title: Exploiting cross-reactivity to neutralize two different scorpion venoms with one single chain antibody fragment.
abstract: We report the optimization of a family of human single chain antibody fragments (scFv) for neutralizing two scorpion venoms. The parental scFv 3F recognizes the main toxins of Centruroides noxius Hoffmann (Cn2) and Centruroides suffusus suffusus (Css2), albeit with low affinity. This scFv was subjected to independent processes of directed evolution to improve its recognition toward Cn2 (Riaño-Umbarila, L., Juárez-González, V. R., Olamendi-Portugal, T., Ortíz-León, M., Possani, L. D., and Becerril, B. (2005) FEBS J. 272, 2591-2601) and Css2 (this work). Each evolved variant showed strong cross-reactivity against several toxins, and was capable of neutralizing Cn2 and Css2. Furthermore, each variant neutralized the whole venoms of the above species. As far as we know, this is the first report of antibodies with such characteristics. Maturation processes revealed key residue changes to attain expression, stability, and affinity improvements as compared with the parental scFv. Combination of these changes resulted in the scFv LR, which is capable of rescuing mice from severe envenomation by 3 LD(50) of freshly prepared whole venom of C. noxius (7.5 μg/20 g of mouse) and C. suffusus (26.25 μg/20 g of mouse), with surviving rates between 90 and 100%. Our research is leading to the formulation of an antivenom consisting of a discrete number of human scFvs endowed with strong cross-reactivity and low immunogenicity.
authors.affiliation: Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62250, México.
authors.forename: Lidia
authors.initials: L
authors.lastname: Riaño-Umbarila
authors.forename: Gabriel
authors.initials: G
authors.lastname: Contreras-Ferrat
authors.forename: Timoteo
authors.initials: T
authors.lastname: Olamendi-Portugal
authors.forename: Citlalli
authors.initials: C
authors.lastname: Morelos-Juárez
authors.forename: Gerardo
authors.initials: G
authors.lastname: Corzo
authors.forename: Lourival D
authors.initials: LD
authors.lastname: Possani
authors.forename: Baltazar
authors.initials: B
authors.lastname: Becerril
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D057134:Antibodies, Neutralizing / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D003429:Cross Reactions / Q000235:genetics / Q000276:immunology; D019020:Directed Molecular Evolution / Q000379:methods; D051379:Mice; D012604:Scorpion Venoms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology* / Q000633:toxicity; D057127:Single-Chain Antibodies / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D012604:Scorpion Venoms; D057127:Single-Chain Antibodies; C066386:scorpion toxin Css II