Cloning and expression of porA gene as the first step of a vaccine candidate study against Neisseria meningitidis serogroup A infection

Introduction: Neisseria meningitidis is a major causative agent of bacterial septicemia and meningitis in human. PorA is a major component of the outer membrane of N. meningitidis and functions as a cationic Porin. This study aimed to clone and determine the expression of PorA as the first step for producing a proper antigen in a vaccine study against N. meningitidis. Methods: An approximately 1200-bp fragment of porA gene was amplified by PCR using                  N. meningitidis serogroup A genomic DNA and then cloned into prokaryotic expression vector pET-28a. The resulting construct (pET28a-porA plasmid) was transformed into competent E.coli BL21 cells for expression of recombinant protein. The proper overexpression of the recombinant protein was verified by SDS-PAGE and Western Blotting. Results: Cloning of porA was confirmed by colony-PCR and enzymatic digestion. The nucleotide sequence homology of the cloned porA gene was 97% , compared to the reference gene (NCBI GenBank accession number AL157959.1). The prokaryotic expression system (pET28a-porA- BL21) could  produce our 45-kDa target recombinant protein, efficiently. Conclusion: The prokaryotic expression system and conditions used in this study provides an applicable method for producing recombinant PorA and possibly many other bacterial outer membrane proteins for future vaccine studies.