Abstract
Shiga toxin (Stx)-producing Escherichia coli (STEC) infections are implicated in the development of the life-threatening Hemolytic Uremic Syndrome (HUS). Despite the magnitude of the social and economic problems caused by STEC infections, no licensed vaccine or effective therapy is presently available for human use. Single chain antibodies (VHH) produced by camelids exhibit several advantages in comparison with conventional antibodies, making them promising tools for diagnosis and therapy. In the present work, the properties of a recently developed immunogen, which induces high affinity and protective antibodies against Stx type 2 (Stx2), were exploited to develop VHHs with therapeutic potential against HUS. We identified a family of VHHs against the B subunit of Stx2 (Stx2B) that neutralize Stx2 in vitro at subnanomolar concentrations. One VHH was selected and was engineered into a trivalent molecule (two copies of anti-Stx2B VHH and one anti-seroalbumin VHH). The resulting molecule presented extended in vivo half-life and high therapeutic activity, as demonstrated in three different mouse models of Stx2-toxicity: a single i.v. lethal dose of Stx2, several i.v. incremental doses of Stx2 and intragastrical STEC infection. This simple antitoxin agent should offer new therapeutic options for treating STEC infections to prevent or ameliorate HUS outcome.
Highlights
Shiga toxin (Stx)-producing Escherichia coli (STEC) infections are implicated in the development of the life-threatening Hemolytic Uremic Syndrome (HUS)
Notwithstanding the magnitude of the social problems caused by STEC infections, no licensed vaccine or effective therapy is presently available for human use
We demonstrated that weaned mice infected with Stx type 2 (Stx2)-producing E. coli O157:H7 strains develop renal dysfunction and die during the following three-four days after infection
Summary
Shiga toxin (Stx)-producing Escherichia coli (STEC) infections are implicated in the development of the life-threatening Hemolytic Uremic Syndrome (HUS). The resulting molecule presented extended in vivo half-life and high therapeutic activity, as demonstrated in three different mouse models of Stx2-toxicity: a single i.v. lethal dose of Stx[2], several i.v. incremental doses of Stx[2] and intragastrical STEC infection. VHH can be expressed as recombinant fragments, and exhibit several valuable characteristics, such as: small size (12–16 kDa), high solubility, high intrinsic stability, easy tailoring into pluripotent constructs (allowing half-life extension strategies), recognition of uncommon or hidden epitopes, low toxicity and ease of manufacture These properties lead to the development of therapeutic agents in which VHHs outperform other antibody formats[16,17]
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