Recombinant Shiga Toxin-Specific Human Antibodies

This proposal is in response to RFA: DK-00-005 "Foodborne Illness, Gastrointestinal and Renal Complications", specifically addressing "Development of interventions and/or clinical strategies to prevent complications of E. coli 0157:H7-related illnesses during the initial critical interval between the occurrence of hemorrhagic colitis and the development of HUS". The goal of this proposal is to develop an effective immune-based formulation which can be administered safely to children at risk of developing Shiga-toxin (Stx)-related hemolytic uremic syndrome (HUS). The target populations for this treatment include children in whom the disease can directly or indirectly be attributed to Stx. Currently there is no effective treatment or prevention for HUS. In this proposal we demonstrate that exogenous Stx-specific human monoclonal antibodies (Hu-mAbs) which we have generated under a separate NIH award, protect gnotobiotic piglets against Stx-mediated fatal neurological symptoms when administered 6-12 hours after oral challenge with E. coli 0157:H7. In contrast, piglets treated with placebo develop vascular-mediated fatal neurological symptoms within 2-3 days after the oral challenge. In this application we wish to express several of these anti-Stx Hu-mAbs in an eukaryotic system. This will allow us to produce them in large quantities (Specific Aim 1) and in different forms, such as isotype-variants (Specific Aim 2) and Fab fragments (aim 3) to determine which form would provide the most effective protection in vitro and in vivo (Specific Aim 4). We anticipate the final product will contain a cocktail of Hu-mAbs active against the A and B subunits of Stx1 and Stx2 (Specific Aim 4). Given our Preliminary Data, we are confident that specifically designed and highly concentrated Hu-mAbs will be safe and effective in protecting children at risk of HUS. We believe recombinant Hu-mAbs, either as whole molecules or Fabs, will be equally effective. Recombinant Hu- mAbs will considerably improve the efficiency of production of these reagents and make them available for clinical use. In contrast to other sources, such as polyclonal antibodies or murine/chimeric mAbs, Hu- mAbs have longer half-life, better affinity for targets, higher potency, require a lower dose, are safer, and are clearly the wave of the future. We are confident that at the end of the five-year support period we will have expressed in an eukaryotic system, a fully characterized panel of effective recombinant Stx-specific Hu-mAbs, ready to be produced under FDA guidelines for clinical evaluation.