Mycobacterium tuberculosis Lipolytic Enzymes as Potential Biomarkers for the Diagnosis of Active Tuberculosis

Belinda Brust,Stéphane Canaan,Viviane Valverde,Edouard Tuaillon,Mélanie Lecoufle,Luc Dedieu,Laurent Kremer,Volker Briken

doi:10.1371/journal.pone.0025078

Abstract

BackgroundNew diagnosis tests are urgently needed to address the global tuberculosis (TB) burden and to improve control programs especially in resource-limited settings. An effective in vitro diagnostic of TB based on serological methods would be regarded as an attractive progress because immunoassays are simple, rapid, inexpensive, and may offer the possibility to detect cases missed by standard sputum smear microscopy. However, currently available serology tests for TB are highly variable in sensitivity and specificity. Lipolytic enzymes have recently emerged as key factors in lipid metabolization during dormancy and/or exit of the non-replicating growth phase, a prerequisite step of TB reactivation. The focus of this study was to analyze and compare the potential of four Mycobacterium tuberculosis lipolytic enzymes (LipY, Rv0183, Rv1984c and Rv3452) as new markers in the serodiagnosis of active TB.MethodsRecombinant proteins were produced and used in optimized ELISA aimed to detect IgG and IgM serum antibodies against the four lipolytic enzymes. The capacity of the assays to identify infection was evaluated in patients with either active TB or latent TB and compared with two distinct control groups consisting of BCG-vaccinated blood donors and hospitalized non-TB individuals.ResultsA robust humoral response was detected in patients with active TB whereas antibodies against lipolytic enzymes were infrequently detected in either uninfected groups or in subjects with latent infection. High specifity levels, ranging from 93.9% to 97.5%, were obtained for all four antigens with sensitivity values ranging from 73.4% to 90.5%, with Rv3452 displaying the highest performances. Patients with active TB usually exhibited strong IgG responses but poor IgM responses.ConclusionThese results clearly indicate that the lipolytic enzymes tested are strongly immunogenic allowing to distinguish active from latent TB infections. They appear as potent biomarkers providing high sensitivity and specificity levels for the immunodiagnosis of active TB.

Highlights

Tuberculosis (TB) which is caused by Mycobacterium tuberculosis (Mtb), remains one of the leading causes of death in the world [1]
The increasing global health burden of TB is further aggravated by the alarming increase of the number of people living with HIV and the emergence of multi- and extensively drug-resistant Mtb strains, which requires a longer, more costly therapeutic regimen [3,4]
The tuberculin skin test based on the use of purified protein derivative (PPD) is the only available immune-based diagnostic test for clinical use in most developing countries

Summary

Introduction

Tuberculosis (TB) which is caused by Mycobacterium tuberculosis (Mtb), remains one of the leading causes of death in the world [1]. Especially in resource constrain areas, the diagnosis of TB largely relies on the detection of acid-fast bacilli in sputum in conjunction with assessment of clinical symptoms and X-ray radiographic evidence. These evaluations offer suboptimal diagnosis performances and are time-consuming. Prior vaccination with BCG and cross-reaction with other mycobacterial species result in a poor specificity of this century-old test [5]. This test does not permit to clearly distinguish between the active and latent form of TB infection. The focus of this study was to analyze and compare the potential of four Mycobacterium tuberculosis lipolytic enzymes (LipY, Rv0183, Rv1984c and Rv3452) as new markers in the serodiagnosis of active TB

Methods

Results

Discussion

Conclusion