Rapid Diagnostic Test for Hepatitis B Virus Viral Load Based on Recombinase Polymerase Amplification Combined with a Lateral Flow Read-Out

Real-Time Monitoring on the Chinese Giant Salamander Using RPA-LFD

The Chinese giant salamander (Andrias davidianus), listed as an endangered species under "secondary protection" in China, faces significant threats due to ecological deterioration and the expansion of human activity. Extensive field investigations are crucial to ascertain the current status in the wild and to implement effective habitat protection measures to safeguard this species and support its population development. Traditional survey methods often fall short due to the elusive nature of the A. davidianus, presenting challenges that are time-consuming and generally ineffective. To overcome these obstacles, this study developed a real-time monitoring method that uses environmental DNA (eDNA) coupled with recombinase polymerase amplification and lateral flow strip (RPA-LFD). We designed five sets of species-specific primers and probes based on mitochondrial genome sequence alignments of A. davidianus and its close relatives. Our results indicated that four of these primer/probe sets accurately identified A. davidianus, distinguishing it from other tested caudata species using both extracted DNA samples and water samples from a tank housing an individual. This method enables the specific detection of A. davidianus genomic DNA at concentrations as low as 0.1 ng/mL within 50 min, without requiring extensive laboratory equipment. Applied in a field survey across four sites in Huangshan City, Anhui Province, where A. davidianus is known to be distributed, the method successfully detected the species at three of the four sites. The development of these primer/probe sets offers a practical tool for field surveying and monitoring, facilitating efforts in population recovery and resource conservation for A. davidianus.

Point-of-Care Testing for Hepatitis Viruses: A Growing Need

Viral hepatitis, caused by hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), or hepatitis E virus (HEV), is a major global public health problem. These viruses cause millions of infections each year, and chronic infections with HBV, HCV, or HDV can lead to severe liver complications; however, they are underdiagnosed. Achieving the World Health Organization's viral hepatitis elimination goals by 2030 will require access to simpler, faster, and less expensive diagnostics. The development and implementation of point-of-care (POC) testing methods that can be performed outside of a laboratory for the diagnosis of viral hepatitis infections is a promising approach to facilitate and expedite WHO's elimination targets. While a few markers of viral hepatitis are already available in POC formats, tests for additional markers or using novel technologies need to be developed and validated for clinical use. Potential methods and uses for the POC testing of antibodies, antigens, and nucleic acids that relate to the diagnosis, monitoring, or surveillance of viral hepatitis infections are discussed here. Unmet needs and areas where additional research is needed are also described.

Preliminary investigation of hepatitis E virus detection by a recombinase polymerase amplification assay combined with a lateral flow strip

Hepatitis E virus (HEV) is a zoonotic pathogen that is a significant public health problem. Detecting HEV relies mainly on conventional PCR, which is time-consuming and requires sophisticated instruments and trained staff. We aimed to establish a reverse-transcription (RT)-recombinase polymerase amplification (RPA) assay (RT-RPA) combined with a lateral flow strip (LFS; RT-RPA-LFS) to rapidly detect HEV RNA in human and rabbit samples. With the optimal reaction conditions (37°C for 30 min), our assay detected as few as 1.0 × 102 copies/mL of HEV and showed no cross-reactivity with other hepatitis viruses. We tested 28 human samples (4 fecal and 24 serum samples) and 360 rabbit samples (180 fecal and 180 serum samples) with our RT-RPA-LFS assay and compared our assay to an RT-qPCR method. There was no significant difference (p > 0.05) in the test results between the 2 assays. Our RT-RPA-LFS assay detected both HEV3 and HEV4 genotypes. Our rapid, sensitive, and specific RT-RPA-LFS assay for the detection of HEV may provide a useful detection tool for limited-resource areas.

Lateral Flow Assay for Hepatitis B Detection: A Review of Current and New Assays

From acute to chronic hepatitis, cirrhosis, and hepatocellular cancer, hepatitis B infection causes a broad spectrum of liver diseases. Molecular and serological tests have been used to diagnose hepatitis B-related illnesses. Due to technology limitations, it is challenging to identify hepatitis B infection cases at an early stage, particularly in a low- and middle-income country with constrained resources. Generally, the gold-standard methods to detect hepatitis B virus (HBV) infection requires dedicated personnel, bulky, expensive equipment and reagents, and long processing times which delay the diagnosis of HBV. Thus, lateral flow assay (LFA), which is inexpensive, straightforward, portable, and operates reliably, has dominated point-of-care diagnostics. LFA consists of four parts: a sample pad where samples are dropped; a conjugate pad where labeled tags and biomarker components are combined; a nitrocellulose membrane with test and control lines for target DNA-probe DNA hybridization or antigen-antibody interaction; and a wicking pad where waste is stored. By modifying the pre-treatment during the sample preparation process or enhancing the signal of the biomarker probes on the membrane pad, the accuracy of the LFA for qualitative and quantitative analysis can be improved. In this review, we assembled the most recent developments in LFA technologies for the progress of hepatitis B infection detection. Prospects for ongoing development in this area are also covered.