Protection of mice orally infected with Shiga toxin-producing Citrobacter rodentium treated with nanobody multimer

Background Shiga toxin (Stx) producing Escherichia coli (STEC) colonize the gut and cause enteritis through bacterial attachment-effacement (A/E) leading to mucosal damage. This facilitates systemic uptake of Stx which can often lead to hemolytic-uremic syndrome (HUS) and acute renal failure, particularly in children under 5 years of age. STEC infections expressing Stx2 variants are a major risk factor for HUS. Beyond patients receiving supportive care, there is no treatment for STEC-mediated HUS, and antibiotics are contraindicated. The 3–7-day prodromal interval between onset of STEC diarrhea and HUS offers a window for intervention for diarrheic patients, contacts thereof, or individuals exposed to the source of infection. Methods Citrobacter rodentium (Cr), a mouse pathogen which exhibits mucosal bacterial A/E, was genetically constructed to express Stx2d (Cr-Stx2d). This, along with a Cr parent strain carrying the kanamycin gene were used to model STEC in mice. Mice were treated intraperitoneally with a broad subtype-specific, Stx-neutralizing nanobody multimer fused to the human IgG1 Fc domain (VNA2-Stx/hFc). Results When a single treatment was administered as late as 4 days after Cr-Stx2d challenge, likely within the human STEC-HUS window of intervention, complete protection of mice was achieved. Conclusions This Cr-Stx2d model, which mimics elements of human STEC infections by causing mucosal gut lesions and systemic Stx2d mediated kidney damage, will help evaluate specific treatments against STEC-HUS, as demonstrated here with VNA2-Stx/hFc -treated mice given a single injection well after bacterial challenge. This product should be safe, simple and economical to manufacture.