Protection of Mice Orally Infected With Shiga Toxin-Producing Citrobacter rodentium Treated With Nanobody Multimer

Shiga toxin (Stx)-producing Escherichia coli (STEC) colonizes the gut and causes 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 <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- to 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.

Citrobacter rodentium (Cr), a mouse pathogen that 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).

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.

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.