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Objective To investigate the function of phosphatidylinositol phospholipase C encoded by LB361 gene of L.interrogans ( L-PI-PLC) and its mechanism in inducing macrophage apoptosis .Meth-ods The PI-PLC domains in the sequence of LB 361 gene of L.interrogans serovar Lai strain were analyzed by bioinformatics method .Prokaryotic expression system was established to express the recombinant L -PI-PLC ( rL-PI -PLC).The enzymatic activity of rL-PI-PLC in hydrolyzing phosphatidylinositol -4,5-bisphos -phate (PIP2) substrate into inositol-1,4,5-trisphosphate (IP3) was determined by IP3 fluorescence polariza-tion assay.LB361gene expressions at mRNA and protein levels as well as the secretion of LB 361gene prod -ucts were detected by real-time fluorescent quantitative RT -PCR and Western blot assay after infection of hu-man THP-1 macrophages with L.interrogans serovar Lai strain.A LB361 gene-transfected THP -1cell line was generated for evaluation of the mechanism of LB 361 gene products in elevating intracellular free Ca 2+( [Ca 2+] i) concentration and inducing the apoptosis of transfected THP -1 cells with the use of laser confocal microscopy and flow cytometry.Re sul ts The rL-PI-PLC hydrolyzed PIP2 into IP3 with a Km of 199 μmol/L and a Kcat of 8.566×10-5 S-1 .The expressions of LB361gene at mRNA and protein levels were both signifi -cantly up-regulated after infection of THP-1 cells with L.interrogans serovar Lai strain .Moreover , the exter-nal secretion of L-PI-PLC was also found during infection .The concentrations of IP 3 and [ Ca2+] i in the LB361 gene-transfected THP-1 cells were significantly increased compared to those in the non-transfected THP-1 cells, resulting in a high [Ca2+]i-dependent apoptosis of partial THP-1 cells.Conclusion PI-PLC is encoded by the LB361 gene of L.interrogans, which could induce the apoptosis of macrophages through el-evating [ Ca2+] i concentration during infection of microphages with L.interrogans.
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Objective To determine the function of toxic protein VapC in toxin/antitoxin system of Leptospira species and the cytotoxicity to host cells of the toxic protein.Methods Using genomic DNA of pathogenic L.interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai as the template,several PCRs were performed to amplify entire vapB,vapC and vapBC genes.Subsequently,the prokaryotic expression systems of vapB,vapC and vapBC genes were constructed.Expression of the target recombinant proteins rVapB and rVapC was detected by SDS-PAGE and the expressed rVapB and rVapC were extracted by NiNTA affinity chromatography.Activity of rVapB and rVapC to lyse the DNAs or RNAs from L.interrogans strain Lai and THP-1 cells were then determined.The changes of transcription and expression of vapB and vapC genes of L.interrogans strain Lai before and after infection of THP-1 cells were detected by real-time fluorescent quantitative RT-PCR and Western blot assay.The eukaryotic expression vectors of the vapB and vapC genes were generated for transfection of host cells and CCK-8 agent was used to detect the effect of leptospiral VapB and VapC proteins on activity of host cells.Results The nucleotide and putative amino acid sequences of the cloned vapB and vapC genes were completely identical with the reported corresponding genes.The constructed prokaryotic expression systems could express rVapB and rVapC,respectively.rVapC displayed RNase avtivity but did not lyse DNA.When L.interrogans strain Lai infected THP-1 cells,the transcription and expression of vapB and vapC genes were upregulated and partial VapC protein was secreted from the leptospiral cells.The mass mortality was observed in HEK293 human renal tubular epithelial ceils containing the vapC gene through transfection.Conclusion VapC protein of L.interrogans strain Lai is a RNase and is secreted during infection of host cells with obvious cytotoxicity.
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ObjectiveTo determine the diversity of outer membrane protein expression of Leptospira interrogans during infection of human THP-1 monocytes,and protein antigen candidates for developing leptospiral genetically engineering vaccines.MethodsThe outer membrane proteins(OMPs) of Leptospira interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai before or after infection of human THP-1 monocyte line were extracted using Triton X-114 method.The OMPs extracts were separated by two-dimensional gel electrophoresis(2-DGE) and then detected using silver staining method.Four up-regulated and four down-regulated OMPs were selected for hydrolysis by trypsin and then identified by using liquid chromatography-tandem mass(LC-MS/MS) method.The transmembrane regions and signal peptides in the eight target OMPs were analyzed using bioinformatic software.Several real-time fluorescent quantitative RT-PCRs were performed to determine the mRNA level changes of the eight target genes of L.interrogans strain Lai before or after infection of THP-1 cells.The prokaryotic expression systems of target genes were generated and the immunoprutection of target recombinant proteins was determined using leptospire-infected guinea pigs model.ResultsAfter a 60 min infection of THP-1 cells,four OMPs( Loa22,GroEL,F0F1 ATP synthase alpha- and beta-subunits) of L interrogans strain Lai were noticeably up-regulated ( P＜0.05 ),while the other four OMPs( FlaB2,LigB,OmpA family protein and OmpA) were significantly down-regulated (P＜0.05).The results of real-time fluorescent quantitative RT-PCRs were coincident with those confirmed by the 2-DGE phus silver staining.The bioinformatic analysis indicated that among the eight OMPs,OmpA and OmpA family protein belonged transmembrane proteins,while the rest had no membrane structure.Loa22,LigB and OmpA family protein contained a signal peptide in their sequences.200 μg of the recombinant proteins rLoa22 and rGroEL presented 75.0％ immunoprotective rates in the infected guinea pigs.Conclusion An obvious change of the OMP expression map of L.interrogans strain Lai occurs during infection of host cells.The up-regulated leptospiral OM Ps during infection,especially for the GroEL and Loa22 proteins,can be used as the immunogen candidates for developing leptospiral genetically engineering vaccines.
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Objective To construct the T-cells and B-cells combined epitope peptide gene based on the LipL32,OmpL1 and LipL21 protein from Leptospira interrogans and E.coli expression system,and better understanding of the immunological activity of the recombinant protein. MethodsThe immunodomaint T- and B-cells combined epitopes of LipL32,OmpL1 and LipL21 were identified and used to synthetic a new gene and then construct its prokaryotic expression system.The expression of recombinant protein was determined by SDS-PAGE; MAT was used to determine the titer of the antiserum to L. interrogans standard strains of China ; Western blot and ELISA were used to identify the immunity activity of the recombinant protein.Results The synthetic gene was effectively expressed in E.coli BL21 ( DE3 ) strain and mainly presented in dissoluble protein.Western blot result showed that the expression protein react well with the antibodies from immunized rabbit by Leptospira or recombinant protein.ELISA and MAT results showed that the multiepitope protein could cross-react with different serogroup or serovar of Leptospira.Conclusion In this study,we successfully constructed the recombinant T- and B-cells combine epitope gene of leptospires and expressed it in E.coli.The recombinant protein had a good immune activity,and could cross-reacted with antibodies from different serogroups Leptospira infected patients.
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Objective To compare the sensitivity and specificity of Leptospira interrogans using loop-mediated isothermal amplification (LAMP) and real-time PCR technology, then looking for a rapid,sensitive and specific methods for the detection of Leptospira interrogans. MethodsIn accordance with lipL41 gene from Leptospira interrogans, primers for LAMP and real-time PCR were designed and used to detect Leptospira interrogans in cultured 15 reference strains of 15 serogroups in China, then compared the sensitivity and specificity of the two methods in the detection of Leptospira interrogans. ResultsThe LAMP reaction could be completed within 30 min, and whole process of it less than 60 min. The whole real-time PCR reaction could be finished at about 60 min. Both of them had the same detection sensitivity and specificity,the lower detection limits in the reactions was approximately 100 copies and there was no false positive occurred. ConclusionBoth LAMP and real-time PCR were time-saving and had the same sensitivity and specificity. But LAMP reaction could be done under a constant temperature conditions, and need not a special expensive equipment. Therefore, as a sensitive and specific method for quantifying Leptospira interrogans,the LAMP assay was more rapidly and convenient than conventional methods.
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Objective To determine the change of expression level of Leptospira interrogans sph2 gene, and hemolytic and cell apoptosis-inducing activities of sphingomyelinase hemolysin Sph2. Methods Entire sph2 gene fragment was amplified by PCR from genomic DNA of L. Interrogans serovar serogroup Icterohaemorrhagiae serovar Lai strain Lai, and sequenced after T-A cloning. Subsequently, a prokaryotic expression system of sph2 gene was constructed. The expression of target recombinant Sph2( rSph2 ) was examined by SDS-PAGE and the expressed rSph2 was extracted by Ni-NTA affinity chromatogaphy. The hemolytic activity of rSph2 was measured by hemolytic test in sheep blood agar plate and spectrophotometry-based hemoglobin measurement, and the apoptosis-inducing activity of rSph2 to murine mononuclear-macrophagelike cell line(J774A. 1) and hepatic cell line(IAR20) was determined by flow cytometry. A real-time fluorescence quantitative RT-PCR was applied to detect the change of sph2 mRNA levels before and after L. Interrogans strain Lai infecting J774A. 1 and IAR20 cells. Results The cloned sph2 gene had 100% sequence identity to the corresponding gene in GenBank. The constructed prokaryotic expression system was able to efficiently express rSph2. The rSph2 could lyse sheep erythrocytes in concentration-dependent pattern. 10μg/ml rSph2 could induce the apoptosis of J774A. 1 cells and IAR20 cells, and the peak apoptotic rates were 23.96% and 32.92%, respectively. The mRNA level of sph2 gene was significantly elevated within 0.5-2 h of L. Interrogans strain Lai infecting either J774A. 1 or IAR20 cells, and then the mRNA level was quickly descended. Conclusion The sph2 gene of L. Interrogans strain Lai has a transient expression when the microbe contacts host cells. rSph2 possesses activities of sheep erythrocyte lysis and inducing macrophage and hepatocyte apoptosis, indicating Sph2 as an important virulence factor during pathogenic process of Leptospira.
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Objective To determine the modality of Leptospira interrogans invading human and murine mononuclear-macrophages and diversity of leptospiral phagocytotic vesicle formation. Methods Transmission electron microscopy was applied to observe the invasion of L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai into murine mononuclear-macrophage-like cell line J774A. 1 and PMA-activated human monocyte line THP-1 and the formation of leptospiral phagocytotic vesicles. By using immunofluorescence plus either laser confocal microscopy or fluorescence spectrophotometry, the changes of intracellular leptospiral numbers in J774A. 1 and PMA-activated THP-1 cells before and after block with endocytosis inhibitors monodansylcadaverin (MDC), phenylarsine oxide (PAO) and clathrin antibody were investigated. Results The leptospires in J774A. 1 cells were located in phagocytotic vesicles while the leptospires in THP-1 cells had no package with phagocytotic vesicle membrane. Both MDC and PAO presented the effect inhibiting endocytosis of L. interrogans into J774A. 1 and THP-1 cells in dose-dependent manner. The numbers of leptospires in J774A. 1 and THP-1 cells that pre-blocked with 10 μmol/L or above MDC and 1 μmol/L or above PAO were significantly less than that in the two cells untreated with MDC and PAO (P＜0.05＝. After J774A. 1 and THP-1 cells were blocked with clathrin antibody, the numbers of intracellular leptospires were also remarkbly decreased ( P<0.05 ).Conclusion Leptospira interrogans can invade into both human and murine mononuclear-macrophages through the way of clathrin-dependent endocytosis. There is an opposite diversity of leptospiral phagocytotic vesicle formations in human and murine mononuclear-macrophages, which may result in the difference of pathogenesis in human and mice after infected with L. interrogans.
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Objective To investigate the effects of different cell cycles and their regulating genes on apoptosis of mononuclear-macrophages induced by Leptospira interrogans. Methods The diversity and alteration of cell cycles of murine mononuclear-macrophage line(J774A. 1 ) and human monocyte line(THP-1 ) before and after infected with L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai were detected using Cell Cycle Stain Kit plus flow cytometer. The cell cycle synchronized J774A. 1 and THP-1 cells were generated and then identified by using different cell cycle blocking agents and flow cytometer. By using Annexin V/PI Detection Kit combined with flow cytometer, the rates of early-apoptosis and late-apoptosis/necrosis in the synchronized and non-synchronized J774A. 1 and THP-1 cells after infection with L. interrogans strain Lai were determined. Several real-time fluorescence quantitative RT-PCRs were performed to the changes of mRNAs levels of p21, p27, p53, c-myc and cycA genes that associated with cell cycle and apoptosis in J774A. 1 and THP-1 cells before and after infected with L. interrogans strain Lai. Results There were G1, S and G2/M phases in both the non-infected normal J774A. 1 and THP-1 cells. On the contrast,the majority of infected J774A. 1 and THP-1 cells were stagnated at G1 phase, but the amount of S phase THP-1 cells was elevated while that of S phase J774A. 1 cells was not(P ＜0.05). No remarkable early-apoptosis in both the infected G1 phase J774A. 1 and THP-1 cells was found, whereas the rates of early-apoptosis and late-apoptosis/necrosis in the infected M phase J774A. 1 and THP-1 cells were significantly increased (P ＜0.05 ). Additionally, late-apoptosis / necrosis rate in the infected G1 phase THP-1 cells (P ＜ 0.05 )that not found in the infected G1 phase J774A. 1 cells. Compared to the non-infected cells, the p21 mRNA levels in the infected J774A. 1 and THP-1 cells were significantly elevated(P ＜0.05), and the c-myc and p27 mRNA levels in the infected J774A. 1 cells and the cycA mRNA level in the infected THP-1 cells were also higher than those in both the non-infected cells ( P ＜ 0.05 ). Conclusion Different cell cycles and their regulating genes have a role to affect the apoptosis of human and murine mononuclear-macrophages caused by L. interrogans with a diversity of cell line origins.
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Objective To determine the hemolytic activity of products of sphingomyelinase hemolysin encoding genes of Leptospira interrogaas, and the transcriptional level alterations in the infected host cells. Methods By using genomic DNAs of pathogenic L. interrogans serovar serogroup Icterohaemorrhagiae serovar Lai strain Lai and serogroup Pomona serovar Pomona strain Luo, and non-pathogenic L. biflexa serogroup Sama-ranga serovar Patoc strain Patoc Ⅰ as templates, PCRs were performed to amplify entire sph1-sph4 genes. The amplified products were sequenced after T-A cloning. Prokaryotic expression systems of sph1-sph4 genes were re-spectively constructed, and the expressions of target recombinant proteins rSph1-rSph4 were examined by SDS-PAGE. Ni-NTA affinity chromatographic column was used to extract the expressed rSph1-rSph4. Hemolytic ac-tivities of rSph1-rSph4 on sheep blood agar plate were identified. Transcription alterations of sphl-sph4 genes in L. interrogans strain Lai after infected J774A. 1 cells were measured by real-time fluorescence quantitative RT-PCR. Results From genomic DNAs of both L. interrogans strain Lai and Luo, but not from that of L. biflexa strain Patoc Ⅰ , the target fragments of sph1-sph4 genes could be amplified. All the cloned sph1-sph4 genes had 100% nucleotide sequence identities compared to the corresponding reported sequences. The constructed pro-karyotic expression systems were able to efficiently express the target recombinant proteins rSph1-rSph4, respec-tively. All the rSph1-rSph4 had hemolytic activities, and among the four products rSph2 displayed the strongest hemolytic activity. After L. interrogaas strain Lai infecting J774A. 1 cells, the transcriptional levels of sph1-sph4 genes were remarkably up-regulated, especially for mRNA levels of sph2 and sph4 genes. Conclusion sph1- sph4 genes exist only in pathogenic L. interrogans species, and their products have hemolytic activity. The up-regulation of sph1-sph4 gene transcriptional levels in L. interrogans strain Lai after infected cells implies that the sphingomyelinase hemolysins may play important roles in the process of L. interrogans infection in hosts.
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Objective To clone mcp1, mcp2 and mop3 genes that encoding methyl-accepting chemotaxis proteins(MCP) of Campy/obacter jejuni for construction of their prokaryotic expression systems, and to establish chemotactic model in vitro of the microbe for determining chemotaxis-inducing substances and to understand relationship among MCPs and chemotactic inducers. Methods The segments of mep1, mcp2 and mcp3 genes were amplified by PCR and then sequenced after T-A cloning. Prokaryofic expression systems of the genes were subsequently constructed. SDS-PAGE pins Bin-Rod Gel Image Analyzer were used to examine the expression of target recombinant proteins rMCP1, rMCP2 and rMCP3, and Ni-NTA affinity chromatography was performed to purify the rMCPs. Rabbits were immunized with each of the three rMCPs to obtain antisera. Immunodiffusion assay was performed to measure the titers of antisera. IgG in each of the antisera were extracted by ammonium sulfate precipitation and DEAE-32 ion exchange chromatography, and IgG F(ab')2 were then prepared by pepsin enzymolysis and Sephadex G-100 chromatography. Chemotactic model in vitro of C. jejuni based on HAP( hard-agar plus) method was established to determine the chemo-taxis-inducing effect of eight candidate substances. Chemotaxis inhibition test based on IgG F(ab')2 bloc-king was applied to determine the function and diversity of MCPs. Results The segments with expected si-zes amplified from mcp1, racp2 and mcp3 genes were obtained by PCRs, and their nucleotide and putative amino acid sequences were completely same as the reported. The constructed prokaryotic systems could effi-ciently express rMCPs with the yields about 10% of the total bacterial proteins. Immunization with rMCP1, MCP2 and rMCP3 enables the rabbits to produce specific antibody. All the antisera had 1: 4 immunodiffusion titers. Both bovine bile and sodium deoxycholate(DOC) were able to induce ehemotactie movement of C. je-juni in a dosage-dependent manner ( P < 0.05 ). When MCP1 and MCP2 were blocked with their IgG F(ab')2, the ehemotaetic ability of C. jejurd were remarkably decreased (P <0. 05). However, MCP3 blocking did not affect the chemotaxis ( P > 0.05 ). Conclusion The C. jejuni MCPs are successfully ex-pressed in this study. Bovine bile and DOC are the inducers for chemotaxis of C. jejuni, and MCP1 and MCP2 are involved in the process of ehemotaxis iadueed by DOC.
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Objective To screen the efficient antigenic epitopes in genus-specific envelope proteins OmpL1 and LipL21 of Leptospira interrogans for further development of multiple antigenic peptide (MAP)vaccine.Methods Based on bioinformatic technique,the combined epitopes of T and B lymphcytes in OmpL1 and LipL21 molecules were screened.Nucleotide fragments of each epitopes were amplified by PCR and then constructed their phage display systems.Using antisera against rOmpL1,rLipL21,L.interrogans serogroup Icterohaemorrhagiae strain Lai and leptospirosis patients' sera as the first antibodies.respectively,Western blot assays were performed to determine the immunoreaetivity and reactive ability of the epitopes with different antisera.Resuits Four combined epitopes of OmpL1 and two combined epitopes of LipL21 were selected out by the predicting procedure.All the amplified epitope fragments were accurately inserted into the region at N end of phage PⅢ protein and successfully expressed.All of the antisera could recognize each of the epitopes.Based on the results of Western blot,the two LipL21 epitopes at 97-112 and 176-184 showed similar strong hybridization signals with any of the antisera,and the hybridization signals of four OmpL1 epitopes with the three antisera were 173-191,87-98,297-320 and 59-78,from strong to weak.Conclusion The six combined epitopes in this study are efficiently antigenic.And the epitopes at positions 97-112 and 176-184 in LipL21 as well as the epitopes at position 87-98 and 173-191 in OmpL1 have a potential for developing leptospiral MAP vaccine.
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Objective To construct the multiple antigenic peptide (MAP) gene and E. coli ex-pression system, based on the out membrane protein OmpL1, LipL21 and LipL32 from Leptospira interro-gans, and better understanding of the immunological activity of the recombinant protein. Methods Using MI3KE display and Western blot, the advantage epitopes of OmpL1, LipL21 and LipL32 were identified and used to synthesize a new gene, then its prokaryotic expression system was constructed. The expression of re-combinant protein was determined by SDS-PAGE. The immunity activity of the recombinant protein was iden-tified by Western blot and ELISA. Results The synthetic gene was effectively expressed in E. coli and mainly presented in soluble form. The expression protein could react with the antileptospirosis antibodies in rabbit and human sera, which contained different serogroups. Conclusion The recombinant MAP gene of leptospires was successfully constructedand and expressed in E. coli. The recombinant protein had a good immune activity, and could cross-reacted with antileptospirosis antibodies from different serogroups.