Harnessing an Integrative In Silico Approach to Engage Highly Immunogenic Peptides in an Antigen Design Against Epsilon Toxin (ETX) of Clostridium perfringens

Epsilon toxin (ETX) is one of four lethal toxins of Clostridium perfringens produced by types B and D of the pathogen. This pore-forming toxin is one of the most potent bioterrorism agents with economic importance. Although an effective vaccine and an equine antitoxin are available to protect livestock against ETX, no approved vaccine or antitoxin is available for humans. In the current study, an integrative, simple, fast, and reliable approach is availed to design a safe and minimized construct based on preexisting experimental linear B cell epitopes. This guideline is designed based on the surface accessibility, flexibility, hydrophilicity, content of beta-turn structure, and antigenicity of potential epitopes. Experimental linear B-cell epitopes were analyzed with respect to antigenicity. Two antigenic regions were introduced based on the distribution of epitopes. Moreover, three constructs were designed based on top ranking epitopes. These constructs were evaluated for their antigenicity, surface accessibility, flexibility, hydrophilicity, and beta-turn content and were compared to the ETX sequence. The 114-aa construct with an antigenicity score of 0.8592 was the most stable, antigenic, hydrophilic, flexible, and surface accessible antigen within the ETX sequence, the selected regions, and the designed constructs. Although the performed in silico analyses revealed that the designed construct could serve as a safe antigen triggering highly reactive and neutralizing anti-ETX antibodies, it should be verified by experimental assays in future studies.