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Objective@#To establish a rapid and sensitive isothermal amplification assay for the detection of human Adenovirus.@*Methods@#Primers and probe used for recombinase polymerase amplification(RPA)were designed based on the conserved region of the adenoviruses hexon gene. After optimizing the reaction temperature and times, the products of RPA were detected by capillary electrophoresis and lateral flow dipstick(LFD). Sensitivity and specicity of the assay were evaluated. The diagnostic value of the RPA-LFD assay was verified using clinical samples which were simultaneously tested by real time PCR assay.@*Results@#The analytical sensitivity of RPA-LFD assay was 2 copies DNA molecules per reaction and no cross reaction with other pathogens was observed. Compared with real-time PCR assay, the sensitivity, and specificity of the present assay were all 100%.@*Conclusions@#The RPA-LFD assay developed in this study has the characteristics of high specificity, sensitivity, rapid and no requirement of expensive equipment which provided a new tool for rapid detection of human adenovirus.
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Objective To establish a double-antibody sandwich ELISA for the rapid detection of shiga toxin typeⅡ ( StxⅡ) in shiga toxin-producing Escherichia coli ( STEC) infection. Methods A pool of murine hybridomas was used to screen out the optimal antibody pair for the establishment of double-anti-body sandwich ELISA. The established ELISA system was used to detect StxⅡin the culture supernatants of 16 clinical strains of STEC. Specificity and sensitivity of the established ELISA system were also evaluated. Results Two antibodies, S2D8 and S2C6, were successfully screened out, based on which the double-anti-body sandwich ELISA was set up. StxⅡand its variants rather than StxⅠwas detected in the culture super-natants of STEC with a lowest detection limit of 4 ng/ml. Its performance was consistent with that of commer-cial colloidal gold test kit, indicating the characteristics of good specificity and sensitivity. Conclusion The S2D8/S2C6-based ELISA laid a foundation for researches which designates the shiga toxin as a potential can-didate on the diagnosis and therapy of STEC infection.
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Objective To evaluate the practicability of using CRISPR/Cas9 genome editing tech-nology for inhibition of hepatitis B virus ( HBV) replication. Methods Two sgRNA targeting sites were de-signed for the S region of HBV genome. The CRISPR/Cas9 expression plasmids specific for HBV were con-structed and then transfected into a cell line expressing HBV genome(HepG2-N10). The cytotoxicity of cells transfected with different expression plasmids were detected by MTT assay. The levels of hepatitis B surface antigen ( HBsAg ) were determined by using chemiluminescent immunoassay ( CLIA ) . The expression of HBV at mRNA level was analyzed by quantitative real-time PCR ( qRT-PCR) . The qPCR was performed for the detection of extracellular and intracellular HBV DNA. The next-generation sequencing ( NGS) Illumina MiSeq Platform was used to analyze HBV genome editing. Results No significant cytotoxic effects were de-tected in HepG2-N10 cells transfected with different expression plasmids. Compared with the cells carrying pCas-Guide-GFP-Scramble, the levels of HBsAg in the supernatants of transfected cell culture harboring pCas-Guide-GFP-G1 and pCas-Guide-GFP-G2 were decreased by 24. 2% (P0. 05), respectively. The levels of HBsAg in cells transfected with pCas-Guide-GFP-G1 and pCas-Guide-GFP-G2 were respectively decreased by 16. 4% (P>0. 05) and 32. 1% (P>0. 05) as compared with that of pCas-Guide-GFP-Scramble transfected group. The expression of HBV at mRNA level was inhibited as indica-ted by the results of qRT-PCR. Moreover, the levels of extracellular HBV DNA were respectively suppressed by 23% (P>0. 05) and 35% (P0. 05) and 18% (P>0. 05). Different types of insertion/deletion mutation were de-tected in HBV genome by high-throughput sequencing. Conclusion HBV-specific CRISPR/Cas9 system could inhibit the expression of HBV gene and the replication of virus. Therefore, the CRISPR/Cas9 genome editing technology might be used as a potential tool for the treatment of persistent HBV infection.
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To prepare the RNAse-resistant virus particles containing the partial gene fragments of avian influenza virus H5N1 for use as RNA standard and control in RNA virus detection, the genes coding the coat protein and maturase of E.coli bacteriophage MS2 were amplified by PCR and then cloned into prokaryotic expression vector pET32a to construct the intermediate vector pET32a-MS2. In addition, the gene sequences coding hemagglutinin (HA), neuraminidase(NA) and M protein of the H5N1 virus were also cloned separately to the down-stream of plasmid pET32a-MS2, thus constructing the prokaryotic expression vectors pET32a-NS2-HA, pET32a-MS2-NA and pET32a-MS2-M. These recombinant plasmids were then transformed separately to E.coli BL21(DE3) with induction by IPTG. to express the virus-like particles. The virus-like particles observed under electron microscopy were identified by RT-PCR ,while their stability was confirmed by real-time RT-PCR. In this way, the virus-like particles were successively constructed and identified through PCR amplification, enzymolysis identification and sequencing analysis. These virus-like particles observed under electron microscopy appeared to be circular in shape with a diameter of about 50 nm. Their stability was proved to be rather good. From these observations, it is apparent that these virus-like particles can be used as RNA standard and quality control in the detection of avian influenza virus H5N1.
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One influenza H3N2 virus, A/swine/Shandong/3/2005 (Sw/SD/3/2005), was isolated from pigs with respiratory disease on a farm in eastern China. Genetic analysis revealed that Sw/SD/3/2005 was a triple-reassortant virus with a PB2 gene from human-like HIN1, NS from classical swine H1NI, and the remaining genes from human-like H3N2 virus. These findings further support the concept that swine can serve as reservoir or mixing vessels of influenza virus strains and maintain genetic and antigenic stability of viruses. Furthermore, we have successfully established a reverse genetics system based on eight plasmids and rescued Sw/SD/3/2005 through cell transfection. HI tests and RT-PCR confirmed that the rescued virus maintained the biological properties of the wild type Sw/SD/3/2005. The successful establishment of the reverse genetics system of Sw/SD/3/2005 will enable us to conduct extensive studies of the molecular evolution of H3N2 influenza viruses in swine.
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Shiga toxin 2 (Stx2) toxoid produced by formaldehyde treatment of purified toxin was used to immunize BALB/c mice for monoclonal antibody (MAb) production.The neutralizing activities of positive clones against Stx2 were screened by in vitro cytotoxicity assay.The isotype and specificity of resultant clone was determined,and its efficacy to neutralize the activity of purified Stx2 was evaluated by in vitro and in vivo toxicity model.Lastly,its spectrum of activity against Stx2 variants was also accessed by mouse toxicity model.It was demonstrated that one of the 12 positive MAb clones against Stx2,designating $2C4 had neutralizing activity.S2C4 belongs to the immunoglobulin G1 subclass and has a K light chain,and it reacts with the A subunit of Stx2 and does not bind to Stx2 B subunit or to Stx1.S2CA could efficiently neutralize the cytotoxicity of Stx2 to Veto cells and mice.It also protected mice against lethal doses of Stx2 variants challenge including Stx2c and Stx2vha.S2C4 is a promising candidate molecule in preventing the progression of hemolytic-uremic syndrome (HUS) mediated mainly by Stx2 in Stx-producing Escherichia coli(STEC)infection.
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Objective To purify Shiga toxin Ⅱ (STX Ⅱ) of enterohaemorrhagic Escherichia coli (EHEC) O157: H7 by affinity chromatography, and characterize its biological function. Methods The immno-affinity chromatography column was prepared by STX Ⅱ A subunit-specific antibody S1D8 coupling to Sepharose 4B matrix. The purity and specificity of STX Ⅱ molecule secreted by EHEC O157:H7 were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot, respectively. The purified toxin was serially diluted and the toxic activities to Vero cell line and mice were observed. The 50% cytotoxic dose (CD50) for Vero cell line and 100% lethal dose (LD100) for mice were calculated. The protection effect of anti-STX Ⅱ polysera to the mice against the purified toxin challenge was also observed. Results STX Ⅱ was successfully purified from culture supernatant of EHEC O157:H7 using affinity chromatography scheme. The relative molecular weights of STX Ⅱ A and B subunits were 32 000 and 7 500 confirmed by SDS-PAGE, respectively. The purified toxin could react with monoclonal antibodies against STX Ⅱ A and B subunits, respectively.The toxin was cytotoxic to Vero cell with CD50 of 20 ng/L and lethal to mice with LD100 of 5 ng.The toxin could be neutralized by anti-STX Ⅱ polysera in vivo. Conclusion STX Ⅱ is successfully purified and its toxic effects are confirmed in both cell line and mouse model.
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Objective To prepare and study the immunogenicity of hepatitis B virus surface anti-gen (HBsAg)-tetanus toxoid (TT) conjugate vaccine. Methods Tr was activated by cyangen bromide and reacted with adipic acid dihydrazide, then HBsAg-TT conjugate was prepared by carbediimide. Conjugate, HBsAg or hepatitis B vaccine was injected subcutaneously into mice. Anti-HBsAg and HBsAg-specific T cell response elicited by these immunogens were assayed. Results New HBsAg-TT conjugate elicited higher levels of anti-HBsAg and HBsAg positive conversion rates after the immunization than did HBsAg alone or hepatitis B vaccine. Conjugate induced mesdy antibodies of the IgG2a subclass, while HBsAg alone or hepa-titis B vaccine mainly elicited anti-HBsAg in the IgG1 subclass. The number of IFN-γand IL-2 secreting T cells induced by conjugate was also significantly higher than that did by HBsAg or hepatitis B vaccine. Con-clusion This study indicated new HBsAg-TT conjugate can induce both stronger humoral and TH1 type of cellular immune response.
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<p><b>OBJECTIVE</b>To understand the Escherichia coli O157:H7 carrier rate of host animals and the toxic gene of the strains in different areas in Jiangsu province.</p><p><b>METHODS</b>Surveillance spots were set up in different areas, to collect feces of pigs, chickens, sheep, cattle to culture for O157:H7 with immunomagnetic separation as well as detection of toxic gene of the strain with MPCR were both carried out.</p><p><b>RESULTS</b>One hundred and seventy strains of O157:H7 were separated from 1 767 feces of different animals in six spots, with a overall positive rate 9.62%. The positive rates of cattle and sheep were 19.05% and 12.01% respectively. Among 85 strains SLT1, SLT2, eaeA and hly toxic genes were detected. In which, 56.47% of the strains were positive curturely while 79.17% of them carried SLT2, eaeA and hly gene simultaneously.</p><p><b>CONCLUSION</b>The positive rate of O157:H7 in animals and the positive rates of strains were correlated to the incidence of the area. The highest rates were seen in areas where there had been O157:H7 epidemic, followed by the areas where there were only scattered cases identified while the lowest was in areas with no patients. Data indicated that it was important to enforce the surveillance of O157:H7 in animals to better predict and control of the disease.</p>