Identification of tuberculosis-associated proteins in whole blood supernatant

Takahiro Tanaka,Luu Thi Lien,Keiko Kano,Takafumi Uchida,Nguyen Thi Le Hang,Yasushi Kaburagi,Kazuki Yasuda,Naoto Keicho,Shinsaku Sakurada,Minako Hijikata,Eri Takahashi,Hisashi Hirano,Ikumi Matsushita,Nobuyuki Kobayashi

doi:10.1186/1471-2334-11-71

Abstract

BackgroundBiological parameters are useful tools for understanding and monitoring complicated disease processes. In this study, we attempted to identify proteins associated with active pulmonary tuberculosis (TB) using a proteomic approach.MethodsTo assess TB-associated changes in the composition of human proteins, whole blood supernatants were collected from patients with active TB and healthy control subjects. Two-dimensional difference gel electrophoresis (2D-DIGE) was performed to analyze proteins with high molecular weights (approximately >20 kDa). Baseline protein levels were initially compared between patients with active TB and control subjects. Possible changes of protein patterns in active TB were also compared ex vivo between whole blood samples incubated with Mycobacterium tuberculosis (Mtb)-specific antigens (stimulated condition) and under unstimulated conditions. Immunoblot and enzyme-linked immunosorbent assays (ELISA) were performed to confirm differences in identified proteins.ResultsUnder the baseline condition, we found that the levels of retinol-binding protein 4 (RBP4), fetuin-A (also called α-HS-glycoprotein), and vitamin D-binding protein differed between patients with active TB and control subjects on 2D gels. Immunoblotting results confirmed differential expression of RBP4 and fetuin-A. ELISA results further confirmed significantly lower levels of these two proteins in samples from patients with active TB than in control subjects (P < 0.0001). Mtb-specific antigen stimulation ex vivo altered clusterin expression in whole blood samples collected from patients with active TB.ConclusionsWe identified TB-associated proteins in whole blood supernatants. The dynamics of protein expression during disease progression may improve our understanding of the pathogenesis of TB.

Highlights

Biological parameters are useful tools for understanding and monitoring complicated disease processes
In our comparison of the protein expression profiles of patients with active TB and control subjects, red indicates proteins increased in the supernatants collected from the patients and green indicates proteins decreased in the patients compared with the control subjects
In 2D gel profiles comparing the antigen-stimulated and unstimulated samples collected from patients with active TB, red indicates proteins increased in the supernatants after Mycobacterium tuberculosis (Mtb)-specific antigen stimulation, and green indicates proteins decreased after stimulation

Summary

Introduction

Biological parameters are useful tools for understanding and monitoring complicated disease processes. We attempted to identify proteins associated with active pulmonary tuberculosis (TB) using a proteomic approach. Recent advances in comprehensive analytical techniques, such as transcriptomics and proteomics, have enabled us to identify proteins associated with active TB in humans. Agranoff et al [4] identified amyloid A and transthyretin in human serum as potential indicators for distinguishing patients with TB from those with non-TB inflammatory conditions. They reported that a combination of four protein markers, including amyloid A and transthyretin, achieved a diagnostic accuracy of up to 78%. The above studies are promising, such comprehensive analytical techniques are still in the developmental stages and further investigations are required before they can be applied clinically

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Discussion

Conclusion