Virus Genome Quantification Does not Predict Norovirus Infectivity After Application of Food Inactivation Processing Technologies

Abstract

When determining the effect of food processing on the infectivity of any contaminating virus, it is necessary to distinguish unambiguously between infectious and noninfectious viruses present. However, this can be difficult in the particular case of noroviruses (NoVs) because no reliable cell culture model is available. The aim of this study was to assess the use of molecular methods-RT real-time PCR (RT-qPCR) and enzymatic treatment (ET) coupled to RT-qPCR-to quantify the infectivity of NoV after application of various inactivating food-processing technologies. RT-qPCR and ET-RT-qPCR gave significantly different (P \ 0.01) results concerning the reduction in viral genome counts by all inactivation procedures and conditions used, except for HHP treatment at 600 MPa for 5 min. These findings indicate that the ET prior to RT-qPCR has an effect on the estimation of the reduction of virus genome counts, and may eliminate genomes of affected virus particles. However, no correlation was found between the results obtained by ET-RT-qPCR and those obtained by cell culture. Therefore, the effect is presumably only partial, and not adequate to allow accurate estimation of virus inactivation. Consequently, our results indicate that the quantification of virus genomes by PCR, regardless of prior ET, is not adequate for establishing virus inactivation and/or infectivity. In addition, our results also illustrate that the general effect of virus inactivation is not directly correlated to effects on the integrity of virus genome and protein capsid. Presumably, inactivation by food processing is the consequence of effects on proteins involved in adhesion and invasion stages.

Evaluation of high hydrostatic pressure effect on human adenovirus using molecular methods and cell culture

“…1 log 10 unit reduction 6 log 10 unit reduction to effects on the virus genome and protein capsid integrity, but rather to effects on proteins associated with adhesion to and invasion of eukaryotic cells, which is in accordance with previous findings (Diez-Valcarce et al, 2011b;Kovač et al, 2012;Tang et al, 2010). As viruses which lose the ability to attach to the cells cannot cause infection, the only real assessment of risk to human health can be obtained by cell culture assay (e.g.…”

Comprehensive Comparison of Cultivable Norovirus Surrogates in Response to Different Inactivation and Disinfection Treatments

“…In addition, TuV consists of at least 4 different genotypes, which display diverse histo-blood group antigen (HBGA) binding patterns mimicking those of human noroviruses (50). Like other investigators, we found that RNA quantitation after treatment of surrogate viruses with chlorine, alcohols, or HHP does not quantitate the loss of virus infectivity (22,23,47,51), although in some treatments an increase in RNA reduction did parallel an increase in infectivity reduction, as was apparent for the chlorine treatments of FCV and the alcohol treatments of MNV. Interestingly, treatments of human norovirus with chlorine, alcohols, and HHP demonstrated that GII viruses are more resistant than GI viruses, as measured by reductions of RNA by RT-qPCR.…”

A systematic review of human norovirus survival reveals a greater persistence of human norovirus RT-qPCR signals compared to those of cultivable surrogate viruses

“…The maximum observed reductions in RT-qPCR signals following heat treatment can reach a plateau, and varies by study design, complicating direct comparison between studies. For surrogate viruses these maximum RT-qPCR signal reductions have been reported to range from b0.5 log 10 for MNV-1 (Diez-Valcarce et al, 2011;Li et al, 2012) to 2 log 10 for FCV F-9 (with RNase pre-treatment, Topping et al, 2009) and N4 log 10 for the bacteriophage MS2 (with proteinase K and RNase pretreatment, Pecson et al, 2009) for temperatures up to 85°C. These differences may be due to inherent differences in the heat resistance of these viruses.…”