Development of a nanoparticle-assisted PCR assay for detection of porcine epidemic diarrhea virus

A portable transistor immunosensor for fast identification of porcine epidemic diarrhea virus

Widespread distribution of porcine epidemic diarrhea virus (PEDV) has led to catastrophic losses to the global pig farming industry. As a result, there is an urgent need for rapid, sensitive and accurate tests for PEDV to enable timely and effective interventions. In the present study, we develop and validate a floating gate carbon nanotubes field-effect transistor (FG CNT-FET)-based portable immunosensor for rapid identification of PEDV in a sensitive and accurate manner. To improve the affinity, a unique PEDV spike protein-specific monoclonal antibody is prepared by purification, and subsequently modified on FG CNT-FET sensor to recognize PEDV. The developed FET biosensor enables highly sensitive detection (LoD: 8.1 fg/mL and 100.14 TCID50/mL for recombinant spike proteins and PEDV, respectively), as well as satisfactory specificity. Notably, an integrated portable platform consisting of a pluggable FG CNT-FET chip and a portable device can discriminate PEDV positive from negative samples and even identify PEDV and porcine deltacoronavirus within 1 min with 100% accuracy. The portable sensing platform offers the capability to quickly, sensitively and accurately identify PEDV, which further points to a possibility of point of care (POC) applications of large-scale surveillance in pig breeding facilities.

A one-step immunoassay based on switching peptides for diagnosis of porcine epidemic diarrhea virus (PEDV) using screened Fv-antibodies

In this study, a one-step immunoassay for porcine epidemic diarrhea virus (PEDV) based on Fv-antibodies and switching peptides was developed, and the assay results of PEDV were obtained by just mixing samples without any further reaction or washing steps. The Fv-antibodies with binding affinity to the spike protein of PEDV were screened from the Fv-antibody library using the receptor-binding domain (RBD) of the spike protein as a screening probe. Screened Fv-antibodies with binding affinities to the RBD antigen were expressed, and the binding constants (KD) were calculated to be 83-142 nM. The one-step immunoassay for the detection of PEDV was configured as a displacement immunoassay using a fluorescence-labeled switching peptide. The one-step immunoassay based on switching peptides was performed using PEDV, and the limit of detection (LOD) values for PEDV detection were estimated to be Ct = 39.7-36.4. Compared with the LOD value for a conventional lateral flow immunoassay (Ct = 33.0), the one-step immunoassay showed a remarkably improved LOD for the detection of PEDV. Finally, the interaction between the screened Fv-antibodies and the PEDV RBD was investigated using docking simulations and compared with the amino acid sequences of the receptors on host cells, such as aminopeptidase N (APN) and angiotensin-converting enzyme-2 (ACE-2).

An ultrasensitive electrochemical sensor for detecting porcine epidemic diarrhea virus based on a Prussian blue-reduced graphene oxide modified glassy carbon electrode

This study developed a novel, ultrasensitive sandwich-type electrochemical immunosensor for detecting the porcine epidemic diarrhea virus (PEDV). By electrochemical co-deposition of graphene and Prussian blue, a Prussian blue-reduced graphene oxide-modified glassy carbon electrode was made, further modified with PEDV-monoclonal antibodies (mAbs) to create a new PEDV immunosensor using the double antibody sandwich technique. The electrochemical characteristics of several modified electrodes were investigated using cyclic voltammetry (CV). We optimized the pH levels and scan rate. Additionally, we examined specificity, reproducibility, repeatability, accuracy, and stability. The study indicates that the immunosensor has good performance in the concentration range of 1 × 10^1.88 to 1 × 10^5.38 TCID₅₀/mL of PEDV, with a detection limit of 1 × 10^1.93 TCID₅₀/mL at a signal-to-noise ratio of 3σ. The composite membranes produced via co-deposition of graphene and Prussian blue effectively increased electron transport to the glassy carbon electrode, boosted response signals, and increased the sensitivity, specificity, and stability of the immunosensor. The immunosensor could accurately detect PEDV, with results comparable to real-time quantitative PCR. This technique was applied to PEDV detection and served as a model for developing additional immunosensors for detecting hazardous chemicals and pathogenic microbes.

Characterization and pathogenicity of the porcine epidemic diarrhea virus isolated in China

Piglet diarrhea caused by the porcine epidemic diarrhea virus (PEDV) is a common problem on pig farms in China associated with high morbidity and mortality rates. In this study, three PEDV isolates were successfully detected after the fourth blind passage in Vero cells. The samples were obtained from infected piglet farms in Jilin (Changchun), and Shandong (Qingdao) Provinces of China and were designated as CH/CC-1/2018, CH/CC-2/2018, and CH/QD/2018. According to the analysis of the complete S protein gene sequence, the CH/CC-1/2018 and CH/CC-2/2018 were allocated to the G2b branch, while CH/QD/2018 was located in the G1a interval and was closer to the vaccine strain CV777. Successful detection and identification of the isolated strains were carried out using electron microscopy and indirect immunofluorescence. Meanwhile, animal challenge experiments and viral RNA copies determination were used to compare the pathogenicity. The results showed that CH/CC-1/2018 in Changchun was more pathogenic than CH/QD/2018 in Qingdao. In conclusion, the discovery of these new strains is conducive to the development of vaccines to prevent the pandemic of PEDV, especially that the CH/CC-1/2018, and CH/CC-2/2018 were not related to the classical vaccine strain CV777.

Application of Nanomaterials to Enhance Polymerase Chain Reaction

Polymerase Chain Reaction (PCR) is one of the most common technologies used to produce millions of copies of targeted nucleic acid in vitro and has become an indispensable technique in molecular biology. However, it suffers from low efficiency and specificity problems, false positive results, and so on. Although many conditions can be optimized to increase PCR yield, such as the magnesium ion concentration, the DNA polymerases, the number of cycles, and so on, they are not all-purpose and the optimization can be case dependent. Nano-sized materials offer a possible solution to improve both the quality and productivity of PCR. In the last two decades, nanoparticles (NPs) have attracted significant attention and gradually penetrated the field of life sciences because of their unique chemical and physical properties, such as their large surface area and small size effect, which have greatly promoted developments in life science and technology. Additionally, PCR technology assisted by NPs (NanoPCR) such as gold NPs (Au NPs), quantum dots (QDs), and carbon nanotubes (CNTs), etc., have been developed to significantly improve the specificity, efficiency, and sensitivity of PCR and to accelerate the PCR reaction process. This review discusses the roles of different types of NPs used to enhance PCR and summarizes their possible mechanisms.

Point-of-Care Tests for Rapid Detection of Porcine Epidemic Diarrhea Virus: A Systematic Review and Meta-Analysis

The timely and accurate diagnosis of porcine epidemic diarrhea virus (PEDV) infection is crucial to reduce the risk of viral transmission. Therefore, the objective of this review was to evaluate the overall diagnostic accuracy of rapid point-of-care tests (POCTs) for PEDV. Studies published before 7 January 2022 were identified by searching PubMed, EMBASE, Springer Link, and Web of Science databases, using subject headings or keywords related to point of care and rapid test diagnostic for PEDV and PED. Two investigators independently extracted data, rated risk of bias, and assessed the quality using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The bivariate model and the hierarchical summary receiver operating characteristic (HSROC) model were used for performing the meta-analysis. Threshold effect, subgroup analysis, and meta-regression were applied to explore heterogeneity. Of the 2908 records identified, 24 eligible studies involving 3264 specimens were enrolled in the meta-analysis, including 11 studies on evaluation of lateral flow immunochromatography assay (ICA)-based, and 13 on nucleic acid isothermal amplification (NAIA)-based POCTs. The overall pooled sensitivity, specificity and diagnostic odds ratio (DOR) were 0.95 (95% CI: 0.92–0.97), 0.96 (95% CI 0.88–0.99) and 480 (95% CI 111–2074), respectively; for ICA-based POCTs and the corresponding values for NAIA-based, POCTs were 0.97 (95% CI 0.94–0.99), 0.98 (95% CI 0.91–0.99) and 1517 (95% CI 290–7943), respectively. The two tests showed highly comparable and satisfactory diagnostic performance in clinical utility. These results support current recommendations for the use of rapid POC tests when PEDV is suspected.

A minireview on nanoparticle-based sensors for the detection of coronaviruses

Coronaviruses (CoVs) are a class of viruses that cause respiratory tract infections in birds and mammals. Severe acute respiratory syndrome and Middle East respiratory syndrome are pathogenic human viruses. The ongoing coronavirus causing a pandemic of COVID-19 is a recently identified virus from this group. The first step in the control of spreading the disease is to detect and quarantine infected subjects. Consequently, the introduction of rapid and reliable detection methods for CoVs is crucial. To date, several methods were reported for the detection of coronaviruses. Nanoparticles play an important role in detection tools, thanks to their high surface-to-volume ratio and exclusive optical property enables the development of susceptible analytical nanoparticle-based sensors. The studies performed on using nanoparticles-based (mainly gold) sensors to detect CoVs in two categories of optical and electrochemical were reviewed here. Details of each reported sensor and its relevant analytical parameters are carefully provided and explained.

A multiplex nanoparticle-assisted polymerase chain reaction assay for detecting three canine epidemic viruses using a dual priming oligonucleotide system

A rapid and accurate diagnosis of mixed viral infections is important for providing timely therapeutic interventions. The aim of this study was to develop a highly sensitive and specific method for the simultaneous detection of canine distemper virus (CDV), canine parvovirus (CPV) and canine coronavirus (CCV) in mixed infections by combining the high specificity of a dual priming oligonucleotide (DPO) primer system with the high sensitivity of a nanoparticle-assisted PCR (nanoPCR) assay. Under the optimised assay conditions, the multiplex DPO-nanoPCR assay developed using DPO primers was 100-fold more sensitive than the multiplex PCR assay using conventional primers. The detection limits of the multiplex DPO-nanoPCR assay for the recombinant plasmids containing the cloned CDV, CPV and CCV target sequences were 5.4 × 10², 6.5 × 10² and 1.6 × 10² copies in a 25 μL assay, respectively. No cross-reaction with other canine viruses was observed. This is the first reported use of a multiplex nanoPCR assay with the DPO primer system for the simultaneous detection of CDV, CPV and CCV in mixed infections. The high sensitivity and specificity of the assay indicated its potential for use in clinical diagnosis and field surveillance of animal epidemics.

Development of a nanoparticle-assisted PCR assay to distinguish canine coronaviruses I and II

Nanoparticle-assisted PCR (nanoPCR) is a novel method for the simple, rapid, and specific detection of viruses. We developed a nanoPCR method to detect and differentiate canine coronavirus I (CCoV I) and II (CCoV II). Primer pairs were designed against the M gene conserved region of CCoV I and CCoV II, producing specific fragments of 239 bp (CCoV I) and 105 bp (CCoV II). We optimized the annealing temperature and primer concentrations for the CCoV nanoPCR assay and assessed its sensitivity and specificity. Under optimized nanoPCR reaction conditions, the detection limits were 6.47 × 10¹ copies/μL for CCoV I and 6.91 × 10² copies/μL for CCoV II. No fragments were amplified using other canine viruses as templates. The sensitivity of the nanoPCR assay was 100-fold higher than that of a conventional RT-PCR assay. Among 60 clinical samples collected from Beijing, China, the assay detected 12% positive for CCoV I and 48% positive for CCoV II. Our nanoPCR method is an effective method to rapidly detect CCoV I and CCoV II alone, or as a mixed infection, in dogs.

Development of a Novel Double Antibody Sandwich Quantitative Enzyme-Linked Immunosorbent Assay for Detection of Porcine Epidemic Diarrhea Virus Antigen

Porcine epidemic diarrhea virus (PEDV) causes acute diarrhea and dehydration in sucking piglets with a high mortality rate. Here, we developed a double antibody sandwich quantitative enzyme-linked immunosorbent assay (DAS-qELISA) for detection of PEDV using a specific monoclonal antibody against PEDV N protein and anti-PEDV rabbit serum. Using DAS-qELISA, the detection limit of recombinant PEDV N protein and virus titer were approximately 1 μg/L and 10^2.0 TCID₅₀/ml, respectively. A total of 90 intestinal and 237 fecal samples were then screened for the presence of PEDV using DAS-qELISA and reverse transcriptase PCR (RT-PCR). DAS-qELISA had a high specificity of 98.1% and sensitivity of 93.5%. The accuracy rate between DAS-qELISA and RT-PCR was 95.7%. More importantly, the viral antigen concentrations remained unchanged before and after one inactivated vaccine preparation by using the DAS-qELISA. These results suggest DAS-qELISA could be used for antigen detection of inactivated vaccine samples and clinical samples. It is a novel method for diagnosing diseases and evaluation of the PEDV vaccine.

The Potential of Various Nanotechnologies for Coronavirus Diagnosis/Treatment Highlighted through a Literature Analysis

With the current COVID-19 outbreak, it has become essential to develop efficient methods for the treatment and detection of this virus. Among the new approaches that could be tested, that relying on nanotechnology finds one of its main grounds in the similarity between nanoparticle (NP) and coronavirus (COV) sizes, which promotes NP-COV interactions. Since COVID-19 is very recent, most studies in this field have focused on other types of coronavirus than COVID-19, such as those involved in MERS or SARS diseases. Although their number is limited, they have led to promising results on various COV using a wide range of different types of nanosystems, e.g., nanoparticles, quantum dos, or nanoassemblies of polymers/proteins. Additional efforts deserve to be spent in this field to consolidate these findings. Here, I first summarize the different nanotechnology-based methods used for COV detection, i.e., optical, electrical, or PCR ones, whose sensitivity was improved by the presence of nanoparticles. Furthermore, I present vaccination methods, which comprise nanoparticles used either as adjuvants or as active principles. They often yield a better-controlled immune response, possibly due to an improved antigen presentation/processing than in non-nanoformulated vaccines. Certain antiviral approaches also took advantage of nanoparticle uses, leading to specific mechanisms such as the blocking of virus replication at the cellular level or the reduction of a COV induced apoptotic cellular death.

Why have nanotechnologies been underutilized in the global uprising against the coronavirus pandemic?

Prior research on nanotechnologies in diagnostics, prevention and treatment of coronavirus infections is reviewed. Gold nanoparticles and semiconductor quantum dots in colorimetric and immunochromatographic assays, silica nanoparticles in the polymerase chain reaction and spike protein nanospheres as antigen carriers and adjuvants in vaccine formulations present notable examples in diagnostics and prevention, while uses of nanoparticles in coronavirus infection treatments have been merely sporadic. The current absence of antiviral therapeutics that specifically target human coronaviruses, including SARS-CoV-2, might be largely due to the underuse of nanotechnologies. Elucidating the interface between nanoparticles and coronaviruses is timely, but presents the only route to the rational design of precisely targeted therapeutics for coronavirus infections. Such a fundamental approach is also a viable prophylaxis against future pandemics of this type.

Rapid and efficient detection methods of pathogenic swine enteric coronaviruses

Abstract

Porcine enteric coronaviruses (CoVs) cause highly contagious enteric diarrhea in suckling piglets. These COV infections are characterized by clinical signs of vomiting, watery diarrhea, dehydration, and high morbidity and mortality, resulting in significant economic losses and tremendous threats to the pig farming industry worldwide. Because the clinical manifestations of pigs infected by different CoVs are similar, it is difficult to differentiate between the specific pathogens. Effective high-throughput detection methods are powerful tools used in the prevention and control of diseases. The immune system of piglets is not well developed, so serological methods to detect antibodies against these viruses are not suitable for rapid and early detection. This paper reviews various PCR-based methods used for the rapid and efficient detection of these pathogenic CoVs in swine intestines.

Key points

Swine enteric coronaviruses (CoVs) emerged and reemerged in past years.

Enteric CoVs infect pigs at all ages with high mortality rate in suckling pigs.

Rapid and efficient detection methods are needed and critical for diagnosis.

Development of real-time RT-PCR assay for diagnosis of viral enteritis in neonatal goat kids

Rotavirus gastroenteritis is a worldwide disease affecting primarily infants, young children and young ones of wide variety of mammalian and avian species. Diarrhoea in goat kids is most frequently found associated with Group A rotavirus (GARV) and another enteric pathogen bovine coronavirus (BCoV), a major viral pathogen associated with neonatal diarrhoea. Enteric BCoV replicates in epithelial cells of gut, destroying villi, resulting in severe, often bloody diarrhoea in calves. It requires highly sensitive and specific assays to diagnose the disease at field level. In the present study, a real-time reverse-transcriptase (RT) polymerase chain reaction (PCR) were developed and validated for specific detection and quantification of GARV and BCoV with high sensitivity and specificity. For real-time RT-PCR, primers were designed to target nucleocapsid gene for BCoV; NSP4 gene and VP6 gene were designed for GARV using discontiguous conserved sequences. Real-time RT-PCR assay was standardized by serial dilution of positive GARV and BCoV RNA. The rotavirus real-time RT-PCR assay was found to be specific to rotavirus, but broadly reactive to GARV. The sensitivity of the assay for detecting rotavirus and BCoV in faecal samples and tissue sample was found to be high in such reactions. The real-time RT-PCR assay was effective in detecting GARV and BCoV in all positive samples obtained from sheds, farms and outbreaks. The results of this study demonstrate that the real-time RT-PCR assay for viral enteritis is broadly reactive, specific, and sensitive for detection of GARV and BCoV in faecal sample and tissue samples.

EuNPs-mAb fluorescent probe based immunochromatographic strip for rapid and sensitive detection of porcine epidemic diarrhea virus

Porcine epidemic diarrhea (PED), induced by porcine epidemic diarrhea virus (PEDV) causes acute diarrhea, vomiting, dehydration and high mortality in neonatal piglets, resulting in significant economic losses in the pig industries. In this study, an immunochromatographic assay (ICA) based on a EuNPs-mAb fluorescent probe was developed and optimized for rapid detection of PEDV. The limit of detection (LOD) of the ICA was 0.218 μg/mL (2.725 × 10³ TCID₅₀/mL) and its linear detection range was 0.03125-8 μg/mL (3.91 × 10²-10⁵ TCID₅₀/mL). The ICA was also validated for the detection of PEDV in swine stool samples. 60 swine stool samples from southern China were analyzed by the ICA and RT-PCR, and the results showed that the coincidence rate of the ICA to RT-PCR was 86.67%, which was significantly higher than that of AuNPs based ICA. The ICA is sensitive and specific and can achieve on-site rapid detection of swine stool samples. Therefore, the ICA has a great potential for PED diagnosis and prevention.

Development of a SYBR green I-based duplex real-time fluorescence quantitative PCR assay for the simultaneous detection of porcine epidemic diarrhea virus and porcine circovirus 3

The development of a rapid, specific, and sensitive SYBR Green I-based duplex real-time quantitative PCR assay is described for the simultaneous detection of porcine epidemic diarrhea virus (PEDV) and porcine circovirus type 3 (PCV3). The assay specifically detected PEDV and PCV3, with no fluorescence detected for other non-targeted pig pathogens. The assay showed a good linear relationship, and the limits of detection for this assay were 34.6 copies/μL and 61.2 copies/μL for PEDV and PCV3, respectively. The assay exhibited high repeatability and reproducibility, with intra-assay and inter-assay variation coefficients less than 2.0%. A clinical evaluation using intestinal tissue and fecal samples from piglets suffering from diarrhea at different pig farms in China revealed that the singular infection rates of PEDV and PCV3 were 43.94% (29/66) and 16.67% (11/66), respectively, while the co-infection rate of PCV3 with PEDV was 27.27% (18/66). The results indicate this assay is a rapid and reliable diagnostic tool for PEDV and PCV3 monitoring and surveillance in the field, and provides technical support for the quantitative detection of clinical samples infected or co-infected with PEDV and PCV3.

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PED outbreaks have been resulted in a huge economic loss in the pig farming industry.

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PCV3 is a novel virus and has been detected in piglets affected with diarrhea.

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A duplex qPCR assay was developed for the simultaneous detection of PEDV and PCV3.

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The LOD for this assay were 34.6 copies/μL and 61.2 copies/μL for PEDV and PCV3, respectively.

Real-time reverse transcription recombinase polymerase amplification assay for rapid detection of porcine epidemic diarrhea virus

Porcine epidemic diarrhea (PED), which is caused by porcine epidemic diarrhea virus (PEDV), is an acute, highly contagious enteric disease characterized by severe watery diarrhea, vomiting, dehydration, and high mortality in suckling piglets. A real-time reverse-transcription recombinase polymerase amplification assay (RT-RPA) was developed based on the nucleocapsid gene of PEDV. RT-RPA assay was performed at 40 °C for 20 min. The assay could detect both the classical and variant PEDV strains, and there was no cross-reaction with other pathogens tested. Using the in vitro transcribed PEDV RNA as template, the analytical sensitivity was 23 copies per reaction. The assay performance was evaluated by testing 76 clinical samples. PEDV RNA positive rate was 55.3% (42/76) by RT-RPA and 59.2% (45/76) by real-time RT-PCR. The diagnostic agreement between the two assays was 96.1% (73/76), and the R² value of the two assays was 0.903 by linear regression analysis. The developed RT-RPA assay provides a useful alternative tool for simple, rapid and reliable detection of PEDV in resource-limited diagnostic laboratories and on-site facilities.

A novel duplex TaqMan probe-based real-time RT-qPCR for detecting and differentiating classical and variant porcine epidemic diarrhea viruses

Two different genotypes of porcine epidemic diarrhea virus (PEDV), the classical and variant strains, are classified by multiple insertions and deletions in their S genes. It is critical to detect and differentiate two genotypes in the pork industry to prevent PEDV outbreaks. In the present study, a novel duplex TaqMan RT-PCR was developed for detecting and differentiating PEDV strains in China. There was no cross-amplification between the two probes when using standard recombinant plasmids, and the specificity was further confirmed by using other seven non-PEDV swine pathogens. The minimum copies required for the detection of both classical and variant PEDV were 4.8 × 10² DNA copies/reaction. The repeatability of TaqMan RT-PCR was evaluated using standard recombinant plasmids and gave coefficients of variation 0.19-4.93. In recent 5 years, 79 clinical samples were collected from piglets with severe diarrhea in the Central China. Among these clinical samples, 51 were confirmed as PEDV positive by conventional RT-PCR, whereas 63 variant PEDV, 3 co-infections and 1 classical PEDV were confirmed by this duplex TaqMan RT-PCR, with viral loads of 10²-10⁸, 10²-10³, and 10⁴ copies/reaction, respectively. Therefore, the duplex TaqMan RT-PCR could be a useful method for detecting and differentiating variant and classical PEDV strains. The results showed that variant PEDV was prevalent in clinical samples in central China. Moreover, in this study, co-infection by PEDV strains was detected for the first time and might help explain the emergence of the novel recombinant PEDV in recent years.

Ultrasensitive Detection of Porcine Epidemic Diarrhea Virus from Fecal Samples Using Functionalized Nanoparticles

Porcine epidemic diarrhea virus (PEDV) is the main causative agent of porcine diarrhea, which has resulted in devastating damage to swine industry and become a perplexed global problem. PEDV infection causes lesions and clinical symptoms, and infected pigs often succumb to severe dehydration. If there is not a timely and effective method to control its infection, PEDV will spread rapidly across the whole swine farm. Therefore, preclinical identification of PEDV is of great significance for preventing the outbreak and spread of this disease. In this study, a functionalized nanoparticles-based PCR method (UNDP-PCR) specific for PEDV was developed through systematic optimization of functionalized magnetic beads and gold nanoparticles which were further used to specifically enrich viral RNA from the lysate of PEDV stool samples, forming a MMPs-RNA-AuNPs complex. Then, oligonucleotides specific for PEDV coated on AuNPs were eluted from the complex and were further amplified and characterized by PCR. The detection limitation of the established UNDP-PCR method for PEDV was 25 copies in per gram PEDV stool samples, which is 400-fold more sensitive than conventional RT-PCR for stool samples. The UNDP-PCR for PEDV exhibited reliable reproducibility and high specificity, no cross-reaction was observed with other porcine viruses. In 153 preclinical fecal samples, the positive detection rate of UNDP-PCR specific for PEDV (30.72%) was much higher than that of conventional RT-PCR (5.88%) and SYBR Green real-time RT-PCR. In a word, this study provided a RNA extraction and transcription free, rapid and economical method for preclinical PEDV infection, which showed higher sensitivity, specificity and reproducibility, and exhibited application potency for evaluating viral loads of preclinical samples.

A sensitive duplex nanoparticle-assisted PCR assay for identifying porcine epidemic diarrhea virus and porcine transmissible gastroenteritis virus from clinical specimens

In this study, a novel duplex nanoparticle-assisted polymerase chain reaction (nanoPCR) assay was developed to detect porcine epidemic diarrhea virus (PEDV) and porcine transmissible gastroenteritis virus (TGEV). Two pairs of primers were designed based on the conserved region within the N gene of PEDV and TGEV. In a screening of 114 clinical samples from four provinces in China for PEDV and TGEV, 48.2 and 3.5 % of the samples, respectively, tested positive. Under optimized conditions, the duplex nanoPCR assay had a detection limit of 7.6 × 10¹ and 8.5 × 10¹ copies μL⁻¹ for PEDV and TGEV, respectively. The sensitivity of the duplex nanoPCR assay was ten times higher than that of a conventional PCR assay. Moreover, no fragments were amplified when the duplex nanoPCR assay was used to test samples containing other porcine viruses. Our results indicate that the duplex nanoPCR assay described here is useful for the rapid detection of PEDV and TGEV and can be applied in clinical diagnosis.

Establishment of a nanoparticle-assisted RT-PCR assay to distinguish field strains and attenuated strains of porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) can cause serious disease and even death in neonatal piglets, resulting in serious damage to the swine industry worldwide. Open reading frame 3 (ORF3) is the only accessory gene in the PEDV genome. Previous studies have indicated that PEDV vaccine strains have a partial deletion in ORF3. In this study, a nanoparticle-assisted polymerase chain reaction (nanoparticle-assisted RT-PCR) assay targeting the ORF3 of PEDV was developed to distinguish PEDV field strains from attenuated strains by using a specific pair of primers. The PCR products of field strains and attenuated strains were 264 bp and 215 bp in length, respectively. The sensitivity and specificity of this assay were also assessed. The nanoparticle-assisted RT-PCR assay was 10-100 times more sensitive than the conventional RT-PCR assay, with no cross-reactions when amplifying porcine pseudorabies virus (PRV), porcine circovirus type 2 (PCV2), classical swine fever virus (CSFV), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine rotavirus (RV), and porcine transmissible gastroenteritis virus (TGEV). The nanoparticle-assisted RT-PCR assay we describe here can be used to distinguish field strains from vaccine strains of PEDV, and it shows promise for reducing economic loss due to PEDV infection.

Reverse transcription-PCR assays for the differentiation of various US porcine epidemic diarrhea virus strains

Concurrently, several porcine epidemic diarrhea virus (PEDV) variants are circulating in US swine farms, including the original US and the spike insertion-deletion (S-INDEL) strains. In this study, reverse transcription (RT)-PCR assays for the detection and differentiation of different US PEDV variants were developed based on the differences in the S1 domain of the spike (S) gene. This assay successfully differentiated three PEDV strains: PC22A (the original US virulent), Iowa106 (S-INDEL), and PC177 (S-197DEL) that was derived from cell culture adaptation and has a 197 amino acid-deletion in the S1 domain. The assays did not amplify the porcine deltacoronavirus OH-FD22 strain or transmissible gastroenteritis virus Miller strain. It is the first report on the development of RT-PCR assays allowing the detection and differentiation of all major types of US PEDV variants.

Reverse Transcription Cross-Priming Amplification-Nucleic Acid Test Strip for Rapid Detection of Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea virus (PEDV) is a highly transmissible coronavirus that causes a severe enteric disease particularly in neonatal piglets. In this study, a rapid method for detecting PEDV was developed based on cross-priming amplification and nucleic acid test strip(CPA-NATS). Five primers specific for the N gene sequence of PEDV were used for the cross-priming amplification. Detection of amplification products based on labeled probe primers was conducted with strip binding antibody of labeled markers. The CPA method was evaluated and compared with a PCR method. The reverse transcription CPA system was further optimized for detecting PEDV RNA in clinical specimens. Results showed that the method was highly specific for the detection of PEDV, and had the same sensitivity as PCR, with detection limit of 10⁻⁶ diluted plasmid containing the target gene of PEDV. It was also successfully applied to detecting PEDV in clinical specimens. The reverse transcription CPA-NATS detection system established in this study offers a specific, sensitive, rapid, and simple detection tool for screening PEDV, which can contribute to strategies in the effective control of PEDV in swine.

The effect of gold nanoparticles on the diagnostic polymerase chain reaction technique for equine herpes virus 1 (EHV-1)

We experimented the effect of 15 nm unmodified citrate coated GNPs on the key PCR reactants to see if these would enhance the overall outcomes of the reaction. Thus, the optimized GNPs-assisted PCR could be used for more efficient diagnosis of EHV-1.