Dynamic antigen-specific T-cell responses after point-source exposure to Mycobacterium tuberculosis

Am J Respir Crit Care Med. 2006 Oct 1;174(7):831-9. doi: 10.1164/rccm.200511-1783OC. Epub 2006 Jun 23.


Rationale: The kinetics of Mycobacterium tuberculosis-specific Th1-type T-cell responses after M. tuberculosis infection are likely to be important in determining clinical outcome.

Objective: To investigate the kinetics of T-cell responses, in the context of a point-source school tuberculosis outbreak, in three groups of contacts who differed by preventive treatment status and tuberculin skin test (TST) results: 38 treated TST-positive students, 11 untreated TST-positive staff, and 14 untreated students with negative or borderline TST results.

Methods: We used the ex vivo IFN-gamma enzyme-linked immunospot assay (ELISpot) to track T cells specific for two region of difference 1 (RD1) antigens, early secretory antigenic target 6 and culture filtrate protein 10, for 18 mo after cessation of tuberculosis exposure.

Main results: The treated TST-positive students had an average 68% decline in frequencies of RD1-specific IFN-gamma-secreting T cells per year (p < 0.0001) and 6 of 38 students had no detectable RD1-specific T cells by 18 mo. No change in frequencies of these cells was observed in the untreated TST-positive staff (p = 0.38) and none were ELISpot-negative at 18 mo. Of the 14 untreated students, 7 were persistently ELISpot-positive (all of whom had borderline TST results), and 7 became ELISpot-negative (all but one had negative TST results) during follow-up.

Conclusions: The decrease in M. tuberculosis-specific T cells and their disappearance in a proportion of treated students likely reflect declining antigenic and bacterial load in vivo induced by antibiotic treatment. The observed disappearance of M. tuberculosis-specific T cells in the untreated TST-negative contacts suggests that an acute resolving infection may occur in some contacts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antigens, Bacterial / immunology*
  • Bacterial Proteins / immunology
  • Contact Tracing
  • Epitopes / immunology*
  • Female
  • Humans
  • Interferon-gamma / metabolism
  • Male
  • Middle Aged
  • Mycobacterium tuberculosis / immunology
  • Mycobacterium tuberculosis / isolation & purification
  • T-Lymphocytes / immunology*
  • Tuberculin Test
  • Tuberculosis, Pulmonary / immunology*
  • Tuberculosis, Pulmonary / transmission


  • Antigens, Bacterial
  • Bacterial Proteins
  • CFP-10 protein, Mycobacterium tuberculosis
  • ESAT-6 protein, Mycobacterium tuberculosis
  • Epitopes
  • Interferon-gamma