Immune response to Mycobacterium tuberculosis specific antigen ESAT-6 among south Indians.

Kumar, M. Meenakshi, N.; Sundaramurthi, J.C.; Kaur, G.; Mehra, N.K.; Raja, A.

Tuberculosis; 2010; 90; 60-69.

Summary: The 6-kDa early secreted antigenic target (ESAT-6) is a T-cell antigen recognized by individuals infected with Mycobacterium tuberculosis. The aim of the study was to identify ‘‘protective epitopes'' of ESAT-6 protein in the south Indian population. Proliferative and Interferon gamma (IFN- g ) responses to ESAT-6 peptides were studied by flow cytometry and Enzyme linked immunosorbent assay (ELISA). Healthy household contacts (HHC) recognized Esp1 (10/17) and Esp6 (9/17) peptides. Among pulmonary tuberculosis patients (PTB), Esp1 (3/11) and Esp6 (5/11) were recognized. Maximal response (7/10) was found for Esp1 and Esp8 in treated patients (TR). Median values for the responding subjects gave the following results: Esp1 (76 pg/ml), Esp6 (64 pg/ml), induced IFN- g production in HHC; PTB gave low IFN- g responses for the peptides. TR responded to the peptides Esp1 (141 pg/ml), Esp8 (102 pg/ml). The proliferation of CD4 cells was similar in both PTB and TR for all peptides; but HHC showed an increase for Esp1 ( p < 0.05 ) and Esp6 ( p < 0.01 ). Esp1 (amino acids aa 1–20) and Esp6 (aa 51–70) were the immunogenic peptides recognized by the alleles HLA DRB1*04 and HLA DRB1*10 among HHC. But the association of the alleles with ESAT-6 peptide presentation needs to be confirmed in a large cohort of subjects. We speculate that ESAT-6 can be used along with other immune-eliciting proteins for vaccine design strategies in south Indian population.

Keywords: Tuberculosis, ESAT-6 peptides, Vaccines, HLA, 20-mer peptides

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