Serum profile of transferrin isoforms in rheumatoid arthritis treated with biological drugs

Background: In the chronic inflammation process in the course of rheumatoid arthritis (RA), many alterations in the expression of plasma proteins, as well as their posttranslational modifications (including glycosylation) can occur. Taking into account the disturbances in protein glycosylation and the emerging new treatment regimens, the aim of this study was to assess the serum profile of transferrin isoforms in RA patients treated with biological drugs. Methods: The study included 20 patients (16 females and 4 males; mean age: 53.4 years; range: 24-67) with rheumatoid arthritis treated with rituximab. Serum samples were taken 3 times: before and 3 and 6 months during treatment. The isoforms of transferrin were separated by capillary electrophoresis (MINICAP electrophoretic system, Sebia, France) into five major fractions: asialo-, disialo-, trisialo-, tetrasialo- and pentasialo-transferrin. The results were calculated as relative concentrations of each fraction. Results: The median trisialotransferrin relative concentrations after 3 and 6 months treatment (4.40% and 4.10%, respectively) were significantly higher (p=0.013, p=0.009, respectively) than before treatment (3.50%). The levels of serum pentasialotransferrin were also increased 3 and 6 months following treatment (16.5% and 17.7%, p=0.005 and p=0.006, respectively) as compared to those before therapy (14.5%), while tetrasialotransferrin concentrations were lower (80.3% and 78.4%, p=0.009 and p=0.008, respectively) than before treatment (81.5%). Trisialotransferrin relative concentration correlated with Hb (p=0.019), whereas pentasialotransferrin with PLT (p=0.036) after treatment. Conclusions: This study indicates that treatment with rituximab of RA patients alters the serum profile of transferrin isoforms. Tri-, tetra- and pentasialotransferrin relative concentrations measurements can be a useful tool to monitor therapy.