Carbamylated vimentin represents a relevant autoantigen in Latin American (Cuban) rheumatoid arthritis patients

Abstract

Smoking produces substances that activate proinflammatory, prothrombotic and vasoconstrictive mediators via posttranslational carbamylation of proteins. As a new consequence of carbamylation, induction of anti-carbamylated autoantibodies were observed in rheumatoid arthritis (RA) patients, sometimes prior to onset of the disease. The overall aim of this study was to characterize the reactivity of different isotypes of autoantibodies against carbamylated antigens of vimentin in relation to established rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) and markers of disease activity in a so far largely uncharacterized population of Latin American (Cuban) patients with RA. Antigenic properties of carbamylated vimentin as well as vimentin peptides were analyzed in 101 patients with RA, 50 disease controls and 51 healthy controls. The diagnostic performance was compared with established commercial ELISA rheumatoid factor, anti-cyclic citrullinated peptide antibodies of second generation (anti-CCP2) and anti-mutated citrullinated vimentin (anti-MCV) antibodies. Prevalence of anti-MCV IgG (86 %), anti-carbamylated vimentin (carbVIM) IgG (77 %) and anti-carbamylated MCV (carbMCV) IgG antibodies (65 %) was higher than the classical RF IgM (60 %) and anti-CCP2 IgG (52 %) in this RA cohort. Of note, smoking status was associated with positive IgG antibody reactivity against CCP2 in 75.0 % and against MCV in 90 % of patients. Furthermore, IgM antibody response against carbMCV and carbVIM was observed in 80 and 90.0 % of smokers, respectively. Due to a high sensitivity of the IgM antibody isotype of anti-carbVIM of 85.2 %, the combination of ACPA with anti-carbVIM IgM provided the best diagnostic performance so far achieved in a RA cohort of this ethnic origin. We demonstrate a high prevalence of anti-carbVIM antibodies and correlation with smoking in Latin American (Cuban) RA patients. Anti-carbVIM IgM represents an useful marker in ACPA-negative patients and, in combination with ACPA IgG assays, optimizes the strategy for autoantibody testing.

Keywords: Anti-cyclic citrullinated peptides; Anti-mutated citrullinated vimentin; Carbamylated vimentin; Citrullinated vimentin; Rheumatoid arthritis.

Fig. 1

Relative frequency of antibodies against citrullinated and carbamylated sequences of vimentin, anti-CCP2 and RF in patients with early and established RA. RA rheumatoid arthritis, RF rheumatoid factor, CCP2 cyclic citrullinated peptides of second generation, MCV mutated citrullinated vimentin, carbVIM carbamylated vimentin, carbMCV carbamylated mutated citrullinated vimentin, CCP VIM cyclic citrullinated peptides of vimentin, Ig immunoglobulin. Cutoff value of anti-CCP2 was 30 U/mL according to manufacturer’s instruction and for others assay was 20 U/mL

Fig. 2

Median of titers of antibodies against citrullinated and carbamylated sequences of vimentin, anti-CCP2 and RF in RA patients. a Early RA. b Established RA. RA: rheumatoid arthritis. RF rheumatoid factor, CCP2 cyclic citrullinated peptides of second generation, MCV mutated citrullinated vimentin, carbVIM carbamylated vimentin, carbMCV carbamylated mutated citrullinated vimentin, CCP VIM cyclic citrullinated peptides of vimentin. Ig: immunoglobulin. Cutoff value of anti-CCP2 was 30 U/mL according to manufacturer’s instruction, and for others assay was 20 U/mL

Fig. 3

Cumulative positive results of ACPA and anti-carbVIMIgM assays in patients with early and established RA. RA rheumatoid arthritis, MCV mutated citrullinated vimentin, carbVIM carbamylated vimentin, Ig immunoglobulin. Positive results were considered according to the manufacturer’s instructions