Background: Ankylosing spondylitis (AS) is an immune-mediated inflammatory disease of the musculoskeletal system, that is often accompanied with a subclinical intestinal inflammation. Inflammatory bowel diseases (IBD), including, Crohn’s disease (CD) and ulcerative colitis (UC), are the most frequent extra-articular manifestation in patients (pts) with AS. Several autoantibodies and antimicrobial antibodies are used as additional non-invasive serological markers for the diagnosis of CD and UC [1]. The evaluation of IBD-associated antibodies in AS pts provided conflicting results [2, 3].

Objectives: The aim of the study was to determine the serum levels of IBD-specific antibodies in AS.

Methods: We studied 51 pts with AS fulfilled modified New York criteria (1984); (40M/11F); median and interquartile range (25th—75th percentile) of age 44.0; 34.0-49.0 years; disease duration 12.0; 5.0-20.0 years; BASDAI - 5.3; 4.5-6.4; ASDAS ESR - 3.6; 3.0-4.4; ASDAS CRP - 3.7; 2.8-4.5; 40% HLA-27 positive. In 22% of pts with AS, IBD (CD and UC) were diagnosed. The control group included 44 healthy donors (HC). Atypical perinuclear anti-neutrophil cytoplasmic antibodies (pANCA) were detected using indirect immunofluorescence. The serum levels of IgA/IgG antibodies to Saccharomyces cerevisiae (ASCA), IgA/IgG antibodies to glycoprotein 2 (GP2), IgG antibodies to cathepsin G, lactoferrin, elastase and bactericidal permeability-increasing protein (BPI) were detected by ELISA.

Results: AS pts without signs of IBD and AS with IBD (AS/IBD) pts had significantly higher serum levels of IgA ASCA, IgA anti-GP2, anti-elastase antibodies than HC (4.5; 2.6-6.4 U/ml and 4.9; 3.7-7.3 U/ml vs 1.9; 0.6-2.6 U/ml, p=0.0008, p=0.001; 1.2; 0.8-5.5 U/ml and 1.2; 0.9-11.8 U/ml vs 0.7; 0.6-1.3 U/ml, p=0.007, p=0.02; 8.2; 5.9-9.9 U/ml and 9.1; 8.5-10.5 U/ml vs 5.6; 4.7-8.3 U/ml, p=0.01, p=0.003). The median concentration of anti-cathepsin G antibodies was greater for AS/IBD pts than AS pts (0.8; 0.5-1.0 U/ml vs 0.4; 0.3-0.6 U/ml, p=0.02). In AS and AS/IBD, the occurrence of anti-elastase antibodies (23.0%, 33.0%) was higher than for HC (0%, p=0.05, p=0.01). The positivity rate of IgA anti-GP2 in AS/IBD exceeded that in HC (27.0% vs 0%, p=0.025). AS/IBD pts demonstrated a higher prevalence of pANCA (36.0%), and anti-BPI antibodies (36.0%), when compared to AS alone (4.8%, p=0.005, and 8.0%, p=0.02) and HC (0%, p=0.0001, and 0%, p=0.008).

Conclusion: Our findings indicate that elevated serum levels of IgA ASCA, IgA anti-GP2, anti-elastase antibodies in AS did not differ from those in AS/IBD and may serve as potential biomarkers for predicting intestinal inflammation at an early stage. For AS/IBD, the most useful diagnostic markers were atypical pANCA, IgA ASCA, IgA anti-GP2, anti-elastase and anti-BPI antibodies.

REFERENCES:

[1]Prideaux L, De Cruz P, Ng SC, Kamm MA. Serological antibodies in inflammatory bowel disease: a systematic review. Inflamm Bowel Dis. 2012; 18(7):1340-55.

[2]Benfaremo D, Luchetti M, Gabrielli A. Biomarkers in inflammatory bowel disease-associated spondyloarthritis: state of the art and unmet needs. J Immunol Res. 2019 May 30; 2019:8630871.

[3]De Vries M, Van Der Horst-Bruinsma I, Van Hoogstraten I., et al. pANCA, ASCA, and OmpC antibodies in patients with ankylosing spondylitis without inflammatory bowel disease. J Rheumatol. 2010; 37(11):2340–4.

Disclosure of Interests: None declared