Investigation of the cause of geographic disparities in IDEXX ELISA sensitivity in serum samples from Mycobacterium bovis-infected cattle

Abstract

Accurately identifying Mycobacterium bovis-infected cattle is critical for bovine tuberculosis prevention and control. One method for identifying infected cattle is an ELISA developed by IDEXX laboratories, which detects antibodies to two M. bovis proteins, MPB70 and MPB83. The assay’s sensitivity varies by geographic region, with sensitivities of 77%, 45%, and 9% in bovine serum samples from the United Kingdom (n = 126), the United States (n = 146), and Mexico (n = 128), respectively. We hypothesized that geographically-biased sequence variation in mpb70 and mpb83, or in the genes that regulate their expression (sigK and rskA), may explain these differing sensitivities. This hypothesis was tested by comparing the sequences of these four genes in 455 M. bovis strains isolated from cattle in the aforementioned countries. For each gene, a single, common sequence was identified in most genomes of the M. bovis strains collected in all three countries. Twelve of the 455 strains were isolated from infected cattle for which the IDEXX ELISA was also performed. Five of the seven ELISA-positive genomes and three of the five ELISA-negative genomes contained the most common sequence of all four genes. Thus, sequence variation in mpb70, mpb83, sigK, and rskA does not explain the geographic disparities in IDEXX ELISA sensitivity.

Identification of Novel Antigens Recognized by Serum Antibodies in Bovine Tuberculosis

“…The intradermal tuberculin test has suboptimal sensitivity and inconsistent performance (1,9,10), while the available blood-based assays, such as the Thermo Fisher Scientific Bovigam TB kit or the Idexx M. bovis antibody (Ab) test, lack the required accuracy and show a significant variability when used in different geographic areas (11)(12)(13). Given the ease of sample collection and the test procedure, antibody detection assays may be useful to identify M. bovis-infected cattle (1,14,15), but the existing methods require improvement.…”

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

“…Positive control and negative control sera were used for each ELISA for validation. ELISA results were analysed according to three criteria, the OD value, S/N ratio, and S/P ratio [1,17,22,23]. The optimal method for effectively diagnosing bovine tuberculosis was determined by comparisons of the sensitivity and specificity of each parameter.…”

“…In this study, the native 20-kDa antigen showed higher sensitivity and specificity than those of PPD. Immunospecific-recombinant proteins of M. bovis have been applied as bTB ELISA antigens, such as MPB70, MPB83, ESAT6, CFP10, Mb0143, PE5, PE13, TB10.4, TB15.3, Rv3615c, Rv3020c, and ESAT6/MPB70/MPB83 (fusion protein)[12,[22][23][24][25][26]. In this study, we newly mixed MPB70 with SahH as a recombinant antigen.…”

Study on a supplemental test to improve the detection of bovine tuberculosis in individual animals and herds

“…Since late 19th century, the Tuberculin Skin Test (TST) has been the primary antemortem test available to support bTB eradication campaigns (9,10). Advantages of the TST and reasons for its wide use are low costs, high availability, long history of use and, for a long time, the lack of alternative methods to detect bTB (9,10,11,12). On the other hand, this test has many known limitations, including di culties in performance and result interpretation, need for a second-step visit, low degree of standardization, and reduced test accuracy (13).…”

“…Moreover, a booster effect on the antibody response caused after injection of tuberculin has been reported and recommended as a strategic option to increase the sensitivity of serological assays (26,27,28). The ELISA using MPB83 and MPB70 antigens (IDEXX M. bovis Ab Test, IDEXX Laboratories, Westbrook, Maine, US) is an immune enzymatic assay promising sensitivity and speci cities superior to most tuberculosis diagnoses for both primary and supplementary diagnosis in cases of inconclusive results of the diagnosis by simple or comparative cervical test (16,31,12).…”