Huiqiong Yin

A nanoparticle-based bio-barcode assay for ultrasensitive detection of ricin toxin

The ultrasensitive bio-barcode amplification assay (BCA) technique was developed for the specific detection of the A chain of ricin toxin. The target antigen A chain was first captured by gold nanoparticles (GNPs) coated with polyclonal antibodies. Magnetic microparticles (MMPs) coated with A chain monoclonal antibody were then added to form a sandwich immuno-complex. After the immuno-complex was formed, signal DNA annealed to DNA strands covalently bound to the GNPs were released by heating and characterized by PCR and real-time fluorescence PCR. A detection limit of 1fg/ml was measured for A chain, six orders of magnitude more sensitive than that of conventional antigen-capture ELISA. The coefficient of variation (CV) of intra-assay and inter-assay ranged from 3.39% to 6.84%. The BCA can detect the A chain in milk and water mimic samples. In the following work it is demonstrated that this assay is a highly sensitive method for the detection of ricin proteins that could be adapted to measure other proteins.

Detection and quantitation of bluetongue virus serotypes by a TaqMan probe-based real-time RT-PCR and differentiation from epizootic hemorrhagic disease virus.

Twenty-four serotypes of bluetongue virus (BTV) have been recognized world wide. Reliable and quantitative assays of virus universal detection are essential for fighting against BT. A real-time reverse transcription-polymerase chain reaction (RT-PCR) with a TaqMan fluorescence probe has been developed for detection of the NS1 gene of different BTV serotypes. In BHK-21 cells, in the assay detected BTV1-22 specifically, and had no cross-reactivity with the closely related epizootic hemorrhagic disease virus (EHDV) serotypes 1-5. The limit of sensitivity of the assay was 0.1 TCID(50)/ml for BTV-1 and 10(2) copies for the control R121/pGEM. Accurate quantitation can be achieved with samples containing between 10(2) and 10(6) copies. The coefficient of variation (CV) of intra-assay and inter-assay ranged from 2.17% to 5.60%. The developed real-time RT-PCR assay showed good coincident rate (99.2%) with duplex RT-PCR in 122 whole blood clinical samples from sheep. Therefore, the real-time RT-PCR can be a reliable method for detection of various serotypes of BTV.

Nanoparticle-based bio-barcode assay for the detection of bluetongue virus

The ultrasensitive bio-barcode amplification assay (BCA) technique was developed for the specific detection of the outer-core protein VP7 of bluetongue virus (BTV). The target antigen VP7 was first captured by gold nanoparticles (GNPs) coated with polyclonal antibodies. Magnetic microparticles (MMP) coated with VP7 monoclonal antibody were then added to form a sandwich immuno-complex. After the immuno-complex was formed, signal DNA annealed to DNA strands covalently bound to the GNPs were released by heating and characterized by PCR and real-time fluorescence PCR. A detection limit of 0.1fg/ml was measured for purified VP7, seven orders of magnitude more sensitive than that of conventional antigen capture ELISA. The BCA demonstrated the same enhanced sensitivity for detecting BTV in serum samples from sheep. In the following work it is demonstrated that this assay is a highly sensitive method for the detection of BTV proteins that could be adapted to measure other proteins.

A pair of novel primers for universal detection of the NS1 gene from various bluetongue virus serotypes

Twenty five serotypes of Bluetongue virus (BTV) have been identified worldwide. Rapid and reliable methods of virus universal detection are essential for fighting against bluetongue (BT). We have therefore developed and evaluated a pair of primers which can detect various serotypes of BTV by RT-PCR. Analysis of the viral protein 7 (VP7) and the non-structural protein (NS1) gene from different serotypes of BTV by DNAstar showed that the 5′ end of the NS1 gene is the most conserved region. The primer pairs (P1 and P2) were designed based on the highly conserved region of NS1. The novel primers were evaluated by detecting BTV serotypes 1, 3, 5, 8, 10, 11, 21 and 22. The specificity of the primers was estimated by comparing to gene sequences of viruses published in GenBank, and further assessed by detecting BTV serotype 1–12 and Epizootic hemorrhagic disease virus (EHDV) serotype 1–4. The sensitivity and repeatability of PCR with the novel primers were evaluated by successfully detecting the recombinant plasmid pGEM-T121 containing the diagnosed nucleotide sequence. Our results suggest that these unique primers can be used in high throughout and universal detection of the NS1 gene from various BTV serotypes.

Evaluation of a novel ultra-sensitive nanoparticle probe-based assay for ricin detection.

Abstract A gold nanoparticle (GNP) probe-based assay (GNPA) modified from the bio-barcode assay (BCA) was developed for ultrasensitive detection of ricin, a potential biothreat agent. In the GNPA, a chain of ricin was captured by a GNP probe coated with polyclonal antibodies and single-stranded signal DNA. A magnetic microparticle (MMP) probe coated with ricin A chain monoclonal antibody was then added to form an immuno-complex. After being magnetically separated, the immuno-complex containing the single-stranded signal DNA was characterized by PCR and real-time PCR. A detection limit of 10−2 fg/ml was determined for the ricin A chain; this is eight orders of magnitude more sensitive than that achieved with an ELISA and two orders more sensitive than that obtained with the BCA. The coefficients of variation (CV) of the intra- and inter-assay values ranged from 3.82–6.46%. The results here show that this novel assay is an ultrasensitive method for detection of ricin proteins and may be suitable for the ultrasensitive detection of other proteins.

Development of a highly sensitive gold nanoparticle probe-based assay for bluetongue virus detection.

A simple gold nanoparticle (GNP) probe based assay (GNPA) that was modified from a bio-barcode assay (BCA) technique, was developed for ultra-sensitive, rapid detection of the bluetongue virus (BTV) VP7 outer-core protein. This assay captures the VP7 target antigen using the GNP probe coated with anti-VP7 polyclonal antibodies and single-stranded signal DNA. Magnetic microparticle (MMP) probes coated with anti-VP7 monoclonal antibodies were then added to form a sandwich immuno-complex. The single-stranded signal DNA coated onto the GNP probe present in the immuno-complex could then be detected by PCR and real-time fluorescence PCR using a TaqMan probe. The assay has a purified VP7 detection limit of 10(-2)fg/ml which is 8 orders of magnitude greater than that of conventional antigen capture ELISAs and 1 order of magnitude more sensitive than that of a conventional BCA. These results indicate that the GNPA is a highly sensitive method for easy detection of BTV proteins and that it can be modified as needed to measure the presence of other proteins.

Construction and characterization of an infectious replication competent clone of porcine endogenous retrovirus from Chinese miniature pigs

BackgroundXenotransplantation from animals has been considered to be a preferable approach to alleviate the shortage of human allografts. Pigs are the most suitable candidate because of the anatomical and physiological similarities shared with humans as well as ethical concerns. However, it may be associated with the risk of transmission of infectious porcine pathogens. Porcine endogenous retroviruses (PERVs) are of particular concern because they have been shown to infect human cells in vitro. To date, researches on the molecular characteristics and potential pathogenicity of PERV are still tenuous. In this report, an infectious replication competent clone of PERV from Wuzhishan pigs (WZSPs) in China was generated and characterized. This infectious clone will contribute to studies on PERV virology and control of PERV in xenotransplantation using Chinese miniature pigs.MethodsThe proviral DNA of PERV from WZSPs was amplified in two overlapping halves. Then the two fragments were isolated, subcloned and fused to generate pBluescriptαSK+-WZS-PERV recombinant clones. Screened with RT-PCR, a molecular clone of PERV designated as WZS-PERV(2) was selected. Its infectivity and replication competency were characterized in HEK293 cells by PCR, real-time fluorescent quantitative RT-PCR, western blot, indirect immunofluorescence assay as well as sequence analysis.ResultsThe ability of WZS-PERV(2) to infect human cells and produce infectious virions were shown after transfection of the clone into HEK293 cells and infection of PERV derived from this recombinant clone. The expression of Gag proteins were detected in HEK293 cells infected with the virus derived from the clone by the indirect immunofluorescence assay and western blot. The results of sequences analysis and comparison combined with the PCR based genotyping result demonstrated that the WZS-PERV(2) belonged to PERV-A subgroup. Compared with a previous proviral DNA clone of PERV (PERV-WZSP), G to A hypermutation occurred in the env gene of WZS-PERV(2) was found, whereas APOBEC proteins have the potential to inhibit the replication of a variety of retroviruses through a cDNA cytosine deamination mechanism, so we presumed these G to A hypermutation might be the contribution of porcine APOBEC3F.ConclusionsAltogether, an infectious replication competent clone of PERV from Chinese miniature pigs (WZSPs) termed WZS-PERV(2) was generated, characterized and sequenced.

A monoclonal antibody-based antigen-capture enzyme-linked immunosorbent assay (ELISA) for the detection of bluetongue virus

A monoclonal antibody-based antigen-capture enzyme-linked immunosorbent assay (ELISA) was developed for the detection of bluetongue virus (BTV) in cell culture lysates and blood samples from sheep. The monoclonal antibody 3E2 and 1C11 specific to BTV VP7 were used as capture antibody and detection antibody, respectively. The assay has detected BTV 1-22 specifically, and had no cross- reactivity with the closely related epizootic hemorrhagic disease virus (EHDV) serotypes 5. The limit of sensitivity of the assay was 9 ng/ml for purified recombinant BTV VP7 and 10 0.5 TCID50/ml for BTV-5. The coefficient of variation (CV) of intra-assay and inter-assay range from 3.45 to 6.10%. The developed antigen-capture ELISA showed good coincident rate (100%) with INGEZIM BTV DAS in 5 serotypes BTV and 8 blood samples from sheep. Therefore, the antigen-capture ELISA may be useful for testing large number of samples in a convenient and short time.

An improved gold nanoparticle probe-based assay for HCV core antigen ultrasensitive detection

A gold nanoparticle probe-based assay (GNPA) was developed for ultrasensitive detection of Hepatitis C virus (HCV) core antigen. In the GNPA, after anti-HCV core antigen polyclonal antibodies and single-stranded barcode signal DNA were labeled on gold nanoparticle probe (NP), DNA enzyme was used to degrade the unbound barcode DNAs. The anti-HCV core antigen monoclonal antibodies were coated on magnetic microparticles probe (MMP). Then the NP-HCV core antigen-MMP sandwich immuno-complex was formed when the target antigen protein was added and captured. Magnetically separated, the immuno-complex containing the single-stranded barcode signal DNA was characterized by TaqMan probe based real-time fluorescence PCR. A detection limit of 1 fg/ml was determined for the HCV core antigen which is magnitude greater than that of ELISA (2ng/ml). The coefficients of variation (CV) of intra-assay and inter-assay respectively ranged from 0.22-2.62% and 1.92-3.01%. The improved GNPA decreased the interference of unbound barcode DNAs and may be an new way for HCV core antigen detection.

Development and evaluation of a novel TaqMan fluorescence probe-based real-time reverse transcriptase polymerase chain reaction assay for detection and quantification of West Nile virus

In order to improve and accelerate the detection of West Nile virus (WNV), a rapid and specific real-time reverse transcription polymerase chain reaction (rtRT-PCR) was established. Primers and probe were designed according to the conservative sequence of capsid protein gene of WNV. Tenfold successive dilutions of positive WNV DNA were used to measure the sensitivity of rtRT-PCR. The amplifying curve showed that this method could successfully amplify 10 1 copies/μl WNV gene, while reference to Japanese encephalitis virus (JEV) and blank control were all negative. The assay system showed high reproducibility with coefficient of variation (CV) < 2%. The detection of WNV can be completed within 2 to 3 h. By detecting cDNA samples (n = 55) with rtRT-PCR and the conventional PCR assay, the established rtRT-PCR showed 96.36% (37 + 16/55) coincidence rate with the conventional PCR. All the results showed that the newly established rtRT-PCR assay was shown to be a rapid, sensitive and specific test for detecting WNV.