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Journal of Clinical Microbiology, Mar 1997, 553-557, Vol 35, No. 3
RJ Wilkinson, K Haslov, R Rappuoli, F Giovannoni, PR Narayanan, CR Desai, HM Vordermeier, J Paulsen, G Pasvol, J Ivanyi and M Singh
The diagnosis of infection caused by Mycobacterium tuberculosis is of
increased public health concern following increases in the number of cases
in developed countries and major increases in developing countries
associated with the spread of human immunodeficiency virus (HIV) infection.
The specificity of purified protein derivative skin testing for the
detection of infection is compromised by exposure to environmental
mycobacteria. Examination of sputum detects the most infectious patients,
but not those with extrapulmonary disease. The 38- kDa antigen of M.
tuberculosis contains two M. tuberculosis-specific B- cell epitopes. We
overexpressed the gene for this antigen in Escherichia coli and evaluated
the recombinant product in in vitro assays of T-cell function and as a
target for the antibody response in humans. The sensitivity and specificity
of the antigen as a skin test reagent were also assessed in outbred guinea
pigs. We found that 69% of healthy sensitized humans recognize the antigen
in vitro, as manifested by both cell proliferation and the production of
gamma interferon. Untreated patients initially have a lower frequency of
response (38%); this recovers to 72% during therapy. A total of 292
patients (20 with HIV coinfection) and 58 controls were examined for
production of antibody to the 38-kDa antigen by using a commercially
available kit. The sensitivity of the test in comparison with that of
culture was 72.6%, and the specificity was 94.9%. The antigen was also
tested for its ability to induce skin reactions in outbred guinea pigs
sensitized by various mycobacterial species. The antigen provoked
significant skin reactions in M. tuberculosis-, M. bovis BCG-, and M.
intracellulare- sensitized animals. The significance of these findings and
the usefulness of this antigen in immunodiagnosis are discussed.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Evaluation of the recombinant 38-kilodalton antigen of Mycobacterium tuberculosis as a potential immunodiagnostic reagent
MRC Tuberculosis and Related Infections Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
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