Quantum dot-based fluorescence-linked immunosorbent assay for the rapid detection of lomefloxacin in animal-derived foods.

Lomefloxacin (LMF), a third-generation fluoroquinolone antibacterial agent, is often used to treat bacterial and mycoplasma infections. However, due to its prolonged half-life and slow metabolism, it is prone to residues in animal-derived foods, posing a potential food safety risk. Therefore, it is particularly urgent and important to establish a method for detecting lomefloxacin. In this study, direct and indirect competitive fluorescence-linked immunosorbent assay (dc-FLISA and ic-FLISA) based on quantum dots (QDs) was established for the detection of LMF. As for dc-FLISA, the half-maximal inhibitory concentration (IC50) and limit of detection (LOD) were 0.84 ng/mL, 0.04 ng/mL, respectively, the detection ranges from 0.08 to 9.11 ng/mL. The IC50 and LOD of ic-FLISA were 0.43 ng/mL and 0.03 ng/mL, respectively, meanwhile the detection ranges from 0.05 to 3.49 ng/mL. The recoveries of dc-FLISA and ic-FLISA in animal-derived foods (milk, fish, chicken, and honey), ranged from 95.8% to 105.2% and from 96.3% to 103.4%, respectively, with the coefficients of variation less than 8%. These results suggest that the dc-FLISA and ic-FLISA methods, which are based on QD labelling, are highly sensitive and cost-effective, and can be effectively used to detect LMF in animal-derived foods.

Establishment of ultrasensitive immunoassay strip based on colloidal gold-McAb probe for detecting cyproheptadine hydrochloride and six phenothiazines in feed.

An ultrasensitive and broad-specific monoclonal antibody recognising cyproheptadine hydrochloride and six phenothiazines was produced. The 50% inhibition concentration against cyproheptadine hydrochloride was 0.036 ng/mL, and the cross-reactivities for six phenothiazines were from 6.33% to 63.16%. Based on the developed monoclonal antibody, an immunochromatographic strip was established, with the visual detection limits (cut-off values) of seven drugs ranging from 5 to 100 ng/g in feedstuffs. With the strip reader, the 50% inhibition concentration of the developed immunochromatographic strip for seven drugs ranged from 0.570 to 7.750 ng/g. The intra-assay recoveries were from 79.8% to 103.4% with the highest coefficient of variation of 11.3%. The inter-assay recoveries were from 79.0% to 96.6% with the highest coefficient of variation of 12.7%. In summary, the proposed immunochromatographic strip was considered suitable for simultaneously monitoring cyproheptadine hydrochloride and phenothiazines in feedstuffs.

Expression of NDV HN protein in rice and development of a semi-quantitative rapid method for detection of antibodies / 生物工程学报

The aim of this study was to develop a semi-quantitative immunochromatographic method for rapid detection of Newcastle disease virus (NDV) antibodies by expressing HN protein in rice endosperm bioreactor. The recombinant plasmid pUC57-HN was digested by MlyⅠ and XhoⅠ to retrieve the HN gene, while the intermediate vector pMP3 containing promoter, signal peptide and terminator was digested by NaeⅠ and XhoⅠ. The HN gene and the linearized pMP3 were purified and ligated to form a recombinant plasmid pMP3-HN1. Subsequently, pMP3-HN1 and plant vector pCAMBIA1300 were digested by EcoRⅠ and Hind Ⅲ, and the HN1 gene was cloned into pCAMBIA1300. The recombinant plasmid pCAMBIA1300-HN1 was introduced into Agrobacterium tumefaciens EHA105 by electrotransformation, and the pCAMBIA1300-HN1 was transferred into rice callus by agrobacterium-mediated method. After dark culture, callus screening, differentiation, rooting and transplanting, transgenic rice seeds were obtained 4 months later. PCR identified that the HN gene has been inserted into the rice genome. SDS-PAGE and Western blotting indicated that the HN protein was successfully expressed in the positive rice endosperm. The purity of the HN protein was more than 90% by SP cation exchange chromatography and gel filtration chromatography. According to the national standards for the diagnostic techniques of Newcastle disease HI test (HI≥4log2, positive antibody reaction), a colloidal gold labeled purified HN protein was used to prepare a semi-quantitative test strip by double-antibody sandwich method for rapid detection of NDV antibody. The results showed that the test strip did not cross-react with positive sera against other viruses, and the sensitivity of the test strip reached 1:102 400 for standard positive sera of Newcastle disease. Testing of a total of 308 clinical sera showed that the compliance rate of the test strip with HI test was 97.08%, and the Kappa value was 0.942. In conclusion, high purity recombinant HN protein was obtained from rice endosperm, and a simple, rapid, highly sensitive and highly specific semi-quantitative immunochromatographic strip was developed. The test strip could be used for immune evaluation of the Newcastle disease vaccine.

A rapid and accurate method for herpesviral gnome editing / 生物工程学报

To rapidly and accurately manipulate genome such as gene deletion, insertion and site mutation, the whole genome of a very virulent strain Md5 of Marek's disease virus (MDV) was inserted into bacterial artificial chromosome (BAC) through homogeneous recombination. The recombinant DNA was electroporated into DH10B competent cells and identified by PCR and restriction fragment length polymorphism analysis. An infectious clone of Md5BAC was obtained following transfection into chicken embryo fibroblast (CEF) cells. Furthermore, a lorf10 deletion mutant was constructed by two step Red-mediated homologous recombination. To confirm the specific role of gene deletion, the lorf10 was reinserted into the original site of MDV genome to make a revertant strain. All the constructs were rescued by transfection into CEF cells, respectively. The successful packaging of recombinant viruses was confirmed by indirect immunofluorescence assay. The results of growth kinetics assay and plaques area measurement showed that the lorf10 is dispensable for MDV propagation in vitro. Overall, this study successfully constructed an infectious BAC clone of MDV and demonstrated its application in genome manipulation; the knowledge gained from our study could be further applied to other hepesviruses.

Porcine parvovirus nonstructural protein NS1 activates NF-κB and it involves TLR2 signaling pathway

Background@#Porcine parvovirus (PPV) is a single-stranded DNA virus that causes porcine reproductive failure. It is of critical importance to study PPV pathogenesis for the prevention and control of the disease. NS1, a PPV non-structural protein, is participated in viral DNA replication, transcriptional regulation, and cytotoxicity. Our previous research showed that PPV can activate nuclear factor kappa B (NF-κB) signaling pathway and then up-regulate the expression of interleukin (IL)-6. @*Objectives@#Herein, the purpose of this study is to determine whether the non-structural protein NS1 of PPV also has the same function. @*Methods@#Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay, western blot, immunofluorescence assay and small interfering RNA (siRNA) were used. @*Results@#Our findings demonstrated that PPV NS1 protein can up-regulate the expression levels of IL-6 and tumor necrosis factor-alpha in a dose-dependent manner. Moreover, PPV NS1 protein was found to induce the phosphorylation of IκBα, then leading to the phosphorylation and nuclear translocation of NF-κB. In addition, the NS1 protein activated the upstream pathways of NF-κB. Meanwhile, TLR2-siRNA assay showed TLR2 plays an important role in the activation of NF-κB signaling pathway induced by PPV-NS1. @*Conclusions@#These findings indicated that PPV NS1 protein induced the up-regulated of IL-6 expression through activating the TLR2 and NF-κB signaling pathways. In conclusion, these findings provide a new avenue to study the innate immune mechanism of PPV infection.

Colloidal gold immunochromatographic strip for rapid detection of Haemophilus influenzae / 生物工程学报

To establish a novel colloidal gold immunochromatography assay (GICA) for rapid, sensitive and accurate detection of Haemophilus influenzae infection by using the outer membrane protein P6 as detection target. First, the linear antigen epitope located in the extracellular domain of the P6 protein (GenBank accession number: AGH02799) was predicted by bioinformatics analysis. The region (62-75 aa of the protein) with strong antigen specificity was chosen and synthesized. Two rabbits were then immunized by the polypeptides (14 aa) for production of polyclonal antibodies. Then, the recombinant P6 proteins were also obtained to produce polyclonal antibodies. Finally, based on the two antibodies, a novel colloidal GICA for detection of Haemophilus influenzae infection was established and the specificity, sensitivity, repeatability and stability of this method were evaluated. At the same time, the method was tested in clinical simulation, and the plate culture method was used to verify its accuracy. The test strip for Haemophilus influenzae infection was successfully prepared. The detection limit of the test strip was as low as 1×105 CFU/mL and the whole process can be completed within 15 minutes. The strip specifically recognized Haemophilus influenzae and did not react with nine of other common respiratory pathogens such as Streptococcus pneumoniae, Moraxella catarrhalis, Mycoplasma pneumonia, and Legionella pneumophila. And the strips could be stored at 25 °C for at least 6 months without losing sensitivity or specificity. The coincidence rate between the results of 200 clinical samples and the plate culture method was 90.5%. Haemophilus influenzae protein P6, which possessed a high degree of surface antigen accessibility and antigencity, could be used as a marker for Haemophilus influenzae detection. The immunochromatographic colloidal gold test strip which bears the features of rapidity, convenience and sensitivity provides a unique tool for the on-site surveillance and diagnosis of Haemophilus influenzae infection in clinical test.

Development of an immunochromatographic strip for detection of antibodies against porcine reproductive and respiratory syndrome virus

A simple and rapid immunochromatographic test strip incorporating a colloidal gold-labeled recombinant Nsp7 antigen probe was successfully developed for the detection of anti-porcine reproductive and respiratory syndrome virus (PRRSV) antibodies in swine. Recombinant Nsp7 protein of PRRSV labeled with colloidal gold was dispensed on a conjugate pad for use as the detector. Staphylococcal protein A and purified porcine anti-Nsp7 antibodies were blotted on a nitrocellulose membrane to form test and control lines, respectively. A comparison of the strip with standard diagnostic tests, enzyme-linked immunosorbent assays and immunoperoxidase monolayer assay, was also performed. The immunochromatographic test strip was shown to be of high specificity and sensitivity. Furthermore, the strip assay is rapid and easy to perform with no requirement for professional-level skills or equipment. It is suggested that the immunochromatographic test strip can be used to quickly and accurately detect PRRSV antibody and to be suitable for diagnostic purposes in the field.

Development and identification of mouse anti-human S100 A9 natural protein / 中国免疫学杂志

Objective:To prepare and identify the mouse anti-human monoclonal antibodies ( mAbs) using leukocytes as im-munogens. Methods: The mice were immunized using human peripheral blood leukocytes. Then, use of B lymphocyte hybridoma technology preparation of mAbs,followed screening by immunocytochemistry and limited dilution. The secreted mAbs were identified by immunoprecipitation,mass spectrometry,Western blot,ELISA and immunohistochemistry. Results:The 35 positive polyclonal cells were obtained,of which 11 strains secreted mAbs against S100A9. And one strain was used to prepare monoclonal antibody. The purified mAb against S100A9 were purified and identified as IgG1 subtype,with the titer,purity and affinity constant was 1∶3. 18×105,95% and 3. 54×108 L/mol,respectively. This mAb generally had 0. 12% crossed reactivity to S100A8 ,and showed little or no cross reactivity to S100A12 and S100A13. The prepared monoclonal antibodies can specifically recognizes the S100A9 antigen in human breast cancer tissues. Conclusion:Successful preparation of mAb against S100A9,which can secrete specific mAb against S100A9 protein with high titers and specificity have been established successfully,which laid the foundation for the immunology application.

Morphological and Immunohistochemical Identification of Villous M Cells in the Small Intestine of Newborn Piglets / Identificación Morfológica e Inmunohistoquímica de los Epiteliocitos Microplegados de las Vellosidades en el Intestino Delgado de Lechones Recién Nacidos

Microfold (M) cells act as antigen-sampling sites for initiating antigen specific mucosal immune responses, but they may also provide a gateway for enteropathogen entry. In this study we demonstrated villous M cells by morphological and immunohistochemical methods to be present in the three regions of the small intestine from newborn piglets. Immunohistochemical analysis, using anti- cytokeratin 18 (CK18) primary antibodies, showed a gradually decreased density of M cells from the lower crypt epithelium to the upper villous epithelium. The proportion of villous M cells was greater in the ileum than in the duodenum or the mid-jejunum. Ultrastructural observation revealed that villous M cells were mainly columnar in shape in the duodenum and the mid-jejunum, and appeared as more pocket-like structure in the ileum. These villous M cells exhibited short and irregular microvilli, rich vesicles and reduced glycocalyx, but lacked the lymphocyte-containing basolateral invagination. Our results support evidence that M cells can develop in the small intestinal villous epithelium of newborn piglets, implying that villous M cells may begin developing in the pig's small intestine during fetal stages, which depends neither on the influence of the mucosal lymphoid tissue nor the antigen from the intestinal lumen stimulation. In addition, the variable morphology and heterogeneity distribution of villous M cells in the three regions of the small intestine may be indicative of its different functional properties. This information extent our understanding of the diversity of M cells and provides important basic knowledge for further research on the actual role of villous M cells in neonate.

Los epiteliocitos microplegados (células M) actúan como receptores de antígeno para iniciar la respuesta inmune específica de las mucosas, pero también pueden proporcionar una puerta de entrada para enteropatógenos. En este estudio, se demostró por métodos morfológicos e inmunohistoquímicos que los epiteliocitos microplegados de las vellosidades están presentes en las tres regiones del intestino delgado de lechones recién nacidos. Se utilizaron anticuerpos primarios de citoqueratina 18 (CK18) para el análisis inmunohistoquímico, el cual mostró una disminución gradual de la densidad de los epiteliocitos microplegados desde el epitelio de las criptas inferiores hasta el epitelio de las vellosidades superiores. La proporción de los epiteliocitos microplegados, fue mayor en el íleon que el duodeno o yeyuno medio. La observación ultraestructural reveló que los epiteliocitos microplegados fueron principalmente de forma columnar en el duodeno y el yeyuno medio. Además, mostraron microvellosidades cortas e irregulares, muchas vesículas y glucocáliz reducidos, pero carecían de invaginaciones basolaterales contenedoras de linfocitos. Nuestros resultados apoyan la evidencia de que los epiteliocitos microplegados pueden desarrollarse en el epitelio de las vellosidades intestinales de los lechones recién nacidos, lo que implica que estas células pueden comenzar a desarrollarse en el intestino delgado del cerdo durante las etapas fetales, y no dependen ni de la influencia del tejido linfoide de las mucosas ni del antígeno para la estimulación del lumen intestinal. Además, la morfología y heterogeneidad de distribución de los epiteliocitos microplegados en las tres regiones del intestino delgado pueden ser indicativas de sus diferentes propiedades funcionales. Esta información mejora nuestra comprensión de la diversidad de los epiteliocitos microplegados y proporciona conocimientos básicos importantes para la investigación sobre el papel de los epiteliocitos microplegados en las vellosidades del neonato.

A Pair of Novel Primers for Universal Detection of the NS1 Gene from Various Bluetongue Virus Serotypes / 中国病毒学·英文版

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.