VHH antibodies against the B subunit of Shiga toxin 2 (Stx2B) as novel therapeutic tools against HUS (Part II).

MEJIAS MP, ; FERNÁNDEZ-BRANDO RJ, ; HIRIART Y., ; BRUBALLA A,; RAMOS MV, ; ABREY-RECALDE MJ, ; GOLDBAUM F ,; ZYLBERMAN V, ; PALERMO MS

Boston

Congreso; 9th International Symposium on Shiga toxin (Verocytotoxin) producing Escherichia coli Infections (VTEC2012),; 2015

VTEC

Introduction: Infection with Stx2-producingEscherichia coli (STEC) canprogress to Hemolytic Uremic Syndrome (HUS),for which no effective therapy is presently available. The variablechains of antibodies produced by camelids (vhh/nanobodies)exhibit characteristics that make them attractive candidates as therapeuticagents. The aim of this work was to evaluate anti-Stx2B nanobodies asprotective anti-Stx2 tools for therapeutic ends. Methods: Three alternative formats were evaluated: amonomeric anti-Stx2B vhh (vhh 2vb27), abivalent molecule (two copies of vhh 2vb27)and a heterotrimeric molecule (two copies of vhh 2vb27 and 1 copy of an anti-human serum albumin vhh). In vitro neutralizing activity wasmeasured by the Vero cell  assay. For in vivo protection studies Balb/c micewere injected i.v. with 1LD100 Stx2 or i.g. with 4x1011CFU/kg of STEC and inoculated i.p. with the different vhh formats. The half-lifeof different vhh formats was determined by persistence of antibody in plasma. Results anddiscussion: The bivalent and trivalent nanobodies showed a higher in vitro neutralizing activity than themonovalent vhh (mean of pmoles that neutralize 1CD50 Stx2 ±SD) monovalent: 0.5±0.13, bivalent: 0.04±0.007*,trivalent: 0.06±0.04* (*p