Zebrafish embryos are more efficient and robust than zebrafish larvae in evaluating human norovirus infectivity

This study reports an essential improvement of the method for replication of human norovirus (hNoV) with the use of zebrafish (Danio rerio) embryos. With three globally prevalent hNoV genotypes and P-types GII.2[P16], GII.4[P16], and GII.17[P31], we demonstrated that this tool had high efficiency and robustness, and enabled continuous virus passaging. This tool is versatile in being applied in hNoV related research. In pathogenesis study, the zebrafish embryo generated hNoVs showed clear binding patterns to human histo-blood group antigens (HBGAs) in human saliva by a simple saliva-binding reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In disinfection study, it was shown that a dose of 6 mJ/cm2 UV254 was able induce > 2-log reduction in hNoV infectivity for all three hNoV strains tested, suggesting that hNoVs were more UV susceptible than multiple enteric viruses and commonly used hNoV surrogates as tested before. IMPORTANCEHNoVs are a leading cause of gastroenteritis outbreaks worldwide. The zebrafish embryo tool as developed in this study serves as an efficient way to generate viruses with high titers and clean background and a straightforward platform to evaluate hNoV inactivation efficacies. It is expected that this tool will not only benefit epidemiological research of hNoV but also be used to generate hNoV inactivation parameters which are highly needed by the water treatment and food industry.