Complement depletion renders C57BL/6 mice sensitive to the Bacillus anthracis Sterne strain

Concerns regarding safety and control of virulent Bacillus anthracis have created substantial hurdles to the study of anthrax. The Sterne strain is considered relatively safe to study, but this acapsular strain has a defect in normal mice and is often studied in A/J mice. A/J mice are highly susceptible to the Sterne strain, due to a defect in the Hc locus, which encodes complement factor 5 (C5). Here we show that normally resistant C57BL/6 mice become highly susceptible to the Sterne strain upon complement depletion with cobra venom factor. This generalizable approach should allow the virulence of anthrax to be studied under relatively safe conditions and using a wide variety of mouse strains.