Development of cross-priming amplification (CPA) combined with colorimetric and lateral flow dipstick visualization for scale drop disease virus (SDDV) detection

A Novel Sample-to-Answer Visual Nucleic Acid Detection System for Adenovirus Detection

Human adenoviruses (HAdVs) are common viruses that can cause local outbreaks in schools, communities and military camps, posing a huge threat to public health. An ideal POCT device for adenovirus detection in resource-limited settings is critical to control the spread of the virus. In this study, we developed an integrated and electricity-independent sample-to-answer system that can complete nucleic acid extraction, amplification, and detection at room temperature. This system is suitable for field and on-site detection because of its rapidity, sensitivity, lack of contamination, and lack of requirements of high-precision instruments and skilled technicians. It consists of two separate modules, ALP FINA (alkaline lysis with the paper-based filtration isolation of nucleic acid) and SV RPA (sealed and visual recombinase polymerase amplification). The extraction efficiency of ALP FINA can reach 48 to 84%, which is close to that of the conventional centrifuge column. The detection sensitivity of SV RPA is close to 10 copies/μL of AdvB and AdvE without aerosol contamination after repeated operations. When SV RPA was applied to the detection of nasopharyngeal swab samples of 19 patients who were infected with AdvB or AdvE as well as 10 healthy volunteers, its sensitivity and specificity reached 100%, respectively. IMPORTANCE HAdV infections are readily transmittable and, in some instances, highly contagious. Early and rapid diagnosis is essential for disease control. In this work, we developed a portable, disposable, and modularized sample-to-answer detection system for AdvB and AdvE, which rendered the entire test to be completely independent of electricity and other laboratory infrastructure. Thus, this detection system can be applied in resource-limited settings, and it has the potential to be further developed as an early diagnosis method in the field.

Research of childhood tuberculosis in suspected populations by molecular methods: A multicenter study in China

The research of childhood tuberculosis is inadequate in china. The cross-priming amplification (CPA) of specific DNA in clinical samples is increasingly adopted for the diagnosis of childhood tuberculosis. In this study, a multicenter research was performed to investigate the incidence and characteristics of childhood tuberculosis in suspected populations mainly by CPA method. 851 children suspected of tuberculosis were enrolled in seven centers across China. All samples were tested by a CPA method and 159 subjects were tested by Xpert MTB/RIF and liquid culture method in parallel to assess the reliability of the CPA method. A positive result in any one of the three methods provided a definitive diagnosis of Mycobacterium tuberculosis complex (MTBC) infection. The MTBC-positive rate was 9.5% (81/851) by the combined methods; 93.8% of the cases were detected by CPA technology (76/81). The rate of pulmonary infection was significantly higher than that of extrapulmonary infection (7.1%, 60/851 vs 2.5%, 21/851; P < 0.001). Scrofula was the predominant type of extrapulmonary tuberculosis. The MTBC positive rates in 12-18-year-old group (middle school), was 28.4% (23/81), higher than in those under-six-year-old (preschool; 39/525) and the 6~11-year-old (primary school; 18/235) groups combined (P < 0.001). The MTBC positive rate in patients with a clear history of tuberculosis exposure was significantly higher than in cases in which there was no history of tuberculosis contact(35.3%, 18/51 vs 7.8%, 61/782; P < 0.001). In conclusion, this multicenter investigation showed that pulmonary tuberculosis and extrapulmonary tuberculosis are not uncommon in children in China, with teenagers being particularly susceptible to infection. The incidence of pulmonary tuberculosis in children is higher than that of extrapulmonary tuberculosis. History of exposure to tuberculosis is a high risk factor for childhood tuberculosis.

CRISPR-based platform for rapid, sensitive and field-deployable detection of scale drop disease virus in Asian sea bass (Lates calcarifer)

Scale drop disease virus (SDDV) is a major pathogen of Asian sea bass that has emerged in many countries across the Asia Pacific since 1992 and carries the potential to cause drastic economic losses to the aquaculture sector. The lack of an approved vaccine for SDDV necessitates timely prevention as the first line of defence against the disease, but current diagnostic platforms still face challenges that render them incompatible with field applications, particularly in resource-limited settings. Here, we developed a novel detection platform for SDDV based on a CRISPR-Cas12a-based nucleic acid detection technology combined with recombinase polymerase amplification (RPA-Cas12a). Using the viral adenosine triphosphatase (SDDV-ATPase) gene as a target, we achieved the detection limit of 40 copies per reaction and high specificity for SDDV. The coupling with fluorescence and lateral flow readouts enables naked-eye visualization and straightforward data interpretation requiring minimal scientific background. Compared with semi-nested PCR in field sample evaluation, our RPA-Cas12a assay is more sensitive and capable of detecting SDDV in asymptomatic fish. Importantly, the entire workflow can be carried out at a constant temperature of 37°C within an hour from start to finish, thus removing the need for an expensive thermal cycling apparatus and long turnaround times associated with PCR-based methods. Therefore, owing to its high accuracy, rapidity and user-friendliness, the developed RPA-Cas12a platform shows the potential for diagnosis of SDDV at point of need and could be a valuable tool to help protect fish farming communities from large-scale epidemics.