Abstract:

Guo Rui, Liu Yuanjun, Zheng Lei, Wang Sheng, Wei Shijuan, Liu Quanzhong Department of Dermatology and Venereology, Tianjin Medical University General Hospital, Tianjin 300052, China Corresponding author: Liu Quanzhong, Email: liuquanzhong@medmail.com.cn 【Abstract】 Objective To clone and express the polymorphic membrane protein I （PmpI） gene of Chlamydia trachomatis （Ct）, and to assess the immunogenicity and biological characteristics of PmpI. Methods A bioinformatic software was used to analyze the sequence of the PmpI gene of Ct, and to predict B cell epitopes in PmpI. With Ct serovar D DNA as the template, PCR was performed to amplify the N-terminal region （from position 90 to 1464） of the PmpI gene, which was cloned into a prokaryotic vector pET28a to express the recombinant protein PmpI. A Ni-ion affinity chromatography column was used to purify the recombinant protein, which was used to immunize New Zealand rabbits for preparation of polyclonal antibodies. Western blot analysis was conducted to evaluate the immunogenicity of this protein. Results A comprehensive analysis was carried out on the secondary structure, flexible regions, hydrophilicity plot, antigenic index and surface probability plot of the protein, which suggested that PmpI had 8 dominant B-cell epitopes. The product of PCR targeting the PmpI gene of Ct serovar D showed a total length of 1 375 bp. The recombinant prokaryotic vector pET28a-PmpI was successfully constructed. A recombi-nant protein with a relative molecular mass of approximately 50 000 was successfully expressed after isopropyl β-d-1-thiogalactopyranoside （IPTG） induction, and purified by affinity chromatography. Polyclonal antibodies against the recombinant protein were successfully prepared. Conclusion The N-PmpI protein of Ct serovar D is cloned and expressed successfully, laying a foundation for further studies on its biological functions.