Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


Antibodies to Sulfated N-Acetyllactosamine (LacNAc) Are Prevalent in Patients with Systemic Sclerosis and Associated with Pulmonary Hypertension

Grader-Beck1,  Thomas, Boin1,  Francesco, von Gunten2,  Stephan, Smith3,  David F., Rosen1,  Antony, Bochner4,  Bruce S.

Johns Hopkins University School of Medicine, Baltimore, MD
University of Bern, Bern, Switzerland
Emory University School of Medicine, Atlanta, GA
Johns Hopkins Asthma and Allergy Center. Baltimore, MD

Purpose:

Differential glycosylation of proteins and lipids plays an important role in the regulation of numerous physiological processes. The endothelium and extracellular matrix, two key tissue components affected in systemic sclerosis (SSc), contain various highly glycosylated structures (glycans). We hypothesized that the immune response in SSc may target distinct glycans, leading to the development of specific anti-glycan antibodies.

Method:

A printed glycan array containing 320 glycans was used to screen pooled sera from 40 randomly selected SSc patients and 40 healthy controls for anti-glycan antibodies. Binding was quantified by fluorescence. Antibodies to sulfated LacNac were determined in 181 individual sera from SSc patients and 40 healthy controls by ELISA using an anti-human Fc gamma specific secondary antibody for detection, a high-titer positive SSc serum as standard and a cut-off of 3 SD above healthy controls. Statistical analysis of clinical associations was performed using student's t-test and logistic regression.

Results:

Sulfated LacNac was identified as a dominant target of SSc sera initially by printed glycan array screening. Immunogenicity was predominantly conferred by sulfation at position 4 of galactose (4S-LacNAc), but not at position 3 or 6 (13.6 fold; 3.0 fold and 0.9 fold compared to controls; respectively). Subsequently, an anti-sulfated LacNAc specific ELISA was developed to screen individual sera. 27/181 (14.9%) patients were positive for anti-4S-LacNAc antibodies compared to only 1/40 (2.5%) of healthy controls. Anti-4S-LacNAc positive SSc patients had a higher prevalence of pulmonary hypertension as determined by an RVSP > 40 mmHg on echocardiogram (15/27; 55.7% versus anti-4S LacNac negative patients 49/154; 31.8% p=0.02). The odds ratio for pulmonary hypertension was 2.6 (1.1, 6.3) after adjusting for age, gender, race and disease type. Anti-4S-LacNAc positive patients accounted for 23.4% of all patients with pulmonary hypertension. There was no association between anti-4S-LacNAc positivity and disease type (limited versus diffuse SSc) or the presence of anti-topoisomerase I or anti-centromere antibodies.

Conclusion:

This is the first study to report that sera from SSc patients contain high titer IgG antibodies targeting glycan structures. 4S-LacNac was identified as a frequent target of the antibody response in SSc and antibody positivity was associated with echocardiographic evidence of pulmonary hypertension. These results suggest that specific posttranslational carbohydrate modifications may act as important immunogens in SSc. Further studies will determine whether these antibodies target 4 sulfated LacNAc expressed on the endothelium or extracellular matrix and thus may play a role in disease pathogenesis.

To cite this abstract, please use the following information:
Grader-Beck, Thomas, Boin, Francesco, von Gunten, Stephan, Smith, David F., Rosen, Antony, Bochner, Bruce S.; Antibodies to Sulfated N-Acetyllactosamine (LacNAc) Are Prevalent in Patients with Systemic Sclerosis and Associated with Pulmonary Hypertension [abstract]. Arthritis Rheum 2009;60 Suppl 10 :455
DOI: 10.1002/art.25537

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