had an optimal sample-to-positive (S/P) ratio cut-off of 0.531. rM70S ELISA showed 94.4% sensitivity and 97.3% specificity with an S/N ratio cutoff of 1.696.Conclusion The assays showed the same sensitivity but the specificity was higher for 20K ELISA than for rM70S ELISA. Both assays had acceptable diagnostic efficiency and are expected to be useful for bTB diagnosis in combination with established methods for herd screening and for expanding the diagnostic window.