Engineering and evaluation of a mouse/human chimeric antibody against Shiga toxin 2

Hemolytic-uremic syndrome (HUS), mainly caused by Shiga toxin (Stx) producingEscherichia coli (STEC) such as E. coli O157:H7 and STEC/EAggEC, is a serious complication predominantly leading to renal failure and even death. We have previously reported that a monoclonal antibody effectively neutralizes Stx2 in vitro and in vivo toxicity models. As a therapeutic agent against HUS, the mouse origin of this antibody can trigger human anti-murine antibody (HAMA) reactions thereby restricting its clinical application. In order to reduce its immunogenicity for use in humans, in this study, a mouse/human chimeric antibody designated rS2C4-IgG1 was developed in baculovirus/insect cell expression system. Analysis of antigen-binding and competitive binding revealed that rS2C4-IgG1 possessed specificity and affinity similar to that of S2C4. Results from cytotoxicity assays and mouse toxicity model analysis showed that rS2C4-IgG1offers neutralizing activity comparable to its parent MAb in vitro and in vivo. Therefore, the chimeric rS2C4-IgG1 had great potential for use in the treatment of STEC infection.   Key words: Shiga toxin 2, HUS, STEC, chimeric rS2C4-IgG1.