POS0829 SPECTRUM OF ANCA-SPECIFICITIES IN EOSINOPHILIC GRANULOMATOSIS WITH POLYANGIITIS IN A RETROSPECTIVE MULTICENTER STUDY

Background

Anti-neutrophil cytoplasmic autoantibodies specific for myeloperoxidase (MPO-ANCA) are found in 10-70% of the patients with eosinophilic granulomatosis with polyangiitis (EGPA) depending on disease activity, methodological aspects and cohort examined [1-3]. Recently, a higher prevalence of anti-pentraxin 3 (PTX3)-ANCA has been reported in EGPA compared to granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) [4].

Objectives

To investigate the spectrum of ANCA specificities in a multicenter cohort of patients with EGPA and identify novel ANCA antigens.

Methods

We conducted a retrospective analysis of 73 patients with EGPA treated between 2015 and 2020 in 3 tertiary referral centers. In addition to in-house ANCA testing with indirect immunofluorescence (IFT) on fixed human granulocytes and antigen-specific enzyme-linked immunosorbent assays (ELISA), ANCA specificities were determined using a cell-based assay (CBA; Euroimmun, Lübeck, Germany). Diagnosis was based on Chapel Hill consensus conference definitions, ACR- and MIRRA-criteria for EGPA. Patient characteristics and clinical manifestations were evaluated and compared based on ANCA status. Fisher`s exact test was employed for comparison of patient groups.

Results

ANCA findings are summarized in Table 1. MPO- and proteinase 3 (PR3)-ANCA positive patients (13.7%) had a higher prevalence of peripheral neuropathy (70% vs. 44.4%, p = 0.0003) and glomerulonephritis (20% vs. 14.3%, not significant). MPO- and PR3-ANCA-negative patients (86.3%) had a higher prevalence of heart (10% vs. 46%, p <0.0001), central nervous system (CNS) (0% vs. 14.3%, p <0.0001) and gastrointestinal (10% vs. 22.2%, p = 0.0327) involvement. PTX3-ANCA were associated with a higher prevalence of ear-nose-throat (ENT) (100% vs. 85.3%, p <0.0001), lung (100% vs. 89.7%, p = 0.0015), gastrointestinal involvement (60% vs. 17.6%, p <0.0001) and peripheral neuropathy (100% vs. 48.5%, p <0.0001). Kidney (0% vs. 16.2%, p <0.0001) and CNS involvement (0% vs. 13.2%, p = 0.0002) occurred less frequently in PTX3-ANCA positive patients. The 2 olfactomedin 4 (OLM4)-ANCA positive patients presented with ENT, lung and kidney involvement, and polyneuropathy, respectively.

Table 1.

ANCA in EGPA cohort (n = 73). BPI = bactericidal permeability-increasing protein.

IFT / ELISANo. of patients (%)P-ANCA11 (15.1)C-ANCA5 (6.8)MPO-ANCA8 (10.9)PR3-ANCA2 (2.7)BPI-ANCA1 (1.4)PTX3-ANCA5 (6.8)OLM4-ANCA2 (2.7)

Conclusion

We report on the detection of PTX3-, BPI- and OLM4-ANCA in addition to MPO- and PR3-ANCA in EGPA. OLM4-ANCA has been reported in 2 patients with non-vasculitic inflammatory symptoms previously [5]. Herein, detection of OLM4-ANCA in EGPA is reported for the first time. Our study shows that the presence of ANCA with various specificities other than MPO and PR3 contribute to a higher prevalence of ANCA in EGPA. Moreover, clinical manifestations differ between ANCA-negative EGPA and ANCA-positive EGPA, and between patients with different ANCA-specificities.

References

[1]Schönermarck U, et al. Prevalence and spectrum of rheumatic diseases associated with proteinase 3-antineutrophil cytoplasmic antibodies (ANCA) and myeloperoxidase-ANCA. Rheumatology 2001;40:178-84.

[2]Bremer P, et al. Getting rid of MPO-ANCA: a matter of disease subtype. Rheumatology 2013:752-4.

[3]Comarmond C, et al. Eosinophilic granulomatosis with polyangiitis (Churg-Strauss): clinical characteristics and long-term followup of the 383 patients enrolled in the French Vasculitis Study Group cohort. Arthritis Rheum 2013;65:270-81.

[4]Padoan R, et al. IgG anti-Pentraxin 3 antibodies are a novel biomarker of ANCA-associated vasculitis and better identify patients with eosinophilic granulomatosis with polyangiitis. J Autoimmun 2021;124:102725.

[5]Amirbeagi F, et al. Olfactomedin-4 autoantibodies give unusual c-ANCA staining patterns with reactivity to a subpopulation of neutrophils. J Leukoc Biol 2015;97:181-9.

Disclosure of Interests

None declared

Use of a Granulocyte Immunofluorescence Assay Designed for Humans for Detection of Antineutrophil Cytoplasmic Antibodies in Dogs with Chronic Enteropathies

BACKGROUND

Perinuclear antineutrophil cytoplasmic antibodies (pANCA) previously have been shown to be serum markers in dogs with chronic enteropathies, with dogs that have food-responsive disease (FRD) having higher frequencies of seropositivity than dogs with steroid-responsive disease (SRD). The indirect immunofluorescence (IIF) assay used in previous publications is time-consuming to perform, with low interobserver agreement.

HYPOTHESIS/OBJECTIVES

We hypothesized that a commercially available granulocyte IIF assay designed for humans could be used to detect perinuclear antineutrophil cytoplasmic antibodies in dogs.

ANIMALS

Forty-four dogs with FRD, 20 dogs with SRD, 20 control dogs, and 38 soft-coated wheaten terrier (SCWT) or SCWT-cross dogs.

METHODS

A granulocyte assay designed for humans was used to detect pANCA, cANCA, and antinuclear antibodies (ANA), as well as antibodies against proteinase-3 protein (PR-3) and myeloperoxidase protein (MPO) in archived serum samples.

RESULTS

Sensitivity of the granulocyte assay to predict FRD in dogs was 0.61 (95% confidence interval (CI), 0.45, 0.75), and specificity was 1.00 (95% CI, 0.91, 1.00). A significant association was identified between positive pANCA or cANCA result and diagnosis of FRD (P < 0.0001). Agreement between the two assays to detect ANCA in the same serum samples from SCWT with protein-losing enteropathy/protein-losing nephropathy (PLE/PLN) was substantial (kappa, 0.77; 95% CI, 0.53, 1.00). Eight ANCA-positive cases were positive for MPO or PR-3 antibodies.

CONCLUSIONS AND CLINICAL IMPORTANCE

The granulocyte immunofluorescence assay used in our pilot study was easy and quick to perform. Agreement with the previously published method was good.