P093 : PRESENTATION OF ESX FAMILY PROTEINS BY CLASSICAL AND NON-CLASSICAL CLASS I HLA AFTER M. TUBERCULOSIS INFECTION

Abstract

Aim CTL responses against M. tuberculosis (Mtb) are known to be restricted primarily by HLA-B and non-classical MHC molecules such as HLA-E, CD1, and MR1. While a few Mtb derived ligands have been identified in the context of these MHC, we do not have a thorough understanding of the proteins that are sampled by HLA molecules following Mtb infection. Here we identify the Mtb proteins sampled by the non-classical class I HLA-E ∗ 01:03 and the classical class I HLA-B ∗ 44:02. Method Soluble HLA-E ∗ 01:03 and HLA-B ∗ 44:01 were harvested from Mtb (strain H37Rv) infected antigen presenting cells U373 glioblastoma cells. Peptide ligand pools from these MHC were isolated and MS spectra collected using 2-dimensional LCMS. Peptide sequences were assigned from fragment spectra analyzed with the PEAKS and Mascot algorithms using the decoy database search at a 1% False Discovery Rate. All sequences were validated with MS fragmentation of the corresponding synthetic peptide. Results In this study we identified a total of 49 Mtb specific ligands presented by HLA. For HLA-E we found 28 ligands from 14 source proteins. In the classical class I HLA-B44, we identified 21 ligands from 8 different proteins. Strikingly, both HLA-E and HLA-B44 frequently sampled esx family proteins with 50% and 66% of the ligands originating from esx proteins for HLA-E and HLA-B44, respectively. Additionally a hypothetical protein lpq1 (Rv0237) was sampled by both HLA-E and HLA-B44. Conclusions Esx family proteins are known virulence factors for Mtb, and are highly antigenic in a natural infection. Further, esx family proteins are absent from widely used the BCG tuberculosis vaccine. Here, we found that both classical and non-classical HLA consistently sample these esx proteins further confirming their role in the adaptive immune response to Mtb.