Bacillus anthracis Sterne Strain 34f2 Vaccine Antibody Dose Response by Subcutaneous and Oral Administration

Anthrax (Bacillus anthracis) is a zoonotic disease endemic to environments worldwide. Spores, the dormant form of the bacteria, can survive for decades in nature’s harshest environments and maintain their viability to cause disease. Outbreaks are common in free-ranging livestock and wildlife, thus making anthrax an economically and ecologically important disease. The currently available vaccine to protect livestock is a suspension of B. anthracis Sterne Strain 34F2 spores in saponin (Sterne vaccine). However, it is only available as a subcutaneous injection which is an impractical method of prevention for wildlife. Oral vaccination is the ideal method for free-ranging wildlife, but the Sterne vaccine has never been thoroughly evaluated for oral administration. The current study evaluated the antibody titers induced in mice by subcutaneous or oral vaccination with three different doses of the Sterne vaccine. Results described here show a gradual increase in antibody titers at each time point following subcutaneous vaccination with all vaccine doses. In contrast, no antibody response was detected from any dose or any time point after oral vaccination. Taken together, these results suggest that the Sterne vaccine is only effective as a subcutaneous injection and that an alternate oral anthrax vaccine formulation must be developed to allow for efficient vaccination of free-ranging livestock and wildlife.