Zebrafish embryo amplifies human norovirus

National University of Singapore (NUS) food virologists have successfully propagated the human norovirus using zebrafish embryos, providing a valuable platform to assess the effectiveness of virus inactivation for the water treatment and food industries.

Human norovirus (HuNoV) is currently the predominant cause of acute gastroenteritis worldwide, contributing to an estimated 684 million diarrhoea cases, resulting in 212,000 annual fatalities. For a substantial period, the absence of an in vitro culture system has been a major hurdle in norovirus research. The most recently optimised human intestinal enteroid model, designed to support HuNoV replication, relies on human biopsy specimens obtained from surgical or endoscopic procedures, which are typically scarce. Moreover, the maintenance of these cells is both labour and resource intensive.

A research team led by Assistant Professor LI Dan from the NUS Department of Food Science and Technology, in collaboration with Professor GONG Zhiyuan from the NUS Department of Biological Sciences, serendipitously discovered that zebrafish embryo can be used as a host for cultivating HuNoV. The zebrafish embryo model is easy to handle, robust and has a capacity to efficiently replicate HuNoVs. This study, to the best of their knowledge, represents an inaugural demonstration of the highest fold-increase over the baseline. Most notably, this model enables the continuous passaging of HuNoV within a laboratory setting. With this model, researchers can effectively propagate and sustain the presence of HuNoV over time, enabling them to study in more depth its behaviour, replication, and other properties.

Prof Li said, “The zebrafish embryo model represents an essential improvement in the HuNoV cultivation method. With its high efficiency and robustness, this tool is able to enhance both the breadth and depth of HuNoV-related research. It is expected that this tool will not only benefit the advancement of epidemiological research on HuNoV but will also be invaluable in establishing HuNoV inactivation parameters. These parameters are highly needed by the water treatment and food industries to develop more effective methods for preventing the spread of the virus.”

This research has been presented at the 8th International Calicivirus Conference organised at Rotterdam, the Netherlands in May 2023, as the “state of the art” talk and published in the journal Applied and Environmental Microbiology.

In the future, the research team plans to utilise the zebrafish embryo model to investigate inactivation methods for HuNoVs in food products. To date, the successful detection of infectious HuNoV in food products remains an elusive goal. While further refinement and optimisation efforts are still required, the research team’s ongoing work holds great promise in tackling this challenging task.

Video clip showing the microinjection of human norovirus in zebrafish embryos. Fertilised eggs were collected and a microinjection needle was used to inject viral suspension (coloured with phenol red in the video) into the yolk of each egg.

Prof Li presenting her research work on human norovirus at the 8th International Calicivirus Conference.

Reference

Tan MTH; Gong ZY; Li D*, “Use of Zebrafish Embryos To Reproduce Human Norovirus and To Evaluate Human Norovirus Infectivity Decay after UV Treatment” Applied and Enviornmental Microbiology DOI: 10.1128/aem.00115-23 Published: 2023.