Identification of Naturally Presented Peptides of the Autoantigen Topoisomerase-I Reveals a Common Pathogenic Mechanism in Patients with Systemic Sclerosis

Eleni Tiniakou¹, Andrea Fava ², Zsuzsanna McMahan* ³, Tara Gurh ⁴, Robert O'Meally ⁴, Ami Shah ⁵, Frederick Wigley ³, Robert Cole ⁴, Francesco Boin ⁶ and Erika Darrah ¹, ¹Johns Hopkins University, Baltimore, MD, ²Johns Hopkins University School of Medicine, Baltimore, MD, ³Johns Hopkins University, Division of Rheumatology, Baltimore, ⁴Johns Hopkins University, Baltimore, ⁵Johns Hopkins Hospital, Baltimore, MD, ⁶UCSF, San Francisco, CA

Meeting: 2019 ACR/ARP Annual Meeting

Keywords: adaptive immunity, antigen-presenting cells, CD T cells and major histocompatibility complex (MHC), Systemic sclerosis

Session Information

Date: Tuesday, November 12, 2019

Title: 5T095: Systemic Sclerosis & Related Disorder – Basic Science (2744–2749)

Session Type: ACR Abstract Session

Session Time: 2:30PM-4:00PM

Background/Purpose: Autoimmune responses to DNA topoisomerase-I (TOP1) are found in a subset of patients with scleroderma at high risk for interstitial lung disease (ILD) and mortality. Anti-TOP1 antibodies (ATA) are associated with specific HLA-DRB1 alleles, and the frequency of HLA-DR-restricted TOP1-specific CD4+ T cells is associated with the presence, severity, and progression of ILD. Although this strongly implicates the presentation of TOP1 peptides by HLA-DR in scleroderma pathogenesis, the processing and presentation of TOP1 has not been studied.

Methods: We developed a novel natural antigen processing assay (NAPA) which relies on the sensitivity and specificity of the cellular MHC class II antigen processing machinery. Monocyte-derived dendritic cells were generated from six SSc patients with anti-Topo-I antibodies (ATA) and pulsed with Topo-I protein. HLA-DR:peptide complexes were isolated by immunoprecipitation and eluted peptides were analyzed by mass spectrometry. We then examined the ability of these naturally presented putative epitopes to induce CD4+ T cell activation, as measured by upregulation of the early activation marker CD154 in PBMCs from ATA-positive (n=11) and ATA-negative (n=11) SSc patients.

Results: Using NAPA, we found that presentation of TOP1 epitopes was restricted to only 10 hot spots within TOP1, across patients with different HLA-DR variants. Further analysis revealed shared peptide-binding motifs within the HLA-DRβ chains of ATA-positive patients and a subset of TOP1 epitopes with distinct sets of anchor residues capable of binding to multiple different HLA-DR variants. The naturally presented TOP1 peptides elicited robust CD4+ T cell responses in ATA-positive patients, and the number of epitopes recognized correlated with the severity of lung fibrosis (Figure 1).

Conclusion: This study suggests a mechanism in which autoimmunity to TOP1 in scleroderma is driven by the presentation of a communal set of TOP1 peptides in patients with diverse HLA-DRB1 alleles.

Figure 1. Distribution and clinical significance of CD4+ T cell responses to naturally presented TOP1 epitopes in SSc. -A- %CD154+CD4+ T cell responses over background observed with media alone for 11 ATA-positive and 11 ATA-negative SSc patients for each of the 10 naturally processed TOP1 peptides identified using NAPA are shown. The dotted line represents the cutoff for positivity that was defined as >95th percentile of the T cell responses observed in ATA-negative patients -95th percentile=0.015%-. Each colored symbol represents a unique patient. -B- The number of peptides eliciting a response in ATA-positive -n=11- and ATA-negative -n=11- SSc patients is shown -Mann-Whitney, p=0.02-. Open symbols represent patients that possess at least one ATA-associated HLA-DRB1 allele. -C- The minimum FVC -% of expected- was plotted against the number of TOP1 epitopes eliciting a T cell response in ATA-positive SSc patients with clinically documented ILD -n=9-. The correlation between minimum FVC and the number of stimulatory TOP1 epitopes was analyzed using a Spearman’s rho test. A p-value <0.05 was considered significant throughout.

Disclosure: E. Tiniakou, None; A. Fava, None; Z. McMahan*, None; T. Gurh, None; R. O'Meally, None; A. Shah, Bristol Meyer Squibb, 5, Bristol-Myers Squibb, 5; F. Wigley, None; R. Cole, None; F. Boin, None; E. Darrah, None.

To cite this abstract in AMA style:

Tiniakou E, Fava A, McMahan* Z, Gurh T, O'Meally R, Shah A, Wigley F, Cole R, Boin F, Darrah E. Identification of Naturally Presented Peptides of the Autoantigen Topoisomerase-I Reveals a Common Pathogenic Mechanism in Patients with Systemic Sclerosis [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/identification-of-naturally-presented-peptides-of-the-autoantigen-topoisomerase-i-reveals-a-common-pathogenic-mechanism-in-patients-with-systemic-sclerosis/. Accessed .

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