Beryllium binding to HLA-DP molecule carrying the marker of susceptibility to berylliosis glutamate β69

Abstract

Berylliosis is a chronic granulomatous disorder caused by inhalation of Be dusts that is driven by the accumulation Be-specific CD4+ Th1-cells at disease sites. Susceptibility to berylliosis has been associated with the supratypic variant of HLA-DP gene coding for glutamate at position β69 (HLA-DPβGlu69). The aim of this study was to test the hypothesis that the HLA-DPβGlu69 residue plays a role in the interaction with Be. To this end, soluble HLA-DP2 molecule (carrying βGlu69) and its mutated form carrying lysine at position β69 (HLA-DP2Lys69) were produced in Drosophila melanogaster and then used in a Be binding assays. BeSO 4 (1–1000 μM) was used to compete for the binding of the biotinilated invariant chain-derived peptide CLIP (50 μM). BeSO 4 was capable of compete out biotin-CLIP binding from the HLA-DP2 (IC50%: 4.5 μM of BeSO 4 at pH 5.0 and 5.5 μM of BeSO 4 at pH 7.5), but not from the HLA-DP2Lys69 molecule (IC50%: 480 μM of BeSO 4 at pH 5.0 and 220 μM of BeSO 4 at pH 7.5). Moreover, the binding of NFLD.M60, a MoAb recognizing an epitope in the HLA-DP peptide binding region, to the HLA-DP2, but not to the HLA-DP2Lys69 soluble molecules was inhibited BeSO 4. NFLD.M60 binding to HLA-DP2, but not to HLA-DP2Lys69 stably transfected murine cells was also inhibited by Be both at pH 5.0 and at pH 7.5. The data indicate a direct interaction of Be with the HLA-DPGlu69 molecule, in the absence of antigen processing.