Concentration of foodborne viruses eluted from fresh and frozen produce: Applicability of ultrafiltration.

Foodborne illnesses involving raw and minimally processed foods are often caused by human noroviruses (HuNoV) and hepatitis A virus (HAV). Since food is contaminated usually with small numbers of virions, these must be eluted from the food surface and then concentrated for detection. The objective of this study was to optimize an ultrafiltration (UF) concentration method for HAV and HuNoVs present on various fresh and frozen produce. The detection range of the optimized method and its applicability to different food matrices was compared to the reference method ISO 15216-1:2017. Strawberry, raspberry, blackberry, lettuce, and green onion (25 g) were contaminated with HAV, HuNoV GI.7 and HuNoV GII.4 and then recovered therefrom by elution. A commercial benchtop UF device was used for the concentration step. Viral RNA was extracted and detected by RT-qPCR. From fresh strawberries, recovery of HAV loaded at 104 genome copies per sample was 30 ± 13 %, elution time had no significant impact, and UF membrane with an 80-100 kDa cut-off in combination with Tris-glycine elution buffer at pH 9.5 was found optimal. At lower copy numbers on fresh strawberry, at least 1 log lower numbers of HuNoV were detectable by the UF method (103 vs 104 GII.4 copies/sample and 101 vs 103 GI.7 copies/sample), while HAV was detected at 101 genome copies/sample by both methods. Except on raspberry, the UF method was usually equivalent to the ISO method regardless of the virus tested. The UF method makes rapid viral concentration possible, while supporting the filtration of large volume of sample. With fewer steps and shorter analysis time than the ISO method, this method could be suitable for routine analysis of viruses throughout the food production and surveillance chain.

Evaluation of a new automated viral RNA extraction platform for hepatitis A virus and human norovirus in testing of berries, lettuce, and oysters.

Fruits, vegetables, and shellfish are often associated with outbreaks of illness caused particularly by human norovirus (HuNoV) and hepatitis A virus (HAV), the leading causative agents of foodborne illness worldwide. The aim of this study was to evaluate a new automated nucleic acid extraction platform (EGENE-UP EASYPREP) for enteric viruses in several at-risk food matrices and to test its limit of detection in comparison to a semi-automated method (EGENE-UP) using Boom methodology for nucleic acid extraction as suggested in the reference method ISO 15216-2:2019. Fresh and frozen raspberries, frozen blackberries, romaine lettuce and oyster digestive glands were artificially contaminated with HAV, HuNoV GII.4 or HuNoV GI.7 at 102, 103 or 104 genome copies/sample. Virus was then recovered from the food matrix using the ISO method. Viral RNA extracted from frozen berry samples by the automated system was purified on a column for additional removal of RT-qPCR inhibitors. For fresh raspberry, oysters, and romaine lettuce, the two extraction platforms were deemed equivalent. For frozen raspberry, the automated platform appeared to be more efficient for viral recovery, particularly for HAV and HuNoV GI at lower concentrations. With frozen blackberries, the two platforms may be considered equivalent for all targeted viruses. However, the automated method led to less sample-associated inhibition of the PCR, 56.5 % of samples versus 95.0 % for the semi-automated. We thus found that the automated extraction can be performed easily by users while obtaining equivalent or even superior results to the ISO 15216-2:2019 method, and therefore appears to be suitable for routine sanitary monitoring in food processing and for tracing outbreaks of illness.

The possibility of spreading herpes simplex virus type 1 via food handling and sharing.

AIMS: Herpes simplex virus type 1 (HSV-1) is an enveloped virus that causes recurrent and incurable diseases in 67% of the world population. Although it is not listed as a foodborne virus, some studies have shown that it can be recovered from surfaces as well as food. METHODS AND RESULTS: We investigated its persistence at -20°C, 4°C, 20°C, or 37°C for up to 7 days on stainless steel, aluminum, glass, polypropylene, cheddar cheese, sliced almond, and apple skin and in cola soft drink, orange juice, coffee, and milk, as well as its transferability from stainless steel to dry or moistened nitrile or latex gloves over time at typical ambient temperatures. Based on the plaque assay on Vero cells, HSV-1 persisted at least 24 h on all surfaces and at least 1 h on food matrices but was inactivated quickly in cola soft drink. Temperature and pH affected HSV-1 infectivity. Transfer of HSV-1 at a contact pressure of 1 kg cm2-1 for 10 s occurred only on latex, especially moistened. CONCLUSIONS: Our data on the persistence of HSV-1 on food-related surfaces suggest that some risk may be associated with sharing foods with infected carriers.

Inactivation of foodborne viruses by novel organic peroxyacid-based disinfectants.

Viruses are responsible for most enteric foodborne illnesses worldwide. The foods most frequently involved are fresh fruits and vegetables since they undergo little or no processing. Washing with a chemical disinfectant is a convenient way of inactivating viruses on foods. Peracetic acid, widely used as a disinfectant in the food industry, has the drawback of leaving a strong odor and is ineffective alone against some foodborne viruses. In this study, four disinfectants, namely per levulinic acid with or without sodium dodecyl sulfate, peracetic acid and a commercial peracetic acid-based disinfectant were tested on murine norovirus 1 (MNV-1), hepatitis A virus (HAV), and hepatitis E virus (HEV). Disinfectant concentrations were 50, 80, 250, 500, and 1000 mg l-1 and contact times were 0.5, 1, 5, and 10 min. Under these conditions, per levulinic acid supplemented with 1% SDS reduced MNV-1 infectious titer by 3 log cycles vs. 2.24 log cycles by peracetic acid within 0.5 min. On stainless steel at 80 ppm, only peracetic acid produced 3-log reductions within 0.5 min. None of these peroxyacids was able to reduce infectious titers of HAV or HEV by even 2 log cycles at any concentration or time-tested. This study will guide the development of new chemical formulas that will be more effective against major foodborne viruses and will have less impact on food quality and the environment.

Prevalence of Foodborne Viruses in Berries Harvested in Canada.

It is known that the transmission of different foodborne viruses can occur either via discharge of contaminated water close to the production environment or via close contact with animal feces. Cranberries are intimately associated with water throughout their production cycle, and blueberries grow close to the ground which could lead to contact with wildlife. The aim of this study was to evaluate the prevalence of human norovirus (HuNoV GI and GII), hepatitis A virus (HAV) and hepatitis E virus (HEV) in two berries produced commercially in Canada. The detection of HuNoV and HAV on RTE cranberries and of HEV on wild blueberries was evaluated using the ISO method 15216-1:2017. Only 3 of 234 cranberry samples tested positive for HuNoV GI (3.6, 7.4, 5.3 genome copies/g, respectively) and all were negative for HuNoV GII and HAV. PMA pre-treatment and sequencing confirmed the absence of potential intact HuNoV GI particles on cranberries. None of the 150 blueberry samples tested positive for HEV. Overall, the prevalence of foodborne viruses in RTE cranberries and wild blueberries harvested in Canada is low, making these products relatively safe for consumers.

FGF21 Normalizes Plasma Glucose in Mouse Models of Type 1 Diabetes and Insulin Receptor Dysfunction.

Fibroblast growth factor (FGF) 21 is a member of the FGF family of proteins. The biological activity of FGF21 was first shown to induce insulin-independent glucose uptake in adipocytes through the GLUT1 transporter. Subsequently, it was shown to have effects on the liver to increase fatty acid oxidation. FGF21 treatment provides beneficial metabolic effects in both animal models and patients with obesity, type 2 diabetes mellitus (T2D) and/or fatty liver disease. In this paper, we revisited the original finding and found that insulin-independent glucose uptake in adipocytes is preserved in the presence of an insulin receptor antagonist. Using a 40-kDa PEGylated (PEG) and half-life extended form of FGF21 (FGF21-PEG), we extended these in vitro results to 2 different mouse models of diabetes. FGF21-PEG normalized plasma glucose in streptozotocin-treated mice, a model of type 1 diabetes (T1D), without restoring pancreatic ß-cell function. FGF21-PEG also normalized plasma glucose levels and improved glucose tolerance in mice chronically treated with an insulin competitive insulin receptor antagonist, a model of autoimmune/type-B insulin resistance. These data extend the pharmacological potential of FGF21 beyond the settings of T2D, fatty liver, and obesity.

Correlation Between Nasal Epithelial Injury and In Vitro Cytotoxicity Using a Series of Small Molecule Protein Tyrosine Phosphatase 1B Inhibitors Investigated for Reversal of Leptin Resistance in Obesity.

This research provides a cautionary example when evaluating changes in behavioral end points with respect to postulated pharmacologic activity. Various small molecule substrate mimetic protein tyrosine phosphatase 1B (PTP1B) inhibitors were investigated as pharmacologic agents for decreasing food consumption using intranasal (IN) dosing as a means for direct nose-to-brain delivery along the olfactory/trigeminal nerve pathways. Although food consumption was decreased in diet-induced obese (DIO) mice, nasal discharge was observed. Studies were conducted to investigate local effects on the nasal airway and to develop structure-activity relationships. Intranasal administration of PTP1B inhibitors at ≥0.03 mg/d to DIO mice produced dose-dependent injury to various cell types of the nasal epithelia. Protein tyrosine phosphatase 1B inhibitors with calculated log octanol >3.0 were the most toxic. Whereas a pharmacologically inactive analog of a PTP1B inhibitor produced nasal injury, along with decreased food consumption, the marketed IN drug ketorolac produced no lesions at the same dose of 0.3 mg/d and only minor changes at 3 mg/d. Rat skin fibroblast cells were exposed in vitro to PTP1B inhibitors, ketorolac, paraquat, and the detergent sodium dodecylbenzene sulfonate (NDS) followed by measures of cytotoxicity. The most potent PTP1B inhibitors were similar to NDS, whereas ketorolac was the least toxic compound. Cytotoxic potency in vitro was similar to in vivo. In conclusion, PTP1B inhibitors injured nasal epithelium through a mechanism independent of PTP1B inhibition and likely due to nonspecific cytotoxicity such as disruption of the cell membrane. Decreased food consumption in DIO mice was due to toxicity rather than a pharmacologic mode of action.

Estrogen-related receptor gamma is a key regulator of muscle mitochondrial activity and oxidative capacity.

Estrogen-related receptor gamma (ERRgamma) regulates the perinatal switch to oxidative metabolism in the myocardium. We wanted to understand the significance of induction of ERRgamma expression in skeletal muscle by exercise. Muscle-specific VP16ERRgamma transgenic mice demonstrated an increase in exercise capacity, mitochondrial enzyme activity, and enlarged mitochondria despite lower muscle weights. Furthermore, peak oxidative capacity was higher in the transgenics as compared with control littermates. In contrast, mice lacking one copy of ERRgamma exhibited decreased exercise capacity and muscle mitochondrial function. Interestingly, we observed that increased ERRgamma in muscle generates a gene expression profile that closely overlays that of red oxidative fiber-type muscle. We further demonstrated that a small molecule agonist of ERRbeta/gamma can increase mitochondrial function in mouse myotubes. Our data indicate that ERRgamma plays an important role in causing a shift toward slow twitch muscle type and, concomitantly, a greater capacity for endurance exercise. Thus, the activation of this nuclear receptor provides a potential node for therapeutic intervention for diseases such as obesity, which is associated with reduced oxidative metabolism and a lower type I fiber content in skeletal muscle.

Investigation of functionally liver selective glucokinase activators for the treatment of type 2 diabetes.

Type 2 diabetes is a polygenic disease which afflicts nearly 200 million people worldwide and is expected to increase to near epidemic levels over the next 10-15 years. Glucokinase (GK) activators are currently under investigation by a number of pharmaceutical companies with only a few reaching early clinical evaluation. A GK activator has the promise of potentially affecting both the beta-cells of the pancreas, by improving glucose sensitive insulin secretion, as well as the liver, by reducing uncontrolled glucose output and restoring post-prandial glucose uptake and storage as glycogen. Herein, we report our efforts on a sulfonamide chemotype with the aim to generate liver selective GK activators which culminated in the discovery of 3-cyclopentyl-N-(5-methoxy-thiazolo[5,4-b]pyridin-2-yl)-2-[4-(4-methyl-piperazine-1-sulfonyl)-phenyl]-propionamide (17c). This compound activated the GK enzyme (alphaK(a) = 39 nM) in vitro at low nanomolar concentrations and significantly reduced glucose levels during an oral glucose tolerance test in normal mice.

Insulin-stimulated mitochondrial adenosine triphosphate synthesis is blunted in skeletal muscles of high-fat-fed rats.

Physiologic elevation of insulin levels induces a significant increase in muscle adenosine triphosphate (ATP) synthesis rate in normal individuals, indicative of an appropriate acceleration in mitochondrial activity. However, the stimulatory effect of insulin is diminished in insulin-resistant patients. In the absence of similar data from preclinical models, the present study investigated the inhibitory effects of increased dietary fat intake on insulin-stimulated ATP synthesis rates in rats. After being placed on a high-fat diet for 8 weeks (n = 10), diet-induced obese male Sprague-Dawley rats were tested against age-matched control rats (n = 9) on a normal chow diet. Muscle ATP synthase flux rates were measured under anesthesia by in vivo (31)P saturation transfer both before and during a euglycemic-hyperinsulinemic clamp. The glucose infusion rates observed during the clamp revealed impaired peripheral insulin sensitivity in the high-fat-fed rats when compared with the age-matched control rats. Under baseline conditions (ie, low insulin), the muscle ATP synthesis rates of high-fat-fed rats were approximately 30% lower (P < .05) than those in chow-fed rats. Moreover, chow-fed animals showed a significant increase (25%, P < .05 vs basal) in muscle ATP synthesis activity upon insulin stimulation, whereas high-fat-fed animals displayed no substantial change. These data demonstrated for the first time in a preclinical model that the insulin challenge not only facilitates an improvement in the dynamic range of ATP turnover measurement by (31)P saturation transfer between normal and insulin-resistant rats, but also mimics challenge that is relevant for pharmacologic studies on antidiabetic drugs aimed at improving mitochondrial function.

Postnatal expression of aquaporins in epithelial cells of the rat epididymis.

The mammalian aquaporins (AQPs) are a family of 13 transmembrane channel proteins that are involved in the transport of water in numerous organs. In the male excurrent duct, the movement of fluid and solutes across the epithelium is essential for establishing the proper luminal environment in which sperm mature and are stored. AQP9 is abundantly expressed in the efferent ducts, the epididymis, and the vas deferens, where it could represent an important apical pathway for transmembrane water and solute movement. However, other organs in which water transport is critical, including the kidney, the lung, or the eye, express several different AQPs with a cell-specific pattern. To undertake a systematic analysis of the expression of known AQPs in the postnatal and adult rat epididymis, we examined the expression of their respective mRNAs in epithelial cells isolated by laser capture microdissection (LCM), and we determined their corresponding protein expression pattern by immunofluorescence and Western blotting. Our data show that, whereas AQP9 is the main AQP of the epididymis, the mRNA specific for Aqp2, 5, 7, and 11 are also expressed in epididymal epithelial cells. AQP5 protein colocalizes with AQP9 in the apical membrane of a subpopulation of principal cells in the corpus and cauda regions. Aqp2 mRNA was detected in epithelial cells after the second postnatal week and the amount significantly increased up to adulthood. However, AQP2 protein was detected only in the distal cauda of young rats (between the second and fourth postnatal week). No AQP2 protein was detected in the adult epididymis, indicating that posttranscriptional mechanisms are involved in the regulation of AQP2 expression. In addition, epididymal epithelial cells express significant amounts of the mRNAs coding for AQP7 and 11. No mRNA or protein for AQPs 0, 4, 6, and 8 were detectable in epithelial cells, and Aqp1 was detected in whole epididymal samples, but not in epithelial cells. Thanks to the recent development of microdissection technologies, our observations suggest that epididymal epithelial cells express several members of the AQP family with a region-specific pattern. AQPs may be involved not only in the transepithelial transport of water in the epididymis but also in the postnatal development of this organ, as suggested by the differential expression of AQP2.

V-ATPase B1-subunit promoter drives expression of EGFP in intercalated cells of kidney, clear cells of epididymis and airway cells of lung in transgenic mice.

The kidney, epididymis, and lungs are complex organs with considerable epithelial cell heterogeneity. This has limited the characterization of pathophysiological transport processes that are specific for each cell type in these epithelia. The purpose of the present study was to develop new tools to study cell-specific gene and protein expression in such complex tissues and organs. We report the production of a transgenic mouse that expresses enhanced green fluorescent protein (EGFP) in a subset of epithelial cells that express the B1 subunit of vacuolar H(+)-ATPase (V-ATPase) and are actively involved in proton transport. A 6.5-kb portion of the V-ATPase B1 promoter was used to drive expression of EGFP. In two founders, quantitative real-time RT-PCR demonstrated expression of EGFP in kidney, epididymis, and lung. Immunofluorescence labeling using antibodies against the B1 and E subunits of V-ATPase and against carbonic anhydrase type II (CAII) revealed specific EGFP expression in all renal type A and type B intercalated cells, some renal connecting tubule cells, all epididymal narrow and clear cells, and some nonciliated airway epithelial cells. No EGFP expression was detected in collecting duct principal cells (identified using an anti-AQP2 antibody) or epididymal principal cells (negative for V-ATPase or CAII). This EGFP-expressing mouse model should prove useful in future studies of gene and protein expression and their physiological and/or developmental regulation in distinct cell types that can now be separated using fluorescence-assisted microdissection, fluorescence-activated cell sorting, and laser capture microdissection.

Modulation of the actin cytoskeleton via gelsolin regulates vacuolar H+-ATPase recycling.

The role of the actin cytoskeleton in regulating membrane protein trafficking is complex and depends on the cell type and protein being examined. Using the epididymis as a model system in which luminal acidification is crucial for sperm maturation and storage, we now report that modulation of the actin cytoskeleton by the calcium-activated actin-capping and -severing protein gelsolin plays a key role in regulating vacuolar H(+)-ATPase (V-ATPase) recycling. Epididymal clear cells contain abundant V-ATPase in their apical pole, and an increase in their cell-surface V-ATPase expression correlates with an increase in luminal proton secretion. We have shown that apical membrane accumulation of V-ATPase is triggered by an elevation in cAMP following activation of bicarbonate-regulated soluble adenylyl cyclase in response to alkaline luminal pH (Pastor-Soler, N., Beaulieu, V., Litvin, T. N., Da Silva, N., Chen, Y., Brown, D., Buck, J., Levin, L. R., and Breton, S. (2003) J. Biol. Chem. 278, 49523-49529). Here, we show that clear cells express high levels of gelsolin, indicating a potential role in the functional activity of these cells. When jasplakinolide was used to overcome the severing action of gelsolin by polymerizing actin, complete inhibition of the alkaline pH- and cAMP-induced apical membrane accumulation of V-ATPase was observed. Conversely, when gelsolin-mediated actin filament elongation was inhibited using a 10-residue peptide (PBP10) derived from the phosphatidylinositol 4,5-bisphosphate-binding region (phosphoinositide-binding domain 2) of gelsolin, significant V-ATPase apical membrane mobilization was induced, even at acidic luminal pH. In contrast, the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) and the phospholipase C inhibitor U-73122 inhibited the alkaline pH-induced V-ATPase apical accumulation. Thus, maintenance of the actin cytoskeleton in a depolymerized state by gelsolin facilitates calcium-dependent apical accumulation of V-ATPase in response to luminal pH alkalinization. Gelsolin is present in other cell types that express the V-ATPase in their plasma membrane and recycling vesicles, including kidney intercalated cells and osteoclasts. Therefore, modulation of the actin cortex by this severing and capping protein may represent a common mechanism by which these cells regulate their rate of proton secretion.

Bicarbonate-regulated adenylyl cyclase (sAC) is a sensor that regulates pH-dependent V-ATPase recycling.

Modulation of environmental pH is critical for the function of many biological systems. However, the molecular identity of the pH sensor and its interaction with downstream effector proteins remain poorly understood. Using the male reproductive tract as a model system in which luminal acidification is critical for sperm maturation and storage, we now report a novel pathway for pH regulation linking the bicarbonate activated soluble adenylyl cyclase (sAC) to the vacuolar H+ATPase (V-ATPase). Clear cells of the epididymis and vas deferens contain abundant V-ATPase in their apical pole and are responsible for acidifying the lumen. Proton secretion is regulated via active recycling of V-ATPase. Here we demonstrate that this recycling is regulated by luminal pH and bicarbonate. sAC is highly expressed in clear cells, and apical membrane accumulation of V-ATPase is triggered by a sAC-dependent rise in cAMP in response to alkaline luminal pH. As sAC is expressed in other acid/base transporting epithelia, including kidney and choroid plexus, this cAMP-dependent signal transduction pathway may be a widespread mechanism that allows cells to sense and modulate extracellular pH.