Interferon-gamma responses to ESAT-6 in tuberculosis patients early into and after anti-tuberculosis treatment.
OBJECTIVE
To investigate T-cell responses to ESAT-6 by an interferon-gamma (IFN-gamma) ex vivo enzyme-linked immunospot (ELISpot) assay in tuberculosis (TB) patients early during treatment and in patients who have completed a course of anti-tuberculosis chemotherapy.


METHODS
T-cell responses following overnight stimulation with 6-kD early secretory antigenic target (ESAT-6) antigen were compared to responses obtained using cells cultured with ESAT-6 for 6 days, using an ELISpot assay.


RESULTS
In the ex vivo ELISpot assay, the median IFN-gamma responses in TB patients, irrespective of treatment status, were significantly higher than in healthy BCG-vaccinated controls. In the 6-day ELISpot assay, median IFN-gamma responses were significantly higher in TB patients who had completed treatment than in patients early during therapy. There was considerable individual variability in the degree of expansion of ESAT-6 specific T-cells from day 1 to day 6 in both treatment groups.


CONCLUSIONS
Further studies are required to assess which type of assay provides the best indicator of a memory T-cell response and how ESAT-6 specific T-cells relate to protective immunity in TB infection.
Ferrand
R A
RA
Immunology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom. rabferr@fastmail.fm
Bothamley
G H
GH
Whelan
A
A
Dockrell
H M
HM
D000328:Adult; D000942:Antigens, Bacterial / Q000276:immunology*; D001426:Bacterial Proteins; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D007371:Interferon-gamma / Q000097:blood*; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D007371:Interferon-gamma