Development of a Quantitative Loop-Mediated Isothermal Amplification Assay for the Rapid Detection of Novel Goose Parvovirus

Development and application of a novel recombinase polymerase amplification-Pyrococcus furiosus argonaute system for rapid detection of goose parvovirus

Rapid and accurate detection of goose parvovirus (GPV) is crucial for controlling outbreaks and mitigating their economic impact on the poultry industry. This study introduces recombinase polymerase amplification combined with the Pyrococcus furiosus argonaute (RPA-PfAgo) system, a novel diagnostic platform designed to address the limitations of traditional GPV detection methods. Capitalizing on the rapid DNA amplification of RPA and stringent nucleic acid cleavage by the PfAgo protein, the RPA-PfAgo system offers high specificity and sensitivity in detecting GPV. Our optimization efforts included primer and probe configurations, reaction parameters, and guided DNA selection, culminating in a detection threshold of 102 GPV DNA copies per microlitre. The specificity of the proposed method was rigorously validated against a spectrum of avian pathogens. Clinical application to lung tissues from GPV-infected geese yielded a detection concordance of 100%, surpassing that of qPCR and PCR in both rapidity and operational simplicity. The RPA-PfAgo system has emerged as a revolutionary diagnostic modality for managing this disease, as it is a promising rapid, economical, and onsite GPV detection method amenable to integration into broad-scale disease surveillance frameworks. Future explorations will extend the applicability of this method to diverse avian diseases and assess its field utility across various epidemiological landscapes.

Simultaneous and rapid detection of avian respiratory diseases of small poultry using multiplex reverse transcription-Polymerase Chain Reaction assay

Major viral infections, such as Newcastle disease virus, infectious bronchitis virus, avian influenza virus, and infectious bursal disease virus, inflict significant injury to small poultry and tremendous economic damage to the poultry sector. This research aims to develop a multiplex reverse transcriptase polymerase chain reaction (m-RT-PCR) approach to simultaneously determine these important viral pathogens. The conserved segment of various viral genetic sequences was used to design and synthesize specific primers. Moreover, as positive controls, recombinant vectors were synthesized in this investigation. The d-optimal approach was used to improve PCR conditions in this investigation. Positive controls and clinical samples were used to assess the m-PCR assay's specificity, sensitivity, repeatability, and reproducibility. According to the sensitivity test findings, the m-PCR technique could generate the 8 target genes from viral genomes using 1 × 102. In addition, 8 viral pathogens were detected from the infected samples. The findings also suggest that live animal oral swabs were not significantly different from tissue sampling of a dead animal (P < 0.05), and this kit had a high sensitivity for analyzing both types of samples. The suggested m-PCR test may detect and evaluate viral infection in birds with excellent specificity, sensitivity, and throughput.

Auto Flow-Focusing Droplet Reinjection Chip-Based Integrated Portable Droplet System (iPODs)

Droplet microfluidics provides powerful tools for biochemical applications. However, precise fluid control is usually required in the process of droplet generation and detection, which hinders droplet-based applications in point-of-care testing (POCT). Here, we present a droplet reinjection method capable of droplet distribution without precise fluid control and external pumps by which the droplets can be passively aligned and detected one by one at intervals. By further integrating the surface-wetting-based droplet generation chip, an integrated POrtable Droplet system (iPODs) is developed. The iPODs integrates multiple functions such as droplet generation, online reaction, and serial reading. Using the iPODs, monodisperse droplets can be generated at a flow rate of 800 Hz with a narrow size distribution (CV <2.2%). Droplets are kept stable, and the fluorescence signal can be significantly identified after the reaction. The spaced droplet efficiency in the reinjection chip is nearly 100%. In addition, we validate digital loop-mediated isothermal amplification (dLAMP) within 80 min with a simple operation workflow. The results show that iPODs has good linearity (R² = 0.999) at concentrations ranging from 10¹ to 10⁴ copies/μL. Thus, the developed iPODs highlights its potential to be a portable, low-cost, and easy-to-deploy toolbox for droplet-based applications.

Rapid and visual detection of an isolated and identified goose parvovirus (GPV) strain by a loop-mediated isothermal amplification assay

Gosling plague caused by goose parvovirus (GPV), a highly infectious septic disease with high mortality, has caused substantial loss in the waterfowl industry. A method for the rapid detection of GPV is needed. In this study, we isolated the virus strain of GPV in May 2020 and applied it to the loop-mediated isothermal amplification (LAMP) assay. We designed five sets of primers for the goose parvovirus VP3 gene by LAMP. The GV-1 primer set was selected to detect GPV sensitively and rapidly. LAMP was more sensitive compared to PCR. In addition, the LAMP method could complete detection within 60 min which was faster than the PCR assay. The LAMP provided a convenient and effective experimental method for detection of GPV for inspection and quarantine departments and health care units in China, and it is expected to become a simple and routine detection method, especially suitable for goose farms.

A quantitative RT-qLAMP for the detection of SARS-CoV-2 and human gene in clinical application

Reverse transcription (RT) - loop-mediated isothermal amplification (LAMP) assay is a rapid and one-step method to detect SARS-CoV-2 in the pandemic. Quantitative estimation of the viral load of SARS-CoV-2 in patient samples could help physicians make decisions on clinical treatment and patient management. Here, we propose to use a quantitative LAMP (qLAMP) method to evaluate the viral load of SARS-CoV-2 in samples. We used threshold time (TT) values of qLAMP, the isothermal incubation time required for the fluorescent or colorimetric signal to reach the threshold, to indicate the viral load of clinical samples. Similar to the cycle threshold (Ct ) values in conventional qPCR, TT values of qLAMP show a linear relationship to the copy numbers of SARS-CoV-2. The higher the viral loadings, the lower qLAMP TT values are. The RT-qLAMP assay was demonstrated to quantify the viral loads of synthesized full-length RNA, inactivated viral particles (BBIBP-CorV), and clinical samples within 15 min by fluorescent reading and 25 min by colorimetric reading. The RT-qLAMP has been applied to detect Alpha, Beta, Kappa, Delta, and Omicron variants of SARS-CoV-2, as well as the human beta-actin gene, and their TT values showed the linear patterns. The RT-qLAMP assays were evaluated by 64 clinical samples (25 positives and 39 negatives) for the assessment of viral loads, and it was also used to quantify the human beta-actin gene, which was used as a control and an indicator of sampling quality in clinical swab samples. The result of RT-qLAMP was in good agreement with the result of RT-qPCR. The RT-qLAMP assay detected all clinical samples, including those with Ct  = 35, within 10 min using fluorescent reading.

Advances in research on genetic relationships of waterfowl parvoviruses

Derzsy’s disease and Muscovy duck parvovirus disease have become common diseases in waterfowl culture in the world and their potential to cause harm has risen. The causative agents are goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV), which can provoke similar clinical symptoms and high mortality and morbidity rates. In recent years, duck short beak and dwarfism syndrome has been prevalent in the Cherry Valley duck population in eastern China. It is characterised by the physical signs for which it is named. Although the mortality rate is low, it causes stunting and weight loss, which have caused serious economic losses to the waterfowl industry. The virus that causes this disease was named novel goose parvovirus (NGPV). This article summarises the latest research on the genetic relationships of the three parvoviruses, and reviews the aetiology, epidemiology, and necropsy characteristics in infected ducks, in order to facilitate further study.

Genetic characterization and phylogenetic analysis of duck-derived waterfowl parvovirus in Anhui province, eastern China

Recently, a novel duck-origin goose parvovirus (N-GPV) was reported to cause short beak and dwarfism syndrome in ducks. In this study, we performed complete genome sequencing and analyzed three different duck-derived parvoviruses that infected different breeds of ducks. Phylogenetic trees based on gene sequences indicated that they were classical goose parvovirus (C-GPV), Muscovy duck parvovirus (MDPV), and N-GPV. Furthermore, potential recombination events were found. These results improve our understanding of the diversity of duck-derived parvoviruses in Anhui province, eastern China, and provide a reference for the prevention of associated diseases.

Closed-tube field-deployable loop-mediated isothermal amplification (LAMP) assay based on spore wall protein (SWP) for the visual detection of Enterocytozoon hepatopenaei (EHP)

Hepatopancreatic microsporidiosis (HPM) is an infectious shrimp disease caused by the microsporidian Enterocytozoon hepatopenaei (EHP). In recent years, the widespread occurrence of EHP poses a significant challenge to the shrimp aquaculture industry. Early, rapid and accurate diagnosis of EHP infection is very much essential for the control of HPM crop-related losses. Loop-mediated isothermal amplification (LAMP) is a robust, sensitive, cost-effective disease diagnostic technique. Here, we demonstrate an improved, simple, closed-tube, colorimetric EHP LAMP diagnostic assay. LAMP assay was illustrated with the specific EHP spore wall protein (SWP) gene primers. Naked eye visual detection of LAMP amplicons was achieved using Hydroxy naphthol blue (HNB) or Phenol red dye without opening the tubes. This LAMP assay is efficient in detecting the EHP pathogen in all clinical samples include shrimp hepatopancreas, FTA card samples, feces, pond water, and soil. Also, the elution of EHP DNA from FTA cards was demonstrated within 17 min using a simple dry bath. In clinical evaluation, the visual LAMP assay established 100% diagnostic sensitivity and 100% diagnostic specificity. The visual LAMP assay is rapid, can detect the EHP pathogen within 40 min using a simple dry bath, and does not require any expensive instruments and technical proficiency. In conclusion, this visual LAMP protocol is a user-friendly, specific assay that can be conceivably operated at the farm-site/ resource-limited settings by the farmer himself with simple equipment.

A quantitative loop-mediated isothermal amplification assay for detecting a novel goose astrovirus

In November 2017, a severe infectious disease that devastated the major goose-producing regions in China was found to be caused by a novel goose astrovirus (N-AstV). The objective of this study was to develop a quantitative loop-mediated isothermal amplification (qLAMP) assay for the rapid diagnosis of N-AstV characterized with gout, hemorrhage, and swellings of the kidneys. A set of 4 specific primers, 2 inner and 2 outer primers, targeting the ORF1a gene of N-AstV were designed for the assay which could be completed within 60 min at 65°C in a water bath or on a real-time PCR instrument for quantitative analysis. The qLAMP assay showed a high sensitivity with a detection limit of 1 × 10¹ copies of the target DNA/μL. There were no cross-reactions with other viruses, and the reproducibility of the assay was confirmed in intrasensitivity and intersensitivity assay tests with variability ranging from 0.61 to 2.21%. The results indicated that the qLAMP assay for N-AstV was a simple, accurate, rapid, sensitive, and specific, especially useful for field detection.

Identification of a common conserved neutralizing linear B-cell epitope in the VP3 protein of waterfowl parvoviruses

Waterfowl parvoviruses (WPVs) including goose parvovirus (GPV), novel GPV-related virus (NGPV) and Muscovy duck parvovirus (MDPV) cause significant economic losses and epizootic threat to the waterfowl industries, and little is known about the B-cell epitopes of WPVs. In this study, a monoclonal antibody (mAb) 5B5 against the VP3 protein of NGPV was used to identify the possible epitope in the three kinds of WPVs. The mAb 5B5 had neutralizing activities to the three viruses, and reacted with the conserved linear B-cell epitopes of ⁴³⁸LHNPPP⁴⁴³ in VP3 protein of GPV, NGPV and MDPV. To the authors' best knowledge, this is the first report on identification of the common conserved neutralizing linear B-cell epitope on VP3 protein of three different WPVs, which would facilitate the development of a novel immunodiagnostic assay for rapid detection of WPV infection.

Droplet and Microchamber-Based Digital Loop-Mediated Isothermal Amplification (dLAMP)

Digital loop-mediated isothermal amplification (dLAMP) refers to compartmentalizing nucleic acids and LAMP reagents into a large number of individual partitions, such as microchambers and droplets. This compartmentalization enables dLAMP to be an excellent platform to quantify the absolute number of the target nucleic acids. Owing to its low requirement for instrumentation complexity, high specificity, and strong tolerance to inhibitors in the nucleic acid samples, dLAMP has been recognized as a simple and accurate technique to quantify pathogenic nucleic acid. Herein, the general process of dLAMP techniques is summarized, the current dLAMP techniques are categorized, and a comprehensive discussion on different types of dLAMP techniques is presented. Also, the challenges of the current dLAMP are illustrated together with the possible strategies to address these challenges. In the end, the future directions of the dLAMP developments, including multitarget detection, multisample detection, and processing nucleic acid extraction are outlined. With recently significant advances in dLAMP, this technology has the potential to see more widespread use beyond the laboratory in the future.

Establishment of a simultaneous detection method for ten duck viruses using MALDI-TOF mass spectrometry

Rapid screening of infectious viral diseases is the key to ensure healthy development of duck livestock industry. Currently routine viral detection methods are primarily used to detect up to 3 viruses. In this study, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) was used for simultaneous detection and genotyping of ten viruses in duck, including Duck hepatitis A virus 1 (DHAV-1), DHAV-3, Duck astrovirus 1 (DAstV-1), DAstV-2, Duck reovirus 1 (DRV-1), DRV-2, Tembusu virus (TMUV), Avian influenza virus (AIV), Goose parvovirus (GPV) and Duck enteritis virus (DEV). The low detection limits of this proposed method for ten duck viruses ranged from 1.3 copies/μl to 7.8 copies/μl. The novel detection method with high sensitivity, good specificity and high throughput has the potential to be applied for disease diagnosis and surveillance.

Evaluation of loop-mediated isothermal amplification assay for detection and typing of human papilloma virus 16 and 18 from endocervical samples

Background

Many human papillomavirus (HPV) types are associated with cervical cancer (CC). Therefore, HPV genotyping has both clinical and epidemiological importance. HPV 16 and 18 are two principal high-risk types responsible for more than 70% of all CC cases. Although several commercial and non-commercial genotyping assays are available, there is a need for a cost-effective and sensitive genotyping method for low- and middle-income countries.

Methods

The study was aimed at evaluation of loop-mediated isothermal amplification (LAMP) assay for HPV genotyping in cervical samples. A total of six primer sets for each HPV type were selected for the assay. The LAMP assay was standardised and validated with HPV control panel. Cervical biopsies were subjected to nested multiplex polymerase chain reaction (NM-PCR; as a part of routine diagnostic workup) and LAMP (HPV 16 and 18) simultaneously.

Results

A total of 225 clinical samples were processed during the study period. The sensitivity of the assay was determined using the 10-fold dilutions of positive controls. Both the HPV 16-LAMP and HPV 18-LAMP assays were shown to detect as low as 10 viral copies per reaction, which is similar to that of NM-PCR. The LAMP assay had a good agreement (new cases; 92%, post-chemoradiotherapy [post-CRT]; 89.1%) with NM-PCR for the detection of both HPV 16 and 18. As compared to histology (new cases; 79.8%, post-CRT; 51.3%), LAMP had better agreement with NM-PCR for detection of HPV from post-CRT cases.

Conclusions

We evaluated the LAMP assay for simultaneous detection and typing of HPV 16 and 18. The assay had good agreement with NM-PCR for detection of both HPV 16 and 18. The LAMP assay is a promising tool for HPV genotyping along with routine cervical cytology, especially in resource-constrained settings.