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Journal Articles Applied and Environmental Microbiology Year : 2015

Tulane Virus as a Potential Surrogate To Mimic Norovirus Behavior in Oysters


Oyster contamination by noroviruses is an important health and economic problem. The present study aimed to compare the behaviors of Norwalk virus (the prototype genogroup I norovirus) and two culturable viruses: Tulane virus and mengovirus. After bioaccumulation, tissue distributions were quite similar for Norwalk virus and Tulane virus, with the majority of viral particles detected in digestive tissues, while mengovirus was detected in large amounts in the gills and mantle as well as in digestive tissues. The levels of persistence of all three viruses over 8 days were comparable, but clear differences were observed over longer periods, with Norwalk and Tulane viruses displaying rather similar half-lives, unlike mengovirus, which was cleared more rapidly. These results indicate that Tulane virus may be a good surrogate for studying norovirus behavior in oysters, and they confirm the prolonged persistence of Norwalk virus in oyster tissues. S hellfish are filter feeders that can accumulate different types of pathogens from human fecal pollution and were identified as vectors for human enteric pathogen transmission more than a century ago. We have known for almost 40 years that bacteria and viruses show differences in terms of concentration and accumulation in and depuration from contaminated shellfish (1). Nowadays the problem of viral contamination has become dominant, and over the last 10 years about 40% of RASFF (Rapid Alert System for Food and Feed) notifications are related to the detection of norovirus (NoV) in oysters (2). Improvements in detection methods , increased epidemiological surveillance, and efforts by authorities to improve the quality of products put on the market have contributed to better recognition of viral contamination. These improvements have assisted in identifying that increases in human populations in coastal areas, as well as climate change, inducing heavy rainfall and associated sewage overflows, constitute risk factors for shellfish contamination (3, 4). Among human enteric viruses, NoVs are recognized as the leading cause of epidemics and sporadic cases of gastroenteritis in all age groups of humans (5, 6). NoVs of human origin are ex-creted in large quantities by ill people, but they may also be present in asymptomatic, healthy individuals (7). As a consequence, they are discharged in large numbers into sewage, and due to their resistance to inactivation, they are frequently detected in waste-water treatment plant effluent and in surface waters (8–10). Sewage treatment which incorporates new technologies, such as membrane filtration, contributes to decreasing the numbers of microorganisms discharged into the coastal environment (11, 12), but this does not prevent accidental contamination. Depuration of shellfish, which was developed to eliminate bacteria, does not efficiently eliminate viruses that persist for several weeks or months in bivalve tissues (13, 14). As a consequence, in most cases of contamination, the only risk management option to prevent consumer infections is the closure of production areas, with viral testing of shellfish to evaluate the level and type of contamination. NoVs are nonenveloped, single-stranded, positive-sense RNA viruses belonging to the Caliciviridae family. The short genome, which is organized into three open reading frames (ORFs), is highly variable (15). Importantly, NoVs were the first viruses for which it was shown that there is genetic sensitivity to infection through the recognition of histo-blood group antigens (HBGAs) (16). HBGAs, which are complex glycans present on many cell types, are synthesized from a series of precursor structures by step-wise addition of monosaccharide units via a set of glycosyltrans-ferases (17). Evidence accumulated from volunteer studies and from analysis of outbreaks indicates that binding to these carbohydrates is required for infection (18, 19). Moreover, various human NoV strains that bind to HBGAs present distinct specificities for HBGAs. As a result, most strains infect only a subset of the population, based on HBGA expression (20, 21). Specific binding of NoVs to the oyster digestive tract through an Alike carbohydrate structure (which is indistinguishable from the human blood group A antigen) and other ligands has been described (22–24). It was also demonstrated that these ligands have an impact on bioaccumulation efficiency, and a seasonal effect was observed for some strains (25, 26). A field study confirmed the preferential selection of genogroup I (GI) NoVs over GII and GIII NoVs by Pacific oysters (27). These observations suggest that oysters have the ability to specifically accumulate and concentrate a human pathogen based on the presence of a shared ligand between the two species rather than through nonspecific interactions only (28). Since different NoV strains show different specificities for HBGAs in humans, all strains may not be captured equally well by oysters. We also hypothesize that such specific ligands have an impact on NoV persistence in oysters. Tulane virus (TV) is the prototype strain of the genus Recovirus


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inserm-01284956 , version 1 (08-03-2016)



Najoua Drouaz, Julien Schaeffer, Tibor Farkas, Jacques Le Pendu, Françoise S Le Guyader. Tulane Virus as a Potential Surrogate To Mimic Norovirus Behavior in Oysters. Applied and Environmental Microbiology, 2015, 81 (15), pp.5249. ⟨10.1128/AEM.01067-15⟩. ⟨inserm-01284956⟩
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