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Specific delayed-type hypersensitivity responses to ESAT-6 identify tuberculosis-infected cattle
J M Pollock1, J McNair, H Bassett
1Veterinary Sciences Division, Department of Agriculture and Rural Development, Belfast, United Kingdom. john.pollack@dardni.gov.uk
Journal of Clinical Microbiology
|May 8, 2003
Summary
New skin tests using ESAT-6 show promise for diagnosing tuberculosis. This specific antigen offers a potential alternative to purified protein derivative (PPD) testing for accurate in vivo detection of bovine and human tuberculosis.
Area of Science:
- Veterinary Immunology
- Mycobacterial Diagnostics
- Infectious Disease Research
Background:
- Traditional tuberculosis detection relies on purified protein derivative (PPD) skin testing, which uses a complex antigen mix with suboptimal specificity.
- ESAT-6, a recombinantly produced antigen, is highly specific for tuberculosis infection and offers potential for improved diagnostics.
Purpose of the Study:
- To investigate the diagnostic potential of ESAT-6 based skin tests for tuberculosis.
- To compare the efficacy of ESAT-6 skin tests with traditional PPD tests in cattle.
Main Methods:
- Skin tests were performed using ESAT-6 and PPD antigens.
- Reactions were measured at different time points (72h and 96h) to assess delayed-type hypersensitivity.
- Optimized strategy involved 400 micro g of ESAT-6 measured between 72 and 96 hours.
Main Results:
- ESAT-6 skin tests demonstrated promising diagnostic potential with 82% sensitivity and 100% specificity in cattle infected with Mycobacterium bovis.
- Compared to PPD (86% sensitivity, 90% specificity), ESAT-6 showed higher specificity.
- The optimal measurement time for ESAT-6 reactions was between 72 and 96 hours, later than PPD.
Conclusions:
- Skin tests based on the specific antigen ESAT-6 show great potential for accurate in vivo diagnosis of tuberculosis.
- Further large-scale investigations are needed to refine cutoff points for ESAT-6 diagnostic tests.
- ESAT-6 offers a promising alternative for tuberculosis diagnosis, potentially improving specificity over PPD.