Antiviral effects of cranberry juice and cranberry proanthocyanidins on foodborne viral surrogates--a time dependence study in vitro

Development of a broad-spectrum therapeutic Fc-nanobody for human noroviruses

Human norovirus was discovered more than five decades ago and is a widespread cause of outbreaks of acute gastroenteritis. There are no approved vaccines or antivirals currently available. However, norovirus inhibitors, including capsid-specific monoclonal antibodies (Mabs) and nanobodies, have recently shown promising results. Several Mabs and nanobodies were found to inhibit norovirus replication using a human intestinal enteroid (HIE) culture system and/or could block norovirus attachment to histo-blood group antigen (HBGA) co-factors. In our pursuit to develop a single broad-spectrum norovirus therapeutic, we continued our analysis and development of a cross-reactive and HBGA interfering nanobody (NB26). To improve NB26 binding capacity and therapeutic potential, we conjugated NB26 onto a human IgG Fc domain (Fc-NB26). We confirmed that Fc-NB26 cross-reacts with genetically diverse GII genotype capsid protruding (P) domains (GII.8, GII.14, GII.17, GII.24, GII.26, and GII.NA1) using a direct enzyme-linked immunosorbent assay. Furthermore, X-ray crystallography structures of these P domains and structures of other GII genotypes reveal that the NB26 binding site is largely conserved, validating its broad reactivity. We showed that Fc-NB26 has ~100-fold higher affinity toward the norovirus P domain compared to native NB26. We also found that both NB26 and Fc-NB26 neutralize human norovirus replication in the HIE culture system. Furthermore, the mode of inhibition confirmed that like NB26, Fc-NB26 caused norovirus particle disassembly and aggregation. Overall, these new findings demonstrate that structural modifications to nanobodies can improve their therapeutic potential.IMPORTANCEDeveloping vaccines and antivirals against norovirus remains a challenge, mainly due to the constant genetic and antigenic evolution. Moreover, re-infection with genetically related and/or antigenic variants is not uncommon. We further developed our leading norovirus nanobody (NB26) that indirectly interfered with norovirus binding to HBGAs, by converting NB26 into a dimeric Fc-linked Nanobody (Fc-NB26). We found that Fc-NB26 had improved binding affinity and neutralization capacity compared with native NB26. Using X-ray crystallography, we showed this nanobody engaged highly conserved capsid residues among genetically diverse noroviruses. Development of such broadly reactive potent therapeutic nanobodies delivered as a slow-releasing prophylactic could be of exceptional value for norovirus outbreaks, especially for the prevention or treatment of severe acute gastroenteritis in high-risk groups such as the young, elderly, and immunocompromised.

Antiviral Activity of Natural Compounds for Food Safety

Gastroenteritis and hepatitis are the most common illnesses resulting from the consumption of food contaminated with human enteric viruses. Several natural compounds have demonstrated antiviral activity against human enteric viruses, such as human norovirus and hepatitis A virus, while little information is available for hepatitis E virus. Many in-vitro studies have evaluated the efficacy of different natural compounds against human enteric viruses or their surrogates. However, only few studies have investigated their antiviral activity in food applications. Among them, green tea extract, grape seed extract and carrageenans have been extensively investigated as antiviral natural compounds to improve food safety. Indeed, these extracts have been studied as sanitizers on food-contact surfaces, in produce washing solutions, as active fractions in antiviral food-packaging materials, and in edible coatings. The most innovative applications of these antiviral natural extracts include the development of coatings to extend the shelf life of berries or their combination with established food technologies for improved processes. This review summarizes existing knowledge in the underexplored field of natural compounds for enhancing the safety of viral-contaminated foods and underscores the research needs to be covered in the near future.

Antibacterial Effect of Pomegranate Juice on Listeria innocua and E. coli in Different Media

The antibacterial effect of pomegranate juice (PJ) at six concentrations (0, 10, 20, 30, 40, and 50%) against Listeria innocua and Escherichia coli was investigated in distilled water (DW) and bacterial culture broth. L. innocua and E. coli at approximately 105 cfu mL-1 were inoculated in PJ samples and incubated at 4, 25, and 37 °C for 0, 6, 24, and 48 h. The bacterial population and pH of culture media were measured at each removal. Results indicated that the antibacterial effect of PJ was dependent upon bacteria species, juice concentration, incubation temperature, and growth medium. Higher juice concentration and incubation temperature resulted in increased antibacterial effects. Bacterial populations were decreased more significantly in DW systems than in the culture broth, while L. innocua was more sensitive to PJ than E. coli in the DW systems. Regardless of PJ concentrations in DW systems, L. innocua, initially inoculated at approximately 105 cfu mL-1, was reduced to undetectable levels at 25 and 37 °C within 24 h. The growth of L. innocua and E. coli was significantly inhibited in bacterial culture broth containing ≥ 20% PJ (p < 0.001). This study provides insight into the potential application of PJ in food and beverage products for food protection.

Optimization of the Use of a Commercial Phage-Based Product as a Control Strategy of Listeria monocytogenes in the Fresh-Cut Industry

A commercial phage biocontrol for reducing Listeria monocytogenes has been described as an effective tool for improving fresh produce safety. Critical challenges in the phage application must be overcome for the industrial application. The validation studies were performed in two processing lines of two industry collaborators in Spain and Denmark, using shredded iceberg lettuce as the ready-to-eat (RTE), high process volume product. The biocontrol treatment optimized in lab-scale trials for the application of PhageGuard ListexTM was confirmed in industrial settings by four tests, two in Spain and two in Denmark. Results showed that the method of application that included the device and the processing operation step was appropriate for the proper application. The proper dose of Phage Guard ListexTM was reached in shredded iceberg lettuce and the surface was adequately covered for the successful application of phages. There was no impact on the headspace gas composition (CO2 and O2 levels), nor on the color when untreated and treated samples were compared. The post-process treatment with PhageGuard ListexTM did not cause any detrimental impact on the sensory quality, including flavor, texture, browning, spoilage, and visual appearance over the shelf-life as the phage solution was applied as a fine, mist solution.

Tiger Nut Milk's Antiviral Properties against Enveloped and Non-Enveloped Viruses: Effect of Concentration and Adding Sugar

The global COVID-19 pandemic has warned scientists of the requirement to look for new antimicrobial compounds to prevent infection by this type of viral pathogen. Natural compounds are becoming a promising avenue of research thanks to their renewable, biodegradable, and non-toxic properties. In this work, tiger nut milk's (TNM) antiviral properties, with and without sugar, were studied against enveloped and non-enveloped viruses. The antiviral properties of TNM were evaluated at different concentrations. The antiviral tests showed that TNM is antiviral against the enveloped bacteriophage phi 6, which is commonly used as a surrogate for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), although it did not have any antiviral effect against the non-enveloped bacteriophage MS2. We also found that adding sugar to this natural drink can improve its antiviral properties against enveloped viruses and render it antiviral against non-enveloped viruses like bacteriophage MS2. The antiviral activity of TNM depends on the TNM concentration. TNM is a natural bioproduct that could help to fight against viral infections and protect against a wide range of viral illnesses. These results confirm that the typical sweetened drink made from tiger nut extract and sugar (known as horchata in Spain) possesses broad-spectrum antiviral properties.

Antiviral Effects of Quillaja saponaria Extracts Against Human Noroviral Surrogates

Aqueous extracts of Quillaja saponaria Molina are US FDA approved as food additives in beverages with known antiviral activity. Due to lack of commercially available vaccines against human noroviruses (HNoVs), alternate methods to prevent their spread and the subsequent emergence of variant strains are being researched. Furthermore, HNoVs are not yet culturable at high enough titers to determine inactivation, therefore surrogates continue to be used. This research analyzed the effect of aqueous Quillaja saponaria extracts (QE) against HNoV surrogates, Tulane virus (TV), murine norovirus (MNV-1), and feline calicivirus (FCV-F9) at room temperature (RT) and 37 °C. Viruses (~ 5 log PFU/mL) were individually treated with 1:1 or 1:5 (v/v) diluted QE (pH ~ 3.75), malic acid control (pH 3.0) or phosphate-buffered saline (pH 7.2, as control) at 37 °C or RT for up to 6 h. Individual treatments were replicated three times using duplicate plaque assays for each treatment. FCV-F9 at ~ 5 log PFU/mL was not detectable after 15 min by 1:1 QE at 37 °C and RT. At RT, 1:5 QE lowered FCV-F9 titers by 2.05, 2.14 and 2.74 log PFU/mL after 0.5 h, 1 h and 2 h, respectively. MNV-1 showed marginal reduction of < 1 log PFU/mL after 15 min with 1:1 or 1:5 QE at 37 °C without any significant reduction at RT, while TV titers decreased by 2.2 log PFU/mL after 30 min and were undetectable after 3 h at 37 °C. Longer incubation with higher QE concentrations may be required for improved antiviral activity against MNV-1 and TV.

Direct Blockade of the Norovirus Histo-Blood Group Antigen Binding Pocket by Nanobodies

Noroviruses are the leading cause of outbreaks of acute gastroenteritis. These viruses usually interact with histo-blood group antigens (HBGAs), which are considered essential cofactors for norovirus infection. This study structurally characterizes nanobodies developed against the clinically important GII.4 and GII.17 noroviruses with a focus on the identification of novel nanobodies that efficiently block the HBGA binding site. Using X-ray crystallography, we have characterized nine different nanobodies that bound to the top, side, or bottom of the P domain. The eight nanobodies that bound to the top or side of the P domain were mainly genotype specific, while one nanobody that bound to the bottom cross-reacted against several genotypes and showed HBGA blocking potential. The four nanobodies that bound to the top of the P domain also inhibited HBGA binding, and structural analysis revealed that these nanobodies interacted with several GII.4 and GII.17 P domain residues that commonly engaged HBGAs. Moreover, these nanobody complementarity-determining regions (CDRs) extended completely into the cofactor pockets and would likely impede HBGA engagement. The atomic level information for these nanobodies and their corresponding binding sites provide a valuable template for the discovery of additional "designer" nanobodies. These next-generation nanobodies would be designed to target other important genotypes and variants, while maintaining cofactor interference. Finally, our results clearly demonstrate for the first time that nanobodies directly targeting the HBGA binding site can function as potent norovirus inhibitors. IMPORTANCE Human noroviruses are highly contagious and a major problem in closed institutions, such as schools, hospitals, and cruise ships. Reducing norovirus infections is challenging on multiple levels and includes the frequent emergence of antigenic variants, which complicates designing effective, broadly reactive capsid therapeutics. We successfully developed and characterized four norovirus nanobodies that bound at the HBGA pockets. Compared with previously developed norovirus nanobodies that inhibited HBGA through disrupted particle stability, these four novel nanobodies directly inhibited HBGA engagement and interacted with HBGA binding residues. Importantly, these new nanobodies specifically target two genotypes that have caused the majority of outbreaks worldwide and consequently would have an enormous benefit if they could be further developed as norovirus therapeutics. To date, we have structurally characterized 16 different GII nanobody complexes, a number of which block HBGA binding. These structural data could be used to design multivalent nanobody constructs with improved inhibition properties.

Persistence and survival of Cryptosporidium parvum oocysts on lamb's lettuce leaves during plant growth and in washing conditions of minimally-processed salads

Cryptosporidium is the causative agent of cryptosporidiosis, which results, among others, in profuse diarrhoea. Transmission to humans occurs via the faecal-oral route directly by contact with infected hosts or indirectly by waterborne or foodborne routes. For the latter, parasite transmission is closely linked to the oocyst's ability to persist and survive in food matrices. In this study, we evaluated the persistence and survival of Cryptosporidium oocysts in lamb's lettuce: i) during plant growth and ii) in conditions mimicking the industrial washing process applied in minimally-processed vegetables (MPV). Results show that oocysts persisted during the growth of lamb's lettuce, i.e. two months from the 2-leaf stage until the 8-leaf harvest time (-0.89 Log10 of oocysts). However, their survival decreased from as early as one week (-0.61 Log10), and only 6 % of oocysts remained infective at the time of harvest. The washing process had a limited effect on parasite load (<0.5 Log10) and no effect on survival; chlorination of washing water did not improve the efficiency (removal and inactivation) of the process. The ability of C. parvum to persist and survive throughout the food chain may drive its transmission to humans through MPV products. Appropriate management measures should be implemented at each operational level to limit contamination and ensure food safety of fresh produce.

How to Tackle Bacteriophages: The Review of Approaches with Mechanistic Insight

Bacteriophage-based applications have a renaissance today, increasingly marking their use in industry, medicine, food processing, biotechnology, and more. However, phages are considered resistant to various harsh environmental conditions; besides, they are characterized by high intra-group variability. Phage-related contaminations may therefore pose new challenges in the future due to the wider use of phages in industry and health care. Therefore, in this review, we summarize the current knowledge of bacteriophage disinfection methods, as well as highlight new technologies and approaches. We discuss the need for systematic solutions to improve bacteriophage control, taking into account their structural and environmental diversity.

Virucidal Activity of Lemon Essential Oil against Feline Calicivirus Used as Surrogate for Norovirus

Norovirus (NoV) is regarded as a common cause of acute gastrointestinal illness worldwide in all age groups, with substantial morbidity across health care and community settings. The lack of in vitro cell culture systems for human NoV has prompted the use of cultivatable caliciviruses (such as feline calicivirus, FCV, or murine NoV) as surrogates for in vitro evaluation of antivirals. Essential oils (EOs) may represent a valid tool to counteract viral infections, particularly as food preservatives. In the present study, the virucidal efficacy of lemon EO (LEO) against FCV was assessed in vitro. The gas chromatography hyphenated with mass spectrometry (GC/MS) technique was used to reveal the chemical composition of LEO. The following small molecules were detected as major components of LEO: limonene (53%), β-pinene (14.5%), γ-terpinene (5.9%), citral (3.8%), α-pinene (2.4%), and β-thujene (1.94%). LEO at 302.0 μg/mL, exceeding the maximum non cytotoxic limit, significantly decreased viral titre of 0.75 log₁₀ TCID50/50 μL after 8 h. Moreover, virucidal activity was tested using LEO at 3020.00 μg/mL, determining a reduction of viral titre as high as 1.25 log₁₀ TCID50/50 μL after 8 h of time contact. These results open up perspectives for the development of alternative prophylaxis approaches for the control of NoV infection.

Screening of natural extracts with anti-norovirus effects and analysis of this mechanism in grape seed extract

Norovirus (NoV）is a major causative virus of viral gastroenteritis and requires a general disinfection method because it is resistant to common disinfectants such as ethanol and chlorhexidine. This study aimed to find natural extracts as candidates for versatile disinfectant ingredients. The antiviral effect of natural extracts against NoV can be evaluated using the feline calicivirus (FCV）-inactivation test and NoV virus-like particle (NoV-VLP）-binding inhibition test. In this study, screening of natural extracts with anti- NoV effects was performed using these two methods. Of the 63 natural extracts examined, 14 were found to have high FCV-inactivation and NoV-VLP-binding inhibitory effects. In addition, we evaluated the NoV-VLPbinding inhibitory effect of grape seed extract（GSE）containing proanthocyanidins under multiple concentration conditions and treatment times and determined that the binding inhibitory effect of GSE was concentration- and time-dependent. Electron microscopy showed that GSE-treated NoV-VLPs aggregated, distorted, and swelled, suggesting that GSE directly interacts with NoV particles. The results suggest that some natural extracts containing GSE can be used as components of disinfectants against NoV.

Antimicrobial Lipstick: Bio-Based Composition against Viruses, Bacteria, and Fungi

The COVID-19 pandemic has speeded up the race to find materials that could help limit or avoid the spread of SARS-CoV-2, while infections by multidrug-resistant bacteria and fungi are now becoming a serious threat. In this study, we developed a novel bio-based lipstick containing cranberry extract, a substance able to inactivate a broad range of microorganisms: enveloped viruses such as bacteriophage Φ6, a surrogate of SARS-CoV-2; non-enveloped viruses including bacteriophage MS2; multidrug-resistant bacteria like methicillin-resistant Staphylococcus aureus, Escherichia coli, and Mycobacterium smegmatis, a surrogate of Mycobacterium tuberculosis; and the Candida albicans fungus. The proposed antimicrobial lipstick offers a new form of protection against a broad range of microorganisms, including enveloped and non-enveloped viruses, bacteria, and fungi, in the current COVID-19 pandemic and microbial-resistant era.

Tackling the Future Pandemics: Broad-Spectrum Antiviral Agents (BSAAs) Based on A-Type Proanthocyanidins

A-type proanthocyanidins (PAC-As) are plant-derived natural polyphenols that occur as oligomers or polymers of flavan-3-ol monomers, such as (+)-catechin and (-)-epicatechin, connected through an unusual double A linkage. PAC-As are present in leaves, seeds, flowers, bark, and fruits of many plants, and are thought to exert protective natural roles against microbial pathogens, insects, and herbivores. Consequently, when tested in isolation, PAC-As have shown several biological effects, through antioxidant, antibacterial, immunomodulatory, and antiviral activities. PAC-As have been observed in fact to inhibit replication of many different human viruses, and both enveloped and non-enveloped DNA and RNA viruses proved sensible to their inhibitory effect. Mechanistic studies revealed that PAC-As cause reduction of infectivity of viral particles they come in contact with, as a result of their propensity to interact with virion surface capsid proteins or envelope glycoproteins essential for viral attachment and entry. As viral infections and new virus outbreaks are a major public health concern, development of effective Broad-Spectrum Antiviral Agents (BSAAs) that can be rapidly deployable even against future emerging viruses is an urgent priority. This review summarizes the antiviral activities and mechanism of action of PAC-As, and their potential to be deployed as BSAAs against present and future viral infections.

Cranberry Pomace Extract Exerts Antiviral Activity against Zika and Dengue Virus at Safe Doses for Adult Zebrafish

Mosquito-borne dengue virus (DENV) and zika virus (ZIKV) infections constitute a global health emergency. Antivirals directly targeting the virus infectious cycle are still needed to prevent dengue hemorrhagic fever and congenital zika syndrome. In the present study, we demonstrated that Cranberry Pomace (CP) extract, a polyphenol-rich agrifood byproduct recovered following cranberry juice extraction, blocks DENV and ZIKV infection in human Huh7.5 and A549 cell lines, respectively, in non-cytotoxic concentrations. Our virological assays identified CP extract as a potential inhibitor of virus entry into the host-cell by acting directly on viral particles, thus preventing their attachment to the cell surface. At effective antiviral doses, CP extract proved safe and tolerable in a zebrafish model. In conclusion, polyphenol-rich agrifood byproducts such as berry extracts are a promising source of safe and naturally derived nutraceutical antivirals that target medically important pathogens.

Natural extracts, honey, and propolis as human norovirus inhibitors

Norovirus is the most important cause of acute gastroenteritis, yet there are still no antivirals, vaccines, or treatments available. Several studies have shown that norovirus-specific monoclonal antibodies, Nanobodies, and natural extracts might function as inhibitors. Therefore, the objective of this study was to determine the antiviral potential of additional natural extracts, honeys, and propolis samples. Norovirus GII.4 and GII.10 virus-like particles (VLPs) were treated with different natural samples and analyzed for their ability to block VLP binding to histo-blood group antigens (HBGAs), which are important norovirus co-factors. Of the 21 natural samples screened, date syrup and one propolis sample showed promising blocking potential. Dynamic light scattering indicated that VLPs treated with the date syrup and propolis caused particle aggregation, which was confirmed using electron microscopy. Several honey samples also showed weaker HBGA blocking potential. Taken together, our results found that natural samples might function as norovirus inhibitors.

Gibberellic Acid and Jasmonic Acid Improve Salt Tolerance in Summer Squash by Modulating Some Physiological Parameters Symptomatic for Oxidative Stress and Mineral Nutrition

Gibberellic acid (GA) and jasmonic acid (JA) are considered to be endogenous regulators that play a vital role in regulating plant responses to stress conditions. This study investigated the ameliorative role of GA, JA, and the GA + JA mixture in mitigating the detrimental effect of salinity on the summer squash plant. In order to explore the physiological mechanisms of salt stress alleviation carried out by exogenous GA and JA, seed priming with 1.5 mM GA, 0.005 mM JA, and their mixture was performed; then the germinated summer squash seedlings were exposed to 50 mM NaCl. The results showed that a 50 mM NaCl treatment significantly reduced shoot and root fresh and dry weight, water content (%), the concentration of carotenoid (Car), nucleic acids, K+, and Mg++, the K+/Na+ ratio, and the activity of catalase (CAT) and ascorbate peroxidase (APX), while it increased the concentration of proline, thiobarbituric acid reactive substances (TBARS), Na+, and Cl- in summer squash plants, when compared with the control. However, seed priming with GA, JA and the GA + JA mixture significantly improved summer squash salt tolerance by reducing the concentration of Na+ and Cl-, TBARS, and the Chl a/b ratio and by increasing the activity of superoxide dismutase, CAT, and APX, the quantities of K+ and Mg++, the K+/Na+ ratio, and the quantities of RNA, DNA, chlorophyll b, and Car, which, in turn, ameliorated the growth of salinized plants. These findings suggest that GA and JA are able to efficiently defend summer squash plants from salinity destruction by adjusting nutrient uptake and increasing the activity of antioxidant enzymes in order to decrease reactive oxygen species accumulation due to salinity stress; these findings offer a practical intervention for summer squash cultivation in salt-affected soils. Synergistic effects of the GA and JA combination were not clearly observed, and JA alleviated most of the studied traits associated with salinity stress induced in summer squash more efficiently than GA or the GA + JA mixture.

Non-Woven Infection Prevention Fabrics Coated with Biobased Cranberry Extracts Inactivate Enveloped Viruses Such as SARS-CoV-2 and Multidrug-Resistant Bacteria

The Coronavirus Disease (COVID-19) pandemic is demanding the rapid action of the authorities and scientific community in order to find new antimicrobial solutions that could inactivate the pathogen SARS-CoV-2 that causes this disease. Gram-positive bacteria contribute to severe pneumonia associated with COVID-19, and their resistance to antibiotics is exponentially increasing. In this regard, non-woven fabrics are currently used for the fabrication of infection prevention clothing such as face masks, caps, scrubs, shirts, trousers, disposable gowns, overalls, hoods, aprons and shoe covers as protective tools against viral and bacterial infections. However, these non-woven fabrics are made of materials that do not exhibit intrinsic antimicrobial activity. Thus, we have here developed non-woven fabrics with antimicrobial coatings of cranberry extracts capable of inactivating enveloped viruses such as SARS-CoV-2 and the bacteriophage phi 6 (about 99% of viral inactivation in 1 min of viral contact), and two multidrug-resistant bacteria: the methicillin-resistant Staphylococcus aureus and the methicillin-resistant Staphylococcus epidermidis. The morphology, thermal and mechanical properties of the produced filters were characterized by optical and electron microscopy, differential scanning calorimetry, thermogravimetry and dynamic mechanical thermal analysis. The non-toxicity of these advanced technologies was ensured using a Caenorhabditis elegans in vivo model. These results open up a new prevention path using natural and biodegradable compounds for the fabrication of infection prevention clothing in the current COVID-19 pandemic and microbial resistant era.

Therapeutic Potential of Nutraceuticals and Dietary Supplements in the Prevention of Viral Diseases: A Review

Nowadays, despite enormous scientific advances, viral diseases remain the leading cause of morbidity worldwide, and their potential to spread is escalating, eventually turning into pandemics. Nutrition can play a major role in supporting the immune system of the body and for the optimal functioning of the cells of the immune system. A healthy diet encompassing vitamins, multi-nutrient supplements, functional foods, nutraceuticals, and probiotics can play a pivotal role in combating several viral invasions in addition to strengthening the immune system. This review provides comprehensive information on diet-based scientific recommendations, evidence, and worldwide case studies in light of the current pandemic and also with a particular focus on virus-induced respiratory tract infections. After reviewing the immune potential of nutraceuticals based on the lab studies and on human studies, it was concluded that bioactive compounds such as nutraceuticals, vitamins, and functional foods (honey, berries, etc.) with proven antiviral efficacy, in addition to pharmaceutical medication or alone as dietary supplements, can prove instrumental in treating a range of virus-induced infections in addition to strengthening the immune system. Milk proteins and peptides can also act as adjuvants for the design of more potent novel antiviral drugs.

Edible fruit extracts and fruit juices as potential source of antiviral agents: a review

Fruits have been widely consumed since the beginning of human evolution and are important source of a healthy being and helpful in treating various diseases as immunity boosters with the presence of a rich amount of health-promoting bioactives. Therapeutic efficacies of fruit extracts are reported to have immune-modulatory properties and influence greatly on the immune system of human body. Given the facts of the efficacy of edible fruits in improving the immunity of body as immune-stimulants, we have tried to consolidate the previously published data on edible fruits and its juices with antiviral potential. The objective of this review was to gather information on edible fruits with antiviral properties and the efforts to obtain their efficient delivery. Online bibliographical databases like PubMed, Scopus, and Web of Science were used to search literature on the antiviral effect of edible fruit extracts and fruit juices. The edible fruits like almond, apple, bael, blackberry, black currants, crane berry, citrus, grapes, Japanese cherry, mango, mulberry, pistachios, pomegranate, and strawberry showed promising antiviral properties against the different pathogenic viruses. The review provided an overview of likely effects of the intake of edible fruit extracts/fruit juices to strengthen the immune cells by reducing the oxidative stress in host body system which in turn inhibits the viral attachment and replication on the host cell. Hence these fruits can also be exploited in combating COVID-19 in the current pandemic situation. To validate the present hypothesis, the proposed edible fruit extracts can be evaluated against the SARS-CoV-2 via in vitro and in vivo models to confirm the fact.

Antiviral Potential of Plants against Noroviruses

Human noroviruses, which belong to the enterovirus family, are one of the most common etiological agents of food-borne diseases. In recent years, intensive research has been carried out regarding the antiviral activity of plant metabolites that could be used for the preservation of fresh food, because they are safer for consumption when compared to synthetic chemicals. Plant preparations with proven antimicrobial activity differ in their chemical compositions, which significantly affects their biological activity. Our review aimed to present the results of research related to the characteristics, applicability, and mechanisms of the action of various plant-based preparations and metabolites against norovirus. New strategies to combat intestinal viruses are necessary, not only to ensure food safety and reduce infections in humans but also to lower the direct health costs associated with them.

Dietary Modulation of Bacteriophages as an Additional Player in Inflammation and Cancer

Natural compounds such as essential oils and tea have been used successfully in naturopathy and folk medicine for hundreds of years. Current research is unveiling the molecular role of their antibacterial, anti-inflammatory, and anticancer properties. Nevertheless, the effect of these compounds on bacteriophages is still poorly understood. The application of bacteriophages against bacteria has gained a particular interest in recent years due to, e.g., the constant rise of antimicrobial resistance to antibiotics, or an increasing awareness of different types of microbiota and their potential contribution to gastrointestinal diseases, including inflammatory and malignant conditions. Thus, a better knowledge of how dietary products can affect bacteriophages and, in turn, the whole gut microbiome can help maintain healthy homeostasis, reducing the risk of developing diseases such as diverse types of gastroenteritis, inflammatory bowel disease, or even cancer. The present review summarizes the effect of dietary compounds on the physiology of bacteriophages. In a majority of works, the substance class of polyphenols showed a particular activity against bacteriophages, and the primary mechanism of action involved structural damage of the capsid, inhibiting bacteriophage activity and infectivity. Some further dietary compounds such as caffeine, salt or oregano have been shown to induce or suppress prophages, whereas others, such as the natural sweeter stevia, promoted species-specific phage responses. A better understanding of how dietary compounds could selectively, and specifically, modulate the activity of individual phages opens the possibility to reorganize the microbial network as an additional strategy to support in the combat, or in prevention, of gastrointestinal diseases, including inflammation and cancer.

Radiosensitivity of Feline Calicivirus F9 on Iceberg Lettuce Surface after Combined Treatments with γ-Radiation

ABSTRACT

The surface of iceberg lettuce (Lactuca sativa L.) is favorable to the survival of pathogens such as bacteria, parasites, and viruses such as norovirus. The present study was conducted to investigate the antiviral properties of treatment with cranberry juice (CJ), ozone (O3), and γ-radiation alone or in combination against feline calicivirus (FCV) F9 present on the surface of iceberg lettuce. The lettuce leaves were inoculated with virus suspensions at ∼6 log TCID50 (50% tissue culture infective dose)/mL and treated with CJ, O3, and γ-radiation alone and in combination during storage at 4°C. The D10-values of 1.21 kGy, 2.23% CJ, and 14.93 ppm of O3 were obtained when samples were treated with various radiation doses, CJ, and O3, respectively. Relative radiosensitization of FCV-F9 virus on lettuce was 1.20, 1.50, 1.09, and 1.00 after combined CJ treatments of 0.1, 0.25, 0.50, and 1.50%, respectively. Optimum treatments were 5 ppm for 7.5 min for O3, 0.25% CJ, and γ-radiation at 1.5 kGy when each treatment was used alone. The combination of the three treatments produced the highest reduction of 2.15 log TCID50/mL (from initial inoculation of ∼7 log TCID50/mL) during 10 days of storage at 4°C. Antibacterial properties of treatments and physicochemical quality of lettuce were investigated during 13 days of storage at 4°C. The treatment of lettuce with γ-radiation alone (1.5 kGy) reduced the total flora by 3 log CFU/g; however, the combination of CJ (0.25%) with irradiation (1.5 kGy) reduced it by ∼5 log CFU/g after 13 days of storage at 4°C. The texture and color of the lettuce treated with the combined treatments changed slightly during storage, and chlorophyll increased by 3.81 μg/mL after 10 days of storage at 4°C. Significant differences in taste and color were observed in lettuce without treatments after 5 days of storage, whereas no difference was observed after the 0.25% CJ or the combined treatments.

HIGHLIGHTS

Natural bioactive substances for the control of food-borne viruses and contaminants in food

Abstract

Food-borne viruses and contaminants, as an important global food safety problem, are caused by chemical, microbiological, zoonotic, and other risk factors that represent a health hazard. Natural bioactive substances, originating from plants, animals, or microorganisms, might offer the possibility of preventing and controlling food-borne diseases. In this contribution, the common bioactive substances such as polyphenols, essential oils, proteins, and polysaccharides which are effective in the prevention and treatment of food-borne viruses and contaminants are discussed. Meanwhile, the preventive effects of natural bioactive substances and the possible mechanisms involved in food protection are discussed and detailed. The application and potential effects of natural bioactive substances in the adjuvant treatment for food-borne diseases is also described.

Graphical abstract

Magnolia officinalis and Its Honokiol and Magnolol Constituents Inhibit Human Norovirus Surrogates

Norovirus is a major cause of foodborne disease and nonbacterial gastroenteritis globally. This study evaluated the antiviral effects of Magnolia officinalis extract and its honokiol and magnolol constituents against human norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV) in vitro, and in model food systems. Pretreatment or cotreatment of M. officinalis extract at 1 mg/mL reduced MNV and FCV titers by 0.6-1.8 log. Honokiol and magnolol, which are the major polyphenols in the extract, showed significant antiviral effects against MNV and FCV. The virus-infected cells that were treated with M. officinalis extract exhibited significantly increased glutathione levels (p < 0.05). The extract, honokiol, and magnolol revealed ferric ion-reducing and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activities in a dose-dependent manner. Furthermore, MNV and FCV titers were reduced by >1.6 log or to undetectable levels in apple, orange, and plum juices and by 0.9 and 1.6 log in milk, respectively, when they were treated with the extract at 5 mg/mL. Therefore, the present study suggests that M. officinalis extract can be used as an antiviral food material to control norovirus foodborne diseases.

Radiosensitivity increase in FCV-F9 virus using combined treatments with natural antimicrobials and γ-irradiation

AIMS

The objective was to evaluate the possible synergistic effect of cranberry juice (CJ) and commercial citrus extract (BS) against FCV-F9 viral titre in vitro in combination with γ-irradiation and to determinate the D₁₀ values and radiosensitivity increase.

METHODS AND RESULTS

Virus samples were treated with a formulation containing a mixture of BS or CJ. Results showed a D₁₀ of 0·05, 0·42% and 1·34 kGy for the virus treated with the BS, the CJ and the irradiation alone respectively. Concentrations needed to reduce 6 log TCID₅₀  ml^-1 of viral titre were BS-0·3%, CJ-2·52% and 8·04 kGy. Irradiation combined with BS-0·01% and CJ-0·1% against FCV-F9 virus showed D₁₀ values of 0·74 and 0·72 kGy, respectively, resulting in a viral radiosensitization of 1·28 and 1·50 for respective treatments.

CONCLUSION

The higher viral radiosensitization observed after combining γ-irradiation with BS-0·01% and CJ-0·1% indicates that CJ and BS could be used as antiviral agents alone or in combination with γ-irradiation to prevent NoV outbreaks.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cranberry juice and BS could be used in hurdle approaches in combined treatment with γ-irradiation to assure food safety without a detrimental effect on nutritional value and maintain low processing cost.

Post-process treatments are effective strategies to reduce Listeria monocytogenes on the surface of leafy greens: A pilot study

Growth of L. monocytogenes is among the most important factors affecting the risk of human listeriosis. In ready to eat leafy greens, the use of anti-Listeria treatments represents a good alternative to inhibit growth during storage. Several commercially available antimicrobial agents have been suggested as effective intervention strategies. Among them, phage preparations and bacteriocin-producing strains have shown promising results against L. monocytogenes. In this study, we investigate the efficacy of two commercially available surface treatments, the bacteriophage formulation PhageGuard Listex (Micreos Food Safety B.V., NL) and the bacteriocin-producing culture SafePro® (CHR Hansen, DK) to inactivate L. monocytogenes in fresh-cut curly endive after processing and during storage. Fresh-cut endive was inoculated with a cold-adapted L. monocytogenes cocktail of 6 strains (4.4 ± 0.0 log cfu/g) and treated with the anti-Listeria treatments. The treatments were applied using a spray system at two different places within the processing line, on the conveyor belt and in the centrifuge. A total of 5 different treatments were applied: i) Untreated (CT); ii) PhageGuard Listex on the conveyor belt (Listex_Conveyor); iii) PhageGuard Listex during centrifugation (Listex_Centrifuge); iv) SafePro on the conveyor belt (SafePro_Conveyor); and v) SafePro during centrifugation (SafePro_Centrifuge). Samples were stored 3 days at 5 °C plus 5 days at 8 °C. PhageGuard Listex treatment reduced L. monocytogenes in fresh-cut endive by 2.5 logs, regardless of the place of treatment application (conveyor belt or centrifuge). On the other hand, SafePro only reduced L. monocytogenes by 0.2 and 0.4 logs, at the conveyor belt and centrifuge, respectively. Maximum L. monocytogenes reductions of about 3.5 log units were observed in fresh-cut endive treated with PhageGuard Listex after 3 days of storage. At the end of the shelf life (8 days), the initial trends were maintained and the fresh-cut curly endive treated with PhageGuard Listex showed the lowest L. monocytogenes concentration. However, by the end of the shelf-life, L. monocytogenes showed higher levels (1.3-fold) than immediately after the application of the treatment. One hypothesis could be that L. monocytogenes cells, which were able to survive the anti-Listeria treatments, were also able to proliferate under the specific storage conditions. Based on the obtained results, PhageGuard Listex seems to be a promising decontamination agent for leafy greens aiming to reduce growth of the bacteria but further work is needed.

Antiviral effects of blueberry proanthocyanidins against Aichi virus

Blueberry polyphenols are known for their high antioxidant and antimicrobial potential. Aichi virus (AiV) is an emerging human enteric virus that causes gastroenteritis outbreaks worldwide. This study aimed to (1) determine the time- and dose-dependent effects of blueberry proanthocyanidins (B-PAC) against AiV over 24 h at 37 °C; (2) gain insights on their mode of action using pre- and post-treatment of host cells and Transmission Electron Microscopy; and (3) determine their anti-AiV effects in model foods and under simulated gastric conditions. AiV at ∼5 log PFU/ml was incubated with equal volumes of commercial blueberry juice (BJ, pH 2.8), neutralized BJ (pH 7.0), B-PAC (2, 4, and 10 mg/ml) prepared either in 10% ethanol, apple juice (AJ), 2% milk, simulated gastric fluid (SGF, pH 1.5) or simulated intestinal fluid (SIF, pH 7.5), and controls (malic acid (pH 3.0), phosphate buffered saline (pH 7.2), apple juice (pH 3.6) and 2% milk) over 24 h at 37 °C, followed by standard plaque assays. Each experiment was replicated thrice and data were statistically analyzed. Differences in AiV titers with 1 mg/ml B-PAC were 2.13 ± 0.06 log PFU/ml lower after 24 h and ≥3 log PFU/ml (undetectable levels) lower with 2 and 5 mg/ml B-PAC compared to AiV titers in PBS after 24 h and 3 h, respectively. BJ at 37 °C resulted in titer differences (lower titers compared to PBS) of 0.17 ± 0.06, 1.27 ± 0.01, and 1.73 ± 0.23 log PFU/ml after 1, 3, and 6 h and ≥3 log PFU/ml after 24 h. Pre- and post-treatment of host cells with 0.5 mg/ml B-PAC caused titer decreases of 0.62 ± 0.33 and 0.30 ± 0.06 log PFU/ml, respectively suggesting a moderate effect on viral-host cell binding. B-PAC at 2 mg/ml in AJ caused titer differences of ≥3 log PFU/ml after 0.5 h, while differences of 0.84 ± 0.03 log PFU/ml with 5 mg/ml B-PAC in milk, and ≥3 log PFU/ml with B-PAC at 5 mg/ml in SIF after 30 min were obtained. This study shows the ability of BJ and B-PAC to decrease AiV titers to potentially prevent AiV-related illness and outbreaks.

Foodborne viruses: Detection, risk assessment, and control options in food processing

In a recent report by risk assessment experts on the identification of food safety priorities using the Delphi technique, foodborne viruses were recognized among the top rated food safety priorities and have become a greater concern to the food industry over the past few years. Food safety experts agreed that control measures for viruses throughout the food chain are required. However, much still needs to be understood with regard to the effectiveness of these controls and how to properly validate their performance, whether it is personal hygiene of food handlers or the effects of processing of at risk foods or the interpretation and action required on positive virus test result. This manuscript provides a description of foodborne viruses and their characteristics, their responses to stress and technologies developed for viral detection and control. In addition, the gaps in knowledge and understanding, and future perspectives on the application of viral detection and control strategies for the food industry, along with suggestions on how the food industry could implement effective control strategies for viruses in foods. The current state of the science on epidemiology, public health burden, risk assessment and management options for viruses in food processing environments will be highlighted in this review.

Image-based phenotyping for identification of QTL determining fruit shape and size in American cranberry (Vaccinium macrocarpon L.)

Image-based phenotyping methodologies are powerful tools to determine quality parameters for fruit breeders and processors. The fruit size and shape of American cranberry (Vaccinium macrocarpon L.) are particularly important characteristics that determine the harvests’ processing value and potential end-use products (e.g., juice vs. sweetened dried cranberries). However, cranberry fruit size and shape attributes can be difficult and time consuming for breeders and processors to measure, especially when relying on manual measurements and visual ratings. Therefore, in this study, we implemented image-based phenotyping techniques for gathering data regarding basic cranberry fruit parameters such as length, width, length-to-width ratio, and eccentricity. Additionally, we applied a persistent homology algorithm to better characterize complex shape parameters. Using this high-throughput artificial vision approach, we characterized fruit from 351 progeny from a full-sib cranberry population over three field seasons. Using a covariate analysis to maximize the identification of well-supported quantitative trait loci (QTL), we found 252 single QTL in a 3-year period for cranberry fruit size and shape descriptors from which 20% were consistently found in all years. The present study highlights the potential for the identified QTL and the image-based methods to serve as a basis for future explorations of the genetic architecture of fruit size and shape in cranberry and other fruit crops.

Massive phenotyping of multiple cranberry populations reveals novel QTLs for fruit anthocyanin content and other important chemical traits

Because of its known phytochemical activity and benefits for human health, American cranberry (Vaccinium macrocarpon L.) production and commercialization around the world has gained importance in recent years. Flavonoid compounds as well as the balance of sugars and acids are key quality characteristics of fresh and processed cranberry products. In this study, we identified novel QTL that influence total anthocyanin content (TAcy), titratable acidity (TA), proanthocyanidin content (PAC), Brix, and mean fruit weight (MFW) in cranberry fruits. Using repeated measurements over the fruit ripening period, different QTLs were identified at specific time points that coincide with known chemical changes during fruit development and maturation. Some genetic regions appear to be regulating more than one trait. In addition, we demonstrate the utility of digital imaging as a reliable, inexpensive and high-throughput strategy for the quantification of anthocyanin content in cranberry fruits. Using this imaging approach, we identified a set of QTLs across three different breeding populations which collocated with anthocyanin QTL identified using wet-lab approaches. We demonstrate the use of a high-throughput, reliable and highly accessible imaging strategy for predicting anthocyanin content based on cranberry fruit color, which could have a large impact for both industry and cranberry research.

Monomeric catechin and dimeric procyanidin B2 against human norovirus surrogates and their physicochemical interactions

Plant polyphenols have shown antiviral activity against several human pathogens, but their physicochemical interactions are not well-understood. The objectives of this study were to compare the antiviral activity between monomeric catechin and dimeric procyanidin B2 (PB2) using cultivable human norovirus surrogates (feline calicivirus (FCV-F9) and murine norovirus (MNV-1)) and to understand their potential antiviral mechanism using virus-like particles (VLPs) and the P domain of human norovirus GII (HNoV GII.4). Surrogate viruses at 5 log PFU/mL were treated with 0.5–5 mg/mL monomeric catechin monohydrate, PB2 or phosphate buffered saline (PBS, pH 7.2; control) at 37 °C over 24 h. Infectivity was determined using plaque assays and data from triplicate experiments were statistically analyzed. PB2 at 0.5 mg/mL and 1 mg/mL reduced FCV-F9 to undetectable levels after 3 h and MNV-1 by 0.21 and 1.23 log PFU after 24 h, respectively. Monomeric catechins at 1 mg/mL reduced FCV-F9 to undetectable levels after 6 h and MNV-1 titers to undetectable levels after 24 h. In addition, PB2 was shown to directly bind the P domain, the main capsid structure of HNoVs in the ratio of 1:1 through spontaneous interactions. Electrostatic interactions played a dominant role between PB2 and the P domain. PB2 significantly altered tertiary but not secondary structures of VLPs. Transmission electron microscopy demonstrated that PB2 aggregated VLPs, further indicating interactions between them. These findings indicate that PB2 causes structural changes of the P domain of VLPs, mainly through direct interaction leading to HNoV inactivation.

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Polymeric procyanidins cause higher reduction of human norovirus surrogate titers than monomers.

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Binding of procyanidin to human norovirus-like particles alters capsid structure.

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Procyanidin binding to viral capsid results in decreased infectivity.

Surfactant-Enhanced Organic Acid Inactivation of Tulane Virus, a Human Norovirus Surrogate

Combination treatments of surfactants and phenolic or short-chain organic acids (SCOA) may act synergistically or additively as sanitizers to inactive foodborne viruses and prevent outbreaks. The purpose of this study was to investigate the effect of gallic acid (GA), tannic acid, p-coumaric acid, lactic acid (LA), or acetic acid (AA), in combination with sodium dodecyl sulfate (SDS), against Tulane virus (TV), a surrogate for human norovirus. An aqueous stock solution of phenolic acids or SCOA with or without SDS was prepared and diluted in a twofold dilution series to 2× the desired concentration with cell growth media (M119 plus 10% fetal bovine serum). The solution was inoculated with an equal proportion of 6 log PFU/mL TV with a treatment time of 5 min. The survival of TV was quantified using a plaque assay with LLC-MK2 cells. The minimum virucidal concentration was 0.5:0.7% (v/v) for LA-SDS at pH 3.5 (4.5-PFU/mL reduction) and 0.5:0.7% (v/v) AA-SDS at pH 4.0 (2.6-log PFU/mL reduction). GA and SDS demonstrated a minimum virucidal concentration of 12.5 mM GA-SDS at pH 7.0 (0.2:0.3% GA-SDS) with an 0.8-log PFU/mL reduction and 50 mM GA-SDS (0.8:1.4% GA-SDS at pH 7.0) increased log reduction to 1.6 log PFU/mL. The combination treatments of AA or LA with SDS at pH 7.0 did not produce significant log reduction, nor did individual treatments of tannic acid, GA, p-coumaric acid, AA, LA, or SDS. This study demonstrates that a surfactant, such as SDS, aids in the phenolic acid and SCOA toxicities against viruses. However, inactivation of TV by combination treatments is contingent upon the pH of the sanitizing solution being lower than the pK_a value of the organic acid being used. This information can be used to develop sanitizing washes to disinfect food contact surfaces, thereby aiding in the prevention of foodborne outbreaks.

Human norovirus inhibition by a human milk oligosaccharide

Human noroviruses are the leading cause of outbreaks of acute gastroenteritis. Norovirus interactions with histo-blood group antigens (HBGAs) are known to be important for an infection. In this study, we identified the HBGA binding pocket for an emerging GII genotype 17 (GII.17) variant using X-ray crystallography. The GII.17 variant bound the HBGA with an equivalent set of residues as the leading pandemic GII.4 variants. These structural data highlights the conserved nature of HBGA binding site between prevalent GII noroviruses. Noroviruses also interact with human milk oligosaccharides (HMOs), which mimic HBGAs and may function as receptor decoys. We previously showed that HMOs inhibited the binding of rarely detected GII.10 norovirus to HBGAs. We now found that an HMO, 2'-fucosyllactose (2'FL), additionally blocked both the GI.1 and GII.17 noroviruses from binding to HBGAs. Together, these findings provide evidence that 2'FL might function as a broadly reactive antiviral against multiple norovirus genogroups.

Reduction of Enteric Viruses by Blueberry Juice and Blueberry Proanthocyanidins

Blueberry and blueberry extracts are known for their health benefits and antimicrobial properties. Natural therapeutic or preventive options to decrease the incidences of foodborne viral illnesses are becoming popular and being researched. This study aimed to determine the antiviral effects of blueberry juice (BJ) and blueberry proanthocyanidins (BB-PAC, B-type PAC structurally different from A-type PAC found in cranberries) against the infectivity of hepatitis A virus (HAV) and human norovirus surrogates (feline calicivirus (FCV-F9) and murine norovirus (MNV-1)) at 37 °C over 24 h using standard plaque assays. Viruses at ~5 log PFU/ml were mixed with equal volumes of BJ (pH 2.8), neutralized BJ (pH 7.0), BB-PAC (1, 2, 4, and 10 mg/ml), malic acid (pH 3.0), or phosphate-buffered saline (pH 7.2) and incubated over 24 h at 37 °C. Each experiment was carried out in duplicate and replicated thrice. FCV-F9 titers were found to be reduced to undetectable levels with 1 and 2 mg/ml BB-PAC after 5 min, with 0.5 mg/ml BB-PAC after 1-h, and with BJ after 3-h. MNV-1 titers were reduced to undetectable levels after 3 h with 1, 2, and 5 mg/ml BB-PAC and after 6 h with BJ. HAV titers were reduced to undetectable levels after 30 min with 2 and 5 mg/ml BB-PAC, after 3 h with 1 mg/ml BB-PAC, and by ~2 log PFU/ml with BJ after 24-h. BB-PAC shows preventive potential against infection by the tested enteric viruses in a dose- and time-dependent manner, although further in vitro studies in model food systems and in vivo studies using animal models are warranted.

Blueberry proanthocyanidins against human norovirus surrogates in model foods and under simulated gastric conditions

Blueberry proanthocyanidins (B-PAC) are known to decrease titers of human norovirus surrogates in vitro. The application of B-PAC as therapeutic or preventive options against foodborne viral illness needs to be determined using model foods and simulated gastric conditions in vitro. The objective of this study was to evaluate the antiviral effect of B-PAC in model foods (apple juice (AJ) and 2% reduced fat milk) and simulated gastrointestinal fluids against cultivable human norovirus surrogates (feline calicivirus; FCV-F9 and murine norovirus; MNV-1) over 24 h at 37 °C. Equal amounts of each virus (5 log PFU/ml) was mixed with B-PAC (1, 2 and 5 mg/ml) prepared either in AJ, or 2% milk, or simulated gastric fluids and incubated over 24 h at 37 °C. Controls included phosphate buffered saline, malic acid (pH 7.2), AJ, 2% milk or simulated gastric and intestinal fluids incubated with virus over 24 h at 37 °C. The tested viruses were reduced to undetectable levels within 15 min with B-PAC (1, 2 and 5 mg/ml) in AJ (pH 3.6). However, antiviral activity of B-PAC was reduced in milk. FCV-F9 was reduced by 0.4 and 1.09 log PFU/ml with 2 and 5 mg/ml B-PAC in milk, respectively and MNV-1 titers were reduced by 0.81 log PFU/ml with 5 mg/ml B-PAC in milk after 24 h. B-PAC at 5 mg/ml in simulated intestinal fluid reduced titers of the tested viruses to undetectable levels within 30 min. Overall, these results show the potential of B-PAC as preventive and therapeutic options for foodborne viral illnesses.

Curcumin Shows Antiviral Properties against Norovirus

Phytochemicals provide environmentally friendly and relatively inexpensive natural products, which could potentially benefit public health by controlling human norovirus (HuNoV) infection. In this study, 18 different phytochemicals were evaluated for antiviral effects against norovirus using murine norovirus (MNV) as a model for norovirus biology. Among these phytochemicals, curcumin (CCM) was the most potent anti-noroviral phytochemical, followed by resveratrol (RVT). In a cell culture infection model, exposure to CCM or RVT for 3 days reduced infectivity of norovirus by 91% and 80%, respectively. To confirm the antiviral capability of CCM, we further evaluated its antiviral efficacy at various doses (0.25, 0.5, 0.75, 1, and 2 mg/mL) and durations (short-term: 10, 30, 60, and 120 min; long-term: 1, 3, 7, and 14 days). The anti-noroviral effect of CCM was verified to occur in a dose-dependent manner. Additionally, we evaluated the inhibitory effect of each phytochemical on the replication of HuNoV using a HuNoV replicon-bearing cell line (HG23). Neither CCM nor RVT had a strong inhibitory effect on HuNoV replication, which suggests that their antiviral mechanism may involve viral entry or other life cycle stages rather than the replication of viral RNA. Our results demonstrated that CCM may be a promising candidate for development as an anti-noroviral agent to prevent outbreaks of foodborne illness.

Natural Virucidal Compounds in Foods

Many plant essential oils, extracts, and individual chemical components have been demonstrated to possess antiviral efficacy against enveloped and/or non-enveloped viruses. In general, plant antimicrobials exhibit greater antiviral efficacy against enveloped viruses than non-enveloped viruses (though not in all cases). There appear to be multiple mechanisms of antiviral action for plant antimicrobials; nevertheless, the majority of antimicrobials appear to act either directly on the virus itself (e.g., on the envelope or capsid) or during the early stages of virus replication following internalization of the virus into its host cell.

Aqueous Extracts of Hibiscus sabdariffa Calyces to Control Aichi Virus

Aqueous Hibiscus sabdariffa extracts possess antimicrobial properties with limited information available on their antiviral effects. Aichi virus (AiV) is an emerging foodborne pathogen that causes gastroenteritis. Vaccines are currently unavailable to prevent their disease transmission. The objective of this study was to determine the antiviral effects of aqueous H. sabdariffa extracts against AiV. AiV at ~5 log PFU/ml was incubated with undiluted (200 mg/ml), 1:1 (100 mg/ml) or 1:5 (40 mg/ml) diluted aqueous hibiscus extract (pH 3.6), phosphate-buffered saline (pH 7.2 as control), or malic acid (pH 3.0, acid control) at 37 °C over 24 h. Treatments were stopped by serially diluting in cell-culture media containing fetal bovine serum and titers were determined using plaque assays on confluent Vero cells. Each treatment was replicated thrice and assayed in duplicate. AiV did not show any significant reduction with 1:1 (100 mg/ml) or 1:5 (40 mg/ml) diluted aqueous hibiscus extracts or malic acid after 0.5, 1, or 2 h at 37 °C. However, AiV titers were reduced to non-detectable levels after 24 h with all the three tested concentrations, while malic acid showed only 0.93 log PFU/ml reduction after 24 h. AiV was reduced by 0.5 and 0.9 log PFU/ml with undiluted extracts (200 mg/ml) after 2 and 6 h, respectively. AiV treated with 1:1 (100 mg/ml) and 1:5 (40 mg/ml) diluted extracts showed a minimal ~0.3 log PFU/ml reduction after 6 h. These extracts show promise to reduce AiV titers mainly through alteration of virus structure, though higher concentrations may have improved effects.

Antiviral effects of black raspberry (Rubus coreanus) seed extract and its polyphenolic compounds on norovirus surrogates

Black raspberry seeds, a byproduct of wine and juice production, contain large quantities of polyphenolic compounds. The antiviral effects of black raspberry seed extract (RCS) and its fraction with molecular weight less than 1 kDa (RCS-F1) were examined against food-borne viral surrogates, murine norovirus-1 (MNV-1) and feline calicivirus-F9 (FCV-F9). The maximal antiviral effect was achieved when RCS or RCS-F1 was added simultaneously to cells with MNV-1 or FCV-F9, reaching complete inhibition at 0.1-1 mg/mL. Transmission electron microscopy (TEM) images showed enlarged viral capsids or disruption (from 35 nm to up to 100 nm) by RCS-F1. Our results thus suggest that RCS-F1 can interfere with the attachment of viral surface protein to host cells. Further, two polyphenolic compounds derived from RCS-F1, cyanidin-3-glucoside (C3G) and gallic acid, identified by liquid chromatography-tandem mass spectrometry, showed inhibitory effects against the viruses. C3G was suggested to bind to MNV-1 RNA polymerase and to enlarge viral capsids using differential scanning fluorimetry and TEM, respectively.

Atomic force microscopy-guided fractionation reveals the influence of cranberry phytochemicals on adhesion of Escherichia coli

Characterization of cranberry juice fractions for their role in anti-adhesive properties against pathogenicE. coliusing Atomic Force Microscopy (AFM).

Aqueous Extracts of Hibiscus sabdariffa Calyces Decrease Hepatitis A Virus and Human Norovirus Surrogate Titers

Hibiscus sabdariffa extract is known to have antioxidant, anti-diabetic, and antimicrobial properties. However, their effects against foodborne viruses are currently unknown. The objective of this study was to determine the antiviral effects of aqueous extracts of H. sabdariffa against human norovirus surrogates (feline calicivirus (FCV-F9) and murine norovirus (MNV-1)) and hepatitis A virus (HAV) at 37 °C over 24 h. Individual viruses (~5 log PFU/ml) were incubated with 40 or 100 mg/ml of aqueous hibiscus extract (HE; pH 3.6), protocatechuic acid (PCA; 3 or 6 mg/ml, pH 3.6), ferulic acid (FA; 0.5 or 1 mg/ml; pH 4.0), malic acid (10 mM; pH 3.0), or phosphate buffered saline (pH 7.2 as control) at 37 °C over 24 h. Each treatment was replicated thrice and plaque assayed in duplicate. FCV-F9 titers were reduced to undetectable levels after 15 min with both 40 and 100 mg/ml HE. MNV-1 was reduced by 1.77 ± 0.10 and 1.88 ± 0.12 log PFU/ml after 6 h with 40 and 100 mg/ml HE, respectively, and to undetectable levels after 24 h by both concentrations. HAV was reduced to undetectable levels by both HE concentrations after 24 h. PCA at 3 mg/ml reduced FCV-F9 titers to undetectable levels after 6 h, MNV-1 by 0.53 ± 0.01 log PFU/ml after 6 h, and caused no significant change in HAV titers. FA reduced FCV-F9 to undetectable levels after 3 h and MNV-1 and HAV after 24 h. Transmission electron microscopy showed no conclusive results. The findings suggest that H. sabdariffa extracts have potential to prevent foodborne viral transmission.

Treatment of norovirus particles with citrate

Human norovirus is a dominant cause of acute gastroenteritis around the world. Several norovirus disinfectants label citric acid as an active ingredient. In this study, we showed that norovirus virus-like particles (VLPs) treated with citrate buffer caused the particles to alter their morphology, including increased diameters associated with a new ring-like structure. We also found that epitopes on the protruding (P) domain on these particles were more readily accessible to antibodies after the citrate treatment. These results suggested that citrate had a direct effect on the norovirus particles. Using X-ray crystallography, we showed that the P domain bound citrate from lemon juice and a disinfectant containing citric acid. Importantly, citrate binds at the histo-blood group antigen binding pocket, which are attachment factors for norovirus infections. Taken together, these new findings suggested that it might be possible to treat/reduce norovirus infections with citrate, although further studies are needed.

Antiviral effects of grape seed extract against feline calicivirus, murine norovirus, and hepatitis A virus in model food systems and under gastric conditions

Grape seed extract (GSE) has antiviral activities against hepatitis A virus (HAV) and human norovirus surrogates (feline calicivirus (FCV-F9) and murine norovirus (MNV-1)). The objectives of this study were to determine (1) time and dose-dependence of GSE against FCV-F9, MNV-1, and HAV at room temperature (RT) and 37 °C over 24 h; and (2) GSE effects in model foods (apple juice (AJ) and 2% milk) and simulated gastric conditions at 37 °C. Viruses at ∼5 log PFU/ml were treated with 0.5-8 mg/ml GSE prepared in water, AJ, milk or gastric juices, or water over 24 h at RT or 37 °C. Infectivity of triplicate treatments was evaluated using plaque assays. GSE effects increased with time and concentration. GSE at 1 mg/ml in AJ reduced MNV-1 to undetectable levels after 1 h and by 1 log in milk after 24 h. GSE at 1 and 2 mg/ml in AJ reduced HAV to undetectable levels after 1 h, while 2 and 4 mg/ml GSE in milk caused ∼1 log reduction after 24 h. GSE at 2 mg/ml in intestinal fluid reduced FCV-F9, MNV-1 and HAV to undetectable levels after 6 h. GSE appears to be a suitable natural option for foodborne viral reduction.