Development of a Reverse Transcription-Recombinase Polymerase Amplification Assay for Duplex Detection of Foodborne Viruses in Oysters

Abstract

Viral contamination may occur at any stage of food processing. The study aim was to develop a two-step reverse transcription (RT)-recombinase polymerase amplification (RPA) assay and evaluate for in-field duplex detection of hepatitis A virus (HAV) and norovirus in oysters. The RNA expression plasmids were generated by amplifying a fragment of the VP1 gene of HAV and norovirus through PCR and cloning it into an expression vector. The RNAs were transcribed in vitro from the plasmids and further used for reverse transcription. The resulting single-stranded cDNAs were used as the purified or spiking templates to determine the sensitivities of simplex and duplex RT-RPA compared with RT-PCR, and RT-qPCR assays. The reproducibility and application of duplex RT-RPA in the field were also evaluated. Our results showed that simplex RT-RPA was at least 100 times more sensitive than RT-PCR and RT-qPCR and even more than duplex detection using purified targets. Unlike RT-PCR, the RT-RPA reaction was unaffected by inhibitors found in food, allowing simple sample preparation methods for detection within a fraction of the time. The duplex assay detected HAV, norovirus, or both in 12/30 (40%) oyster samples tested. Duplex RT-RPA proved to be a rapid, accurate, and reproducible method in a field test for detecting HAV and norovirus. Thus, duplex RT-RPA should be suitable for use in minimally equipped laboratories and field settings. If in-field RT-RPA services are provided to oyster farmers, the technique can minimize the risk of infection to consumers, thereby improving food safety. Keywords: Food safety, Hepatitis A virus, Direct extraction, Norovirus, Nucleic acid amplification