Michael A. Cremer

Collagen-induced arthritis, an animal model of autoimmunity

Collagen induced arthritis (CIA) is an autoimmune model that in many ways resembles rheumatoid arthritis (RA). Immunization of genetically susceptible strains of rodents and primates with type II collagen (CII) leads to the development of a severe polyarticular arthritis that is mediated by an autoimmune response. Like RA, synovitis and erosions of cartilage and bone are hallmarks of CIA, and susceptibility to both RA and CIA is linked to the expression of specific MHC class II molecules. Although not identical to RA, CIA clearly establishes the biological plausibility that an autoimmune reaction to a cartilage component can lead to a chronic, destructive, polyarthritis. Although it is induced in susceptible animals by immunization with heterologous CII, it is the autoreactive component of the immune response that leads to disease. A wealth of evidence indicates that synovitis is initiated by the production of pathogenic autoreactive antibodies capable of fixing and activating complement. The elucidation of the specific amino acid sequences of collagen that are recognized by the MHC molecules has enabled at least two approaches to specific immunotherapy to be considered. Firstly, small synthetic peptides representing dominant epitopes have been used as effectively as the original antigen as a tolerogen. The rather fastidious physicochemical properties of collagen that make it difficult for its routine use in therapy are thereby circumvented by the use of oligopeptides. Secondly, analysis of the specific amino acid side chains that are involved in MHC contact and TCR recognition enables analog peptides to be devised which can specifically and exquisitely inhibit the response to CII, preventing the onset of arthritis. Further investigations involving this model may contribute to the development of specific immunotherapies in the human disorder.

The cartilage collagens: a review of their structure, organization, and role in the pathogenesis of experimental arthritis in animals and in human rheumatic disease

Abstract This contribution reviews the structure and organization of collagen molecules found in cartilage and the roles that they may play in rheumatic diseases. Cartilage is unique in its physical properties and molecular composition, and contains sufficient amounts of types II, IX, X, and XI collagen to deem these molecules as ”cartilage-specific.” The vitreous body of the eye, a ”cartilagelike” tissue is also rich in the same collagens but is type X deficient. Types VI and XII collagen are present in cartilage as well as noncartilaginous tissues. Types II, IX, and XI collagen are organized into matrix fibrils, where type II constitutes the bulk of the fibril, type XI regulates fibril size, and type IX facilitates fibril interaction with proteoglycan macromolecules. Genetic defects in these collagens can produce mild to severe developmental abnormalities, including spondyloepiphyseal dysplasia often accompanied by an accelerated form of osteoarthritis. Sensitization with collagen can produce experimental rheumatic diseases. Type II collagen induces an erosive polyarthritis in certain strains of rats, mice, and higher primates which can resemble rheumatoid arthritis and relapsing polychondritis. Type XI collagen is arthritogenic in rats but not mice; type IX induces autoimmunity in both species but not arthritis. Arthritis is initiated by complement fixing antibodies that bind to type II collagen in autologous cartilage, and the production of these antibodies is MHC restricted and T cell dependent. It is unclear whether T cells alone can induce arthritis, although they probably help sustain it. Mapping and characterizing the of T cell epitopes on type II collagen has resulted in the synthesis of small homolog and substituted peptides of type II collagen which suppress arthritis in an antigen-specific manner by a variety of routes, including mucosal. Moreover, collagen-induced arthritis has proven a valuable model to study the contribution of cytokines and other biological agents in the pathogenesis of joint injury and how they might be used to develop new therapies. Collagen autoimmunity has been implicated in the pathogenesis rheumatoid arthritis and polychondritis. Circulating antibodies to type II collagen are found in both diseases. Antibodies to types IX and XI collagen are also present in rheumatoid sera but are less prevalent. Rheumatoid cartilage and synovium contain antibodies to type II collagen at a prevalence far greater than serum, suggesting an intra-articular antigen-driven immune process. Although effective in animal models, attempts to treat rheumatoid arthritis with orally administered type II collagen have proven elusive. Different approaches using newer formulations and selected or modified oligopeptides remain to be tested and could prove effective in the treatment of the human rheumatic diseases.

Collagen-Induced Arthritis in Mice: Synergistic Effect of E. Coli Lipopolysaccharide Bypasses Epitope Specificity in the Induction of Arthritis with Monoclonal Antibodies to Type II Collagen

DBA/1 mice develop a chronic peripheral arthritis after immunization with type II collagen termed collagen-induced arthritis. We have localized the main arthritogenic determinants of CB11, a CNBr-generated arthritogenic fragment of chick type II collagen (CII), using 3 smaller peptide fragments of CB11 generated by endoproteinase LysC, LysC1 (CII 124-290), LysC2 (CII 291-374) and LysC3 (CII 375-402) and a panel of monoclonal antibodies (mAb) specific to CB11. MAb specific to the arthritogenic region of CB11 were also used to study the synergistic effect of E. coli lipopolysaccharide (LPS) on antibody-mediated arthritis in naive DBA/1 mice. LysC2 contained a minimum essential arthritogenic fragment of type II collagen: LysC2 induced arthritis by active immunization, also, a combination of four mAb specific to LysC2 passively transferred arthritis to naive mice. A single i.p. injection of LPS (50 micrograms/mouse) reduced the threshold values of the arthritogenic dose of mAb from 1 mg to 50 micrograms/clone per mouse, and decreased the number of mAb required for inducing arthritis from 4 to 2 clones. These observations suggest that LysC2, an 84 amino acid residue fragment, contains the main arthritogenic determinants within chick CB11. Importantly, LPS, a strong inducer of pro-inflammatory cytokines, negates the required multiple epitope specificity of autoantibodies in the passive transfer model and acts synergistically in the induction of arthritis by autoantibody.

LACK OF EFFICACY OF ORAL BOVINE TYPE II COLLAGEN ADDED TO EXISTING THERAPY IN RHEUMATOID ARTHRITIS

OBJECTIVE To investigate the efficacy of oral type II collagen (CII) in the treatment of rheumatoid arthritis (RA), when added to existing therapy. METHODS Patients with active RA (n = 190) were randomized into a 6-month, double-blind, placebo-controlled trial. Patients continued to take their current arthritis medications. Patients received either placebo or bovine CII, 0.1 mg/day for 1 month, then 0.5 mg/day for 5 months. RESULTS There were no significant differences between the baseline characteristics of either group. The primary response parameter was the American College of Rheumatology (ACR) preliminary definition of improvement in RA (ACR 20). There was no statistically significant difference in the ACR 20 after 6 months (20.0% of placebo patients; 16.84% of bovine CII patients). There were significant differences in several clinical variables after treatment, all favoring the placebo group. CONCLUSION Oral solubilized bovine CII, added to existing therapy, did not improve disease activity in patients with RA.

Collagen-induced arthritis.

The mouse model collagen‐induced arthritis (CIA) is a widely studied autoimmune model of rheumatoid arthritis. In this model, autoimmune arthritis is induced by immunization with type II collagen (CII) emulsified in complete Freunds adjuvant. This unit describes the steps necessary for the acquisition, handling, and preparation of CII, in addition to the selection of mouse strains, proper immunization technique, and methods for evaluation of the incidence and severity of arthritis. In this model, the first signs of arthritis appear approximately 21 to 28 days after immunization. The protocols in this unit should provide the investigator with all the necessary information required to reproducibly induce a high incidence of CIA in genetically susceptible strains of mice, and to critically evaluate the pathology of the disease. Curr. Protoc. Immunol. 89:15.5.1‐15.5.25.

Relevance of Posttranslational Modifications for the Arthritogenicity of Type II Collagen

To establish the role of posttranslational modification in modulating the immune response to collagen, recombinant human type II collagen (rCII) was produced using a yeast expression system (rCIIpic) and a baculovirus expression system (rCIIbac). The biosynthesis of CII requires extensive posttranslational modification including the hydroxylation of prolyl and lysyl residues and glycosylation of selected hydroxylysyl residues. Amino acid analyses indicated that the rCIIbac was adequately hydroxylated at prolyl residues but underhydroxylated at lysyl residues and underglycosylated compared with tissue-derived CII, whereas rCIIpic was adequately hydroxylated at prolyl residues but unhydroxylated at lysyl residues and had no glycosylation. When DBA/1 mice were immunized with rCII, rCIIpic induced a lower incidence of arthritis than tissue-derived CII, whereas rCIIbac induced an intermediate level of arthritis. The severity of the arthritis was significantly lower in mice immunized with rCIIpic compared with mice immunized with tissue-derived CII, whereas that of rCIIbac was intermediate. These data indicate that the degree of lysine hydroxylation and glycosylation plays a role in the induction of arthritis. The recombinant collagens were then compared with tissue-derived CII when given as i.v. or oral tolerogens to suppress arthritis. Both recombinant collagens were less potent than tissue-derived CII, and this decrease in arthritis was associated with a decrease in Ab response to CII. These data suggest that the degree of glysosylation affects the immune response to CII, so that underglycosylated CII is less effective in the induction of arthritis and in its ability to suppress collagen-induced arthritis.

The roles of interleukin‐18 in collagen‐induced arthritis in the BB rat

Interleukin (IL)‐18 is a member of the IL‐1 cytokine family. Its expression is increased in rheumatoid arthritis synovium, and its proinflammatory effects have been demonstrated in experimental models of murine arthritis. Here, we investigate the actions of varying doses of recombinant rat IL‐18 (rIL‐18) on the course of type II collagen‐induced arthritis (CIA) in BB rats, including clinical and immune events, plus splenic cytokine production. Small doses of rIL‐18 (10 and 50 µg/rat) administered intraperitoneally (i.p.) increased arthritis incidence and severity (P < 0·01) when a low‐potency CII preparation was used for immunization. IgG1 and IgG2a anti‐CII antibody levels were significantly greater in rats given 10 and 50 µg rIL‐18 doses than controls. rIL‐18 significantly increased levels of proinflammatory cytokines [interferon (IFN)‐γ, IL‐2, tumour necrosis factor (TNF)‐α and IL‐6] produced by splenocyte cultures. Larger doses of rIL‐18 (300 µg/rat) suppressed arthritis and immunity. To ascertain whether the pro‐arthritic effects of IL‐18 could be attenuated, rats were treated with neutralizing rabbit anti‐rIL‐18 IgG before immunization with a high‐potency CII preparation. When given serially for 3 weeks, the incidence and severity of CIA, in addition to anti‐CII IgG2a and splenic IL‐6 and IFN‐γ production, were all significantly reduced. Similar results were noted when antibody was given twice, just before arthritis onset. These results demonstrate that IL‐18 plays an important proinflammatory role in the pathogenesis of CIA which is achieved, in part, by an immunostimulatory action. Neutralizing endogenous IL‐18 with antibodies attenuated CIA, CII immunity and cytokine responses. These studies support the use of IL‐18 antagonists as treatments for inflammatory arthritis.

Effects of long-term administration of methotrexate on bone mineral density in rheumatoid arthritis.

Abstract. Because previous studies of high-dose methotrexate usage have demonstrated an effect on bone formation and resorption, this study was done to determine whether long-term, low-dose use of methotrexate for the treatment of rheumatoid arthritis causes bone loss. Bone mineral density (BMD) of the lumbar spine and hip was measured in 10 Caucasian postmenopausal women who had never received methotrexate and 10 Caucasian postmenopausal women who had received the drug for 3 or more years. There were no significant differences in BMD at the lumbar spine (L2–L4) between patients who had used long-term methotrexate compared with patients never treated with methotrexate (1.08 ± 0.08 g/cm2 versus 0.98 ± 0.14 g/cm2, respectively; P= 0.08). Similarly, there were no significant differences in BMD at the femoral neck between methotrexate users and nonusers (0.81 ± 0.08 g/cm2 versus 0.76 ± 0.15 g/cm2, respectively; P= 0.42). These results suggest that long-term low-dose methotrexate treatment for rheumatoid arthritis is not associated with accelerated bone loss.

Physicochemical and Immunological Studies of the Renatured α1(II) Chains and Isolated Cyanogen Bromide Peptides of Type II Collagen

The alpha 1(II) and cyanogen bromide (CB)1-generated peptides of chick type II collagen were isolated, purified, renatured and examined for their physicochemical and immunological properties. The alpha 1(II) chains and peptides CB-6 through CB-12 (3,000 to 40,000 daltons) formed renatured thermostable products as determined by measurements of reduced viscosity, optical rotation and Stokes radius. Moreover, renatured alpha 1 (II) chains and CB-10 were observed to form segment-long-spacing (SLS) crystallites under appropriate conditions. When examined for immunoreactivity with defined rat polyclonal and mouse monoclonal antibodies to chick type II collagen, conformation-dependent epitopes were detected on renatured alpha 1(II) chains and renatured peptides, CB-8, CB-10 and CB-11. Conformation-independent epitopes were also detected on all CB-peptides in their denatured form. These studies demonstrate that the alpha 1 (II) chains and CB-peptides of chick type II collagen can be efficiently renatured and that the renatured products retain some conformation-dependent epitopes present on the naive molecule.

Type XI and II Collagen-Induced Arthritis in Rats: Characterization of Inbred Strains of Rats for Arthritis-Susceptibility and Immune-Responsiveness to Type XI and II Collagen

To determine the relationship between susceptibility to bovine type XI and II (BXI and BII) collagen-induced arthritis, we immunized 14 inbred and one outbred strains of rats with BXI and BII. Susceptibility to BXI-arthritis corresponded largely with susceptibility, or resistance, to BII-arthritis. LEW, BB, WF, DA, and WKY were readily susceptible to BXI- and BII-arthritis. Likewise, BII-resistant F344 and BN rats were BXI-resistant. Some strains responded differently to BXI and BII. BUF and COP, which are moderately susceptible to BII, were BXI-resistant, whereas the BII-resistant rats, DA.1N and WF.1N, were partially susceptible to BXI. (F344 x BN) F1 hybrids responded to both collagens suggesting gene complementation. Arthritis occurred in all strains producing the highest titer antisera (LEW, WF and BB). Antibody responses to BXI and BII were generally commensurate within individual strains. DA were susceptible to arthritis but produced low levels of antibody comparable to BN rats which were arthritis-resistant. BXI and BII-susceptibility was variable in rats producing intermediate antibody responses. Antibodies to RXI were detected in all BXI-immunized rats, whereas antibodies to RV and RII were uniformly weaker. DTH to RXI and RII was strong in both groups of rats, correlating poorly with arthritis and antibody responses. These studies show that phenotypic susceptibility to BXI- and BII-arthritis are largely concordant among inbred rat strains but clear differences exist in certain strains; multiple genes are likely involved.