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 expression 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 expression vector pET28a?PmpI was successfully constructed. A recombi?nant protein with a relative molecular mass of approximately 50 000 was successfully expressed after isopropylβ?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.
ABSTRACT
Objective To obtain the full length (FL ) and C‐terminal fragment of polymorphic membrane protein I (PmpI) of Chlamydia trachomatis serovar D ,and to study the immunogenicity of these proteins .Methods The target genes of PmpI‐FL and PmpI‐C were amplified by polymerase chain reaction (PCR) and inserted into the prokaryotic plasmid vector pGEX‐6P‐1 .The recombinant plasmids pGEX‐6P‐1/PmpI‐FL and pGEX‐6P‐1/PmpI‐C were separately transformed into Escherichia .coli ( E . coli) DH5αand were identified by enzyme digestion ,sequencing and PCR .After the identification ,the recombinant plasmids were separately transformed into E .coli BL21 and induced to express the proteins . The expected proteins were identified by Coomassie brilliant blue staining and Western blot ,then purified by glutathione S‐transferase (GST) MagBeads .The purified proteins were then injected into BALB/c mice to prepare the polyclonal antibodies against PmpI‐FL or PmpI‐C .Enzyme‐linked immune sorbent assay (ELISA) was used for the quantitative detection of the specific antibody .Results The lengths of cloned target genes PmpI‐FL and PmpI‐C were 2 659 bp and 1 195 bp ,respectively ,and the sequences were consistent with those of Chlamydia trachomatis serovar D in GenBank .The molecular masses of target proteins were 122 000 and 69 000 ,respectively ,which were confirmed by Coomassie brilliant blue staining and Western blot and then purified .The titers of the antibodies (anti‐PmpI‐FL and anti‐PmpI‐C) in sera of immunized mice detected by ELISA were 1∶12 800 and 1∶6 400 ,respectively .Conclusion The PmpI‐FL‐GST and PmpI‐C‐GST fusion proteins with high immunogenicity are successfully expressed and purified , which lays the foundation for further study .
ABSTRACT
<p><b>OBJECTIVE</b>Chlamydia psittaci is an avian respiratory pathogen and zoonotic agent. The wide prevalence of C. psittaci poses a threat to the poultry industry and its employees. However, few commercial kits are available for detecting avian antibodies excluding the in-house ELISA kit. In this study, we developed a novel ELISA kit for detecting antibodies against C. psittaci based on the N-terminal fragment of polymorphic outer membrane protein D (PmpD-N) as the coating antigen.</p><p><b>METHODS</b>The antigen concentrations, primary antibody, and cut-off value were determined and optimized. The ELISA, designated PmpD-N ELISA, was assessed for sensitivity, specificity, and concordance using sera samples from 48 experimentally infected and 168 uninfected SPF chickens.</p><p><b>RESULTS</b>The sensitivity and specificity of PmpD-N ELISA were 97.9%, 100%, respectively, while the concordance was 98.1% as compared to that of MOMP-ELISA. No cross-reaction with positive sera for other avian pathogens was found. Using PmpD-N ELISA, 799/836 clinical samples were positive, including 93.0% and 98.1% positivity in layers and broilers, respectively.</p><p><b>CONCLUSION</b>These data indicate that indirect ELISA with PmpD-N as the antigen candidate is a promising approach for the surveillance of C. psittaci infection.</p>