Anticorpos recombinantes contra as toxinas Stx1 e Stx2 produzidas por Escherichia coli produtora da toxina de Shiga: obtenção e caracterização dessas ferramentas para o imunodiagnóstico e terapia

Abstract

Shiga toxin-producing Escherichia coli (STEC) causes hemorrhagic colitis and hemolytic uremic syndrome by producing Shiga toxin (Stx), a AB5 type toxin. The B subunit binds to ganglioside receptors, and the active A subunit is translocated into the cell, where it inhibits protein synthesis by acting on rRNA, leading to cell death. Diagnosis of these strains is not commonly done in the routine laboratory of low-income countries. Besides, therapy for intoxication is based on minimizing the symptoms, since no toxin antidote is available. Thus, the development of effective tools for toxin detection and therapy is highly relevant. Antibodies exhibit excellent high affinity for their specific antigens. To maintain the homogeneity and specificity of monoclonal antibodies, together with largescale production and low cost, genetic engineering has been used to develop recombinant antibodies. These include single chain variable fragments and antigenbinding fragments, which consist of antibody fragments that have antigen recognition regions. In the present study we obtained and characterized two different recombinant antibody fragments (Fab and scFv), produced in bacteria, against Stx toxins from STEC isolates. Furthermore, for the first time a human monovalent fragment was constructed (Fab), which was able to recognize and neutralize Stx toxins. These fragments obtained are promising tools for its use in the diagnosis and therapy of intoxication by STEC.