Development of a Novel Double Antibody Sandwich ELISA for Quantitative Detection of Porcine Deltacoronavirus Antigen

Establishment of ELISA method for canine adenovirus type 1

Canine adenovirus (CAdV) had a high prevalence in fox populations and induced fox encephalitis. No ELISA kits specifically for CAdV-1 antigen had been commercialized for foxes in China. It is crucial to develop a rapid and accurate ELISA method for detecting of CAdV-1. The monoclonal antibodies (mAbs, IgG1A) and HRP-labeled polyclonal antibodies (pAbs) were used to establish the ELISA method in this experiment. The results showed that the optimal concentration and coating time for the mAbs (IgG1A) were 2.15 μg/mL and overnight at 4°C, respectively. The dilution ratio of the HRP-labeled pAbs was 1:2000. Five percent skimmed milk was selected as the blocking agent. The optimal incubation times for blocking, CAdV-1, and HRP-labeled pAbs were all 1 h. The cut-off value for negative rectal swab was determined to be 0.366 ± 0.032. The maximum dilution ratio was 100 TCID50/mL. The ELISA method was positive to CAdV-1, and that was negative to CAdV-2, Canine Parvovirus (CPV) and Canine Distempervirus (CDV). The ELISA method showed good repeatability, sensitivity, and specificity. Compared with RT-PCR, the sensitivity, specificity, and coincidence rates of the ELISA method were 93.75, 90.9, and 92.86%, respectively. These results indicate that the established ELISA method can be used for the large-scale screening and epidemiology surveillance of CAdV-1 in foxes.

Establishment and application of PDCoV antigen-specific DAS-ELISA detection method

BACKGROUND

Porcine deltacoronavirus (PDCoV) is a swine enteropathogenic coronavirus that affects young pigs, causing vomiting, acute diarrhea, dehydration, and even death. There is growing evidence that PDCoV can undergo cross-species as well as zoonotic transmissions. Due to the frequent outbreaks of this deadly virus, early detection is essential for effective prevention and control. Therefore, developing a more convenient and reliable method for PDCoV detection is the need of the hour.

RESULTS

This study utilized a high-affinity monoclonal antibody as the capture antibody and a horseradish peroxidase labeled polyclonal antibody as the detection antibody to develop an enzyme-linked immunosorbent assay (DAS-ELSA) for PDCoV detection.Both antibodies target the PDCoV nucleocapsid (N) protein. The findings of this study revealed that DAS-ELISA was highly specific to PDCoV and did not cross-react with other viruses to cause swine diarrhea. The limit of detection of the virus titer using this method was 103 TCID50/mL of PDCoV particles. The results of a parallel analysis of 239 known pig samples revealed a coincidence rate of 97.07% (κ = 0.922) using DAS-ELISA and reverse transcriptase PCR (RT-PCR). The DAS-ELISA was used to measure the one-step growth curve of PDCoV in LLC-PK cells and the tissue distribution of PDCoV in infected piglets. The study found that the DAS-ELISA was comparable in accuracy to the TCID50 method while measuring the one-step growth curve. Furthermore, the tissue distribution measured by DAS-ELISA was also consistent with the qRT-PCR method.

CONCLUSION

The developed DAS-ELISA method can be conveniently used for the early clinical detection of PDCoV infection in pigs, and it may also serve as an alternative method for laboratory testing of PDCoV.

Preparation and Epitope Identification of Monoclonal Antibodies against the NS6 Protein of Porcine Deltacoronavirus (PDCoV)

Porcine deltacoronavirus (PDCoV) is an emerging enteric pathogen that causes substantial economic losses in the swine industry worldwide. The PDCoV NS6 protein is an accessory protein that plays a pivotal role in the viral life cycle and immune evasion. However, the functions of NS6 and its role in PDCoV pathogenesis remain largely unknown. In this study, we prepared a monoclonal antibody (mAb) 5-A11 that specifically recognizes the PDCoV NS6 protein. The mAb 5-A11 exhibited high specificity for PDCoV, with no cross-reactivity with several major porcine pathogenic viruses. Furthermore, the epitope recognized by mAb 5-A11 was precisely mapped to residues 70EYGSIYGKDFI80 of the NS6 protein using Western blot analysis. Notably, this epitope is highly conserved among different PDCoV isolates. Substantial variations were observed when comparing this epitope with the corresponding regions in the NS6 proteins of other δ coronaviruses, suggesting potential differences in the structure, function, and antigenicity of their NS6 proteins. Our findings provide valuable tools and insights for further elucidating the functions of the NS6 protein and its role in PDCoV pathogenesis, as well as for developing diagnostic and therapeutic strategies against PDCoV infection.

A novel host restriction factor MRPS6 mediates the inhibition of PDCoV infection in HIEC-6 cells

Introduction

Porcine deltacoronavirus (PDCoV) is a zoonotic pathogen with a global distribution, capable of infecting both pigs and humans. To mitigate the risk of cross-species transmission and potential outbreaks, it is crucial to characterize novel antiviral genes, particularly those from human hosts.

Methods

This research used HIEC-6 to investigate PDCoV infection. HIEC-6 cells were infected with PDCoV. Samples were collected 48 h postinfection for proteomic analysis.

Results

We discovered differential expression of MRPS6 gene at 48 h postinfection with PDCoV in HIEC-6 cells. The gene expression initially increased but then decreased. To further explore the role of MRPS6 in PDCoV infection, we conducted experiments involving the overexpression and knockdown of this gene in HIEC-6 and Caco2 cells, respectively. Our findings revealed that overexpression of MRPS6 significantly inhibited PDCoV infection in HIEC-6 cells, while knockdown of MRPS6 in Caco2 cells led to a significant increase of virus titer. Furthermore, we investigated the correlation between PDCoV infection and the expression of MRPS6. Subsequent investigations demonstrated that MRPS6 exerted an augmentative effect on the production of IFN-β through interferon pathway activation, consequently impeding the progression of PDCoV infection in cellular systems. In conclusion, this study utilized proteomic analysis to investigate the differential protein expression in PDCoV-infected HIEC-6 cells, providing evidence for the first time that the MRPS6 gene plays a restrictive role in PDCoV virus infection.

Discussion

Our findings initially provide the validation of MRPS6 as an upstream component of IFN-β pathway, in the promotion of IRF3, IRF7, STAT1, STAT2 and IFN-β production of HIEC-6 via dual-activation from interferon pathway.

Development of an indirect ELISA system for diagnosis of porcine edema disease using recombinant modified Stx2e antigen

AIM

This study aimed to develop a sensitive and specific recombinant antigen protein indirect enzyme-linked immunosorbent assay (ELISA) kit to detect the Shiga toxin (Stx)-producing Escherichia coli (STEC) antibodies against porcine edema disease (ED).

METHODS AND RESULTS

The recombinant antigen was co-expressed with the STEC-derived Stx2e A2-fragment and Stx2e B protein in E. coli BL21(DE3) pLysS cells and purified using maltose-binding protein open columns. We used a Shiga-like toxin 2 antibody to test the specificity of the recombinant antigen in an indirect ELISA, which was detected in antigen-coated wells but not in uncoated wells. We tested the indirect ELISA system using samples from the STEC-immunized pig group, the commercial swine farm group, and healthy aborted fetal pleural effusion group; five and twenty samples, respectively, were positive for STEC in the former, whereas all three samples were negative for STEC in the latter.

CONCLUSIONS

This newly developed indirect ELISA may be a specific method for diagnosing STEC infections in pigs.

Development of a double-antibody sandwich enzyme-linked immunosorbent assay for rapid detection of VZV

BACKGROUND

Varicella zoster virus (VZV) is the pathogen of varicella and herpes zoster, it is necessary to develop a rapid, sensitive and specific detection method for the prevention and control of related diseases.

METHODS

We inserted the gB protein extracellular region gene (gB-ex, 1-2208 bp) of VZV into lentivirus vector, and then obtained the recombinant gB protein through mammalian expression system. BALB/c mice were immunized multiple times with purified gB protein as immunogen. Then four strains of high affinity monoclonal antibodies targeting gB protein were prepared by cell fusion technique. Monoclonal antibodies 5G4 and HRP-4E9 were selected as capture and detection antibodies respectively, and a double-antibody sandwich ELISA method was established for detection.

RESULTS

The detection limit of the DAS-ELISA was 156 PFU/mL, and there was no cross-reaction with Herpes simplex virus-1/Herpes simplex virus-2/Pseudorabies virus. The coefficients of variation of intra-assay and inter-assay repeatability were less than 5%.

CONCLUSIONS

In this study, a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was established for the detection of VZV. The assay has good sensitivity, specificity and repeatability, which provides strong technical support and product guarantee for the rapid clinical detection of VZV.

Liquid crystal biosensor based on AuNPs signal amplification for detection of human chorionic gonadotropin

The detection of human chorionic gonadotropin (HCG) allows for the determination of pregnancy and is thus crucial during early pregnancy testing. This study introduces a novel liquid crystal (LC) biosensor that employs Au nanoparticles (AuNPs) for signal amplification, thus enabling the detection of the HCG antigen in a micro, efficient, and cost-effective manner. The sensor design capitalizes on the unique properties of LC to facilitate the detection of HCG. In this research, the surface of the base substrate was first modified with material from DMOAP and APTES, and EDC/sulfo-NHS was used to couple AuNPs and β-hCG to form an AuNP-β-hCG conjugate that improves the coupling rate. The carboxyl group of the antibody was reacted with the aldehyde group of glutaraldehyde, which helps to fix the β-hCG antibody to the surface of the substrate. The HCG sample is immobilized on the surface of the substrate via antigen-antibody immunobinding. As signal amplifiers, the AuNPs can have a significant effect on the topology of the interface and the vertical order of the LC molecules, thus reducing the limit of detection. Finally, the limit of detection was calculated using the SPSS system, and the relationship between grey values and concentrations was also obtained. The detection limit for HCG can be as low as 1.916 × 10-3 mIU·mL-1 under ideal conditions. Compared to other detection methods for HCG, this structure provides a detection pathway with excellent sensitivity, low detection limits, and better specificity, thus offering a new idea for HCG or any other target requiring trace detection.

Oilomics: An important branch of foodomics dealing with oil science and technology

Oil is one of three nutritious elements. The application of omics techniques in the field of oil science and technology is attracted increasing attention. Oilomics, which emerged as an important branch of foodomics, has been widely used in various aspects of oil science and technology. However, there are currently no articles systematically reviewing the application of oilomics. This paper aims to provide a critical overview of the advantages and value of oilomics technology compared to traditional techniques in various aspects of oil science and technology, including oil nutrition, oil processing, oil quality, safety, and traceability. Moreover, this article intends to review major issues in oilomics and give a comprehensive, critical overview of the current state of the art, future challenges and trends in oilomics, with a view to promoting the optimal application and development of oilomics technology in oil science and technology.

Apple consumption affects cecal health by regulating 12S-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid (12(S)-HETE) levels through modifying the microbiota in rats

Apples are rich in many nutrients and functional components. However, the mechanism of the effect of fresh apple consumption on rats remains unclear. In the present study, fresh apples (10 g kg-1) were added to the diet of Wistar rats, and changes in the microbiota and metabolite content of the cecum were analyzed after 28 days of feeding, and changes in the 12S-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid (12(S)-HETE) content and indicators related to inflammation, oxidative stress, and apoptosis were detected. Subsequently, a fecal microbiota transplantation (FMT) protocol was designed and carried out to verify the relationship between the microbiota and 12(S)-HETE, the cecal structure, and inflammatory factors. The results show that apple consumption significantly reduced the serum levels of alanine aminotransferase (ALT) and immunoglobulin G (IgG), altered the cecal histomorphology, and significantly upregulated the gene expression of claudin-1 and zonula occludens-1 (ZO-1), which encode tight junction proteins. Apple consumption also changed the structure of the cecal microbiota, increasing the abundance of some species (such as Shuttleworthia) and decreasing the abundance of others (such as Alphaproteobacteria). Metabolomic screening identified 64 significantly different metabolites. The FMT results showed that apple consumption reduced 12(S)-HETE metabolite levels in the cecal contents, improved the intestinal structure, and reduced the levels of proinflammatory factor expression by altering the cecal microbiota. In conclusion, this study provides further insight into the effects of apples on animals using rats as experimental animals. It provides basic data for future exploration of the mechanisms of the effect of apple consumption on humans.

Identification of a Monoclonal Antibody against Porcine Deltacoronavirus Membrane Protein

Porcine deltacoronavirus (PDCoV) is an emerging virus that poses a significant threat to the global swine industry. Its membrane (M) protein is crucial for virion assembly and virus-host interactions. We selected the hydrophilic region of M protein for prokaryotic expression, purification, and recombinant protein production. Utilizing hybridoma technology, we prepared the monoclonal antibody (mAb) 24-A6 against M protein. The mAb 24-A6 was shown to be suitable for use in immunofluorescence assays, western blotting, and immunoprecipitation, with specificity for PDCoV and no cross-reactivity with other five porcine viruses. The M protein was observed to be expressed as early as 3 h after PDCoV infection, increasing its expression over the duration of infection. Notably, the antigenic epitope of the M protein identified as 103SPESRL108 recognized by mAb 24-A6 was found within a conserved structural domain (SWWSFNPETNNL) of the coronavirus M protein, indicating a crucial overlap between a functionally important viral assembly region and a region recognized by the immune system. Our findings provide valuable insights into mAb 24-A6 targeting the antigenic epitope of M protein and may contribute to the development of diagnostic tools for PDCoV infection and fundamental research into the function of PDCoV M protein.

Development of a novel double-antibody sandwich quantitative ELISA for detecting SADS-CoV infection

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is an emerging swine enteric alphacoronavirus that can cause acute diarrhea, vomiting, dehydration, and death of newborn piglets. In this study, we developed a double-antibody sandwich quantitative enzyme-linked immunosorbent assay (DAS-qELISA) for detection of SADS-CoV by using an anti-SADS-CoV N protein rabbit polyclonal antibody (PAb) and a specific monoclonal antibody (MAb) 6E8 against the SADS-CoV N protein. The PAb was used as the capture antibodies and HRP-labeled 6E8 as the detector antibody. The detection limit of the developed DAS-qELISA assay was 1 ng/mL of purified antigen and 10^1.08TCID₅₀/mL of SADS-CoV, respectively. Specificity assays showed that the developed DAS-qELISA has no cross-reactivity with other swine enteric coronaviruses, such as porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), and porcine deltacoronavirus (PDCoV). Three-day-old piglets were challenged with SADS-CoV and collected anal swab samples which were screened for the presence of SADS-CoV by using DAS-qELISA and reverse transcriptase PCR (RT-PCR). The coincidence rate of the DAS-qELISA and RT-PCR was 93.93%, and the kappa value was 0.85, indicating that DAS-qELISA is a reliable method for applying antigen detection of clinical samples. KEY POINTS: • The first double-antibody sandwich quantitative enzyme-linked immunosorbent assay for detection SADS-CoV infection. • The custom ELISA is useful for controlling the SADS-CoV spread.

Special Issue "State-of-the-Art Porcine Virus Research in China"

China is one of the major countries involved in pig production and pork consumption [...].

Development of a colloidal gold immunochromatographic assay strip using monoclonal antibody for rapid detection of porcine deltacoronavirus

Porcine deltacoronavirus (PDCoV) cause diarrhea and dehydration in newborn piglets and has the potential for cross-species transmission. Rapid and early diagnosis is important for preventing and controlling infectious disease. In this study, two monoclonal antibodies (mAbs) were generated, which could specifically recognize recombinant PDCoV nucleocapsid (rPDCoV-N) protein. A colloidal gold immunochromatographic assay (GICA) strip using these mAbs was developed to detect PDCoV antigens within 15 min. Results showed that the detection limit of the GICA strip developed in this study was 10³ TCID₅₀/ml for the suspension of virus-infected cell culture and 0.125 μg/ml for rPDCoV-N protein, respectively. Besides, the GICA strip showed high specificity with no cross-reactivity with other porcine pathogenic viruses. Three hundred and twenty-five fecal samples were detected for PDCoV using the GICA strip and reverse transcription-quantitative real-time PCR (RT-qPCR). The coincidence rate of the GICA strip and RT-qPCR was 96.9%. The GICA strip had a diagnostic sensitivity of 88.9% and diagnostic specificity of 98.5%. The specific and efficient detection by the strip provides a convenient, rapid, easy to use and valuable diagnostic tool for PDCoV under laboratory and field conditions.

A nucleic acid detection assay combining reverse transcription recombinase-aided amplification with a lateral flow dipstick for the rapid visual detection of porcine deltacoronavirus

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogen causing severe diarrhoea, dehydration, and death in nursing piglets and enormous economic losses for the global swine industry. Furthermore, it can infect multiple animal species including humans. Therefore, a rapid, definitive diagnostic assay is required for the effective control of this zoonotic pathogen. To identify PDCoV, we developed a nucleic acid detection assay combining reverse transcription recombinase-aided amplification (RT-RAA) with a lateral flow dipstick (LFD) targeting the highly conserved genomic region in the ORF1b gene. The RT-RAA-LFD assay exhibited good PDCoV detection reproducibility and repeatability and could be completed within 11 min. Ten minutes at 40 °C was required for nucleic acid amplification and 1 min at room temperature was needed for the visual LFD readout. The assay specifically detected PDCoV and did not cross-react with any other major swine pathogens. The 95% limit of detection (LOD) was 3.97 median tissue culture infectious dose PDCoV RNA per reaction. This performance was comparable to that of a reference TaqMan-based real-time RT-PCR (trRT-PCR) assay for PDCoV. Of 149 swine small intestine, rectal swab, and serum samples, 71 and 75 tested positive for PDCoV according to RT-RAA-LFD and trRT-PCR, respectively. The diagnostic coincidence rate for both assays was 97.32% (145/149) and the kappa value was 0.946 (p < 0.001). Overall, the RT-RAA-LFD assay is a user-friendly diagnostic tool that can rapidly and visually detect PDCoV.

Development of Comprehensive Serological Techniques for Sensitive, Quantitative and Rapid Detection of Soybean mosaic virus

Soybean is an important grain and oil crop worldwide; however, the yield and seed quality of which are seriously affected by Soybean mosaic virus (SMV). As efficient detection technology is crucial for the field management of SMV, novel immunological detection methods were developed in the present study. According to the phylogenetic analysis, the CP coding sequence of SMV-SC7 was selected for the prokaryotic expression of the recombinant SMV-CP. Purified SMV-CP was used for the development of polyclonal antibodies (PAb) against the SMV-CP (PAb-SMV-CP) and monoclonal antibodies (MAb) against SMV-CP (MAb-SMV-CP). Subsequently, the PAb-SMV-CP was used for the development of a novel DAS- quantitative ELISA (DAS-qELISA) kit, of which the sensitivity was greater than 1:4000, and this could be used for the quantitative detection of SMV in China. Meanwhile, the MAb-SMV-CP was labeled with colloidal gold, and then was used for the development of the SMV-specific gold immunochromatography strip (SMV-GICS). The SMV-GICS gives accurate detection results through observed control lines and test lines in 5 to 10 min, sharing the same sensitivity as RT-PCR, and can be used for rapid, accurate and high-throughput field SMV detection. The DAS-qELISA kit and the SMV-GICA strip developed in this study are SMV-specific, sensitive, cheap and easy to use. These products will be conducive to the timely, efficient SMV epidemiology and detection in major soybean-producing regions in China and abroad.

Development of a Nucleocapsid Protein-Based Blocking ELISA for the Detection of Porcine Deltacoronavirus Antibodies

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogen which mainly causes diarrhea, dehydration and death in nursing piglets, threatening the global swine industry. Moreover, it can infect multiple animal species and humans. Hence, reliable diagnostic assays are needed to better control this zoonotic pathogen. Here, a blocking ELISA was developed using a recombinant nucleocapsid (N) protein as the coating antigen paired with an N-specific monoclonal antibody (mAb) as the detection antibody. The percent inhibition (PI) of the ELISA was determined using 384 swine serum samples, with an indirect immunofluorescence assay (IFA) as the reference method. Through receiver operating characteristic analysis in conjunction with Youden’s index, the optimal PI cut-off value was determined to be 51.65%, which corresponded to a diagnostic sensitivity of 98.79% and a diagnostic specificity of 100%. Of the 330 serum samples tested positive via IFA, 326 and 4 were tested positive and negative via the ELISA, respectively, while the 54 serum samples tested negative via IFA were all negative via the ELISA. The overall coincidence rate between the two assays was 98.96% (380/384). The ELISA exhibited good repeatability and did not cross-react with antisera against other swine pathogens. Overall, this is the first report on developing a blocking ELISA for PDCoV serodiagnosis.

Biological sensing using anomalous hall effect devices

This paper outlines an approach to biological sensing involving the use of spintronic devices to sense magnetic particles attached to biological carriers. We developed an enzyme-linked immunosorbent assay (ELISA)-based Anomalous Hall Effect magnetic sensor via surface functionalization using Triethoxysilylundecanal (TESUD). The proposed sensor uses a CoFeB/MgO heterostructure with a perpendicular magnetic anisotropy. Through several sets of magnetic layer thickness, this work also explored the optimization process of ferromagnetic layer used. Our spintronics-based biosensor is compatible with semiconductor fabrication technology and can be effectively miniaturized to integrate with semiconductor chips, which has the advantage of reduced manufacturing cost and reduced power consumption. The proposed sensor provides real-time measurement results and it is competitive to conventional biological colorimetric measurement systems in terms of accuracy and immediacy.