Clinical Features of Patients with Anti-Neutrophil Cytoplasmic Autoantibodies Targeting Native Myeloperoxidase Antigen

Yuji Yamanishi¹, Toshiko Ito-Ihara², Shigeto Kobayashi³, Peter Y. Shane⁴, Gary S. Firestein⁵, Hiroshi Hashimoto⁶ and Kazuo Suzuki⁷, ¹Division of Rheumatology, Hiroshima Rheumatology Clinic, Hiroshima, Japan, ²Department of Clinical Innovative Medicine, Translational Research Center, Kyoto University Hospital, Kyoto, Japan, ³Department of Internal Medicine, Juntendo University Koshigaya Hospital, Tokyo, Japan, ⁴Tokyo Medical and Dental University, Tokyo, Japan, ⁵Div of Rheumatology, UCSD School of Medicine, La Jolla, CA, ⁶Juntendo Tokyo Koto Geriatric Center, Tokyo, Japan, ⁷National Institute of Infectious Diseases, Tokyo, Japan

Meeting: 2012 ACR/ARHP Annual Meeting

Keywords: ANCA, Enzyme-Linked Immunoabsorbant Assays (ELISA), myeloperoxidase (MPO) and vasculitis

Session Information

Title: Vasculitis

Session Type: Abstract Submissions (ACR)

Background/Purpose: ANCA is a useful diagnostic marker in systemic vasculitic disorders with small-vessel involvement, but depending on the particular test used the myeloperoxidase (MPO)-ANCA results are variable. Unfortunately, the exact origins of the antigens used in most commercial assays have been confidential. In the present study, we performed a comparative analysis between a novel MPO-ANCA assay that targets the native MPO (nMPO) antigen and commercially available assays using sera of patients with clinical features of ANCA-associated vasculitis (AAV).

Methods: Serum samples from 24 patients strongly suspected of having AAV were tested for the presence of MPO-ANCAs by the novel nMPO-ANCA assay and by other commercial-based MPO-ANCA assays. These results were correlated to indirect immunofluorescence microscopy staining patterns and patient clinical parameters.

Results: Eighteen out of 24 patients (75%) were positive for nMPO-ANCA compared to 13 out of 24 patients (54%) by one of the most frequently used commercial-based MPO-ANCA ELISA assays in Japan. Interestingly, the patients that tested positive with our nMPO-ANCA assay alone showed clinical features of AAV marked by prolonged fever, polyarthritis, and mild nephritis. The titers of nMPO-ANCA decreased in association with clinical improvement after treatment.

Conclusion: Our data suggest that a positive nMPO-ANCA result, which identifies antibodies to human native MPO antigen, identifies patients with a subset of patients with AAV and a distinct clinical profile. In addition, the titer appeared to correlate with AAV disease activity. While additional studies in larger patient populations will be needed, the nMPO-ANCA test could have clinical utility in detecting AAV-affected patients who have tested negative using commercially available assays.

Disclosure:

Y. Yamanishi,
None;

T. Ito-Ihara,
None;

S. Kobayashi,
None;

P. Y. Shane,

UCB Japan,

G. S. Firestein,
None;

H. Hashimoto,
None;

K. Suzuki,
None.

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