HLA-A02 restricted T-cell cross-reactivity to a microbial antigen

Area of Science:

• Immunology
• Molecular Biology
• Microbiology

Background:

• Molecular mimicry is a proposed mechanism for autoimmunity, potentially causing diseases like Type 1 diabetes (T1D).
• A key T1D target in the NOD mouse model is a peptide from the islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP).
• HLA-A02 is the most common human MHC-I allele, making it a relevant focus for T1D research.

Purpose of the Study:

• To identify a potential human IGRP epitope restricted by HLA-A0201.
• To investigate if bacterial proteins can mimic this epitope and trigger an immune response.
• To explore the role of molecular mimicry in initiating T-cell-mediated autoimmunity.

Main Methods:

• Identified a potential HLA-A0201-restricted human IGRP epitope (YLKTNLFLFL).
• Discovered a homologous HLA-A0201-restricted peptide in an Enterococcal protein.
• Incubated CD8+ T-cells from healthy human donors with the synthetic bacterial peptide.

Main Results:

• Healthy HLA-A0201+ donor CD8+ T-cells showed increased staining for human IGRP-peptide-dextramer after incubation with the bacterial peptide.
• Control cultures lacked significant dextramer-staining CD8+ T-cells.
• This suggests the bacterial peptide can elicit a cross-reactive immune response.

Conclusions:

• Bacterial proteins can mimic human autoantigens, such as IGRP.
• This mimicry can initiate CD8+ T-cell-mediated immune reactions towards self-antigens.
• Bacterial infections may play a role in the induction of Type 1 diabetes and other autoimmune diseases.