Optimization and Validation of Reverse Transcription Recombinase-Aided Amplification (RT-RAA) for Sorghum Mosaic Virus Detection in Sugarcane

Integrated Device for Cancer Nucleic Acid Biomarker Detection at Body Temperature

The quantitative analysis of nucleic acid markers is extensively utilized in cancer detection. However, it faces significant challenges, such as the need for specialized detection devices and the inherent complexity of testing procedures. To address these issues, this study proposes a simplified, rapid, and user-friendly platform for cancer nucleic acid marker detection. We firstly designed a polydimethylsiloxane (PDMS) device for the isothermal amplification reaction of nucleic acid biomarkers based on reverse-transcription recombinase-aided amplification (RT-RAA) technology. Specifically, three potential cancer nucleic acid biomarkers, carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), and prostate cancer antigen 3 (PCA3) were amplified from human serum or urine samples in the PDMS device at body temperature. The reaction chamber was directly integrated with nucleic acid test strips labeled with colloidal gold nanoparticles, allowing for the visual observation of the detection results for the amplification products. The optimal reaction conditions, such as pH, reaction time, antibody, and streptavidin concentration, were defined after a series of optimization studies. The findings demonstrated that the optimal RT-RAA reaction time was 20 min, the primary antibodies were labeled with colloidal gold to the greatest extent at pH 8.5, and the optimal concentrations of secondary antibody and streptavidin were 1.0 mg/mL and 0.5 mg/mL, respectively. Furthermore, this novel detection approach could not only exhibit excellent sensitivity and specificity but also show high accuracy for the analysis of nucleic acid biomarkers in both clinical serum and urine samples. Therefore, the simplified and more convenient operation platform provides a new insight for the semi-quantitative analysis of cancer nucleic acid biomarkers and the rapid screening of early cancer, thereby offering a promising alternative to oncological point-of-care testing (POCT) diagnostics.

Dual-CRISPR/Cas12a-assisted RT-RAA visualization system for rapid on-site detection of nervous necrosis virus (NNV)

BACKGROUND

Nervous necrosis virus (NNV) poses a severe threat to the aquaculture industry, particularly infecting fish fry with devastating mortality rates and inflicting heavy economic losses. Traditional detection methods, such as cell culture and conventional RT-PCR, are not only time-consuming and require specialized laboratory facilities but also hard to eliminate contamination. Rapid and accurate on-site detection methods in aquaculture settings are crucial for effective control of NNV outbreaks in fish farms.

RESULTS

This study developed a one-tube visualization system for rapid and precise identification of NNV in a pond-side setting. This system utilizes the dual-clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a-assisted reverse transcription-recombinase aided amplification (RT-RAA) detection method, employing fluorescence intensity to indicate positive results for easy interpretation by field operators. The key to this system involved the meticulous selection of RT-RAA primer sets and CRISPR RNA (crRNA) primer sets targeting two genes of NNV, the capsid protein (CP) and RNA-dependent RNA polymerase (RdRp), distributing on two particles of genomic sequences. The assay demonstrated a speed and efficiency process within 30 min and a detection limit of 0.5 copies/μL, achieving 100 % accuracy when compared to qRT-PCR. The practical utility and effectiveness were validated by using 32 field samples. The results underscored the simplicity, rapidity, and reliability of the system, confirming its potential as a robust tool for NNV diagnosis in fish farms.

SIGNIFICANCE

This study introduces the first application of a dual-CRISPR/Cas12a-assisted RT-RAA visualization system for diagnosing NNV infections. The novel approach substantially enhances on-site diagnostic capabilities, offering a rapid, reliable, and cost-effective solution for fish farm operators. This innovation not only streamlines the detection process but also ensures timely intervention, thereby mitigating the impact of NNV on aquaculture.

Specific and sensitive detection of bovine coronavirus using CRISPR-Cas13a combined with RT-RAA technology

Introduction

Bovine coronavirus (BCoV) is an important pathogen of enteric and respiratory disease in cattle, resulting in huge economic losses to the beef and dairy industries worldwide. A specific and sensitive detection assay for BCoV is critical to the early-stage disease prevention and control.

Methods

We established a specific, sensitive, and stable assay for BCoV nucleic acid detection based on CRISPR/Cas13a combined with reverse transcription recombinase-aided amplification (RT-RAA) technology. The specific primers for RT-RAA and CRISPR RNA (crRNA) were designed in the conserved region of the BCoV nucleocapsid (N) gene.

Results

The detection limit of the RT-RAA CRISPR/Cas13a assays for BCoV detection was 1.72 copies/μl, and there were no cross-reactions with the other 10 common bovine enteric and respiratory disease-associated pathogens. The coefficient of variations (CVs) of within and between batches were less than 4.98 and 4.58%, respectively. The RT-RAA-CRISPR/Cas13a assays work well in clinical samples of cattle and yak, the BCoV positive rate of 84 clinical samples detected by RT-RAA-CRISPR/Cas13a assays was 58.3% (49/84), it was notably higher than that of RT-qPCR (2.4%, 2/84; p < 0.001). The 49 positive samples detected by RT-RAA-CRISPR/Cas13a assays were further confirmed as BCoV by Sanger sequencing.

Discussion

A specific, sensitive, and stable assay based on RT-RAA-CRISPR/Cas13a assays for BCoV was developed, providing new technical support for the clinical detection and epidemiological monitoring of BCoV.

Pyrococcus furiosus Argonaute-mediated porcine epidemic diarrhea virus detection

Porcine epidemic diarrhea virus (PEDV), an enteric coronavirus, induces severe vomiting and acute watery diarrhea in unweaned piglets. The pig industry has suffered tremendous financial losses due to the high mortality rate of piglets caused by PEDV. Consequently, a simple and rapid on-site diagnostic technology is crucial for preventing and controlling PEDV. This study established a detection method for PEDV using recombinase-aided amplification (RAA) and Pyrococcus furiosus Argonaute (PfAgo), which can detect 100 copies of PEDV without cross-reactivity with other pathogens. The entire reaction of RAA and PfAgo to detect PEDV does not require sophisticated instruments, and the reaction results can be observed with the naked eye. Overall, this integrated RAA-PfAgo cleavage assay is a practical tool for accurately and quickly detecting PEDV. KEY POINTS: • PfAgo has the potential to serve as a viable molecular diagnostic tool for the detection and diagnosis of viral genomes • The RAA-PfAgo detection technique has a remarkable level of sensitivity and specificity • The RAA-PfAgo detection system can identify PEDV without needing advanced equipment.

Recombinase-aided amplification coupled with lateral flow dipstick for efficient and accurate detection of Bombyx mori nucleopolyhedrovirus

The infection of Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the main causes of economic losses in sericulture. Thus, it is essential to establish rapid and effective method for BmNPV detection. In the present study, we have developed a recombinase-aided amplification (RAA) to amplify the BmNPV genomic DNA at 37 °C within 30 min, and achieved a rapid detection method by coupling with a lateral flow dipstick (LFD). The RAA-LFD method had a satisfactory detection limit of 6 copies/μL of recombinant plasmid pMD19-T-IE1, and BmNPV infection of silkworm can be detected 12 h post-infection. This method was highly specific for BmNPV, and without cross-reactivity to other silkworm pathogens. In contrast to conventional polymerase chain reaction (PCR), the RAA-LFD assay showed higher sensitivity, cost-saving, and especially is apt to on-site detection of BmNPV infection in the sericulture production.