Intravenous adenovirus expressing a multi-specific, single-domain antibody neutralizing TcdA and TcdB protects mice from Clostridium difficile infection.

Clostridium difficile infection (CDI) is the most common cause of antibiotic-associated diarrhea and colitis in developed countries. The disease is mainly mediated via two major exotoxins TcdA and TcdB secreted by the bacterium. We have previously developed a novel, potently neutralizing, tetravalent and bispecific heavy-chain-only single domain (VHH) antibody to both TcdA and TcdB (designated as ABA) that reverses fulminant CDI in mice. Since ABA has a short serum half-life, in this study a replication-deficient recombinant adenovirus expressing ABA was generated and the long-lasting expression of functional ABA was demonstrated in vitro and in vivo Mice transduced with one dose of the adenovirus displayed high levels of serum ABA for more than1 month and were fully protected against systemic toxin challenges. More importantly, the ABA delivered by the adenovirus protected mice from both primary and recurrent CDI. Thus, replication-deficient adenoviral vector may be used to deliver neutralizing antibodies against the toxins in order to prevent CDI and recurrence.