Modern approaches to the immunotherapy of <i>Clostridioides difficile</i>

Clostridioides difficile is a leading cause of diarrhea and pseudomembranous colitis associated with antibiotic therapy. Hypervirulent strains of C. difficile, such as ribotype 027, have high mortality rates. Recurrent C. difficile infection is extremely difficult to treat. Symptoms of the disease are caused by two toxins, TcdA and TcdB. These toxins are targets for therapeutic antibodies. The TcdB-specific monoclonal antibody bezlotoxumab (Zinplava ©, Merck & Co. Inc., USA), approved for the prevention of recurrent C. difficile infection, has some effectiveness against a limited set of C. difficile strains. Having a lower cost compared to monoclonal antibodies, high affinity for the antigen, and unique structural and functional properties, nanoantibodies are a promising strategy for the immunotherapy of diseases associated with C. difficile.