Improving methods for the assessment of infectious human enteric virus survival in produce

Improving methods for the assessment of infectious human enteric virus survival in produce

Jan. 1, 2024 - Dec. 31, 2025

2024CPS04

University of Barcelona

$326,230.00

Susana Guix, Ph.D.
University of Barcelona

Gloria Sanchez Moragas, Ph.D.

Produce may occasionally become contaminated by human viruses and cause sporadic cases of disease as well as outbreaks in the community. Viruses most commonly associated with disease from consumption of produce are human noroviruses and hepatitis A virus, which may cause acute gastroenteritis and hepatitis, respectively. Detection of viruses in produce items, such as leafy greens and berries, is difficult because contamination usually occur at low numbers and because available methods show limited recovery efficiencies and provide information on contamination by viral genomes, which do not always indicate a real risk of infection. This project aims at optimizing current norovirus and hepatitis A concentration and detection methods in leafy greens and berries, to increase their efficiency, reduce their turnaround time and provide estimates of viral infectivity and risk of infection, by combining them with a recently published cell-culture system for noroviruses based on salivary-gland continuous cell lines. The optimized methods will be consistently compared to the two reference methods currently available for virus analysis in foods. Optimized methods will also be implemented at laboratory scale experiments to fill critical knowledge gaps regarding detection and persistence of infectious viruses in leafy greens and berries during post-harvest storage and disinfection scenarios.

Technical Abstract

Despite the occurrence of human enteric viruses like norovirus (HuNoV) and hepatitis A virus (HAV) in produce is documented, data are limited mainly due to the lack of rapid economically feasible methods for the analysis of viral contamination along the food chain. Understanding of the risk associated to produce contamination by viruses and the best industry practices to prevent it is hampered by the difficulty of measuring HuNoV and HAV infectivity. Detection of viral pathogens in produce is challenging due to the usual low concentrations of contaminating viruses, the low process recoveries of current extraction methods, the time required for analysis, and the reliability solely on standardized molecular detection of viral genome equivalents, which do not correspond to infectious viruses. Despite Human Intestinal Organoids (HIOs) have represented a breakthrough in supporting HuNoV replication, there are not available for a routine bases due to the high cost and dependence on proficiency skilled personnel for manipulation. Early this year, salivary gland (SG)-derived continuous cell lines have been reported to support HuNoV replication, suggesting their potential for generating a scalable and manageable system of production. Facing difficulties to detect/quantify infectious enteric viruses from foods, recent studies have also proposed the use of viability PCR-based methods for assessing capsid-integrity and estimating infectivity of enteric viruses in several types of food and water samples, but complete elimination of signals from unviable viruses has remained a challenge.

In this proposal, our main aim is to optimize current HuNoV and HAV concentration and detection methods in leafy greens and berries, to increase their efficiency, reduce their turnaround time and provide estimates of viral infectivity. Two alternative virus concentration protocols based on fast procedures widely used for the concentration of viruses (aluminum hydroxide adsorption-precipitation method and InnovaPrep Concentrating Pipette) will be tested and compared to the FDA and ISO reference protocols. We also want to validate the use of SG-derived cell culture system to detect infectious HuNoV, adapt it as a novel method to determine HuNoV infectivity in produce, and answer critical knowledge gaps regarding survival of infectious virus under selected post-harvest scenarios, as compared to HAV. A correlation analysis between the SG-derived cell culture system, standardized direct RTqPCR genome quantification, and optimized capsid-integrity alternative assays will also be performed to provide information on die-off rates and infectious:GE ratios over time. An improved understanding of the efficacy of current industry practices and other alternative potential decontamination methods will help to develop interventions to minimize contamination and mitigate the risk of viral infections through the consumption of produce.