[Isolation of MPB63 in the culture fluid of Mycobacterium bovis BCG Tokyo: genetical and immunological characterization].
MPT63 is a secretory protein first isolated from a culture fluid of M. tuberculosis H37Rv by Nagai et al. In this study, this protein was isolated from an 8-day-culture fluid (Sauton synthetic medium) of M. bovis BCG Tokyo 172 according to Nagai's method. It was shown that M. bovis BCG Tokyo 172 secreted this protein in the medium. The mpt63 gene was detected only in the species of M. tuberculosis complex by polymerase chain reaction (PCR) among 40 different mycobacterial species. Therefore, it is appropriate to designate this protein as MPB63 or MPB/T63 from M. bovis BCG, in similar way as other major secretory proteins of Mycobacteria, such as MPB59 and MPB64. Comparison of the nucleotide sequences of the genes encoding MPB63 protein of M. bovis BCG and MPT63 protein of M. tuberculosis showed only single nucleotide difference at the position 474 where thymine (T) in the former was replaced by adenine (A) in the latter. Amino acid sequences of both proteins were completely identical. MPB63 didn't show delayed-type hypersensitivity (DTH) skin reaction in the sensitized guinea pigs with live or heat-killed M. bovis BCG or heat-killed M. tuberculosis. However, the measurements of serum IgG antibody titers of active tuberculosis patients by enzyme-linked immunosorbent assay (ELISA) showed 74% sensitivity and 96% specificity compared to healthy subjects. Therefore, MPB63 seems to be a promising candidate as an antigen for serodiagnosis of active tuberculosis.
Kawajiri
Katsuhide
K
Japan BCG Laboratory, 3-1-5, Matsuyama, Kiyose-shi, Tokyo 204-0022, Japan. kawajiri@bcg.gr.jp
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D006168:Guinea Pigs; D006801:Humans; D009163:Mycobacterium bovis / Q000235:genetics* / Q000276:immunology*; D016133:Polymerase Chain Reaction
D001426:Bacterial Proteins; C103339:MPT63 antigen, Mycobacterium tuberculosis