Mycobacterium leprae virulence-associated peptides are indicators of exposure to M. leprae in Brazil, Ethiopia and Nepal

Kidist Bobosha,Kees Lmc Franken,Jemal Hussien,Marcia Vsb Martins,Abraham Aseffa,Chhatra B Kunwar,Saraswoti Khadge,Maria Araci De Andrade Pontes,Maria Cristina Vidal Pessolani,Deanna A Hagge,Geraldo Mb Pereira,Ole Lund,Sheila Tuyet Tang,Pratibha Thapa,Jolien J Van Der Ploeg-Van Schip,Heitor De Sá Gonçalves,Annemieke Geluk,Yonas Bekele,Tom Hm Ottenhoff

doi:10.1590/s0074-02762012000900018

Abstract

Silent transmission of Mycobacterium leprae, as evidenced by stable leprosy incidence rates in various countries, remains a health challenge despite the implementation of multidrug therapy worldwide. Therefore, the development of tools for the early diagnosis of M. leprae infection should be emphasised in leprosy research. As part of the continuing effort to identify antigens that have diagnostic potential, unique M. leprae peptides derived from predicted virulence-associated proteins (group IV.A) were identified using advanced genome pattern programs and bioinformatics. Based on human leukocyte antigen (HLA)-binding motifs, we selected 21 peptides that were predicted to be promiscuous HLA-class I T-cell epitopes and eight peptides that were predicted to be HLA-class II restricted T-cell epitopes for field-testing in Brazil, Ethiopia and Nepal. High levels of interferon (IFN)-γ were induced when peripheral blood mononuclear cells (PBMCs) from tuberculoid/borderline tuberculoid leprosy patients located in Brazil and Ethiopia were stimulated with the ML2055 p35 peptide. PBMCs that were isolated from healthy endemic controls living in areas with high leprosy prevalence (EChigh) in Ethiopia also responded to the ML2055 p35 peptide. The Brazilian EChigh group recognised the ML1358 p20 and ML1358 p24 peptides. None of the peptides were recognised by PBMCs from healthy controls living in non-endemic region. In Nepal, mixtures of these peptides induced the production of IFN-γ by the PBMCs of leprosy patients and EChigh. Therefore, the M. leprae virulence-associated peptides identified in this study may be useful for identifying exposure to M. leprae in population with differing HLA polymorphisms.

Highlights

Maria Araci de Andrade Pontes6, Heitor de Sá Gonçalves6, Jemal Hussien2, Pratibha Thapa5, Chhatra B Kunwar5, Deanna A Hagge5, Abraham Aseffa2, Maria Cristina Vidal Pessolani4, Geraldo multibacillary leprosy (MB) Pereira7, Tom HM Ottenhoff1, Annemieke Geluk1/+
In vitro analysis of these synthetic peptides was performed using peripheral blood mononuclear cells (PBMCs) or whole blood isolated from lepromatous leprosy/borderline tuberculoid (TT/BT) and borderline lepromatous/lepromatous leprosy (BL/LL) patients and healthy endemic controls (ECs) who were located in Brazil, Ethiopia and Nepal in areas with high (EChigh) or low (EClow) leprosy prevalence
Using genomic sequences that are available and these improved bio-informatics tools, we identified unique M. leprae candidate antigens that were screened in silico to identify potential T-cell epitopes (Fig. 1, Materials and Methods section)

Summary

Introduction

Maria Araci de Andrade Pontes, Heitor de Sá Gonçalves, Jemal Hussien, Pratibha Thapa, Chhatra B Kunwar, Deanna A Hagge, Abraham Aseffa, Maria Cristina Vidal Pessolani, Geraldo MB Pereira, Tom HM Ottenhoff, Annemieke Geluk1/+. The recent availability of improved bioinformatics tools and the genome sequence of M. leprae have resulted in new possibilities for leprosy research These advances have enabled the prediction of relevant M. leprae proteins and potential human leukocyte antigen (HLA) class I and class II epitopes that can activate T-cells (Geluk et al 2011). The use of unique M. leprae antigens that were identified using post-genomic approaches has resulted in the detection of M. leprae protein or peptide-specific T-cell responses These responses may help identify M. leprae-exposed or infected individuals (Geluk et al 2005, 2009, Spencer et al 2005, Araoz et al 2006, Bobosha et al 2011, 2012). In vitro analysis of these synthetic peptides was performed using peripheral blood mononuclear cells (PBMCs) or whole blood isolated from lepromatous leprosy/borderline tuberculoid (TT/BT) and borderline lepromatous/lepromatous leprosy (BL/LL) patients and healthy endemic controls (ECs) who were located in Brazil, Ethiopia and Nepal in areas with high (EChigh) or low (EClow) leprosy prevalence

Objectives

Results

Conclusion