anti-etanercept antibody production, along with the antibody's potential interfering effects on the biological function of etanercept, in mice with collagen-induced arthritis

Etanercept is a widespread biological drug for the treatment of rheumatoid arthritis, which inhibits tumor necrosis factor-α (TNF-α). Recently, the presence of antibodies targeting TNF-α inhibitors such as infliximab and adalimumab, was reported. However, few reports have studied etanercept in a mouse model of arthritis. We investigated the induction of anti-etanercept antibody production, along with the antibody's potential interfering effects on the biological function of etanercept, in mice with collagen-induced arthritis (CIA). CIA mice received an intraperitoneal injection of etanercept (25, 100 or 400 μg per mouse). The degree of inflammation and cartilage erosion was evaluated, and the number of osteoclasts in the ankle joints was assessed by TRAP staining. The level of pro-inflammatory cytokines in the serum was measured. To analyze the anti-osteoporotic effect of etanercept, microfocal computed tomography analyses of femurs and tibias were performed. Etanercept treatment decreased both the incidence and severity of arthritis in a dose-dependent manner, except for the highest dose of 400 μg. The mice that were treated with 25 and 100 μg etanercept showed an improvement in inflammation, cartilage damage, and even bone loss. However, mice treated with 400 μg etanercept showed no significant improvement in any of the tested parameters. Using a customized enzyme-linked immunosorbent assay (ELISA), the presence of the anti-etanercept antibody was detected in the serum in this treatment-refractory group. The therapeutic effect of etanercept was reduced in the CIA mice that developed the anti-etanercept antibody. In conclusion, the production of an anti-etanercept antibody can be induced in CIA mice, and this antibody can considerably reduce the anti-arthritic and anti-osteoporotic effects of etanercept. Introduction Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, associated with focal and systemic bone loss. Structural changes such as joint damage and osteoporosis are the most suitable symptoms for distinguishing RA from other diseases (1). The level of tumor necrosis factor-α (TNF-α) is markedly increased in most patients with RA, and thus, the protein is considered a main pathological player in inflammation. As a result, many TNF-α inhibitors, including infliximab (Remicade®), adalimumab (Humira®), and etanercept (Enbrel®), were developed and have been widely used to treat RA (2,3). Etanercept, one of the most commonly used TNF-α inhibitors, consists of two human TNF receptor 2 (TNFR2) extracellular domains conjugated to the Fc portion of the human IgG1. The anti-inflammatory effect of etanercept in patients with RA is widely accepted (4-7). Although a previous study indicated that inhibiting inflammation in RA is insufficient to inhibit bone destruction (8), another study showed that TNF-α blockers directly mitigate osteoporosis (9). It was also suggested that TNF-α inhibitors prevent resorption of the bone adjacent to the joints (10). Despite the efficiency of TNF-α inhibition in RA treatment, it is commonly not feasible to prescribe TNF-α inhibitors to patients with early RA, due to its high cost and insurance regulations (3,11). British guidelines require limitation of prescriptions of TNF-α inhibitors to patients with active RA who do not have a satisfactory response to at least two disease-modifying antirheumatic drugs (DMARDs) (12). However, since it has been reported that etanercept is effective when administered to patients with early RA (5,13), the importance of using this drug in the treatment of early RA is being reassessed (14). Furthermore, there has been limited clinical research on the anti-osteoporotic effects of TNF-α inhibitors in patients with early RA. In this study, we simulated this clinical condition in mice by transiently injecting etanercept at the early stage of CIA induction. Since TNF inhibitors have become popular drugs for the treatment of RA, clinicians are increasingly interested in the subgroup of the patients who show a refractory response to etanercept. One explanation for refractoriness is the Induced production of anti-etanercept antibody in collagen-induced arthritis HYOJU YI, JURYUN KIM, HYERIN JUNG, YERI ALICE RIM, YOUNGKYUN KIM, SEUNG MIN JUNG, SUNG-HWAN PARK and JI HYEON JU Division of Rheumatology, Department of Internal Medicine, CiSTEM Laboratory, Convergent Research Consortium for Immunological Disease (CRCID), Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea Received September 17, 2013; Accepted March 12, 2014 DOI: 10.3892/mmr.2014.2127 Correspondence to: Professor Ji Hyeon Ju, Division of Rheumatology, Department of Internal Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea, 505 Banpodong, Seochogu, Seoul 137-701, Republic of Korea E-mail: [email protected]