Topoisomerase I peptide-loaded dendritic cells induce autoantibody response as well as skin and lung fibrosis

Abstract

DNA Topoisomerase I (TopoI) is a candidate autoantigen for diffuse cutaneous systemic sclerosis (dcSSc) associated with fatal lung disease. Dendritic cells (DCs) contribute to bleomycin-induced lung fibrosis. However, the possibility that TopoI-loaded DCs are involved in the initiation and/or perpetuation of dcSSc has not been explored. Here, we show that immunization with TopoI peptide-loaded DCs induces anti-TopoI autoantibody response and long-term fibrosis. Mice were repeatedly immunized with unpulsed DCs or DCs loaded with either TOPOIA or TOPOIB peptides, selected from different regions of TopoI. At week 12 after initial DC immunization, TOPOIA DCs but not TOPOIB DCs immunization induced mixed inflammation and fibrosis in lungs and skin. At a late time point (week 18), both TOPOIA DCs and TOPOIB DCs groups displayed increased alpha-smooth muscle actin expression in lungs and dermis along with skin fibrosis distal from the site of injection when compared with unpulsed DCs. Both TopoI peptide-DC-immunized groups developed IgG2a anti-TopoI autoantibody response. At week 10, signs of perivascular, peribronchial, and parenchymal pulmonary inflammation were already observed in the TOPOIA DCs group, together with transient elevation in bronchoalveolar lavage cell counts, IL-17A expression, and CXCL4 production, a biomarker of early human dcSSc. Collectively, TopoI peptide DCs induce progressive autoantibody response as well as development of protracted skin and lung dcSSc-like disease. Pronounced lung inflammation, transient IL-17A, and CXCL4 expression precede fibrosis development. Our immunization strategy, that uses self immune system and autoantigen, will help to further investigate the pathogenesis of this complex autoimmune disorder with unmet medical needs.

Keywords:

• Systemic sclerosis
• dendritic cells
• inflammation
• fibrosis
• anti-Topoisomerase I

Acknowledgements

The authors thank Véronique Barrès, Gabriela Fragoso, and Christine Caron of the cytometry, cell imaging and molecular pathology core facility of the CRCHUM for performing the immunohistochemistry and scanning.

Declaration of interest

The authors declare no conflict of interest. This work was supported by an operating grant from the CRCHUM, by research grants from Sclérodermie Québec, Scleroderma Society of Ontario and Scleroderma Canada. Donations were given by Mrs Gisèle Sarrazin-Locas in support of the Laboratory for Research in Autoimmunity. J. L. S. holds the University of Montreal Scleroderma Research Chair.

Supplementary material available online.

Supplementary Figures S1–S3.