Molecular recognition patterns of anti-topoisomerase I-antibodies in patients with systemic sclerosis before and after autologous stem cell transplantation

Objective. To evaluate the effect of autologous stem cell transplantation (aSCT) on antibody (ab) reactivity towards linear epitopes of topoisomerase-I (topo-I/Scl70) in patients with systemic sclerosis (SSc) and to correlate antibody reactivities with clinical outcome after aSCT. Methods. Fourteen anti-topo-I/Scl70-positive SSc-patients were analysed before and after non-myeloablative aSCT. Five patients showed ongoing good response (group 1), 9 had primarily responded but later relapsed or did not respond (group 2). Patients' sera were tested by ELISA against full length (fl) topo-I and 45 overlapping 25-mer peptides. Furthermore, for comparison sera from patients with anti-topo-I-negative SSc (n=12), other collagen disorders (n=6), and from 21 healthy controls (HC) were analysed. Results. Anti-topo-I-positive SSc-sera showed significantly higher IgG-reactivity as compared to HC towards 34 of the 45 peptides. Especially peptide 39 (aa647-671) emerged as a immunodominant epitope being recognised predominantly by anti-topo-I-positive SSc-sera. Reactivity towards 17 of the 45 peptides decreased after aSCT in group 1- and 2-patients. Before aSCT, group 1-patients had lower antibody reactivity towards peptide 39 than group 2-patients. There was no change in peptide-specificity after aSCT. Conclusion. Reactivity towards topo-I-epitopes is heterogeneous in SSc, but peptide 39 (aa647-671) may be another immunodominant epitope besides the published epitope aa489-573. Antibody reactivity to this peptide 39 was higher in group 2-than in group 1-patients. Peptide recognition pattern did not change after aSCT.