BMC Infectious Diseases (Jul 2007)

T-cell and serological responses to Erp, an exported <it>Mycobacterium tuberculosis </it>protein, in tuberculosis patients and healthy individuals

  • Ottenhoff Tom,
  • Arend Sandra M,
  • Bricaire François,
  • Truffot Chantal,
  • Sellier Pierre,
  • Mauger Isabelle,
  • Jouan Marc,
  • Badell Edgar,
  • Carcelain Guislaine,
  • Martinez Valérie,
  • Autran Brigitte,
  • Gicquel Brigitte

DOI
https://doi.org/10.1186/1471-2334-7-83
Journal volume & issue
Vol. 7, no. 1
p. 83

Abstract

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Abstract Background The identification of antigens able to differentiate tuberculosis (TB) disease from TB infection would be valuable. Cellular and humoral immune responses to Erp (Exported repetitive protein) – a recently identified M. tuberculosis protein – have not yet been investigated in humans and may contribute to this aim. Methods We analyzed the cellular and humoral immune responses to Erp, ESAT-6, Ag85B and PPD in TB patients, in BCG+ individuals without infection, BCG+ individuals with latent TB infection (LTBI) and BCG- controls. We used lymphoproliferation, ELISpot IFN-γ, cytokine production assays and detection of specific human antibodies against recombinant M. tuberculosis proteins. Results We included 22 TB patients, 9 BCG+ individuals without TB infection, 7 LTBI and 7 BCG- controls. Erp-specific T cell counts were higher in LTBI than in the other groups. Erp-specific T cell counts were higher in LTBI subjects than TB patients (median positive frequency of 211 SFC/106 PBMC (range 118–2000) for LTBI subjects compared to 80 SFC/106 PBMC (range 50–191), p = 0.019); responses to PPD and ESAT-6 antigens did not differ between these groups. IFN-γ secretion after Erp stimulation differed between TB patients and LTBI subjects (p = 0.02). Moreover, LTBI subjects but not TB patients or healthy subjects produced IgG3 against Erp. Conclusion The frequencies of IFN-γ-producing specific T cells, the IFN-γ secretion and the production of IgG3 after Erp stimulation are higher in LTBI subjects than in TB patients, whereas PPD and ESAT-6 are not.