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LC3-associated phagocytosis (LAP) is a special phagocytosis occurring at the intersection of the two pathways of phagocytosis and autophagy. A hallmark event of the LAP process is the recruitment of microtubule-associated proteinⅠlight chain type 3-Ⅱ(LC3Ⅱ) to the phagosome surface of the monolayer membrane structure. The LAP pathway relies on the functions of the RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein (Rubicon) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The LC3-associated phagosome (LAPosome) binds to the lysosome to digest and degrade the contents. In recent years, increasing studies have found that LAP plays an important role in the infections caused by pathogenic microorganisms including fungi and bacteria. LAP is a crucial way in the host to resist and degrade the infection of pathogenic microorganisms. However, some pathogenic microorganisms can effectively escape from LAP in the host and even use LAPosome as a place for colonization and replication. This article summarized the recent progress in the role of LAP in host defense against pathogenic microorganism infection and the significance of it in the occurrence and development of diseases.
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Objective:To investigate the role of NOD-like receptor protein 3 (NLRP3) in the regulation of phagocytosis in Vibrio vulnificus ( V. vulnificus)-infected macrophages. Methods:Expression profiles of phagocytosis-related genes in PBS- and V. vulnificus-infected J774A.1 cells were analyzed by RNA-Seq. NLRP3-knockout (NLRP3 KO) J774A.1 cells were constructed using CRISPR-Cas9 gene-editing system. The phagocytosis of V. vulnificus and pHrodo RED-labelled Escherichia coli ( E. coli) bioparticles in parental and NLRP3 KO J774A.1 cells was detected by flow cytometry. Real-time PCR was performed to measure the expression of Fgr2 b gene at mRNA level in PBS- and V. vulnificus-treated parental and NLRP3 KO J774A.1 cells. Results:The expression of 18 phagocytosis-related genes was upregulated in V. vulnificus-infected J774A.1 cells than in PBS-treated J774A.1 cells ( P<0.05). There was a 5 bp deletion in the exon 2 of NLRP3 gene in NLRP3 KO J774A.1 cells, resulting in frameshift mutation and complete loss of NLRP3 expression. NLRP3 KO J774A.1 cells exhibited enhanced phagocytosis of V. vulnificus and pHrodo RED-labelled E. coli bioparticles than parental J774A.1 cells ( P<0.05). Besides, the expression of Fgr2 b gene at mRNA level was significantly increased in V. vulnificus-infected NLRP3 KO J774A.1 cells than in parental J774A.1 cells ( P<0.05). Conclusions:The phagocytosis of V. vulnificus in macrophages could be negatively regulated by NLRP3, which was possibly mediated through the regulation of Fgr2 b gene expression.
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Objective:To investigate the cytotoxicity of a recombinant Vibrio vulnificus cytolysin membrane pore-forming peptide (rMpf) to J774A.1 cells as well as its influences on reactive oxygen species (ROS) and lysosomes, and to analyze the cellular localization of the rMpf. Methods:The rMpf was expressed using an Escherichia coli expression system and then used to treat murine J774A.1 cells in vitro. The viability of rMpf- and PBS-treated J774A.1 cells and the levels of ROS and lysosomes in these cells were analyzed by flow cytometry. Confocal microscopy was used to observe the cellular localization of rMpf in the J774A.1 cells. Results:No significant differences in cell viability, ROS production or lysosome formation in J774A.1 cells were found between low-dose (4 μg/ml) rMpf-treated and untreated groups. However, the cell viability, ROS production and lysosome formation were significantly decreased after treating J774A.1 cells with higher doses of rMpf (20 and 60 μg/ml). Moreover, the rMpf was found to localize in both the cytoplasm and nuclei of J774A.1 cells in a dose-dependent manner.Conclusions:The rMpf could localize in both the cytoplasm and nuclei of J774A.1 cells. It would inhibit the cellular ROS production and lysosome formation to damage macrophage function. This study provided a novel sight for understanding the cytotoxic domain and pathogenesis of Vibrio vulnificus cytolysin and other membrane pore-forming cytolysins.
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Objective:To investigate the effects of TNF-α knockout on liver and spleen neutrophil responses to Vibrio vulnificus bloodstream infection in a mouse model. Methods:(1) TNF-α-knockout (TNF-α -/-) and wild-type (WT) C57BL/6J mice aged 6-8 weeks were randomly divided into four groups with six in each group: uninfected WT group, infected WT group, uninfected TNF-α -/- group and infected TNF-α -/- group. The mouse model of bloodstream infection was constructed by intraperitoneal injection of Vibrio vulnificus CGMCC1.1758 (2×10 8 CFU/200 μl), while the mice in the uninfected groups were injected intraperitoneally with equal amount of PBS. (2) Liver immune cells and splenocytes were isolated 4 h after infection and subjected to analyze the percentages and numbers of neutrophils, and the changes in cell viability, cellular reactive oxygen species (ROS) level and phagocytosis by flow cytometry. In addition, effects of Vibrio vulnificus bloodstream infection on mTOR signaling pathway in murine neutrophils were evaluated in vivo. Results:(1)Compared with the uninfected WT group, the percentages and numbers of neutrophils in liver and spleen tissues of the infected WT group increased significantly. The percentage and number of liver neutrophils were significantly higher in the infected TNF-α -/- group than in the infected WT group, but no significant difference in spleen neutrophils was detected between the two groups. (2) Compared with the infected WT group, the phagocytosis of liver neutrophils rather than that of spleen neutrophils was enhanced in the infected TNF-α -/- group. (3) The survival rates of neutrophils in both liver and spleen were decreased, while the cellular ROS level was significantly increased in the infected WT group compared with those of the uninfected WT group. Compared with the infected WT group, the infected TNF-α -/- group had increased survival rates of both liver and spleen neutrophils, but decreased level of ROS. (4) The levels of p-AKT (S473) in liver and spleen neutrophils of the infected WT group were lower than those of the uninfected WT group. Compared with the infected WT group, the infected TNF-α -/- group had lower level of p-AKT (S473) in liver neutrophils, but higher p-AKT (S473) level in spleen neutrophils. There were no significant differences in p-4E-BP1(T37/46) levels between the uninfected WT group and the infected WT group. The p-4E-BP1 (T37/46) level in liver neutrophils was lower in the infected TNF-α -/- group than in the infected WT group, but no significant difference in p-4E-BP1 (T37/46) levels in spleen neutrophils was observed between the two groups. Conclusions:TNF-α had different effects on the neutrophils in spleen and liver tissues of mice with Vibrio vulnificus bloodstream infection. It played a critical role in regulating the recruitment, phagocytic function and mTOR signaling of liver neutrophils after Vibrio vulnificus infection in vivo.
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Objective@#To establish and evaluate a multiplex PCR method for rapid identification of Mycobacterium species in order to provide an approach for rapid diagnosis of pathogens causing tuberculosis.@*Methods@#Four genes including 16S rRNA, Rv0577, RD9 and mtbk_20680 were selected to establish the multiplex PCR method. Specific primers were designed and the reaction system and conditions were optimized. The sensitivity and specificity of the multiplex PCR method were evaluated through identifying Mycobacterium africanum (M.africanum), Mycobacterium bovis (M.bovis), M. bovis BCG, seven common non-tuberculosis Mycobacterium (NTM), seven reference species of common respiratory bacteria and 93 clinical strains of Mycobacterium tuberculosis (MTB) isolated from patients with tuberculosis in Gansu Province of China.@*Results@#The fragments of 16S rRNA, Rv0577, RD9 and mtbk_20680 genes were 543 bp, 786 bp, 369 bp and 231 bp in length, respectively. MTB strains of the Beijing genotype were positive for all of the four genes, while the non-Beijing genotype strains were negative for mtbk_20680. M. africanum, M. bovis and M. bovis BCG strains were negative for 16S rRNA and Rv0577. NTM strains only carried 16S rRNA and none of four genes were detected in the seven species of respiratory bacteria. Among the 93 clinical MTB strains, 80 (86.02%) belonged to the Beijing genotype and the other 13 (13.98%) were non-Beijing genotype strains. The specificity of the multiplex PCR method was 100%.@*Conclusions@#The established multiplex PCR method could accurately distinguish Mycobacterium, Mycobacterium tuberculosis complex (MTBC), NTM, MTB, and Beijing and non-Beijing genotype MTB with high sensitivity and specificity.
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Objective To establish and evaluate a multiplex PCR method for rapid identification of Mycobacterium species in order to provide an approach for rapid diagnosis of pathogens causing tuberculo-sis. Methods Four genes including 16S rRNA, Rv0577, RD9 and mtbk_20680 were selected to establish the multiplex PCR method. Specific primers were designed and the reaction system and conditions were opti-mized. The sensitivity and specificity of the multiplex PCR method were evaluated through identifying Myco-bacterium africanum (M. africanum), Mycobacterium bovis (M. bovis), M. bovis BCG, seven common non-tuberculosis Mycobacterium (NTM), seven reference species of common respiratory bacteria and 93 clinical strains of Mycobacterium tuberculosis (MTB) isolated from patients with tuberculosis in Gansu Province of China. Results The fragments of 16S rRNA, Rv0577, RD9 and mtbk_20680 genes were 543 bp, 786 bp, 369 bp and 231 bp in length, respectively. MTB strains of the Beijing genotype were positive for all of the four genes, while the non-Beijing genotype strains were negative for mtbk_20680. M. africanum, M. bovis and M. bovis BCG strains were negative for 16S rRNA and Rv0577. NTM strains only carried 16S rRNA and none of four genes were detected in the seven species of respiratory bacteria. Among the 93 clinical MTB strains, 80 (86. 02％ ) belonged to the Beijing genotype and the other 13 (13. 98％ ) were non-Beijing gen-otype strains. The specificity of the multiplex PCR method was 100％ . Conclusions The established multi-plex PCR method could accurately distinguish Mycobacterium, Mycobacterium tuberculosis complex (MTBC), NTM, MTB, and Beijing and non-Beijing genotype MTB with high sensitivity and specificity.
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Objective To evaluate the antigenicity of two proteins of Mycobacteium tuberculosis (M. tuberculosis), Dnak(Rv0350) and MPT83(Rv2873), in order to provide a scientific basis for immuno-logical diagnosis of tuberculosis and research on vaccines. Methods The two antigen proteins, Dnak (Rv0350) and MPT83(Rv2873), were cloned, expressed and purified using the methods of genetic recom-bination and protein purification technology. Blood samples were collected from subjects including tuberculo-sis patients ( TB) , non-tuberculosis patients with other pulmonary diseases ( non-TB) and healthy volunteers (HV). To analyze the immunological properties of the recombinant Dnak (Rv0350) and MPT83 (Rv2873) proteins, they were used as antigens to detect humoral and cellular immunity in the subjects with enzyme linked immunosorbent assay ( ELISA ) and effector T cell enzyme-linked immunospot assay ( ELISPOT ) . Results The recombinant and purified Dnak (Rv0350) and MPT83 (Rv2873) proteins of M. tuberculosis were successfully obtained and used as antigens in the detection of humoral and cellular immunity in the sub-jects. Specific antibodies ( IgG) in the serum samples of 135 TB, 56 non-TB and 94 HV were tested with ELISA. The results showed that the sensitivity, specificity and accuracy of Dnak ( Rv0350 ) protein were 77. 80％ (105/135), 56. 70％ (85/150) and 66. 67％ (190/285). Similarly, the sensitivity, specificity and accuracy of MPT83 (Rv2873) protein were 76. 30％ (103/135), 43. 30％ (65/150) and 58. 95％(168/285). Cellular immunity was tested with the levels of IFN-γproduced by effector T lymphocytes after stimulating peripheral blood monouclear cells ( PBMC) collected form subjects of 59 TB, 65 non-TB and 64 HV with Dnak (Rv0350) and MPT83 (Rv2873) protein antigens. The results showed that the sensitivity, specificity and accuracy of Dnak (Rv0350) and MPT83 (Rv2873) proteins were 66. 10％ (39/59), 62. 79％ (81/129) and 63. 83％ (120/188), and 47. 46％ (28/59), 79. 84％ (103/129) and 69. 68％(131/188), respectively. Conclusions M. tuberculosis Dnak (Rv0350) and MPT83 (Rv2873) proteins have good antigenicity and could stimulate T cells to produce stronger immune responses. The two proteins used in combination might have promising potential in the research of immunodiagnosis of tuberculosis and the development of new anti-tuberculosis vaccines.
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Objective To construct a mutant strain of Nocardia farcinica ( N. farcinica ) IFM10152 with mammalian cell entry 4A gene (mce4A) deletion and to analyze the function of that gene dur-ing infection. -ethods The mutant strain of N. farcinica was constructed through in-frame deletion without antibiotic labeling and verified by PCR and sequencing analysis. To analyze the function of mce4A gene in the interaction between N. farcinica and host cells, in vitro growth experiment, macrophage killing experi-ment using THP-1 ( a human leukemia mononuclear cell line) as the model and adhesion and invasion exper-iments using HeLa cells ( cervical cancer epithelial cells) were carried out. Results The mutant strain with mce4A gene deletion was successfully constructed and named △mce4A. No significant difference in growth rate was observed between the mutant and the wild-type strains. After knocking out the mce4A gene, the ability of N. farcinica to resist macrophage killing was obviously weakened as well as its ability to adhere and invade. Conclusions The mutant strain of N. farcinica with mce4A gene deletion was successfully construc-ted. The mce4A gene might play an important role in the adhesion and invasion of N. farcinica to host cells and its survival in macrophages.
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Objective To investigate the effects of high glucose and lysophosphatidylcholine (LPC) on the immune function of in vitro cultured macrophages during Nocardia farcinica infection. Meth-ods RAW264.7 macrophages were cultured in vitro under different conditions as follows: routine culture (control group),50 mmol/L glucose (high glucose group),10 mg/L LPC(LPC groupⅠ),25 mg/L LPC (LPC groupⅡ) and 50 mmol/L glucose+25 mg/L LPC(high glucose and LPC group). The activity of mac-rophages in each group was tested after 6,12,24 and 36 h of culture. After 24 h of culture, macrophages were collected from every group and co-cultured with Nocardia farcinica. Dynamic phagocytosis rates were detected at 1,2,3,4,5 and 6 h after co-culture. Toxic effects of Nocardia farcinica on macrophages and concentrations of IL-10 and TNF-α were measured at 1,3 and 6 h after co-culture. Results Macrophages in all four experimental groups showed decreased activity as compared with those in the control group (P<0.01). Phagocytosis of Nocardia farcinica by macrophages was also reduced by high glucose and LPC. Phagocytosis rates of high glucose group and LPC groupⅡ at 1 and 2 h,LPC groupⅠat 1,2 and 3 h,and high glucose and LPC group at 1,2,3 and 4 h after co-culture were significantly lower than that of the con-trol group (P<0.05 or P<0.01). Compared with the control group, significantly reduced toxic effects on macrophages caused by Nocardia farcinica was observed in the experimental groups (P<0.05 or P<0.01). Compared with the control group,LPC groupsⅠand Ⅱ and high glucose and LPC group had decreased se-cretion of IL-10 at 3 h,and high glucose group and LPC groupⅠhad decreased secretion of TNF-α at 1 h(P<0.05). Conclusion Culture macrophages under the conditions of high glucose and LPC would reduce their activity and impair their ability to phagocytose Nocardia farcinica. Moreover, high glucose and LPC might have impacts on the toxic effects of Nocardia farcinica on macrophages and the secretion of IL-10 and TNF-α.
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Objective To evaluate the serological diagnostic value of Mycobacterium (M.)tuberculosis four new antigens Rv0432,Rv0674,Rv1566c and Rv1547.Methods Rv0432,Rv0674,Rv1566c and Rv1547 were amplified from M.tuberculosis strain H37Rv genomic DNA by using PCR,among which Rv1547 was divided into two segments for amplification (Rv1547-1 and Rv1547-2).The segments were cloned into expression vector PET-32a while the recombinant proteins were purified by affinity chromatography.Serums were incubated with BL21 (DE3) proteins.Antibodies IgG against M.tuberculosis were tested with 151 serum samples (41 healthy people and 110 TB patients) by using ELISA.The diagnostic efficiency of antigens was analyzed by means of receiver operating characteristic curve.Difference of the objective proteins in TB patients and healthy controls was compared by t-test.Results Recombinant antigens Rv0432,Rv0674,Rv1566c,Rv1547-1 and Rv1547-2 were successfully expressed and purified.Results from ELISA showed that the sensitivity,specificity,positive predictive value,negative predictive value,Youden index and area under the curve of Rv0432,Rv0674,Rv1566c,Rv1547-1 and Rv1547-2,as 43.64％-92.73％,80.49％-92.68％,0.92-0.94,0.38-0.80,0.363-0.732 and 0.649-0.915.All the objective proteins showed significantly higher antibody levels in TB patients,when compared to the healthy controls (P＜0.000 1).Condnsion The newly identified antigens Rv0432,Rv0674,Rv1566c,Rv1547-1 and Rv1547-2 all performed well when being used for TB serological diagnosis,thus were expected to be new candidate antigens used for TB diagnosis.
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Objective To evaluate the serological diagnostic value of Mycobacterium (M.)tuberculosis four new antigens Rv0432,Rv0674,Rv1566c and Rv1547.Methods Rv0432,Rv0674,Rv1566c and Rv1547 were amplified from M.tuberculosis strain H37Rv genomic DNA by using PCR,among which Rv1547 was divided into two segments for amplification (Rv1547-1 and Rv1547-2).The segments were cloned into expression vector PET-32a while the recombinant proteins were purified by affinity chromatography.Serums were incubated with BL21 (DE3) proteins.Antibodies IgG against M.tuberculosis were tested with 151 serum samples (41 healthy people and 110 TB patients) by using ELISA.The diagnostic efficiency of antigens was analyzed by means of receiver operating characteristic curve.Difference of the objective proteins in TB patients and healthy controls was compared by t-test.Results Recombinant antigens Rv0432,Rv0674,Rv1566c,Rv1547-1 and Rv1547-2 were successfully expressed and purified.Results from ELISA showed that the sensitivity,specificity,positive predictive value,negative predictive value,Youden index and area under the curve of Rv0432,Rv0674,Rv1566c,Rv1547-1 and Rv1547-2,as 43.64％-92.73％,80.49％-92.68％,0.92-0.94,0.38-0.80,0.363-0.732 and 0.649-0.915.All the objective proteins showed significantly higher antibody levels in TB patients,when compared to the healthy controls (P＜0.000 1).Condnsion The newly identified antigens Rv0432,Rv0674,Rv1566c,Rv1547-1 and Rv1547-2 all performed well when being used for TB serological diagnosis,thus were expected to be new candidate antigens used for TB diagnosis.
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Objective To investigate the correlation between Streptococcus pneumoniae (S.pneumoniae) StkP kinase and drug resistance and to analyze the binding ability of StkP extracellular region (EC-StkP) to β-lactam antibiotics.Methods A stkP gene knockout (ΔstkP) mutant was constructed from S.pneumoniae strain ATCC6306 by insertional inactivation method.E-test was performed to detect the minimum inhibitory concentrations (MIC) of penicillin (PCN) and cefotaxime (CTX) against ΔstkP mutant and its wild-type strain.Bioinformatic softwares were used to predict the EC-StkP of S.pneumonia strain ATCC6306,to generate the three-dimensional structure model of EC-StkP and to analyze the correlation between the structure and functions of EC-StkP.PCR was performed to amplify the extracellular segment of stkP (EC-stkP) gene and the product of it was sequenced after T-A cloning.A prokaryotic expression system of EC-stkP gene was constructed.SDS-PAGE in combination with a gel image analysis system was used to detect the expression of the recombinant EC-StkP (EC-rStkP).The expressed EC-rStkP was extracted by Ni-NTA affinity chromatography.The binding abilities of EC-rStkP to PCN and CTX were detected by isothermal titration calorimetry (VT-ITC) and surface plasmon resonance (Biacore).Results S.pneumonia strain ATCC6306 was sensitive to PCN (MIC=0.06 μg/ml) and CTX (MIC=0.12 μg/ml),but its ΔstkP mutant was resistant to the two antibiotics (PCN MIC=16 μg/ml,CTX MIC=32 μg/ml).The 295 aa segment was predicted as the extracellular region at C-end of StkP of S.pneumoniae strain ATCC6306,containing four penicillin-binding proteins and Ser/Thr kinase-associated (PASTA) domains.The cloned EC-stkP segment and the EC-stkP segment in GenBank shared 99.6% similarity in nucleotide sequence and 100% in amino acid sequence.The constructed prokaryotic expression system for EC-stkP gene expressed EC-rStkP in soluble form.Both PCN and CTX could bind to EC-rStkP and CTX was better than PCN in term of binding ability.Conclusion The stkP gene of S.pneumonia is closely related to drug resistance and the encoded protein,Ser/Thr kinase StkP,can recognize and bind to β-lactam antibiotics.
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Objective To understand how Vibrio vulnificus hemolysin (VvhA) affects the viability of murine liver CD4+ T cells as well as its effects on the numbers of mitochondria and the expression of CD62L. Methods The primary murine liver monocytes (MNs) were isolated from C57BL/ 6 mice and then treated with recombinant VvhA (rVvhA) for 6 hours in vitro. The viability of murine liver CD4+T cells and the expression of CD62L were measured by staining with anti-mouse CD4, CD8, CD44, CD62L and cell via-bility fluorescent dye or fluorescent antibody. Moreover, the cells were simply incubated with MitoTracker or JC-1 probes to label mitochondria and mitochondrial membrane potential, which were further analyzed by using flow cytometry analysis. Results With the increase in the doses of rVvhA, the viability of murine liv-er CD4+T cells was decreased from 81. 5% to 15. 8% . The expression of CD62L on the surface of murine liver CD4+T cells was dramatically decreased. Both the murine liver na?ve and effector CD4+ T cells were sensitive to the cytotoxicity of rVvhA. Moreover, treating murine liver CD4+ T cells with rVvhA resulted in significantly decreased numbers of mitochondria and lower mitochondrial membrane potential. Conclusion The cytotoxicity of rVvhA to murine liver CD4+T cells might be achieved through inhibiting the expression of CD62L, decreasing the numbers of mitochondria and lowering mitochondrial membrane potential.
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Objective To express the receptor binding domain (RBD) protein of the Middle East respiratory syndrome coronavirus (MERS-CoV) and to characterize the antigenicity of the purified recombi-nant protein. Methods The codon-optimized gene encoding the RBD protein of MERS-CoV was synthesized and then cloned into the pET30a ( +) vector to construct the recombinant expression plasmid. The trans-formed E. coli BL21 (DE3) strains carrying expression plasmid were induced by IPTG under different condi-tions. The expressed products were purified by using nickel affinity chromatography and further analyzed by SDS-PAGE and Western blot assay. Indirect ELISA was performed to analyze the antigenicity and specificity of RBD proteins expressed in prokaryotic expression systems in human serological test. Results The recom-binant RBD proteins were mainly expressed as conclusion body in an optimal induction condition of 37℃ and 0. 5 mmol/ L IPTG for 4 h. The high purified recombinant RBD proteins were obtained through denaturation and renaturation with a relative molecular mass of about 29×103 . Results of the Western blot assay showed that the recombinant RBD proteins could have specific reaction with the serum samples collected form mice with MERS-CoV infection. Indirect ELISA revealed that the RBD proteins expressed in the prokaryotic ex-pression system showed better sensitivity and specificity in the detection of antibodies against MERS-CoV in human serum samples. Conclusion This study reported the prokaryotic expression and purification of RBD protein of MERS-CoV for the first time, which might pave the way for further investigation on immunological detection of MERS-CoV and development of vaccines against MERS-CoV infection.
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Objective To construct a mutant strain of Streptococcus pneumoniae ( S.pneumoniae) with ciaH gene-knockout (ΔciaH) and to analyze the correlation between the ciaH gene and the bacterial re-sistance against β-lactam antibiotics.Methods The ciaH gene segament of S.pneumoniae strain ATCC6306 was amplified by PCR.The PCR product was sequenced after T-A cloning.A suicide plasmid pEVP3ciaH was constructed for the deletion of ciaH gene and then transformed into the ATCC 6306 strain by using the CaCl2 method .The mutant strain of S.pneumonia strain ATCC6306 with ciaH gene-knockout (ΔciaH) was genera-ted through homologous recombination , insertion inactivation and amphemycin screening , which was further identified by PCR , sequencing analysis and laser confocal microscopy .Double agar dilution method was used to detect the minimal inhibitory concentrations ( MICs ) of penicillin G ( PCN ) and cefotaxime ( CTX ) against theΔciaH mutant strain and the wild type strain .The differences between the MICs were further ana-lyzed.The changes of ciaH gene expression at mRNA level after treatment with 1/4 MIC of PCN or CTX were detected by real-time fluorescent quantitative RT-PCR ( qRT-PCR ) .Results The ciaH gene in the genomic DNA of the generated ΔciaH mutant strain was inactivated by insertion as indicated by PCR and se-quencing analysis .Results of the immunofluorescence assay showed that the ΔciaH mutant strain did not ex-press the CiaH protein .The MICs of PCN and CTX against the ΔciaH mutant strain were 32 μg/ml and 64μg/ml, respectively, which were significantly higher than that of the wild type strain (0.06 μg/ml and 1μg/ml) (P<0.01).The expression of ciaH gene at mRNA level was significantly elevated after treatment S.pneumoniae ATCC6306 strain with 1/4 MIC PCN or CTX (P<0.01).Conclusion The CiaH protein in the CiaH/CiaR two-component signaling system is involved in the resistance of S.pneumoniae against β-lac-tam antibiotics.
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Objective To employ Borrelia burgdorferi( B. burgdorferi) , a culturable and genetical-ly transformable spirochete, as a surrogate system to study Treponema pallidum ( T. pallidum) gene function. Methods Bioinformatic analysis revealed that the T. pallidum gene tp0111 encodes the putative sigma factor RpoN. We constructed a B. burgdorferi shuttle vector harboring tp0111. The shuttle vector was then trans-formed into the B. burgdorferi rpoN mutant strain. The phenotype of the resulting B. burgdorferi strain was then determined. Results We successfully constructed the B. burgdorferi rpoN mutant carrying the T. palli-dum gene tp0111. We found that tp0111 could partially complement the B. burgdorferi rpoN mutant. Con-clusion This work provides the first experimental evidence showing that tp0111 is the rpoN gene of T. palli-dum. It also demonstrates that B. burgdorferi can be used as a surrogate system for studying T. pallidum gene function.
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Objective To clone and express the outer surface protein C ( OspC) from a Chinese Borrelia afzelli FP1 strain and to evaluate the immune protectivity of the recombinant OspC protein ( rOspC) . Methods The gene encoding OspC protein of Borrelia afzelli FP1 strain was amplified by polymerase chain reaction (PCR) and then inserted into pET-30a plasmid to construct the recombinant expression plasmid pET-30a-OspC. The transformed E. coli BL21 strains carrying pET-30a-OspC plasmid were induced by IPTG to express OspC protein. The expressed proteins were purified by Ni-IDA resin chromatography and analyzed by SDS-PAGE and Western blot assay. Indirect immunofluorescence assay ( IFA) was performed to detect anti-rOspC protein antibodies in serum samples from rabbits immunized with rOspC protein. In vitro neutral-ization test was performed for evaluation the immune protectivity of rOspC protein. Results The recombi-nant expression plasmid pET-30a-OspC was successfully constructed and highly expressed in E. coli BL21. A strong antigen-antibody reaction between the rOspC protein and polyclonal antibody against Borrelia afzelli FP1 strain was detected by Western blot assay. The titers of IgG in serum samples from rabbits immunized with rOspC protein were significantly elevated. The in vitro neutralization test indicated that 106/ml of Borre-lia afzelli FP1 strains were neutralized by every anti-OspC protein serum sample from the experiment group. Conclusion The rOspC protein showed a strong immune protectivity against Borrelia afzelli, which could be used in the development of polyvalent subunit vaccine against lyme disease.
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<p><b>OBJECTIVE</b>To develop an one-tube multiplex RT-PCR assay for simultaneous detection of six human coronaviruses (HCoVs).</p><p><b>METHODS</b>Genbank sequences of six human coronaviruses, including HCoV-NL63, HCoV-229E, SARS-CoV, HCoV-OC43, MERS-CoV, and HCoV-HKU1, were included as reference sequences. Primers were designed based on multiple alignment of reference sequences, targeting the conserved regions of each species of HcoV. Virus strains and nucleic acid preserved in our lab were used as template in developing this automatic-electrophoresis-based one-tube multiplex RT-PCR assay. Detection limits and reproducibility were also evaluated with these templates. Samples with infection of other respiratory viruses preserved in our lab were used to evaluate specificity of this assay. Finally, we tested this assay with 140 clinical samples that were validated by real-time PCR in parallel.</p><p><b>RESULTS</b>This automatic-electrophoresis-based multiplex RT-PCR assay was able to detect six human coronaviruses simultaneously. All positive samples in this study were detected with at least one specific fragment of anticipated length (195, 304, 332, 378, 415, 442 bp) . No fragment was detected in negative controls. Detection limits of 1.0×10(1-1.0)×10(2) copies/µl were achieved in tests of single virus. No cross reaction was observed with other respiratory viruses. This multiplex RT-PCR assay showed the same sensitivity and specificity to that of individual real-time RT-PCR validated with clinical samples. Both methods detected 28 positive samples (20%) .</p><p><b>CONCLUSIONS</b>Six HCoVs can be detected in one tube by this novel multiplex RT-PCR assay with high sensitivity and specificity.</p>
Subject(s)
Humans , Coronavirus , Multiplex Polymerase Chain Reaction , Real-Time Polymerase Chain Reaction , Methods , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Objective To construct a prokaryotic expression system for expressing the phosphatase-encoding gene phpP in StkP/PhpP signaling couple in Streptococcus pneumonia ( S.pneumoniae) strains, and to further understand the phosphatase activity of the recombinant protein rPhpP.Methods The entire phpP gene of S.pneumoniae strain ATCC6306 was amplified by PCR.The PCR products were sequenced.A prokaryotic ex-pression system for expressing the phpP gene was constructed by the genetic engineering technique.The ex-pressed protein rPhpP and the solubility of rPhpP were assessed by SDS-PAGE and gel image analyzer.Ni-NTA affinity chromatography was performed to purify rPhpP.The changes of phpP gene transcription after the treat-ment with sublethal dosages of penicillin and cefotaxime were determined by real-time fluorescent quantitative RT-PCR.The functional domain in the sequence of the phpP gene and its type was analyzed by bioinformatic softwares.The activity of rPhpP in hydrolyzing the substrate of PP2C phosphotase was measured with Serine/Threonine Phosphotase Assay Kit.The enzyme kinetic parameters of rPhpP were calculated.Results The se-quence of the cloned phpP gene was identical with that reported in GenBank.The rPhpP in soluble form was ex-pressed in the constructed prokaryotic expression system.An increased expression of phpP gene at mRNA level was induced by sublethal dosage of penicillin or cefotaxime.The domain of PP2Cc type phosphatase was detec-ted in the sequence of phpP gene.The purified rPhpP protein could hydrolyze phosphopeptides [ RRA ( pT) VA], a substrate of PP2C type phosphatase, in a dose-dependent manner with Km and Kcat values of 277.35μmol/L and 0.71 S-1 ,respectively.Conclusion The protein encoded by phpP gene of S.pneumoniae was a PP2C type phosphatase.The expression of phpP gene could be enhanced by sublethal dosage of penicillin or ce-fotaxime.
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Objective To construct a shuttle plasmid for inducible gene expression in Borrelia burgdorferi (B.burgdorferi) with an advantage of flexible genetic manipulation.Methods The IPTG-inducible lac repressor/operator system from Escherichia coli (E.coli) was adopted and modified in the current study.The plasmid shuttle vector was developed by inserting multiple cloning sites,FLAG and HA tags into the shuttle vector by molecular cloning approaches.The target gene was inserted at the site under the control of the promoter (Tn5 derivate) in plasmid pQE30.This promoter contained two lac operators and a codonoptimized lacI gene driven by flaB promoter.Results A plasmid shuttle vector,pJJ275,was successfully constructed with the ability to express target genes in B.burgdorferi in the presence of IPTG.By using this system,a HA-tagged rpoS gene was introduced into the typical infectious strain B.burgdorferi B31.The target gene expression induced by IPTG was confirmed at transcriptional and translational levels.The RpoS dependent virulence factor of Borrelia,OspC,was also detected,indicating that the expressed protein was functional.Conclusion The constructed plasmid shuttle vector can express exogenous genes in B.burgdorferi with an inducible feature and an advantage of flexible genetic manipulation.It can be applied for genetic manipulation of B.burgdorferi involved in gene regulation and complementation.