Identification of novel Mycobacterium tuberculosis peptides as diagnostic reagents for tuberculosis among human immunodeficiency virus infected population

Abstract

Objective To screen and validate the major histocompatibility complex class-Ⅰ(MHC-Ⅰ) restricted tuberculosis peptides as potential diagnostic reagents in tuberculosis interferon-gamma release assay (IGRA) used among human immunodeficiency (HIV)-infected population. Methods Candidate peptides were encoded by Mycobacterium tuberculosis (TB) RD (Region of difference). Computer software was used to predict and select CD8+ T cell epitopes restricted by MHC-Ⅰ molecules with high frequency and high affinity among HIV-infected people. Then peptides containing CD8+ T cell epitope were synthesized and screened in vitro. The sensitivity and specificity of IGRA using the above mixed peptides as stimulants were compared with those of IGRA using early secretory antigen target-6 (ESAT-6, molecular weight of 6 000) and culture filtrate protein-10 (CFP-10, molecular weight of 10 000) as stimulants among HIV-infected population. Results Eight overlapping peptides, including Rv0222176-191, Rv1980c122-138, Rv1985c105-120, Rv3425141-165, Rv3873133-151, Rv3873158-166, Rv387878-86, Rv3879c673-690, were obtained finally, which were able to stimulate the production of interferon-gamma from peripheral CD8+ T cells of tuberculosis patients, but not from peripheral blood mononuclear cells (PBMC) of healthy controls. Among the 25 patients with HIV/TB co-infection, the sensitivities of IGRA using the combination peptides (CP) and that using rESAT-6/CFP-10 (CE) were low (68% vs 48%, χ2=2.052, P=0.152). However, the sensitivity increased to 92% by using the combination of CP and CE, which was significantly higher than that using rESAT-6/CFP-10 alone (χ2=11.523, P<0.01), and the specificity was not affected. Conclusion These RD peptides with CD8+ T cell epitopes can increase the sensitivity of IGRA in detecting HIV/TB co-infection, which may improve the detection rate of tuberculosis in HIV infected population. Key words: TB/HIV coinfection; CD8-positive T-lymphocytes; Major histocompatibility complex class-Ⅰ; Epitope prediction; M. tuberculosis RD; Interferon gamma release assay