RESEARCH ARTICLE Development and Characterization of Recombinant Antibody Fragments That Recognize and Neutralize In Vitro Stx2 Toxin from Shiga Toxin-Producing Escherichia coli

Background Stx toxin is a member of the AB5 family of bacterial toxins: the active A subunit has N-glyco-sidase activity against 28S rRNA, resulting in inhibition of protein synthesis in eukaryotic cells, and the pentamer ligand B subunits (StxB) bind to globotria(tetra)osylceramide recep-tors (Gb3/Gb4) on the cell membrane. Shiga toxin-producing Escherichia coli strains (STEC) may produce Stx1 and/or Stx2 and variants. Strains carrying Stx2 are considered more virulent and related to the majority of outbreaks, besides being usually associated with hemolytic uremic syndrome in humans. The development of tools for the detection and/ or neutralization of these toxins is a turning point for early diagnosis and therapeutics. Anti-bodies are an excellent paradigm for the design of high-affinity, protein-based binding re-agents used for these purposes. Methods and Findings In this work, we developed two recombinant antibodies; scFv fragments from mouse hybrid-omas and Fab fragments by phage display technology using a human synthetic antibod