Assessment of Mycobacterium tuberculosis OmpATb as a novel antigen for the diagnosis of bovine tuberculosis.
In the search for better tools to control bovine tuberculosis, the development of diagnostic tests with improved specificity and sensitivity has a high priority. We chose to search for novel immunodiagnostic reagents. In this study, Rv0899 (outer membrane protein A of Mycobacterium tuberculosis [OmpATb]) was evaluated as a stimulation antigen in a gamma interferon (IFN-gamma) release assay to diagnose bovine tuberculosis. OmpATb induced IFN-gamma responses in cattle experimentally infected with M. bovis as early and as persistently as ESAT-6 and CFP-10, the current lead diagnostic antigens. In naturally infected cattle, OmpATb stimulated IFN-gamma production in 22 of 26 animals (85%). Importantly, OmpATb detected a portion of M. bovis-infected cattle which did not respond to ESAT-6 and CFP-10 (five of six cattle). The combined diagnostic sensitivity of OmpATb, ESAT-6, and CFP-10 for a preselected group consisting of naturally infected cattle with an overrepresentation of ESAT-6/CFP-10 nonresponders was 96% (25 of 26 animals). The specificity of OmpATb for uninfected cattle was 100% (27 cattle were tested; 12 of them gave false-positive results with tuberculins). In summary, our results indicate that OmpATb has the potential to enhance the sensitivity of previously described diagnostic tests based on ESAT-6 and CFP-10 and that the combined use of OmpATb, ESAT-6, CFP-10, and other proteins may achieve at least equal sensitivity to that obtained with purified protein derivative, but at a higher specificity. Further studies evaluating the diagnostic performance of OmpATb in combination with other proteins are ongoing.
Schiller
Irene
I
Prionics AG, Schlieren, Switzerland.
Vordermeier
H Martin
HM
Waters
W Ray
WR
Palmer
Mitchell
M
Thacker
Tyler
T
Whelan
Adam
A
Hardegger
Roland
R
Marg-Haufe
Beatrice
B
Raeber
Alex
A
Oesch
Bruno
B
D000818:Animals; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D002417:Cattle; D007118:Immunoassay / Q000379:methods*; D007371:Interferon-gamma / Q000378:metabolism; D018272:Porins; D012680:Sensitivity and Specificity; D014380:Tuberculosis, Bovine / Q000175:diagnosis*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C113302:OmpATb protein, Mycobacterium tuberculosis; D018272:Porins; D007371:Interferon-gamma