Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: July 22, 2010
Publication Date: November 1, 2010
Citation: Richards, G.P. 2010. Pursuit of methods to propagate norovirus: decades of research. Pursuit of human norovirus propagation methods: decades of research. Edited by P.Lassus. Proceedings of the 7th International Conf. on Molluscan Shellfish Safety, Nantes, France, 14-19, June, 2009, pages 100-107
Noroviruses are a significant cause of foodborne illness globally. In spite of four decades of research to develop simple assays for norovirus detection in shellfish and other foods, there still exist major obstacles. The greatest obstacle is the inability to propagate noroviruses in any of the cell culture systems that are commonly used to detect other viruses. Another obstacle is the inability of norovirus to infect non-primate laboratory animals, like mice. Studies have reported infection or seroconversion in chimpanzees and other primates after administration of norovirus, but these animals did not develop typical symptoms of human norovirus infection (diarrhea and vomiting). In vivo propagation in human volunteers or in unsuspecting consumers of contaminated products is currently the only method to determine the infectivity of noroviruses. Immunoelectron microscopy, enzyme-linked immunosorbent assays and radioimmunoassays for norovirus detection have given way to more modern molecular biological techniques (reverse transcription-PCR) to detect virus presence, but these methods are unable to differentiate infectious from inactivated viruses, thus limiting the practical application of molecular approaches for regulatory purposes. This researcher has spent 25 years exploring various avenues to propagate noroviruses using a wide variety of primary and secondary tissues or cell lines in both monolayer and suspension culture, under static versus rocked conditions, after virus or cell treatment with human bile and digestive enzymes, with the alteration of pH and salinity during virus adsorption, and with serial inoculation of cells with viruses over long time periods. More recently, studies have reported limited norovirus replication after the artificial introduction of norovirus RNA into cell. Others have reported a limited propagation of norovirus in cells grown in a microgravity environment, an approach we are also evaluating in our laboratory. This presentation covers procedures that have been tried, with limited success, as well as emerging methods that offer some promise in developing the next generation of norovirus assays.