CVI Accepts, published online ahead of print on 28 October 2009

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Clin. Vaccine Immunol. doi:10.1128/CVI.00208-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Peptide microarray – based identification of Mycobacterium tuberculosis epitope binding to HLA-DRB1*0101, DRB1*1501 and DRB1*0401

Simani Gaseitsiwe, Davide Valentini, Shahnaz Mahdavifar, Marie Reilly, Anneka Ehrnst, and Markus Maeurer^*

Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet Stockholm, Sweden; The Swedish Institute for Infectious Disease Control (SMI), Stockholm, Sweden; Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden

^* To whom correspondence should be addressed. Email: markus.maeurer{at}ki.se.

A more effective vaccine against Mycobacterium tuberculosis (Mtb) is needed and a number of Mtb vaccine candidates are currently in preclinical or clinical phase I/II studies. One of the strategies to select Mtb (protein) targets to elicit CD8+ or CD4+ T-cell response is to gauge binding of candidate peptides to MHC class I or – class II molecules, a prerequisite for successful peptide presentation and to expand antigen-specific T-cells. We scanned 61 proteins from the Mtb proteome for potential MHC class II – presented epitopes which could serve as targets for CD4+ T-cell responses. We constructed a peptide microarray, consisting of 7466 unique peptides, derived from 61 Mtb proteins. The peptides are 15mers overlapping by 12 amino acids. Soluble recombinant DRB1*0101(DR1), DRB1*1501(DR2) and DRB1*0401(DR4) monomers were used to gauge binding to individual peptide species. Out of 7466 peptides, 1282, 674, and 1854 peptides formed stable complexes with HLA-DR1, -DR2 and -DR4, respectively. 544 peptides bound to all three MHC class II molecules, 609 only to two, and 756 bound only to a single MHC class II molecule: this allows to rank Mtb proteins by epitope density. Mtb proteins contained ‘hotspots’, i.e. regions with enriched MHC class II-binding epitopes. 222 peptides, which formed MHC-class II/peptide complexes, have previously been described to be exclusively recognized by IgG in serum from patients with active pulmonary TB, but not in serum from healthy individuals, suggesting that these peptides serve as B- and CD4+ T cell epitopes. This work helps to identify not only Mtb peptides with immunogenic potential, but also the most immunogenic proteins. This information is useful for vaccine design and the development of future tools to explore immune responses to Mtb.