A novel B-cell epitope identified within Mycobacterium tuberculosis CFP10/ESAT-6 protein

PLoS One. 2013;8(1):e52848. doi: 10.1371/journal.pone.0052848. Epub 2013 Jan 7.

Abstract

Background: The 10-kDa culture filtrate protein (CFP10) and 6-kDa early-secreted target antigen (ESAT-6) play important roles in mycobacterial virulence and pathogenesis through a 1:1 complex formation (CFP10/ESAT-6 protein, CE protein), which have been used in discriminating TB patients from BCG-vaccinated individuals. The B-cell epitopes of CFP10 and ESAT-6 separately have been analyzed before, however, the epitopes of the CE protein are unclear and the precise epitope in the positions 40 to 62 of ESAT-6 is still unknown.

Methods: In the present study, we searched for the B-cell epitopes of CE protein by using phage-display library biopanning with the anti-CE polyclonal antibodies. The epitopes were identified by sequence alignment, binding affinity and specificity detection, generation of polyclonal mouse sera and detection of TB patient sera.

Results: One linear B-cell epitope (KWDAT) consistent with the 162(nd)-166(th) sequence of CE and the 57(th)-61(st) sequence of ESAT-6 protein was selected and identified. Significantly higher titers of E5 peptide-binding antibodies were found in the sera of TB patients compared with those of healthy individuals.

Conclusion: There was a B-cell epitope for CE and ESAT-6 protein in the position 40 to 62 of ESAT-6. E5 peptide may be useful in the serodiagnosis of tuberculosis, which need to be further confirmed by more sera samples.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies, Bacterial / blood
  • Antibodies, Bacterial / immunology
  • Antigens, Bacterial / analysis
  • Antigens, Bacterial / immunology*
  • Epitopes, B-Lymphocyte / analysis*
  • Epitopes, B-Lymphocyte / immunology*
  • Female
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Models, Molecular
  • Molecular Sequence Data
  • Mycobacterium tuberculosis / chemistry
  • Mycobacterium tuberculosis / immunology*
  • Mycobacterium tuberculosis / pathogenicity*
  • Peptide Library
  • Peptides / chemistry
  • Peptides / immunology
  • Sequence Alignment
  • Tuberculosis / blood
  • Tuberculosis / immunology
  • Tuberculosis / microbiology*

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Epitopes, B-Lymphocyte
  • Peptide Library
  • Peptides
  • Mycobacterium tuberculosis antigens

Grants and funding

This work was supported by grant from the National Key Project for Infectious Disease (No. 2012ZX10003002-008), the Science and Technology Commission of Shanghai Municipality, Shanghai, PR China (No. 124119a1500), and the Fundamental Research Funds for the Central Universities (No. 1511219013). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.