C1Q-MIMIKING SCFV FRAGMENTS BINDING ANTI-C1Q AUTOANTIBODIES HAS DISEASE-PROGRESSION EFFECT IN MRL/LPR MOUSE MODEL OF SYSTEMIC LUPUS ERYTHEMATOSUS

PV016 / #588 Poster Topic: AS02 - Animal Models Background/Purpose Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease characterized by tissue damage in multiple organs caused by autoantibodies and the resulting immune complexes. C1q is the first component of the classical complement pathway and primary or acquired C1q deficiencies are directly linked to development and severity of SLE. While the primary C1q deficiency is not frequent among SLE patients, 20-50% of them developed elevated levels of anti-C1q autoantibodies, which may be are responsible for low C1q levels. One possible way for complement system contribution to onset of autoimmune disorder could be realized by the impairment of C1q-mediated apoptotic clearance as part of human homeostasis. The capacity of C1q to bind early apoptotic cells could be decreased or even lost in the presence of anti-C1q antibodies which are specific for epitopes within gC1q. Methods A phage-displayed library expressing single-chain recombinant antibodies (scFv Ab) was screened to select scFv specific for anti-C1q autoantibodies from different sera of lupus nephritis patients. Such a monoclonal anti-idiotype scFv antibody selected from the Griffin.1 phage library was used to treat MRL/lpr mice. Two groups of MRL/lpr mice were used for in vivo and ex vivo experiments: disease free 7 weeks old mice and 16 weeks old animals with advanced disease manifestations. The mice were injected weekly with 20 µg/mouse of scFv A1 fragments binding anti-C1q antibodies. Blood samples were collected weekly and the sera were stored at -80 ºС for subsequent analyses. The number of in vitro and ex vivo studies with collected cells, sera and organs from the treated animals have been performed. The effects of therapy with the scFv A1 fragments were evaluated using flow cytometry, histology analyses, ELISpot and ELISA assays. Results An scFv specific for anti-C1q autoantibodies was generated and administered to MRL/lpr mice. Data show that scFv treatment changes the percentage of different B, T and NK cell subpopulations as well as plasma cells and plasmablasts in the spleen and bone marrow. An increase in the levels of splenocyte proliferation, anti-C1q antibodies, and the number of plasma cells producing anti-dsDNA and anti-C1q antibodies were also observed in both groups of scFv-treated animals. Administration of scFv A1 fragments binding anti-C1q antibodies increase the pathological findings in kidney histology in both young and sick animals. High levels of proteinuria and hematuria combined with increased unstable levels of IL10 and IFNγ promote the development of severe lupus and shorten the survival of treated MRL/lpr mice. Conclusions The treatment with anti-idiotypic scFv antibodies has disease-progression effect on lupus symptoms in MRL/lpr murine model of SLE. Binding of anti-C1q antibodies by scFv fragments neutralizes their ability to contact C1q, but the scFv is also able to bind B cell receptors on the surface of C1q-specific B cells, which enhances disease activity (Figure 1). Figure 1.