Therapeutic Antibodies Against Shiga Toxins: Trends and Perspectives.

Shiga toxins (Stx) are AB5-type toxins, composed of five B subunits which bind to Gb3 host cell receptors and an active A subunit, whose action on the ribosome leads to protein synthesis suppression. The two Stx types (Stx1 and Stx2) and their subtypes can be produced by Shiga toxin-producing Escherichia coli strains and some Shigella spp. These bacteria colonize the colon and induce diarrhea that may progress to hemorrhagic colitis and in the most severe cases, to hemolytic uremic syndrome, which could lead to death. Since the use of antibiotics in these infections is a topic of great controversy, the treatment remains supportive and there are no specific therapies to ameliorate the course. Therefore, there is an open window for Stx neutralization employing antibodies, which are versatile molecules. Indeed, polyclonal, monoclonal, and recombinant antibodies have been raised and tested in vitro and in vivo assays, showing differences in their neutralizing ability against deleterious effects of Stx. These molecules are in different phases of development for which we decide to present herein an updated report of these antibody molecules, their source, advantages, and disadvantages of the promising ones, as well as the challenges faced until reaching their applicability.

Therapeutic antibodies against shiga toxins: trends and perspectives

Shiga toxins (Stx) are AB5-type toxins, composed of five B subunits which bind to Gb3 host cell receptors and an active A subunit, whose action on the ribosome leads to protein synthesis suppression. The two Stx types (Stx1 and Stx2) and their subtypes can be produced by Shiga toxin-producing Escherichia coli strains and some Shigella spp. These bacteria colonize the colon and induce diarrhea that may progress to hemorrhagic colitis and in the most severe cases, to hemolytic uremic syndrome, which could lead to death. Since the use of antibiotics in these infections is a topic of great controversy, the treatment remains supportive and there are no specific therapies to ameliorate the course. Therefore, there is an open window for Stx neutralization employing antibodies, which are versatile molecules. Indeed, polyclonal, monoclonal, and recombinant antibodies have been raised and tested in vitro and in vivo assays, showing differences in their neutralizing ability against deleterious effects of Stx. These molecules are in different phases of development for which we decide to present herein an updated report of these antibody molecules, their source, advantages, and disadvantages of the promising ones, as well as the challenges faced until reaching their applicability.

The deleterious effects of Shiga toxin type 2 are neutralized in vitro by fabF8:Stx2 recombinant monoclonal antibody

Hemolytic Uremic Syndrome (HUS) associated with Shiga-toxigenic Escherichia coli (STEC) infections is the principal cause of acute renal injury in pediatric age groups. Shiga toxin type 2 (Stx2) has in vitro cytotoxic effects on kidney cells, including human glomerular endothelial (HGEC) and Vero cells. Neither a licensed vaccine nor effective therapy for HUS is available for humans. Recombinant antibodies against Stx2, produced in bacteria, appeared as the utmost tool to prevent HUS. Therefore, in this work, a recombinant FabF8:Stx2 was selected from a human Fab antibody library by phage display, characterized, and analyzed for its ability to neutralize the Stx activity from different STEC-Stx2 and Stx1/Stx2 producing strains in a gold standard Vero cell assay, and the Stx2 cytotoxic effects on primary cultures of HGEC. This recombinant Fab showed a dissociation constant of 13.8 nM and a half maximum effective concentration (EC50) of 160 ng/mL to Stx2. Additionally, FabF8:Stx2 neutralized, in different percentages, the cytotoxic effects of Stx2 and Stx1/2 from different STEC strains on Vero cells. Moreover, it significantly prevented the deleterious effects of Stx2 in a dose-dependent manner (up to 83%) in HGEC and protected this cell up to 90% from apoptosis and necrosis. Therefore, this novel and simple anti-Stx2 biomolecule will allow further investigation as a new therapeutic option that could improve STEC and HUS patient outcomes.