Binding of conserved islet peptides by human and murine MHC class II molecules associated with susceptibility to type I diabetes

Abstract

The major histocompatibility complex (MHC) is the most important susceptibility locus for type I diabetes in humans and NOD mice. NOD mice express a single MHC class II molecule (I‐Ag7) which carries a unique β chain sequence. In humans, DQ alleles that encode DQ8 and DQ2 confer the highest risk for the disease. Soluble DQ8 and I‐Ag7 were used to directly compare the binding specificity of these MHC molecules. Peptides from three islet antigens – insulin, GAD 65 and HSP 60 – bound to both CQ8 and I‐Ag7. These peptides included epitopes that are immunodominant in NOD mice, namely insulin (9 – 23), GAD (206 – 220) and HSP 60 (441 – 460). All of these peptide sequences are highly conserved between the human and murine antigens. The binding specificity of DQ8 and I‐Ag7 was similar, but not identical, since two peptides eluted from splenocytes of NOD mice did not bind to DQ8. DQ8 formed long‐lived complexes with the majority of these peptides, indicating that DQ8 is not a poor peptide binder. These results demonstrate functional similarities between human and murine MHC class II molecules that confer susceptibility to type I diabetes.

The Insulin-Specific T Cells of Nonobese Diabetic Mice Recognize a Weak MHC-Binding Segment in More Than One Form

“…Truncation of the B:(9 -23) segment by one or two aminoterminal residues, to 10 -23 or 11-23, did not affect the binding. The dissociation of the B:(9 -23) peptide was found to be relatively fast with loss of 45-75% of the bound peptide in 2 h, in agreement with the data previously published by Wucherpfennig's laboratory (18), which also demonstrated the poor binding of insulin peptides.…”

“…Indeed, the insulin B:(9 -23) peptide was shown to bind to I-A g7 (16 -19); however, the detailed nature of its binding to the MHC molecule was not evaluated, although the issue of a weak interaction has been alluded to as evidenced by its fast dissociation rate (18).…”

HLA-DQ8-Associated T Cell Responses to the Diabetes Autoantigen Phogrin (IA-2β) in Human Prediabetes

“…Thus, peptides from the humoral autoantigens insulin, GAD65, and heat shock protein 60 (including the immunodominant peptides of these Ags in the NOD mouse) bind to both HLA-DQ8 and I-A g7 (29), albeit with differing affinities. Similarly, PBMC responses to (pro)insulin and GAD65 and their corresponding peptide epitopes have been observed (24,30).…”

Promiscuous binding of proinsulin peptides to Type 1 diabetes-permissive and -protective HLA class II molecules

“…Synthetic preproinsulin peptides were assessed for their ability to bind soluble HLA-class II molecules in vitro in a direct competition binding assay against a biotinylated indicator peptide. These indicator peptides comprised residues 98-117 of the MHC class II invariant chain peptide (PKPPKPVSKMRMATPLLMQA, for HLA-DR4 and -DQ6.2) [13], residues 430-444 of the HSV-2 transcriptional activator VP16 (EEVDMTPADALDDFD, for HLA-DQ8) [14] and residues 307-319 of influenza haemagglutinin (PKYVKQNTLKLAT, for HLA-DR2) [12]. We then incubated 12 µg of immunoaffinity-purified HLA class II protein with 2.5 µmol·l −1 biotinylated indicator peptide and test peptide or non-biotinylated indicator peptide at a range of concentrations (0.1-100 µmol·l −1 ) in a final DMSO concentration of 20% in 20 mmol·l −1 2-[N-morpholino]ethanesulfonic acid, 1% w/v n-octylglucoside, 140 mmol·l −1 sodium chloride, 0.05% sodium azide, pH 5, for 20 h at room temperature.…”