Prokaryotic expression and potential as a candidate vaccine of peptidyl-prolyl isomerase from Neisseria gonorrhoeae

Abstract:

[Background] Gonorrhoea is one of the major sexually transmitted diseases in China, and the infection with Neisseria gonorrhoeae (NG) can promote the transmission and infection of HIV. The incidence of gonorrhoea in China is on the rise, and the emergence of multidrug resistant strains makes it an urgent need to develop protective vaccines for preventing the spread and infection of gonorrhea. [Objective] To unveil the advanced structure and epitopes of peptidyl-prolyl isomerase (PPIase) of NG, and explore the potential of PPIase as a vaccine and a molecular diagnostic target. [Methods] Bioinformatics tools were employed to analyze the polarity, hydrophilicity, flexibility, surface accessibility, secondary and tertiary structures, and T and B cell epitopes of PPIase. The prokaryotic expression system of PPIase was constructed with pET32a(+), and the recombinant protein was purified. The BALB/c mice were immunized with the purified recombinant protein and the NG cells disrupted by ultrasound, respectively, and the sera were then harvested. The surface antigens of NG whole cells were prepared. The binding of serum antibody induced by PPIase to the surface antigens of NG whole cells was examined by the enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence assay, respectively. [Results] The secondary structure of PPIase was mainly composed of α helix (39.34%), random coil (30.51%), and extended strand (20.59%). The epitope analysis revealed 5 B cell dominant epitopes, 9 cytotoxic T lymphocyte dominant epitopes, and 18 helper T cell dominant epitopes. The recombinant PPIase protein was expressed and purified by the prokaryotic expression system. The purified recombinant protein can stimulate BALB/c mice to produce high-titer antibodies, and the serum antibody induced by the recombinant PPIase protein can bind to the NG surface antigen. [Conclusion] PPIase as an outer membrane protein demonstrates good immunogenicity and immunoreactivity, and the specific antibody induced by this protein can bind to the surface antigen of NG. Therefore, PPIase has the potential as a candidate vaccine against NG.