Human Intestinal Enteroids to Evaluate Human Norovirus GII.4 Inactivation by Aged-Green Tea.

Walter Randazzo,Esther K Morantz,Veronica Costantini,Jan Vinjé

doi:10.3389/fmicb.2020.01917

Walter Randazzo, Esther K Morantz + Show 2 more

Open Access

https://doi.org/10.3389/fmicb.2020.01917

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Abstract

Human noroviruses are the leading cause of epidemic and sporadic acute gastroenteritis worldwide and the most common cause of foodborne illness in the United States. Several natural compounds, such as aged-green tea extract (aged-GTE), have been suggested as ingestible antiviral agents against human norovirus based on data using murine norovirus and feline calicivirus as surrogates. However, in vitro data showing their effectiveness against infectious human norovirus are lacking. We tested the activity of aged-GTE to inhibit human norovirus in a human intestinal enteroids (HIEs) model and Tulane virus in LLC-monkey kidney (LLC-MK2) cell culture. HIE monolayers pretreated with aged-GTE at different temperatures showed complete inhibition of human norovirus GII.4 replication at concentrations as low as 1.0 mg/ml for 37°C, 1.75 mg/ml for 21°C, and 2.5 mg/ml for 7°C. In contrast, a moderate decrease in Tulane virus infectivity of 0.85, 0.75, and 0.65 log TCID50/ml was observed for 2.5 mg/ml aged-GTE at 37, 21, and 7°C, respectively. Our findings demonstrate that GTE could be an effective natural compound against human norovirus GII.4, while only minimally effective against Tulane virus.

Highlights

Human noroviruses are the leading cause of epidemic and sporadic acute gastroenteritis worldwide and the most common cause of foodborne illness in the United States and Europe, with a societal cost of $60 billion dollars (Ahmed et al, 2014; Havelaar et al, 2015; Bartsch et al, 2016)
We evaluated the antiviral activity of green tea extract (GTE) against GII.4 norovirus in human intestinal enteroids (HIEs) and Tulane virus in LLC-monkey kidney (LLC-MK2) cells
Microscopical visual inspection of HIEs monolayers exposed to GTE for 1 h at 37°C in 5% CO2 showed no cytotoxic effect

Summary

INTRODUCTION

Human noroviruses are the leading cause of epidemic and sporadic acute gastroenteritis worldwide and the most common cause of foodborne illness in the United States and Europe, with a societal cost of $60 billion dollars (Ahmed et al, 2014; Havelaar et al, 2015; Bartsch et al, 2016). In the absence of a robust in vitro cell culture system for human noroviruses (Moore et al, 2015; Manuel et al, 2018), antimicrobial activity of GTE against these viruses has been inferred by quantitative reverse transcription polymerase chain reactions (RT-qPCRs) and capsid binding assays as indirect approximations (Falcó et al, 2019). Compared to other surrogate viruses such as FCV and MNV, Tulane virus is one of the most promising to use experimentally, as this virus is an enteric virus and displays diverse histo-blood group antigen (HBGA) binding patterns similar to human noroviruses (Cromeans et al, 2014; Farkas, 2015; Polo et al, 2018). We evaluated the antiviral activity of GTE against GII. norovirus in HIEs and Tulane virus in LLC-monkey kidney (LLC-MK2) cells

MATERIALS AND METHODS

RESULTS

DISCUSSION