The antibody atliximab attenuates collagen-induced arthritis by neutralizing AIMP1, an inflammatory cytokine that enhances osteoclastogenesis.

ARS-interacting multifunctional protein 1 (AIMP1) induces production of inflammatory cytokines from immune cells. Since osteoclastogenesis is promoted by positive regulation of inflammatory cytokines, whether AIMP1 could promote osteoclastogenesis was investigated. AIMP1 induced osteoclastogenesis and acted synergistically with RANKL to promote osteoclastogenesis. Down-regulation of CD23, an AIMP1 receptor, abolished AIMP1-mediated osteoclastogenesis. Enzyme-linked immunosorbent assays showed that the AIMP1 level was significantly higher in the peripheral blood (PB) and synovial fluid of rheumatoid arthritis patients than in normal PB. A monoclonal antibody (clone 15B3AF) that blocked the cytokine activity of AIMP1 inhibited the AIMP1-mediated production of inflammatory cytokines. Clone 15B3AF inhibited the AIMP1-mediated osteoclastogenesis in vitro. We then cloned the complementary determining regions of clone 15B3AF and generated a chimeric antibody (atliximab). In a collagen-induced arthritis mouse model (CIA), atliximab administration significantly attenuated disease severity and improved various histopathological parameters. Three-dimensional micro-computed tomography scanning confirmed that atliximab enhanced the joint structures in CIA mice. Furthermore, atliximab decreased the expression of inflammatory cytokines in the serum and inflamed joints of CIA mice. Taken together, our findings suggest that AIMP1 exacerbates RA by promoting inflammation and osteoclastogenesis and that atliximab could be developed as a therapeutic antibody to target inflammatory diseases, including RA.