Secretory expression of hemagglutinin globular domain (HA۱) of the influenza A (H۵N۱) virus in Bacillus subtilis

Background and Aim: H۵N۱ influenza viruses may acquire the ability to transmit between humans thus, there is the possibility of a pandemic event. HA۱ protein has been shown to play a major role in binding the virus to its target cell and the main neutralizing antibody responses elicit against this region. Bacillus subtilis has been identified as a free endotoxin host for expression and secretion of heterologous proteins with immunological activity. Although the bacteria is not capable of making glycosylated proteins, it has been shown that glycosylation of HA is not much necessary for its immunogenicity. Here we produced secretory recombinant HA۱ protein in B. subtilis. Materials and Methods: HA۱ sequence was cloned into pGEM® ۵Zf(–)vector. It was then subcloned into shuttle vector PHT۴۳ and transferred to E.coli for replication. The recombinant plasmid was extracted from E.coli and used to transform of B.subtilis by electroporation. After induction of recombinant B.subtilis by IPTG, total cell protein and the protein secreted into media were analysed through a time course using SDS-PAGE. Results: The accuracy of PHT۴۳-HA۱ construct was confirmed by Sequencing and enzymatic digestion analysis. SDS-PAGE results showed that the recombinant HA۱ protein was successfully expressed and secreted into medium. Conclusions: B.subtilis is a free endotoxin host which could be a favorite prokaryotic platform for production of the recombinant HA۱ protein.The HA۱ protein produced here could be considered and evaluated as a candidate vaccine which its immunogenicity potential needs to be assessed in animal models along with proper control groups.