Feasibility study for in vitro analysis of infectious foodborne HEV

Hepatitis E virus (HEV) is a member of the Hepeviridae family capable of infecting humans producing a range of symptoms from mild disease to kidney failure. Epidemiological evidence suggests that hepatitis E genotype III and IV cases may be associated with the consumption of undercooked pork meat, offal and processed products such as sausages [1]. A study carried out by the Animal Health and Veterinary Laboratories Agency (AHVLA), found hepatitis E virus contamination in the UK pork production chain and that 10% of a small sample of retail pork sausages were contaminated with the virus [2]. Furthermore, studies have confirmed the presence of HEV in the food chain and the foodborne transmission of Hepatitis E virus to humans [reviewed in 5]. Likewise, Scottish shellfish at retail [6] have also been found positive for HEV viral nucleic acid and some preliminary studies indicate that the virus is also detectable in soft fruits (L Scobie; unpublished data). There are current misunderstandings in what this data represents, and these studies have raised further questions concerning the infectivity of the virus, the processing of these foods by industry and the cooking and/or preparation by caterers and consumers. There are significant gaps in the knowledge around viral infectivity, in particular the nature of the preparation of food matrices to isolate the virus, and also with respect to a consistent and suitable assay for confirming infectivity [1,3]. Currently, there is no suitable test for infectivity, and, in addition, we have no knowledge if specific food items would be detrimental to cells when assessing the presence of infectious virus in vitro. The FSA finalised a comprehensive critical review on the approaches to assess the infectivity of the HEV virus which is published [3] recommending that a cell culture based method should be developed for use with food. In order to proceed with the development of an infectivity culture method, there is a requirement to assess if food matrices are detrimental to cell culture cell survival. Other issues that may have affected the ability to develop a consistent method are the length of time the virally contaminated sample is exposed to the cells and the concentration of the virus present. In most cases, the sample is only exposed to the cells for around 1 hour and it has been shown that if the concentration is less that 1x103 copies then infection is not established [3,5,10,11].