Development of a lateral flow immunochromatographic assay for the rapid diagnosis of Orf virus infections

Recent advances in diagnostic approaches for orf virus

Orf virus (ORFV), the prototype species of the Parapoxvirus genus, is an important zoonotic virus, causing great economic losses in livestock production. At present, there are no effective drugs for orf treatment. Therefore, it is crucial to develop accurate and rapid diagnostic approaches for ORFV. Over decades, various diagnostic methods have been established, including conventional methods such as virus isolation and electron microscopy; serological methods such as virus neutralization test (VNT), immunohistochemistry (IHC) assay, immunofluorescence assay (IFA), and enzyme-linked immunosorbent assay (ELISA); and molecular methods such as polymerase chain reaction (PCR), real-time PCR, loop-mediated isothermal amplification (LAMP), recombinase polymerase amplification (RPA), and recombinase-aided amplification (RAA) assay. This review provides an overview of currently available diagnostic approaches for ORFV and discusses their advantages and limitations and future perspectives, which would be significantly helpful for ORFV early diagnosis and surveillance to prevent outbreak of orf. KEY POINTS: • Orf virus emerged and reemerged in past years • Rapid and efficient diagnostic approaches are needed and critical for ORFV detection • Novel and sensitive diagnostic methods are required for ORFV detection.

Polycaprolactone/silk fibroin electrospun nanofibers-based lateral flow test strip for quick and facile determination of bisphenol A in breast milk

This study aimed to develop a sensitive lateral flow test strip for the detection of bisphenol A (BPA) in breast milk. Conventional nitrocellulose test membrane was coated with the coaxial nanofiber, consisting of the inner polycaprolactone (PCL) and the outer PCL/silk fibroin (SF) mixture, to decrease the flow rate of the breast milk in the lateral flow assay (LFA). The nanofiber was prepared by using coaxial electrospinning, and BPA antibody was immobilized physically to the nanofiber. This nanofiber was used as a test membrane in the LFA. Color changes on the test membrane were evaluated as the signal intensity of the BPA. Breast milk creates a background on surfaces due to its structural properties. This background was detected by comparing the signal intensity with the signal intensity of water. The higher signal intensity was found in water samples when compared to breast milk samples. Although the detection limit is 2 ng/ml in both coaxial PCL/SF nanofiber and nitrocellulose (NC) test membranes, the color intensity increased with the increasing BPA concentration in the coaxial PCL/SF nanofiber. As a new dimension, the coaxial PCL/SF nanofiber provided higher color intensity than the NC membrane. In conclusion, a sensitive onsite method was developed for the detection of BPA in breast milk by using new coaxial PCL/SF nanofiber as a test membrane in LFA.

Development and application of multiplex PCR method for simultaneous detection of seven viruses in ducks

BACKGROUND

Major viruses, including duck-origin avian influenza virus, duck-origin Newcastle disease virus, novel duck parvovirus, duck hepatitis A virus, duck Tembusu virus, fowl adenovirus, and duck enteritis virus, pose great harm to ducks and cause enormous economic losses to duck industry. This study aims to establish a multiplex polymerase chain reaction (m-PCR) method for simultaneous detection of these seven viruses.

RESULTS

Specific primers were designed and synthesized according to the conserved region of seven viral gene sequences. Then, seven recombinant plasmids, as the positive controls, were reconstructed in this study. Within the study, D-optimal design was adopted to optimize PCR parameters. The optimum parameters for m-PCR were annealing temperature at 57 °C, Mg²⁺ concentration at 4 mM, Taq DNA polymerase concentration at 0.05 U/μL, and dNTP concentration at 0.32 mM. With these optimal parameters, the m-PCR method produced neither cross-reactions among these seven viruses nor nonspecific reactions with other common waterfowl pathogens. The detection limit of m-PCR for each virus was 1 × 10⁴ viral DNA copies/μL. In addition, the m-PCR method could detect a combination of several random viruses in co-infection analysis. Finally, the m-PCR method was successfully applied to clinical samples, and the detection results were consistent with uniplex PCR.

CONCLUSION

Given its rapidity, specificity, sensitivity, and convenience, the established m-PCR method is feasible for simultaneous detection of seven duck-infecting viruses and can be applied to clinical diagnosis of viral infection in ducks.