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Published Articles from USDA ARS National Program 108: Food Safety
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Title: Inactivation of Tulane virus, a novel surrogate for human norovirus
Authors: Tian P, Yang D, Quegley C, Chou M, Xi J
Journal: J Food Prot
Accepted date: 2012 Dec 1
Interpretive summary: Human noroviruses (HuNoV) are pathogens of significant concern, but as of current they cannot be cultured, which limits the ways in which they can be studied. Surrogates for HuNoV have been used to this end, but they are not perfect and often differ from HuNoV in fundamental ways. Tulane virus (TV) is a recently-discovered candidate for being an experimental surrogate of HuNoV. The conditions required to inactivate TV is an important characteristic that can be suggestive of how well it can serve as a surrogate to HuNoV, but have not yet been thoroughly-documented. We have tested different types of inactivation conditions and agents across a range of intensities, and quantitated the results using the TCID50 assay. Molecular-based virus quantitation assays, notably qRT-PCR, have been used in lieu of in vivo/ex vivo assays for a number of reasons, including speed, ease, and feasibility. It is, however, questionable that what they quantitate is any accurate reflection of actual virus activity. Building on the results of our ex vivo assays, we tested the same inactivation conditions and agents to see if there is any correlation. We have found that TV is comparable to HuNoV and its existing surrogates in a variety of ways, and is closer to some than others for different methods of inactivation. We have also found that there is mostly little-to-no correlation between the virus counts obtained from the TCID50 assays and the virus signal obtained from the qRT-PCR assay, as the latter really only measures for the integrity of the targeted amplicon. This notably omits viral inactivation from degradation of the capsid required for binding and infection, not to mention critical damage to other areas of the viral genome not covered by the qRT-PCR target amplicon. We believe that a new technique that involves isolating viruses using their functional receptors, followed by qRT-PCR, is a molecular-based method that will better reflect the virus counts from the TCID50 assay.
Publication date: 2013 Apr
Volume: 76
Issue: 4
Pages: 712-8