Molecular and immunological characterization of Mycobacterium tuberculosis CFP-10, an immunodiagnostic antigen missing in Mycobacterium bovis BCG.
In order to identify antigens that may be used in the serodiagnosis of active tuberculosis (TB), we screened a Mycobacterium tuberculosis genomic expression library with a pool of sera from patients diagnosed with active pulmonary TB. The sera used lacked reactivity with a recombinant form of the M. tuberculosis 38-kDa antigen (r38kDa), and the goal was to identify antigens that might complement r38kDa in a serodiagnostic assay. Utilizing this strategy, we identified a gene, previously designated lhp, which encodes a 100-amino-acid protein referred to as culture filtrate protein 10 (CFP-10). The lhp gene is located directly upstream of esat-6, within a region missing in M. bovis BCG. Immunoblot analysis demonstrated that CFP-10 is present in M. tuberculosis CFP, indicating that it is likely a secreted or shed antigen. Purified recombinant CFP-10 (rCFP-10) was shown to be capable of detecting specific antibody in a percentage of TB patients that lack reactivity with r38kDa, most notably in smear-negative cases, where sensitivity was increased from 21% for r38kDa alone to 40% with the inclusion of rCFP-10. In smear-positive patient sera, sensitivity was increased from 49% for r38kDa alone to 58% with the inclusion of rCFP-10. In addition, rCFP-10 was shown to be a potent T-cell antigen, eliciting proliferative responses and gamma interferon production from peripheral blood mononuclear cells in 70% of purified protein derivative-positive individuals without evident disease. The responses to this antigen argue for the inclusion of rCFP-10 in a polyvalent serodiagnostic test for detection of active TB infection. rCFP-10 could also contribute to the development of a recombinant T-cell diagnostic test capable of detecting exposure to M. tuberculosis.
Dillon
D C
DC
Corixa Corporation, Seattle, Washington 98104, USA. dillon@corixa.com
Alderson
M R
MR
Day
C H
CH
Bement
T
T
Campos-Neto
A
A
Skeiky
Y A
YA
Vedvick
T
T
Badaro
R
R
Reed
S G
SG
Houghton
R
R
D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D015151:Immunoblotting; D008213:Lymphocyte Activation; D008297:Male; D008969:Molecular Sequence Data; D009163:Mycobacterium bovis / Q000235:genetics / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; D011994:Recombinant Proteins