Noroviruses (NoV) are the leading cause of non-bacterial gastroenteritis. They are frequently associated with foodborne outbreaks, where large numbers of people are simultaneously exposed to infection. In order to control the spread of NoV disease, it is important to have effective methods to detect contamination of food items. The methods developed must have a high degree of sensitivity, since NoV are infectious at low doses (10 - 100 viral particles).
A detection and genotyping method is currently being developed in our laboratory for a number of enteric viruses. In the course of these studies, we have discovered that the cationic beads used for viral isolation, while highly effective at capturing other enteric viruses from a variety of food matrices, have not been as efficient in achieving the 10 particle detection limit targeted for NoV. The DNA microarray platform developed in the above project is working well for the identification and genotyping of NoV, however, it is important to develop a more efficient capture system to isolate and concentrate these most prevalent enteric viruses.
Capture systems exist that could be implemented for the NoV, but these use antibodies specific to each strain of NoV as the capture reagent. There are three different genogroups of noroviruses known to infect humans, encompassing 29 different genetic clusters and an untold number of different strains. Thus, the immunological approach is too specific. In addition, antibodies to new emerging strains may not be available. In our proposed method, we will take advantage of the histo-blood group antigen receptors used by NoV for entry into host cells. The naturally high affinity of NoV for these carbohydrates cannot be altered without rendering the viral particle non-infectious and, as such, all current and emerging strains of NoV will be captured by our system.
We propose the testing of different carbohydrate sources as well as different immobilization methods, each of which has their own inherent advantages and disadvantages. We will empirically determine which method provides the most sensitivity and specificity in NoV detection using samples spiked with up to ten different strains of NoV. Naturally contaminated food samples will also be tested as they become available. This method of virus capture will provide us with the tools necessary for the efficient isolation and subsequent rapid and sensitive detection of the highly infectious NoV in foods.
Benefit to Food Safety in Ontario:
The major benefit of this work will be the development of a method with improved sensitivity and specificity for the detection of NoV in foods which will be suitable for rapid and routine use. After development and technology transfer, this method will increase the number of facilities that are able to perform diagnostic testing of food in Ontario. The result will be to facilitate the identification, prevention and control of NoV in Ontario, aid in epidemiological investigations of outbreaks of NoV infection and help in performing risk assessment of potential exposure to contaminated items. Taken together, these benefits will lead to an improvement in the safety of food products and the protection of public health. If contaminated foods can be accurately identified and the source of contamination pinpointed, the financial losses associated with NoV contamination may be reduced. The method and its implementation across Ontario will also provide the necessary tools for regulators and the food industry to initiate programs aimed at monitoring foods for the presence of NoV. In addition to the improvement in public safety this provides, it will also enhance the Ontario food industry's economic opportunities for trade by increasing the confidence that its agri-food products are NoV free.<P> For more information, please visit the <a href="http://www.omafra.gov.on.ca/english/research/foodsafety/index.html" target="_blank">Ontario Ministry of Agriculture, Food & Rural Affairs (OMAFRA) Food Safety Research Program</a>.