In silico analysis of a chimeric fusion protein as a new vaccine candidate against Clostridium perfringens type A and Clostridium septicum alpha toxins.

In silico analysis is the most important approach to understand protein structure and functions, and the most important problem for designing and producing a fusion construct is producing large amounts of functional protein. Clostridium perfringens type A and Clostridium septicum produce alpha (plc) and alpha toxins respectively. C. perfringens can cause gas gangrene and gastrointestinal diseases. C. septicum can cause traumatic and non-traumatic gas gangrene. The aim of current research was in silico analysis of a chimeric fusion protein against C. perfringens type A and C. septicum alpha toxins. Firstly, the chimeric fusion gene was designed according to nucleotide sequences of C. perfringens type A alpha (KY584046.1) and C. septicum alpha (JN793989.2) toxin genes and then its fusion protein is constructed by amino acid sequences of C. perfringens type A and C. septicum alpha toxins. Secondly, online software was used to determine prediction of secondary and tertiary structures and physicochemical characteristics of the fusion protein. Finally, the validation of the fusion protein was confirmed by Rampage and proSA program. The designed fusion protein has 777 amino acids in length. TASSER server and physicochemical parameters are showed: C-score = - 2.68 and molecular weight = 87.9 KD respectively. Rampage and proSA software revealed the fusion protein is valid. Deposited accession number for the sequence of the fusion gene in the GenBank is MK908396. The designed fusion protein is valid and functional. Thus, the fusion gene could be used for clone and expression in a proper prokaryotic cell and also as a recombinant vaccine candidate.

Design and expression of a chimeric vaccine candidate for avian necrotic enteritis.

Necrotic enteritis is an economically important disease of poultry mainly caused by Clostridium perfringens The bacteria release multiple toxins of which NetB, alpha toxin and TpeL have been reported to play important roles in pathogenicity and/or severity of the disease. In this study, the sequence of clostridial toxins NetB, alpha toxin and TpeL were analyzed using bioinformatics tools to determine protein domains with high immunogenicity factor. Several chimeric trivalent proteins consisting of the immunogenic regions of the three toxins were designed and evaluated. The separate regions were fused together using rigid linkers. Based on a modeled tertiary structure, a proper combination was selected and expressed in a bacterial host (Escherichia coli) and successfully purified. The expression of the chimeric protein was further verified by western blotting. The ability of the immunized serum in recognizing each individual subunit of the chimeric protein was also examined. Circular dichroism was used to evaluate the predicted secondary structure of the chimeric protein. In vitro potency test demonstrated that the serum from a rabbit immunized with the chimeric protein is able to partially neutralize Alpha toxin, hence the construct can potentially be used as a vaccine against C. perfringens.