Specific glycosylation of α1-acid glycoprotein characterises patients with familial Mediterranean fever and obligatory carriers of MEFV

Abstract

Background - Familial Mediterranean fever (FMF) is a periodic febrile disorder, characterised by fever and serositis. The acute phase response during attacks of FMF results from the release of cytokines, which in turn induce increased expression and changed glycosylation of acute phase proteins. A recent study indicated that attacks in FMF are accompanied by a rise of plasma concentrations of serum amyloid A (SAA) and C reactive protein (CRP), which remain significantly raised during remission relative to healthy controls. Another study suggested that obligatory heterozygotes also display an inflammatory acute phase response. Objective - To determine the state of inflammation in homozygotic and heterozygotic MEFV genotypes. Methods - CRP and SAA were studied by enzyme linked immunosorbent assay (ELISA). The glycosylation of the acute phase protein, α1-acid glycoprotein (AGP), was visualised with crossed affinoimmuno-electrophoresis with concanavalin A as diantennary glycan-specific component and Aleuria aurantia lectin as fucose-specific affinity component. Results - FMF attacks were associated with an increase (p<0.05) in the serum inflammation parameters CRP, SAA, and AGP. The glycosylation of AGP showed an increase (p<0.05) in fucosylated AGP glycoforms, whereas the branching of the glycans remained unaffected. The glycosylation of AGP in the MEFV carrier group, compared with that in a healthy control group, was characterised by a significant increase (p<0.05) in branching of the glycans, whereas the fucosylation remained unaffected. Conclusion - The findings suggest an FMF-specific release of cytokines, resulting in a different glycosylation of AGP between a homozygotic and heterozygotic MEFV genotype.