Antibodies to type II and XI collagens: evidence for the formation of antigen specific as well as cross reacting antibodies in patients with rheumatoid arthritis

Rheumatoid arthritis in a patient with compound heterozygous variants in the COL11A2 gene and progressive hearing loss: A case report

RATIONALE

Collagen type XI alpha 2 chain is a component of type XI collagen and is expressed in various tissues including articular cartilage and tectorial membrane of the cochlea. Variants in the COL11A2 gene, which encodes collagen type XI alpha 2 chain, has been reported to cause hearing loss and has been associated with osteoarthritis and ossification of the posterior longitudinal ligament of the spine. Despite the importance of type XI collagen in the joints, association of rheumatoid arthritis (RA) with COL11A2 has not been reported.

PATIENT CONCERNS

The patient is a 60-year-old female, born to Japanese parents of no known consanguinity. She had progressive hearing loss since childhood. Her father also had progressive hearing loss before middle age. She developed joint pain in the knees and the hips in her forties. When she was 56, she developed polyarthritis. Rheumatoid factor and anti-CCP antibodies were positive.

DIAGNOSES

She was diagnosed with osteoarthritis and RA. Whole exome analysis detected 2 rare variants, c.4201C>T, p.(Arg1401Trp) and c4265C>T, p.(Pro1422Leu), in the COL11A2 gene (NM_080680.2). Whole genome analysis with a long insert size confirmed 2 variants that are in trans.

INTERVENTIONS AND OUTCOMES

She received a cochlear implant, which improved her hearing. She was treated with methotrexate, golimumab, tocilizumab, and upadacitinib with partial responses for her RA.

LESSONS

We herein report a patient with RA with compound heterozygous variants in the COL11A2 gene. Autoantibodies against type XI collagen are detected in the sera of patients with RA, suggesting the possibility that type XI collagen may be involved in the pathogenesis of RA as an autoantigen. The hearing loss and osteoarthritis in this patient may be due to the compound heterozygous variants in the COL11A2 gene, and the conformational changes induced by the variants may have changed the immunogenicity of type XI collagen, leading to the development of RA.

Extra-articular cartilage affected in collagen-induced, but not pristane-induced, arthritis models

Rheumatoid arthritis (RA) is a chronic inflammatory disease primarily affecting cartilaginous joints but also extra-articular tissues such as the nose and upper respiratory tract. We have investigated extra-articular cartilage involvement in two commonly used animal models for RA, collagen-induced and pristane-induced arthritis, by immunizing rats with different susceptibility to disease (LEW.1 A, LEW.1F and DA rats). We found that nasal and tracheolaryngeal cartilage is affected in LEW.1 A and DA rats to varying degrees in collagen-induced arthritis but not in any strain in the pristane-induced model. Antibodies to matrilin-1, a cartilage-specific protein expressed mainly in tracheolaryngeal and nasal cartilage but not in joints, were positively associated with the presence of inflammation in nasal cartilage. In contrast, no antibody response to matrilin-1 could be detected in pristane-induced arthritis. In addition, nasal vaccination with collagen type II prior to immunization in DA rats significantly decreased the antibody response to matrilin-1 at day 56, but not at earlier time points, indicating a late protective effect on extra-articular cartilage. We conclude that pristane-induced arthritis is a joint-specific model whereas collagen-induced arthritis affect joints as well as extra-articular cartilage. Furthermore, collagen immunization induces an antibody response to matrilin-1.

Identification of antibody epitopes in the CB-11 peptide of bovine type II collagen recognized by sera from arthritis-susceptible and -resistant rhesus monkeys

Sera from eight rhesus monkeys that had been immunized with native bovine type II collagen were tested for antibodies to cyanogen bromide peptides (CB peptides) of type II collagen by Western blotting. The monkeys produced IgG antibodies to a number of different CB peptides, with five out of eight animals producing antibodies to the CB-11 peptide (four arthritic, one non-arthritic). Antibody epitopes on the CB-11 peptide of bovine type II collagen recognized by these sera were investigated by epitope mapping. Peptides (8-mers overlapping by seven amino acids) representing the CB-11 region were synthesised and the sera screened for binding to these peptides to determine areas of high IgG antibody binding to this region of type II collagen. The profiles obtained were not identical, though there were some epitopes that were commonly recognized. Antibodies to one epitope, also present in human type II collagen, were found only in the sera of two animals with the severest arthritis. The technique of epitope mapping has successfully identified a number of epitopes within the CB-11 peptide of type II collagen recognized by antibodies from bovine type II collagen-immunized monkeys. Studies on the relevance of responses to the identified epitopes can now be undertaken.

IgE antibodies specific for cartilage collagens type II, IX and XI in rheumatic diseases

Serum samples from 149 patients with RA and other rheumatological diseases, and 57 non-arthritic controls have been assayed for IgE antibodies to the cartilage collagen types II, IX and XI in their native and denatured state. Using an improved ELISA technique together with antigen-binding inhibition studies to confirm specificity, 10 of the 149 (7%) patients showed IgE antibodies to human collagen type II and bovine collagen types II, IX or XI. Some patients responded to only one collagen type whereas others had IgE positive responses to two or all three collagen species. Most of the IgE responses detected were directed towards the denatured collagens. Those sera showing an IgE response to bovine type II collagen produced a similar response to the human equivalent, including two patients with SLE. None of 57 control subjects demonstrated IgE specificity for any of the cartilage collagens. Patients with IgE specificity for the cartilage collagens did not demonstrate IgM or IgA specificity for these antigens, but two of these patients showed IgG responses to type II and XI collagens. Whereas eight patients were exclusively IgE-positive for the cartilage collagens, others expressed specificities for IgG, IgM or IgA. It therefore appears that the specific autoimmune profile for each patient is often different from others, both in terms of the class of immunoglobulin expressed and the collagen antigens recognised. At present no correlations were observed between the IgE-positive patients and their clinical assessment and/or prognosis.

Antibodies to extracellular matrix proteins in the sera of MRL-lpr mice

Autoimmune MRL-lpr mice develop a spontaneous arthritis displaying similar articular and extra-articular features to rheumatoid arthritis in humans. In this study we used an ELISA assay to evaluate the serological responses of MRL-lpr mice to select extracellular matrix proteins associated with the joint. Significant levels of antibodies to collagens types I, II, III, IV, and V were demonstrated starting between 17 and 20 weeks of age. Moreover, the sera contained a strong reactivity to fibronectin. Responses to proteoglycans and laminin were weaker but still detectable. Specificity studies on pooled sera from MRL-lpr mice suggest that the autoantibodies produced are highly cross-reactive. The results indicate that the MRL-lpr mouse strain exhibits similar anti-extracellular matrix antibody profiles to those seen in varying frequencies in the sera and synovial fluid of patients with rheumatoid arthritis.

Identification of antibody epitopes within the CB-11 peptide of type II collagen. I: Detection of antibody binding sites by epitope scanning

Using epitope scanning, the precise location of antibody binding sites on the CB-11 peptide of bovine type II collagen have been identified for the first time. Two hundred and seventy two peptides (8 amino acids in length and overlapping by seven amino acids), representing the complete CB-11 sequence, were synthesised on solid phase supports, in duplicate, and were screened with sera from arthritic and non-arthritic, bovine type II collagen-immunised rats. A total of twenty one different antibody binding sites were identified with no epitope being uniquely recognised by sera from arthritic, as compared to non-arthritic, rats although differences in the relative amount of antibody binding were seen. Individual sera identified between two and thirteen epitopes with one epitope being recognised by all sera. Some of the amino acid sequences, of the CB-11 region of bovine type II collagen, recognised by the rat sera are identical to the sequences in human type II collagen and thus these epitopes may be relevant to autoimmunity to type II collagen in patients with rheumatoid arthritis.