Mechanism underlying the anti-apoptotic activity of pORF5 plasmid protein in Chlamydia trachomatis via high-mobility group box 1 protein: a preliminary study / 中华皮肤科杂志

Objective To explore the molecular mechanism underlying the anti-apoptotic activity of pORF5 plasmid protein of Chlamydia trachomatis,so as to provide an experimental basis for further clarifying the pathogenesis of Chlamydia trachomatis.Methods HeLa cells were divided into two groups:carbonyl cyanide m-chlorophenyl hydrazone (CCCP,an apoptosis inducer) group was stimulated by CCCP for 30 minutes,and pORF5 + CCCP group was pretreated with pORF5 plasmid protein for 18 hours followed by CCCP for 30 minutes.Then,Western blot analysis was performed to determine the expression of apoptosisrelated proteins Bcl-2,Bax and caspase-3,JC-1 fluorescent probe was used to detect changes in the mitochondrial membrane potential in HeLa cells,and cytochrome c release from mitochondria was analyzed by indirect immunofluorescence assay.To analyze whether high-mobility group box 1 (HMGB1) protein participated in the anti-apoptotic role of pORF5 plasmid protein,HMGB 1 shRNA and control RNA were separately transfected into the HeLa cells,which were then stimulated by pORF5 plasmid protein and CCCP.Then,the protein expression of Bcl-2,Bax,activated caspase-3 was determined,and cytochrome c release was analyzed.Data were compared between two groups by using paired t test.Results pORF5 plasmid protein could antagonize the CCCP-induced decrease of mitochondrial membrane potential,and the red/green fluorescence intensity ratio was significantly lower in the CCCP group (0.4 ± 0.1) than in the pORF5 + CCCP group (1.7 ± 0.3;t =6.95,P ＜ 0.01).The protein expression of Bcl-2 in the HeLa cells in the pORF5 + CCCP group was 5.3 ± 0.6 times more than that in the CCCP group (t =8.62,P ＜ 0.01),while the protein expression of Bax and activated caspase-3 in the pORF5 + CCCP group significantly decreased by 79％ ± 10％ (t =9.23,P ＜ 0.01) and 75％ ± 8％ (t =4.26,P ＜ 0.05) respectively compared with the CCCP group.Compared with the control RNA transfection group,the HMGB1 shRNA transfection group showed significantly decreased mitochondrial membrane potential in the HeLa cells (t =11.23,P ＜ 0.01),increased cytochrome c release,decreased Bcl-2 expresson (t =7.19,P ＜ 0.05) and increased Bax expression (t =13.06,P ＜ 0.01) after stimulation with pORF5 and CCCP.Conclusion Chlamydia trachomatis plasmid protein pORF5 plays an anti-apoptosis role by blocking the mitochondrial apoptotic pathway through HMGB1 protein.

Inhibitory effect of Chlamydia trachomatis plasmid-encoded protein pORF5 on HeLa cell apoptosis induced by tumor necrosis factor-alpha / 中华皮肤科杂志

Objective To evaluate inhibitory effect of Chlamydia trachomatis plasmid-encoded protein pORF5 on HeLa cell apoptosis induced by tumor necrosis factor-alpha(TNF-α). Methods The recombinant lentiviral expression vector containing pORF5 gene and helper plasmids were co-transfected into 293T cells to prepare the recombinant lentivirus. Then, the lentivirus particles were collected and concentrated, and used to infect HeLa cells. Flow cytometric screening identified stable pORF5-expressing HeLa (pORF5-HeLa) cells. Meanwhile, the empty plasmid was transfected into HeLa cells to prepare control HeLa cells. The two cell lines were both divided into two subgroups to be treated with 20μg/L TNF-αand fresh culture medium respectively for 6 hours. Then, Hoechst 33258 staining was performed to observe morphological changes of apoptotic cells, flow cytometry to detect cell apoptosis, real-time PCR to measure the mRNA expression of Caspase3, Bax and Bcl-2, and Western blot analysis to determine the protein expression of Bax and Bcl-2. Results After 6-hour treatment with TNF-α, Hoechst 33258 staining showed variable degrees of karyopyknosis and karyorrhexis, and highly-refractive blue apoptotic bodies in the pORF5-HeLa cells and control HeLa cells. The pORF5-HeLa cells and control HeLa cells both showed significantly higher apoptosis rate in the treated subgroup than in the untreated subgroup (pORF5-HeLa cells:35.5%± 4.5%vs. 9.5%± 1.5%, t=13.53, P<0.01;control HeLa cells:63.6%± 5.8%vs. 7.9%± 0.9%, t=32.36, P<0.01). Compared with treated control HeLa cells, treated pORF5-HeLa cells showed significant decreases in mRNA expression of Bax(72.8%)and Caspase 3(84.5%)(t = 35.29, 42.25, respectively, both P < 0.01), as well as in Bax protein expression(t = 17.58,P < 0.01), but significant increases in Bcl-2 mRNA and protein(6.8 times)expression(t = 87.12, 18.93, respectively, both P <0.01). Conclusion pORF5 plasmid protein can inhibit TNF-α-induced HeLa cell apoptosis likely by increasing the expression of anti-apoptotic protein bcl-2 and decreasing the expression of pro-apoptotic proteins Caspase-3 and Bax.

Screen and identification of immunodominant fragment of pORF5 plasmid protein from Chlamydia trachomatis / 中国免疫学杂志

Objective:To investigate the immunogenicity of pORF5 plasmid protein,and further to screen and identify its im-munodominant domian.Methods: 10 different fragments of pORF5 gene including full length were amplified from the DNA of Chlamydia trachomatis serovar D by PCR and cloned into appropriate site of pGEX-6p vector to construct recombinant vectors after digested with BamHⅠand NotⅠrestriction endonucleases.After identification by PCR and sequencing,the recombinant plasmids were transformed into XL1 Blue E.coli to express the GST fusion proteins.ELISA and Western blot were carried out to identify the immunogenicity and immunoreaction of pORF5 plasmid protein.10 different fragments were reacted with sera from patients urogenitally infected with Chlamydia trachomatis, mouse polyclonal antibodies and mouse monoclonal antibodies of pORF5 plasmid protein with ELISA method.Results: pORF5 plasmid protein displayed strong immunogenicity and could induce a strong antibody response in human.The reactivity of human antibodies almost completely disappeared,when the native structure of pORF5 plasmid protein was de-stroyed.F6 that only lacked the N-terminal 66 amino acids was recognized by antibodies in ELISA as strongly as the whole pORF5 plasmid protein was.However,no other fragments were significantly recognized although there was a minimal reactivity of F2 and F3 with antibodies.Conclusion:pORF5 plasmid protein was an immunodominant antigen containing conformation-dependent epitope,and the C-terminal three quarters of pORF5 amino acid sequence was required for maintaining its immune dominance and conformation.The significance of the above findings lay a foundation for the further study on pORF5 protein function and vaccine development.

pORF5 plasmid protein of Chlamydia trachomatis induces IL-1βand IL-18 production through NALP3 inflammasome activation / 中国免疫学杂志

Objective:To investigate whether pORF5 plasmid protein of Chlamydia trachomatis(Ct) induces 1L-1βand 1L-18 production in THP-1 cells,and its potential molecular mechanism.Methods:pORF5 plasmid protein was used to stimulate THP-1 cells at different concentrations(0,3,6,12,24,36 μg/ml),then the inflammatory cytokines IL-18 and IL-1βwere detected by ELISA at the time of 0,8,16,24,36 h;The mRNA expression of NALP3 inflammasome were detected by Realtime-PCR,and Caspase-1 activity was determined by Western blot analysis.THP-1 cells were transfected with siRNA targeting NALP3 and ASC gene for 24 h or pretreated with Caspase-1 inhibitor(Z-YVAD-FMK) for 30 min,and subsequently stimulated with pORF5(24 μg/ml) for 24 h,then secretion of IL-1βand IL-18 were analyzed by ELISA.Results: The pORF5 plasmid protein induced THP-1 cells to secrete IL-1βand IL-18 by dose-and time-dependent manners,production of IL-1βand IL-18 reached their peaks(491 pg/ml and 186 pg/ml) at concentration of 24 μg/ml,and the peak amount of IL-1βand IL-18 occurred at 24 h and 16 h post-stimulation respectively.pORF5 plasmid protein in-creased mRNA expression of NALP3 inflammasome and activated Caspase-1 in THP-1 cells.NALP3 siRNA,ASC siRNA and Z-YVAD-FMK reduced pORF5-induced IL-1βand IL-18 production when compared with control groups(P<0.05).Conclusion:pORF5 plasmid protein could induce THP-1 cells to produce IL-1βand IL-18 through NALP3 inflammasome activation,which may play an important role in the pathogenesis in Ct infection.

Preliminary study on genital tract immune injury in mice induced by pORF5 plasmid protein of Chlamydia trachomatis / 中华微生物学和免疫学杂志

Objective To investigate the immune injury in genital tract of BALB/c mice induced by plasmid protein pORF5 of Chlamydia trachomatis and its possible mechanism.Methods GST(glutathione-S-transferases)-pORF5 fusion protein was expressed and digested with PreScission Protease to obtain the target protein without GST tag.After further purification and endotoxin removal,pORF5 protein was injected into the posterior fornix of BALB/c mice on day 1,3 and 6,while the control groups were injected with PBS or GST protein respectively,and then all the mice were sacrificed on day 7 to evaluate genital tract gross pathology and histopathological characterization.The levels of TNF-α,IL-1β and IL-6 in serum,splenocytes culture supernatant and vaginal douche were detected by ELISA.Results Mice in pORF5 group developed different degrees of swelling in isthmic portion and ampulla of uterine tube,connective tissue adhesion and hydrosalpinx in the genital tract tissues,while the PBS group and the GST group did not show any obvious change.The inflammatory score showed that the genital tract pathology in pORF5 group was much more severe than PBS and GST control groups (P＜0.O1).The levels of TNF-α,IL-1β and IL-6 in vaginal douche and splenocytes culture supernatants in pORF5 group were obviously higher than those of PBS and GST groups (P＜0.05).The levels of TNF-α and IL-1β in serum were also higher than those of GST and PBS groups (P＜0.01).Conclusion pORF5 plasmid protein could induce pathological immune response in the genital tract of BALB/c mice,which may be associated with the increase of the production of the inflammatory cytokines TNF-α,IL-1β and IL-6 in BALB/c mice.

Purification and immunological characteristics of monoclonal antibody 2H4 against Chlamydia trachomatis pORF5 plasmid protein / 中华微生物学和免疫学杂志

ObjectiveTo purify and characterize the monoclonal antibody (McAb) against Chlamydia trachomatis pORF5 plasmid protein.Methods The hybridoma cells stably secreting specific McAb against pORF5 were cultured in a large scale,and protein G purification by affinity chromatography was used to purify 2H4 McAb.ELISA was used to determine the antibody titer,and identify McAb isotype.Immunofluorescence assay (IFA) and Western blot were performed to detect McAb specificity.Results The purity of 2H4 antibody was 93％,the titer reached 1:1024,and 2H4 McAb was identified to belong to IgG2a isotype,2H4 McAb reacted strongly with the GST-pORF5 fusion protein and endogenous pORF5 protein expressed by Chlamydia trachomatis serovar A,D,L2,Chlamydia muridarum ( MoPn ),Chlamydia psittaci 6BC,but not other chlamydial plasmid proteins and Chlamydia pneumoniae(Cpn) AR39 strain.Conclusion2H4 McAb against pORF5 protein was successfully purified with a high titer and specificity which lay a foundation for further study on pORF5 protein structure and function.