Determination of the Rituximab Binding Site to the CD20 Epitope Using SPOT Synthesis and Surface Plasmon Resonance Analyses

Antibodies not only play a major role in clinical diagnostics and biopharmaceutical analysis but also are a class of drugs that are regularly used to treat numerous diseases. The identification of antibody-epitope binding sites is then of great interest to many emerging medical and bioanalytical applications, particularly to design monoclonal antibodies (mAb) mimics taking advantage of amino acid residues involved in the binding. Among relevant antibodies, the monoclonal antibody rituximab has received significant attention as it is exploited to treat several cancers including non-Hodgkin's lymphoma and chronic lymphocytic leukemia, as well as some autoimmune disorders such as rheumatoid arthritis. The binding of rituximab to the targeted cells occurs via the recognition of the CD20 epitope. A crystallographic study has shown that the binding area, named paratope, is located at the surface of rituximab. Combining the SPOT method and the complementary surface plasmon resonance technique allowed us to detect an extended recognition domain buried in the pocket of the rituximab Fab formed by four beta-sheets. More generally, the present study offers a comprehensive approach to identify antibody-epitope binding sites.

Automated summary

Antibodies are not only important for clinical diagnostics and biopharmaceutical analysis, but also as drugs for treating various diseases. The identification of antibody-epitope binding sites, particularly for designing monoclonal antibody mimics like rituximab, is crucial for medical and bioanalytical applications. Rituximab, a monoclonal antibody used to treat cancers and autoimmune disorders, binds to targeted cells via the recognition of the CD20 epitope, with its binding area located on the surface of rituximab.