Cloning, expression and purification of outer membrane secretin PilQ406-770 of Neisseria meningitidis serogroup B

Neisseria meningitidis is a major cause of bacterial septicemia and meningitis. Currently, there are no vaccines to prevent disease caused by strains of N. meningitidis serogroup B, since cross-reactivity of the serogroup B capsule with human tissue has hampered efforts to develop a reliable vaccine. PilQ is an antigenically conserved outer membrane protein which is essential for meningococcal pilus expression at the cell surface. In the current study, we selected a 1095bp fragment of C-terminal of secretin pilQ and evaluated the immunogenicity of this recombinant fragment. This fragment was amplified by PCR from genomic DNA isolated from N. meningitidis serogroup B and cloned into the pET-28a expression vector. PilQ406-770 was over-expressed with IPTG and then affinity-purified by Ni2+-Sepharose resin. The recombinant PilQ406-770 was reacted with rabbit anti-N. meningitidis polyclonal antibody in western-blot analysis. Mice were immunized subcutaneously with purified rPilQ406-770 mixed with an equal volume of Freund's adjuvant and evaluated specific serum antibody responses. Our results show pilQ406-770 cloned in pET28a vector, while the cloning of pilQ406-770 was confirmed by colony-PCR and enzymatic digestion. SDS-PAGE analysis showed that our constructed prokaryotic expression system pET28a- pilQ406-770-BL21efficiently produces target recombinant protein with molecular weight of 43 kDa in the form of dissoluble inclusion body. Our results confirmed that a prokaryotic expression system for PilQ406-770 protein was successfully constructed