Evaluation of antibodies against human HSP60 in patients with MPO-ANCA associated glomerulonephritis: a cohort study.
Slot MC, Theunissen R, van Paassen P, Damoiseaux JG, Cohen Tervaert JW.
Dept, of Clinical and Experimental Immunology, University Hospital Maastricht, P,O, Box 5800, 6202 AZ Maastricht, The Netherlands. m.slot@immuno.unimaas.nl
BACKGROUND: Human Heat Shock Protein 60 (hHSP60) has been implicated in autoimmunity through molecular mimicry, based on the high degree of homology with HSP65 of micro-organisms leading to autoimmune recognition of the human protein. Additionally, sequence homology between hHSP60 and myeloperoxidase (MPO) has been described. MPO is a major autoantigen in vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA). We hypothesized that infections may trigger the ANCA response against MPO through hHSP60. METHODS: In 86 consecutive patients with ANCA-associated vasculitis (AAV), anti-hHSP60 and anti-mycobacterial HSP65 were measured by ELISA. Patients were compared with 69 healthy controls (HC). Continuous data between groups were compared using Wilcoxon signed rank test and Kruskal-Wallis test with Dunn's post-test when appropriate. Correlations between data were derived using Spearman correlation. Odds ratios and 95% confidence intervals were obtained using Fisher's exact test. RESULTS: At diagnosis, median anti-mHSP65 level was higher in AAV (median [range]: 42.5 [0-500]), and subsequently in MPO-ANCA (44 [7-500]), compared to HC (22 [0-430]). Anti-hHSP60 levels in AAV were not higher compared to HC (18 [0-319] and 18.5 [0-98], respectively). However, in MPO-ANCA anti-hHSP60 levels were increased (32.5 [0-319]) compared to PR3-ANCA (13 [0-79]) and HC. We could not detect cross-reactivity between hHSP60 and MPO-ANCA. There was a correlation between anti-mHSP65 and anti-hHSP60 levels (r = 0.32, P = 0.003) but not between anti-hHSP60 and MPO-ANCA (r = -0.064, P = 0.69). CONCLUSION: Antibodies against mHSP65 are higher in AAV compared to HC, and anti-hHSP60 antibodies are higher in patients with MPO-ANCA than in patients with PR3-ANCA and HC. Although this finding may be indicative for cross-reactivity between MPO-ANCA and hHSP60, additional assays did not support this hypothesis.
PMID: 16677376 [PubMed]PMCID: PMC1526731