Response of IFN-gamma and IgG to ESAT-6 and 38 kDa recombinant proteins and their peptides from Mycobacterium tuberculosis in tuberculosis patients and asymptomatic household contacts may indicate possible early-stage infection in the latter.
BACKGROUND
The ESAT-6 antigen from Mycobacterium tuberculosis evokes a protective immune response in murine models and is widely recognized by tuberculosis patients (TB) and healthy household contacts (HHC). However, little is known about human immune response to this antigen in populations from areas of high endemicity. This study aimed to determine the capacity of T-cells from a group of TB patients and HHC for cell proliferation and production of cytokines type Th1 or Th2 (IL-4, IL-10, and IFN-gamma) and to identify total IgG reactivity to the recombinant protein rESAT-6 and five overlapping synthetic peptides as well as to r38 kDa and two peptides.


METHODS
T-cells from nine TB patients and nine HHC were stimulated with rESAT-6 and five overlapping synthetic peptides, previously selected from a set of 21 peptides and each of 16 amino acids in length (P1, P4, P6, P8, and P20). Similar experiments were carried out with r38 kDa and two peptides of 20 amino acids in length (38G and 38K). Cytokines in supernatants and total IgG from serum were determined by ELISA.


RESULTS
Stimulation index (SI) was highest in HHC to rESAT-6 and peptides P1, P8, and P20. Differences in response to 38 kDa and 38G peptide between TB patients and HHC were not demonstrated. Cytokines from T-cell cultures were tested with a resulting SI=3.0. IFN-gamma was produced predominantly in HHC to rESAT-6, P8, and P20, while in TB patients production of IL-10 was detected in relation to r38 kDa. IL-4 was detected in minimal amounts in both groups. IgG from TB patients was predominantly recognized in connection with rESAT-6 and the P4 peptide, with an important response against r38 kDa detected in HHC.


CONCLUSIONS
ESAT-6 recognition by HHC could indicate that these responses represent possible early-stage infections.
López-Vidal
Yolanda
Y
Programa de Inmunología Molecular Microbiana, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico. lvidal@servidor.unam.mx
de León-Rosales
Samuel Ponce
SP
Castañón-Arreola
Mauricio
M
Rangel-Frausto
M Sigfrido
MS
Meléndez-Herrada
Enrique
E
Sada-Díaz
Eduardo
E
D000328:Adult; D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology*; D008074:Lipoproteins / Q000235:genetics / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D014397:Tuberculosis, Pulmonary / Q000276:immunology* / Q000378:metabolism
C075966:Ag38 antigen, Mycobacterium tuberculosis; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D016207:Cytokines; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D007074:Immunoglobulin G; D008074:Lipoproteins; D010455:Peptides; D011994:Recombinant Proteins; D007371:Interferon-gamma