Oral vaccination with an adenovirus-vectored vaccine protects against botulism

We have previously shown that an adenovirus vectored vaccine delivered intramuscularly or intranasally was effective in protection against botulism in a mouse model. The adenoviral vector encodes a human codon-optimized heavy chain C-fragment (H_C50) of botulinum neurotoxin type C (BoNT/C). Here, we evaluate the same vaccine candidate as an oral vaccine against BoNT/C in a mouse model. To elicit protective immunity, the mice were orally vaccinated with a single dose of 1 × 10⁴ to 1 × 10⁷ plaque forming units (pfu) of the adenoviral vector. The immune sera, collected six weeks after oral vaccination with 2 × 10⁷ pfu adenovirus, have shown an ability to neutralize the biological activity of BoNT/C in vitro. Additionally, animals receiving a single dose of 2 × 10⁶ pfu adenovirus or greater were completely protected against challenge with 100 × MLD₅₀ of BoNT/C. The data demonstrated the feasibility to develop an adenovirus-based oral vaccine against botulism.