Norovirus gastroenteritis

Household economic costs of norovirus gastroenteritis in two community cohorts in Peru, 2012-2019

While costs of norovirus acute gastroenteritis (AGE) to healthcare systems have been estimated, out-of-pocket and indirect costs incurred by households are not well documented in community settings, particularly in developing countries. We conducted active surveillance for AGE in two communities in Peru: Puerto Maldonado (October 2012-August 2015) and San Jeronimo (April 2015-April 2019). Norovirus AGE events with PCR-positive stool specimens were included. Data collected in follow-up interviews included event-related medical resource utilization, associated out-of-pocket costs, and indirect costs. There were 330 norovirus-associated AGE events among 3,438 participants from 685 households. Approximately 49% of norovirus events occurred among children <5 years of age and total cost to the household per episode was highest in this age group. Norovirus events cost a median of US $2.95 (IQR $1.04-7.85) in out-of-pocket costs and $12.58 (IQR $6.39-25.16) in indirect costs. Medication expenses accounted for 53% of out-of-pocket costs, and productivity losses accounted for 59% of the total financial burden on households. The frequency and associated costs of norovirus events to households in Peruvian communities support the need for prevention strategies including vaccines. Norovirus interventions targeting children <5 years of age and their households may have the greatest economic benefit.

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.

Presentation, management, and outcomes of norovirus in adult and pediatric solid organ and hematopoietic stem cell transplant recipients: A multicenter, retrospective study

BACKGROUND

Norovirus (NoV) can cause chronic relapsing and remitting diarrhea in immunocompromised patients.  Few multicenter studies have described the clinical course, outcomes, and complications of chronic NoV in transplant recipients.

METHODS

A multicenter retrospective study of adult and pediatric SOT and HSCT recipients diagnosed with NoV between November 1, 2017, and February 28, 2021. Data were obtained from electronic medical records (EMR) and entered into a central REDCap database. Descriptive statistics were calculated.

RESULTS

A total of 280 NoV+ patients were identified across eight sites. The majority were adults (74.1%) and SOT recipients (91.4%). Initial diagnosis of NoV occurred a median of 36 months post-Tx (IQR [15.0, 90.0]). Most NoV cases had >3 diarrheal episodes daily (66.0%), nausea and vomiting (60.1%). Duration of diarrhea varied greatly (median = 10 days, mean = 85.9 days, range (1, 2100)). 71.3% were hospitalized. Adjustment of immunosuppression, including reduction and discontinuation of mToR inhibitor, CNI, and/or MMF, was the most common management intervention for NoV. Other therapies resulted only in temporary improvement. Four patients died within 30 days and three others died by 180 days postdiagnosis. Clinically significant renal dysfunction was observed in 12.5% by 30 days and 21.4% by 180 days post-NoV diagnosis.

CONCLUSION

In HSCT and SOT patients, NoV frequently resulted in severe symptoms, prolonged diarrhea (30% persistent with diarrhea for >30 days), and clinically significant renal dysfunction (up to 21% of patients). Utilized therapies did not reliably result in the resolution of infection demonstrating the need for more effective treatment.

Function of autophagy genes in innate immune defense against mucosal pathogens

Mucosal immunity is posed to constantly interact with commensal microbes and invading pathogens. As a fundamental cell biological pathway affecting immune response, autophagy regulates the interaction between mucosal immunity and microbes through multiple mechanisms, including direct elimination of microbes, control of inflammation, antigen presentation and lymphocyte homeostasis, and secretion of immune mediators. Some of these physiologically important functions do not involve canonical degradative autophagy but rely on certain autophagy genes and their 'autophagy gene-specific functions.' Here, we review the relationship between autophagy and important mucosal pathogens, including influenza virus, Mycobacterium tuberculosis, Salmonella enterica, Citrobacter rodentium, norovirus, and herpes simplex virus, with a particular focus on distinguishing the canonical versus gene-specific mechanisms of autophagy genes.

Improving the Detection and Understanding of Infectious Human Norovirus in Food and Water Matrices: A Review of Methods and Emerging Models

Human norovirus (HuNoV) is a leading global cause of viral gastroenteritis, contributing to numerous outbreaks and illnesses annually. However, conventional cell culture systems cannot support the cultivation of infectious HuNoV, making its detection and study in food and water matrices particularly challenging. Recent advancements in HuNoV research, including the emergence of models such as human intestinal enteroids (HIEs) and zebrafish larvae/embryo, have significantly enhanced our understanding of HuNoV pathogenesis. This review provides an overview of current methods employed for HuNoV detection in food and water, along with their associated limitations. Furthermore, it explores the potential applications of the HIE and zebrafish larvae/embryo models in detecting infectious HuNoV within food and water matrices. Finally, this review also highlights the need for further optimization and exploration of these models and detection methods to improve our understanding of HuNoV and its presence in different matrices, ultimately contributing to improved intervention strategies and public health outcomes.

Collision induced unfolding and molecular dynamics simulations of norovirus capsid dimers reveal strain-specific stability profiles

Collision induced unfolding (CIU) is a method used with ion mobility mass spectrometry to examine protein structures and their stability. Such experiments yield information about higher order protein structures, yet are unable to provide details about the underlying processes. That information can however be provided using molecular dynamics simulations. Here, we investigate the gas-phase unfolding of norovirus capsid dimers from the Norwalk and Kawasaki strains by employing molecular dynamics simulations over a range of temperatures, representing different levels of activation, together with CIU experiments. The dimers have highly similar structures, but their CIU reveals different stability that can be explained by the different dynamics that arises in response to the activation seen in the simulations, including a part of the sequence with previously observed strain-specific dynamics in solution. Our findings show how similar protein variants can be examined using mass spectrometric techniques in conjunction with atomistic molecular dynamics simulations to reveal differences in stability as well as differences in how and where unfolding takes place upon activation.

Advances in wastewater analysis revealing the co-circulating viral trends of noroviruses and Omicron subvariants

Co-presence of enveloped and non-enveloped viruses is common both in community circulation and in wastewater. Community surveillance of infections requires robust methods enabling simultaneous quantification of multiple viruses in wastewater. Using enveloped SARS-CoV-2 Omicron subvariants and non-enveloped norovirus (NoV) as examples, this study reports a robust method that integrates electronegative membrane (EM) concentration, viral inactivation, and RNA preservation (VIP) with efficient capture and enrichment of the viral RNA on magnetic (Mag) beads, and direct detection of RNA on the beads. This method provided improved viral recoveries of 80 ± 4 % for SARS-CoV-2 and 72 ± 5 % for Murine NoV. Duplex reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays with newly designed degenerate primer-probe sets offered high PCR efficiencies (90-91 %) for NoV (GI and GII) targets and were able to detect as few as 15 copies of the viral RNA per PCR reaction. This technique, combined with duplex detection of NoV and multiplex detection of Omicron, successfully quantified NoV (GI and GII) and Omicron variants in the same sets of 94 influent wastewater samples collected from two large wastewater systems between July 2022 and June 2023. The wastewater viral RNA results showed temporal changes of both NoV and Omicron variants in the same wastewater systems and revealed an inverse relationship of their emergence. This study demonstrated the importance of a robust analytical platform for simultaneous surveillance of enveloped and non-enveloped viruses in wastewater. The ability to sensitively determine multiple viral pathogens in wastewater will advance applications of wastewater surveillance as a complementary public health tool.

Human intestinal enteroids and predictive models validate the operational limits of sanitizers used for viral disinfection of vegetable process wash water

Vegetables are globally associated with a considerable number of foodborne outbreaks caused by viral infections, specifically human norovirus. In fresh produce industry, washing represents a critical step for food safety as process wash water (PWW) needs to be maintained at appropriate microbial quality to prevent water-mediated cross-contamination. This study aimed to explore the disinfection efficacy of chlorine (free chlorine, FC), chlorine dioxide (ClO2) and peracetic acid (PAA) in PWW against infectious human norovirus and Tulane virus (TV). First, we tested the extent of TV inactivation in baby leaf, bell pepper, and vegetables mix PWW and monitored the viral decay by cell culture. Then, inactivation kinetics were defined for infectious human norovirus exposed to FC, ClO2 and PAA in baby leaves PWW using the human intestinal enteroids (HIE) system. Finally, kinetic inactivation models were fitted to TV reduction and decay of sanitizers to aid the implementation of disinfection strategies. Results showed that >8 log10 human norovirus and 3.9 log10 TV were inactivated by 20 ppm FC within 1 min; and by 3 ppm ClO2 in 1 min (TV) or 5 min (norovirus). PAA treatment at 80 ppm reduced ca. 2 log10 TV but not completely inactivated the virus even after 20 min exposure, while 5 min treatment prevented norovirus replication in HIE. TV inactivation in PWWs was described using an exponential decay model. Taking these data together, we demonstrated the value of applying the HIE model to validate current operational limits for the most commonly used sanitizers. The inactivation kinetics for human norovirus and TV, along with the predictive model described in this study expand the current knowledge to implement post-harvest produce safety procedures in industry settings.

A Viral Protein 4-Based Trivalent Nanoparticle Vaccine Elicited High and Broad Immune Responses and Protective Immunity against the Predominant Rotaviruses

The current live rotavirus (RV) vaccines show reduced effectiveness in developing countries, calling for vaccine strategies with improved efficacy and safety. We generated pseudovirus nanoparticles (PVNPs) that display multiple ectodomains of RV viral protein 4 (VP4), named S-VP4e, as a nonreplicating RV vaccine candidate. The RV spike protein VP4s that bind host receptors and facilitate viral entry are excellent targets for vaccination. In this study, we developed scalable methods to produce three S-VP4e PVNPs, each displaying the VP4e antigens from one of the three predominant P[8], P[4], and P[6] human RVs (HRVs). These PVNPs were recognized by selected neutralizing VP4-specific monoclonal antibodies, bound glycan receptors, attached to permissive HT-29 cells, and underwent cleavage by trypsin between VP8* and VP5*. 3D PVNP models were constructed to understand their structural features. A trivalent PVNP vaccine containing the three S-VP4e PVNPs elicited high and well-balanced VP4e-specific antibody titers in mice directed against the three predominant HRV P types. The resulting antisera neutralized the three HRV prototypes at high titers; greater than 4-fold higher than the neutralizing responses induced by a trivalent vaccine consisting of the S60-VP8* PVNPs. Finally, the trivalent S-VP4e PVNP vaccine provided 90-100% protection against diarrhea caused by HRV challenge. Our data supports the trivalent S-VP4e PVNPs as a promising nonreplicating HRV vaccine candidate for parenteral delivery to circumvent the suboptimal immunization issues of all present live HRV vaccines. The established PVNP-permissive cell and PVNP-glycan binding assays will be instrumental for further investigating HRV-host cell interactions and neutralizing effects of VP4-specific antibodies and antivirals.

A DNA vaccine against GII.4 human norovirus VP1 induces blocking antibody production and T cell responses

Human noroviruses (HuNoVs) are highly contagious and a leading cause of epidemics of acute gastroenteritis worldwide. Among the various HuNoV genotypes, GII.4 is the most prevalent cause of outbreaks. However, no vaccines have been approved for HuNoVs to date. DNA vaccines are proposed to serve as an ideal platform against HuNoV since they can be easily produced and customized to express target proteins. In this study, we constructed a CMV/R vector expressing a major structural protein, VP1, of GII.4 HuNoV (CMV/R-GII.4 HuNoV VP1). Transfection of CMV/R-GII.4 HuNoV VP1 into human embryonic kidney 293T (HEK293T) cells resulted in successful expression of VP1 proteins in vitro. Intramuscular or intradermal immunization of mice with the CMV/R-GII.4 HuNoV VP1 construct elicited the production of blocking antibodies and activation of T cell responses against GII.4 HuNoV VP1. Our collective data support the utility of CMV/R-GII.4 HuNoV VP1 as a promising DNA vaccine candidate against GII.4 HuNoV.

Estimation of Norovirus infections in Japan: An application of wastewater-based epidemiology for enteric disease assessment

Noroviruses of genogroup I (NoV GI) and NoV GII are the primary causes of acute gastroenteritis (AGE) in developed countries. However, asymptomatic and untested NoV infections lead to an underestimation of AGE cases, and the lack of mandatory viral identification in clinical cases hinders precise estimation of NoV infections. Back estimation of NoV infections in the community using a wastewater-based epidemiology (WBE) approach can provide valuable insights into the disease's extent, progression, and epidemiology, aiding in developing effective control strategies. This study employed a one-step reverse transcription-quantitative PCR to quantify NoVs GI and GII in wastewater samples (n = 83) collected twice a week from June 2022 to March 2023 in Japan. All samples from the Winter-Spring (n = 27) tested positive for NoV GI and GII RNA, while 73 % and 88 % of samples from the Summer-Autumn (n = 56) were positive for NoV GI and NoV GII RNA, respectively. Significantly higher concentrations of NoV GI/GII RNA were found in the Winter-Spring season compared to the Summer-Autumn season. NoV RNA was consistently detected in wastewater throughout the year, demonstrating the persistence of AGE cases in the catchment, suggesting an endemic NoV infection. Estimates of NoV infection incorporated viral RNA concentrations, wastewater parameters, and signal persistence in a mass balance equation using Monte Carlo Simulation. The median estimated NoV GI infections per 100,000 population for Summer-Autumn was 133 and for the Winter-Spring season, it was 881. Estimated NoV GII infections were 1357 for Summer-Autumn and 11,997 for the Winter-Spring season per 100,000 population. The estimated NoV infections exceeded by 3.2 and 23.9 folds than the reported AGE cases in Summer-Autumn and Winter-Spring seasons, respectively. The seasonal trend of estimated NoV infections closely matched that of AGE cases, highlighting the utility of WBE in understanding the epidemiology of enteric infections.

Monitoring and Genotyping of Norovirus in Bivalve Molluscan Shellfish from Northern Italian Seas (2018-2020)

Norovirus (NoV) is an enteric virus with foodborne transmission. Bivalve shellfish are a main source of infections and outbreaks. In Italy a voluntary based monitoring plan to check the safety of bivalve shellfish was set up at provincial level. This study describes the occurrence and distribution of NoV in the Northern Adriatic Sea and in the Ligurian Sea. From October 2018 to September 2020, 807 bivalve shellfish samples (n = 205 oysters, n = 182 mussels, n = 348 clams, n = 72 other bivalve shellfish) were tested by One-Step Retrotranscription Real-time polymerase chain reaction for NoV GI and GII and quantified according to the ISO 15216-2:2013 and ISO 15216-1:2017. Positive samples were further analyzed to determine genotype by sequencing of the ORF1/ORF2 junction of the viral genome. A total of 126 samples were positive for NoV, mussels, and oysters had the highest probability of being positive and positive samples were found mainly in the colder season. Of these samples, 46% were NoV GII, 13% NoV GI, and 40% carried both genogroups. Thirty-seven samples were typeable (GI n = 12 and GII n = 25) with GI samples belonging to four genotypes and GII samples belonging to five genotypes. GII.3 genotype was the most prevalent, followed by GII.4, particularly Sydney 2012 subtype, a leading cause of infections worldwide, was found in three oysters' and three clams' samples. The phylogenetic analysis revealed a high heterogeneity among the species that are scattered in several clusters. Considering the low infectious dose the overall presence of NoV in edible shellfish, particular those to be eaten raw or undercooked, is moderately high. The presence of genotypes frequently involved in human infections strengthens the need for ongoing monitoring, which should be extended at national level.

Predominance of Recombinant Norovirus Strains in Greece, 2016-2018

GII.4 noroviruses have caused the overwhelming majority of norovirus-related gastroenteritis cases during the past two decades. However, a trend towards the emergence of new genotypes and novel GII.4 variants provided the impetus to explore further the changing patterns in norovirus epidemiology during the present study. Genotyping of 60 norovirus strains detected during a period of 33 months (January 2016-October 2018) was performed on the basis of the capsid VP1-coding ORF2 gene sequence. All norovirus strains detected were classified into seven genotypes, six of which belonged to genogroup GII. GII.2 was the dominant genotype till February 2017, whereas GII.4 prevailed thereafter. Most of the GII.4 strains were of the Sydney_2012 variant, whereas five strains could not be classified. Further recombination analysis at the ORF1/ORF2 gene junction revealed that 23 out of 24 strains were recombinant, thereby showcasing the significant role of genetic recombination in norovirus evolution and epidemiology. Continuous genomic surveillance and molecular characterization are essential for tracking norovirus evolution, which could contribute to the elucidation of new aspects of virus-host interactions that potentially affect host morbidity and epidemiology.

Biological and physico-chemical characterization of human norovirus-like particles under various environmental conditions

Human noroviruses (HuNoVs) are the predominant etiological agent of viral gastroenteritis in all age groups worldwide. Mutations over the years have affected noroviruses' responses to environmental conditions due to the arrangement of amino acid residues exposed on the VP1 capsid surface of each strain. The GII.4 HuNoV genotype has been the predominant variant for decades, while the GII.17 genotype has often been detected in East Asia since 2014. Here, GII.17 and GII.4 baculovirus-expressed VLPs (virus-like particles) were used to study the biological (binding to HuNoV ligand, namely the ABO and Lewis antigens) and physicochemical properties (size, morphology, and charge) of the HuNoV capsid under different conditions (temperature, pH, and ionic strength). GII.17 showed stability at low and high ionic strength, while GII.4 aggregated at an ionic strength of 10 mM. The nature of the buffers influences the morphology and stability of the VLPs. Here, both VLPs were highly stable from pH 7-8.5 at 25 °C. VLPs retained HBGA binding capability for the pH, ionic strength and temperature encountered in the stomach (fed state) and the small intestine. Increasing the temperature to above 65 °C altered the morphology of VLPs, causing aggregation, and decreased their affinity to HBGAs. Comparing both isolates, GII.17 showed a better stability profile and higher affinity to HBGAs than GII.4, making them interesting candidate particles for a future norovirus vaccine. Biological and physicochemical studies of VLPs are as pertinent as ever in view of the future arrival of VLP-based HuNoV vaccines.

Chimeric virus-like particles of human norovirus constructed by structure-guided epitope grafting elicit cross-reactive immunity against both GI.1 and GII.4 genotypes

IMPORTANCE

Human norovirus (HuNoV) is highly infectious and can result in severe illnesses in the elderly and children. So far, there is no effective antiviral drug to treat HuNoV infection, and thus, the development of HuNoV vaccines is urgent. However, NoV evolves rapidly, and currently, at least 10 genogroups with numerous genotypes have been found. The genetic diversity of NoV and the lack of cross-protection between different genotypes pose challenges to the development of broadly protective vaccines. In this study, guided by structural alignment between GI.1 and GII.4 HuNoV VP1 proteins, several chimeric-type virus-like particles (VLPs) were designed through surface-exposed loop grafting. Mouse immunization studies show that two of the designed chimeric VLPs induced cross-immunity against both GI.1 and GII.4 HuNoVs. To our knowledge, this is the first designed chimeric VLPs that can induce cross-immune activities across different genogroups of HuNoV, which provides valuable strategies for the development of cross-reactive HuNoV vaccines.

A household survey of intrafamily norovirus transmission

Norovirus (NoV) is a leading cause of epidemic and sporadic gastroenteritis in people of all ages. Humans are the primary source of NoV and household contact is one of the risk factors for NoV transmission. However, the mechanisms underlying person-to-person NoV transmission are poorly understood. Here we conducted a survey to profile the frequency and characteristics of intrafamily NoV transmission. Stool samples were collected every week from three households between 2016 and 2020; the total number of samples was 1105. The detection of NoV and the genotyping were performed by reverse transcription-polymerase chain reaction targeting the capsid region and direct sequencing methods. NoV was detected in 3.4% of all samples. Eight NoV genotypes were identified. The most common genotype was GII.17, followed in order by GII.6, GI.6, GII.4, GI.3, and GI.2/GI.8/GI.9. Most NoV-positive samples were obtained from asymptomatic individuals. The highest number of NoV transmissions was found in household 3 (6 infections), followed by household 2 (2 infections), while household 1 had no NoV transmission, suggesting that asymptomatic NoV carriers play a major role in infection as NoV reservoirs in the households. Further clarification of the mode of infection will contribute to improved understanding and an appropriate prevention.

Development and characterization of a plant-derived norovirus-like particle vaccine

BACKGROUND

Norovirus (NoV) is the most common cause of diarrheal episodes globally. Issues with in vitro cultivation systems, genetic variation, and animal models have hindered vaccine development. Plant-derived virus-like particles (VLPs) may address some of these concerns because they are highly immunogenic, can be administered by different routes, and can be rapidly produced to accommodate emerging viral strains.

METHODS

NoV VLPs (NoVLP) composed of the surface viral protein (VP) 1 of the GI and GII genogroups were produced in Nicotiana benthamiana using an Agrobacterium tumefaciens-based recombinant transient expression system. Leaves from infiltrated plants were harvested and NoVLPs were extracted and purified. The safety and immunogenicity of the GII.4 NoVLP, the genotype currently causing most human disease, were subsequently examined in rabbits and mice.

RESULTS

Fifteen GI and GII NoVLPs were successfully expressed in N. benthamiana and were structurally similar to NoV virions, as determined by cryogenic transmission electron microscopy. The NoVLP was well-tolerated, with no local or systemic signs of toxicity in rabbits. Three intramuscular doses of the GII.4 NoVLP adjuvanted with aluminum hydroxide induced robust IgG titers, IgG-secreting cells, histo-blood group antigen blocking titers, and IFNγ-secreting T cells in mice. In addition to circulating antibodies, oral administration of the NoVLP in mice induced significant IgA levels in feces, indicative of a mucosal response.

CONCLUSIONS

The plant-made NoVLP vaccine was safe and immunogenic in mice and rabbits. Multi-modal vaccination, combining oral and intramuscular administration could be considered for future clinical development to maximize systemic and mucosal immune responses.

Genetic characterization of rarely reported GII.3[P25] norovirus strain detected in patients with acute gastroenteritis in Huzhou, China, 2021

•The first genome of GII.3 [P25] strain isolated in China was determined by NGS. •About 19 unique amino acid substitutions were identified in the VP1 region of GII.3 [P25]. •Antigenic variation may have contributed to the re-emerge of GII.3 [P25] strains.

Application of Baculovirus Expression Vector System (BEVS) in Vaccine Development

Vaccination is one of the most effective strategies to control epidemics. With the deepening of people's awareness of vaccination, there is a high demand for vaccination. Hence, a flexible, rapid, and cost-effective vaccine platform is urgently needed. The baculovirus expression vector system (BEVS) has emerged as a promising technology for vaccine production due to its high safety, rapid production, flexible product design, and scalability. In this review, we introduced the development history of BEVS and the procedures for preparing recombinant protein vaccines using the BEVS platform and summarized the features and limitations of this platform. Furthermore, we highlighted the progress of the BEVS platform-related research, especially in the field of vaccine. Finally, we provided a new prospect for BEVS in future vaccine manufacturing, which may pave the way for future BEVS-derived vaccine development.

Effectiveness of Saccharomyces Boulardii CNCM I-745 probiotic in acute inflammatory viral diarrhoea in adults: results from a single-centre randomized trial

BACKGROUND

Probiotics are effective for treating acute infectious diarrhoea caused by bacteria, but there are inconsistent results for the effectiveness of probiotics for diarrhoea caused by viruses. In this article we want to determine whether Sb supplementation has an effect on acute inflammatory viral diarrhoea diagnosed with the multiplex panel PCR test. The aim of this study was to evaluate the efficacy of Saccharomyces boulardii (Sb) as a treatment in patients diagnosed with viral acute diarrhoea.

METHODS

From February 2021 to December 2021, 46 patients with a confirmed diagnosis of viral acute diarrhoea diagnosed with the polymerase chain reaction multiplex assay were enrolled in a double-blind, randomized placebo-controlled trial. Patients received paracetamol 500 mg as a standard analgesic and 200 mg of Trimebutine as an antispasmodic treatment plus 600 mg of Sb (n = 23, 1 × 109/100 mL Colony forming unit) or a placebo (n = 23) orally once daily for eight days. The improvement in and severity of symptoms were measured using a symptom diary, the Patient Global Impression and the Patient Global Impression of Change scales (days 4 and 8), both answered and recorded by the patient.

RESULTS

Of the 46 patients who completed treatment, 24 (52%) were men and 22 (48%) were women. The average age was 35.6 ± 12.28 years (range 18 to 61 years). The average duration of the evolution of illness at the time of diagnosis was 0.85 ± 0.73 days (maximum 2 days). On day 4 after the diagnosis, 20% reported pain and 2% reported fever, but on day 8, no patient reported pain or fever. On day 4, 70% of patients in the Sb group and 26% in the placebo group reported improvement (P = 0.03), based on the Patients' Global Impression of Change scale, which assesses patient's rating of overall improvement. These findings suggest that 3 to 4 days of treatment with Sb helped to improve symptoms of diarrhoea caused by a virus.

CONCLUSION

Treatment with Sb on acute inflammatory diarrhoea of viral aetiology shows no changes regarding the severity of the symptoms; nevertheless, it seems to impact improvement positively.

TRIAL REGISTRATION

22CEI00320171130 dated on 16/12/2020, NCT05226052 dated on 07/02/2022.

Norovirus and sapovirus infections after allogeneic hematopoietic stem cell transplantation: is it worth it to look for them?

Norovirus (NoV) and Sapovirus (SaV) are potential causative agents of diarrhea after allogeneic HSCT but little is known in this population. We performed a retrospective analysis by RT-PCR of calicivirus (NoV and SaV), Human adenovirus (HAdV), rotavirus (RV), Aichi virus (AiV), enterovirus (EV), human parechovirus (HPeV) and Human bocavirus (HBoV) in the diarrheal stools of patients after allogeneic HSCT. 49/162 patients had positive viral assays: HAdV (17%), EV (7%), NoV (4.3%), RV and HBoV (3.1% each), SaV (1.9%), AiV (1.2%), HPeV (0.6%). Seven patients were positive for NoV and 3 for SaV. Among viruses-positive samples, the frequency of caliciviruses cases was 7% in the 6 months post-HSCT compared to 40% after (p < 0.0001). The median duration of symptom was 0.7 months but 2 cases, occurring more than one year after HSCT, were chronic, undiagnosed and strongly contributed to morbidity. Systematic testing of caliciviruses appears especially useful in late chronic diarrhea.

Immune responses in healthy adults elicited by a bivalent norovirus vaccine candidate composed of GI.4 and GII.4 VLPs without adjuvant

The development of an efficacious vaccine against norovirus is of paramount importance given its potential to reduce the global burden of norovirus-associated morbidity and mortality. Here, we report a detailed immunological analysis of a phase I, double-blind, placebo-controlled clinical trial performed on 60 healthy adults, ages 18 to 40. Total serum immunoglobulin and serum IgA against vaccine strains and cross-reactive serum IgG against non-vaccine strains were measured by enzyme immunoassays, whereas cell-mediated immune responses were quantified using intracellular cytokine staining by flow cytometry. A significant increase in humoral and cellular responses, e.g., IgA and CD4⁺ polypositive T cells, was triggered by the GI.4 Chiba 407 (1987) and GII.4 Aomori 2 (2006) VLP-based norovirus vaccine candidate rNV-2v, which is formulated without adjuvant. No booster effect was observed after the second administration in the pre-exposed adult study population. Furthermore, a cross-reactive immune response was elicited, as shown by IgG titers against GI.3 (2002), GII.2 OC08154 (2008), GII.4 (1999), GII.4 Sydney (2012), GII.4 Washington (2018), GII.6 Maryland (2018), and GII.17 Kawasaki 308 (2015). Due to viral infection via mucosal gut tissue and the high variety of potentially relevant norovirus strains, a focus should be on IgA and cross-protective humoral and cell-mediated responses in the development of a broadly protective, multi-valent norovirus vaccine.

Clinical trial registration

https://clinicaltrials.gov, identifier NCT05508178. EudraCT number: 2019-003226-25.

Prevalence and Etiological Characteristics of Norovirus Infection in China: A Systematic Review and Meta-Analysis

Norovirus is a common cause of sporadic cases and outbreaks of gastroenteritis worldwide, although its prevalence and the dominant genotypes responsible for gastroenteritis outbreaks remain obscure. A systematic review was conducted on norovirus infection in China between January 2009 and March 2021. A meta-analysis and beta-binomial regression model were used to explore the epidemiological and clinical characteristics of norovirus infection and the potential factors contributing to the attack rate of the norovirus outbreaks, respectively. A total of 1132 articles with 155,865 confirmed cases were included, with a pooled positive test rate of 11.54% among 991,786 patients with acute diarrhea and a pooled attack rate of 6.73% in 500 norovirus outbreaks. GII.4 was the predominant genotype in both the etiological surveillance and outbreaks, followed by GII.3 in the etiological surveillance, and GII.17 in the outbreaks, with the proportion of recombinant genotypes increasing in recent years. A higher attack rate in the norovirus outbreaks was associated with age group (older adults), settings (nurseries, primary schools, etc.) and region (North China). The nation-wide pooled positive rate in the etiological surveillance of norovirus is lower than elsewhere in the global population, while the dominant genotypes are similar in both the etiological surveillance and the outbreak investigations. This study contributes to the understanding of norovirus infection with different genotypes in China. The prevention and control of norovirus outbreaks during the cold season should be intensified, with special attention paid to and enhanced surveillance performed in nurseries, schools and nursing homes from November to March.

Species-Specific N-Glycomes and Methylation Patterns of Oysters Crassostrea gigas and Ostrea edulis and Their Possible Consequences for the Norovirus-HBGA Interaction

Noroviruses, the major cause of acute viral gastroenteritis, are known to bind to histo-blood group antigens (HBGAs), including ABH groups and Lewis-type epitopes, which decorate the surface of erythrocytes and epithelial cells of their host tissues. The biosynthesis of these antigens is controlled by several glycosyltransferases, the distribution and expression of which varies between tissues and individuals. The use of HBGAs as ligands by viruses is not limited to humans, as many animal species, including oysters, which synthesize similar glycan epitopes that act as a gateway for viruses, become vectors for viral infection in humans. Here, we show that different oyster species synthesize a wide range of N-glycans that share histo-blood A-antigens but differ in the expression of other terminal antigens and in their modification by O-methyl groups. In particular, we show that the N-glycans isolated from Crassostrea gigas and Ostrea edulis exhibit exquisite methylation patterns in their terminal N-acetylgalactosamine and fucose residues in terms of position and number, adding another layer of complexity to the post-translational glycosylation modifications of glycoproteins. Furthermore, modeling of the interactions between norovirus capsid proteins and carbohydrate ligands strongly suggests that methylation has the potential to fine-tune the recognition events of oysters by virus particles.

Advances in paper based isothermal nucleic acid amplification tests for water-related infectious diseases

Water-associated or water-related infectious disease outbreaks are caused by pathogens such as bacteria, viruses, and protozoa, which can be transmitted through contaminated water sources, poor sanitation practices, or insect vectors. Low- and middle-income countries bear the major burden of these infections due to inadequate hygiene and subpar laboratory facilities, making it challenging to monitor and detect infections in a timely manner. However, even developed countries are not immune to these diseases, as inadequate wastewater management and contaminated drinking water supplies can also contribute to disease outbreaks. Nucleic acid amplification tests have proven to be effective for early disease intervention and surveillance of both new and existing diseases. In recent years, paper-based diagnostic devices have made significant progress and become an essential tool in detecting and managing water-associated diseases. In this review, we highlight the importance of paper and its variants as a diagnostic tool and discuss the properties, design modifications, and various paper-based device formats developed and used for detecting water-associated pathogens.

Molecular and Genetics-Based Systems for Tracing the Evolution and Exploring the Mechanisms of Human Norovirus Infections

Human noroviruses (HuNoV) are major causes of acute gastroenteritis around the world. The high mutation rate and recombination potential of noroviruses are significant challenges in studying the genetic diversity and evolution pattern of novel strains. In this review, we describe recent advances in the development of technologies for not only the detection but also the analysis of complete genome sequences of noroviruses and the future prospects of detection methods for tracing the evolution and genetic diversity of human noroviruses. The mechanisms of HuNoV infection and the development of antiviral drugs have been hampered by failure to develop the infectious virus in a cell model. However, recent studies have demonstrated the potential of reverse genetics for the recovery and generation of infectious viral particles, suggesting the utility of this genetics-based system as an alternative for studying the mechanisms of viral infection, such as cell entry and replication.

HuNoV Non-Structural Protein P22 Induces Maturation of IL-1β and IL-18 and N-GSDMD-Dependent Pyroptosis through Activating NLRP3 Inflammasome

Norovirus infection is the leading cause of foodborne gastroenteritis worldwide, causing more than 200,000 deaths each year. As a result of a lack of reproducible and robust in vitro culture systems and suitable animal models for human norovirus (HuNoV) infection, the pathogenesis of HuNoV is still poorly understood. In recent years, human intestinal enteroids (HIEs) have been successfully constructed and demonstrated to be able to support the replication of HuNoV. The NLRP3 inflammasome plays a key role in host innate immune responses by activating caspase1 to facilitate IL-1β and IL-18 secretion and N-GSDMD-driven apoptosis, while NLRP3 inflammasome overactivation plays an important role in the development of various inflammatory diseases. Here, we found that HuNoV activated enteric stem cell-derived human intestinal enteroids (HIEs) NLRP3 inflammasome, which was confirmed by transfection of Caco2 cells with full-length cDNA clones of HuNoV. Further, we found that HuNoV non-structural protein P22 activated the NLRP3 inflammasome and then matured IL-1β and IL-18 and processed the cleavage of gasdermin-D (GSDMD) to N-GSDMD, leading to pyroptosis. Besides, berberine (BBR) could ameliorate the pyroptosis caused by HuNoV and P22 by inhibiting NLRP3 inflammasome activation. Together, these results reveal new insights into the mechanisms of inflammation and cell death caused by HuNoV and provide potential treatments.

Infections after organ transplantation and immune response

Organ transplantation has provided another chance of survival for end-stage organ failure patients. Yet, transplant rejection is still a main challenging factor. Immunosuppressive drugs have been used to avoid rejection and suppress the immune response against allografts. Thus, immunosuppressants increase the risk of infection in immunocompromised organ transplant recipients. The infection risk reflects the relationship between the nature and severity of immunosuppression and infectious diseases. Furthermore, immunosuppressants show an immunological impact on the genetics of innate and adaptive immune responses. This effect usually reactivates the post-transplant infection in the donor and recipient tissues since T-cell activation has a substantial role in allograft rejection. Meanwhile, different infections have been found to activate the T-cells into CD₄⁺ helper T-cell subset and CD₈⁺ cytotoxic T-lymphocyte that affect the infection and the allograft. Therefore, the best management and preventive strategies of immunosuppression, antimicrobial prophylaxis, and intensive medical care are required for successful organ transplantation. This review addresses the activation of immune responses against different infections in immunocompromised individuals after organ transplantation.

Norovirus MLKL-like protein initiates cell death to induce viral egress

Non-enveloped viruses require cell lysis to release new virions from infected cells, suggesting that these viruses require mechanisms to induce cell death. Noroviruses are one such group of viruses, but there is no known mechanism that causes norovirus infection-triggered cell death and lysis1-3. Here we identify a molecular mechanism of norovirus-induced cell death. We found that the norovirus-encoded NTPase NS3 contains an N-terminal four-helix bundle domain homologous to the membrane-disruption domain of the pseudokinase mixed lineage kinase domain-like (MLKL). NS3 has a mitochondrial localization signal and thus induces cell death by targeting mitochondria. Full-length NS3 and an N-terminal fragment of the protein bound the mitochondrial membrane lipid cardiolipin, permeabilized the mitochondrial membrane and induced mitochondrial dysfunction. Both the N-terminal region and the mitochondrial localization motif of NS3 were essential for cell death, viral egress from cells and viral replication in mice. These findings suggest that noroviruses have acquired a host MLKL-like pore-forming domain to facilitate viral egress by inducing mitochondrial dysfunction.

Elucidating the Implications of Norovirus N- and O-Glycosylation, O-GlcNAcylation, and Phosphorylation

Norovirus is the most common cause of foodborne gastroenteritis, affecting millions of people worldwide annually. Among the ten genotypes (GI-GX) of norovirus, only GI, GII, GIV, GVIII, and GIX infect humans. Some genotypes reportedly exhibit post-translational modifications (PTMs), including N- and O-glycosylation, O-GlcNAcylation, and phosphorylation, in their viral antigens. PTMs have been linked to increased viral genome replication, viral particle release, and virulence. Owing to breakthroughs in mass spectrometry (MS) technologies, more PTMs have been discovered in recent years and have contributed significantly to preventing and treating infectious diseases. However, the mechanisms by which PTMs act on noroviruses remain poorly understood. In this section, we outline the current knowledge of the three common types of PTM and investigate their impact on norovirus pathogenesis. Moreover, we summarize the strategies and techniques for the identification of PTMs.

Norovirus MLKL-like pore forming protein initiates programed cell death for viral egress

Non-enveloped viruses require cell lysis to release new virions from infected cells, suggesting that these viruses require mechanisms to induce cell death. Noroviruses are one such group of viruses, but a mechanism of norovirus-infection triggered cell death and lysis are unknown. Here we have identified a molecular mechanism of norovirus-induced cell death. We found that the norovirus-encoded NTPase contains a N-terminal four helix bundle domain homologous to the pore forming domain of the pseudokinase Mixed Lineage Kinase Domain-Like (MLKL). Norovirus NTPase acquired a mitochondrial localization signal, thereby inducing cell death by targeting mitochondria. NTPase full length (NTPase-FL) and N-terminal fragment (NTPase-NT) bound mitochondrial membrane lipid cardiolipin, permeabilized mitochondrial membrane and induced mitochondrial dysfunction. Both the N-terminal region and the mitochondrial localization motif of NTPase were essential for cell death, virus egress from cells and virus replication in mice. These findings suggest that noroviruses stole a MLKL-like pore forming domain and co-opted it to facilitate viral egress by inducing mitochondrial dysfunction.

In vivo efficacy of alcohol based hand rubs against noroviruses: A novel standardized European test method simulating practical conditions

BACKGROUND

Non-enveloped viruses are particularly resistant to disinfectants, so to prevent and control the spread of virus infections, disinfectants with proven virucidal activity must be used. However, a test such as EN 1500, which uses an internal standard as reference treatment for determining the bactericidal efficacy of hand rubs, is still lacking. We aimed to establish a European standard for testing the in vivo efficacy of hand rubs against non-enveloped viruses.

METHOD

First, concentration and mode of application of ethanol as reference were determined. Afterwards, the efficacies of two commonly used hand rubs were compared to this reference. Hands of volunteers were contaminated with the murine norovirus strain S99.

RESULTS

70% wt/wt ethanol (2 x 3 mL in 2 x 30 seconds) was defined as internal reference treatment. The commercial ethanol based hand rub could significantly reduce the titre of norovirus in 30 seconds whereas a rub based on ethanol and propan-2-ol was significantly less effective compared to the reference.

CONCLUSION

We have established a possible standard for testing the in vivo efficacy of hand rubs against non-enveloped viruses using murine norovirus, a low contamination volume technique and ethanol as internal reference. Nevertheless our findings have to be confirmed in European ring trials.

Persistence of Human Norovirus (GII) in Surface Water: Decay Rate Constants and Inactivation Mechanisms

Human norovirus (HuNoV) is an important cause of acute gastroenteritis and can be transmitted by water exposures, but its persistence in water is not well understood. Loss of HuNoV infectivity in surface water was compared with persistence of intact HuNoV capsids and genome segments. Surface water from a freshwater creek was filter-sterilized, inoculated with HuNoV (GII.4) purified from stool, and incubated at 15 or 20 °C. We measured HuNoV infectivity via the human intestinal enteroid system and HuNoV persistence via reverse transcription-quantitative polymerase chain reaction assays without (genome segment persistence) or with (intact viral capsid persistence) enzymatic pretreatment to digest naked RNA. For infectious HuNoV, results ranged from no significant decay to a decay rate constant ("k") of 2.2 day^-1. In one creek water sample, genome damage was likely a dominant inactivation mechanism. In other samples from the same creek, loss of HuNoV infectivity could not be attributed to genome damage or capsid cleavage. The range in k and the difference in the inactivation mechanism observed in water from the same site could not be explained, but variable constituents in the environmental matrix could have contributed. Thus, a single k may be insufficient for modeling virus inactivation in surface waters.

A “peptide-target-aptamer” electrochemical biosensor for norovirus detection using a black phosphorous nanosheet@Ti3C2-Mxene nanohybrid and magnetic covalent organic framework

Norovirus (NoV) is a major foodborne pathogen responsible for acute gastroenteritis epidemics, and establishing a robust detection method for the timely identification and monitoring of NoV contamination is of great significance. In this study, a peptide-target-aptamer sandwich electrochemical biosensor for NoV was fabricated using Au@BP@Ti₃C₂-MXene and magnetic Au@ZnFe₂O₄@COF nanocomposites. The response currents of the electrochemical biosensor were proportional to the NoV concentrations ranging from 0.01-10⁵ copies/mL with a detection limit (LOD) of 0.003 copies/mL (S/N = 3). To our best knowledge, this LOD was the lowest among published assays to date, due to the specific recognition of the affinity peptide and aptamer for NoV and the outstanding catalytic activity of nanomaterials. Furthermore, the biosensor showed excellent selectivity, anti-interference performance, and satisfactory stability. The NoV concentrations in simulative food matrixes were successfully detected using the constructed biosensor. Meanwhile, NoV in stool samples was also successfully quantified without complex pretreatment. The designed biosensor had the potential to detect NoV (even at a low level) in foods, clinical samples, and environmental samples, providing a new method for NoV detection in food safety and diagnosing foodborne pathogens.

Epidemiology and Economic Burden of Acute Infectious Gastroenteritis Among Adults Treated in Outpatient Settings in US Health Systems

INTRODUCTION

Acute infectious gastroenteritis (AGE) is a common reason for outpatient visits and hospitalizations in the United States. This study aimed to understand the demographic and clinical characteristics, common pathogens detected, health care resource utilization (HRU), and cost among adult outpatients with AGE visiting US health systems.

METHODS

A retrospective cohort study was conducted using one of the largest hospital discharge databases (PINC AI Healthcare Database) in the United States. Adult patients (aged ≥18 years) with a principal diagnosis of AGE during an outpatient visit between January 1, 2016, and June 30, 2021, were included. Pathogen detection analysis was performed in those with microbiology data available.

RESULTS

Among 248,896 patients, the mean age was 44.3 years (range 18-89+ years), 62.9% were female, and 68.5% were White. More than half (62.0%) of the patients did not have any preexisting comorbidity, and only 18.3% underwent stool workup at the hospital. Most patients (84.7%) were seen in the emergency department, and most (96.4%) were discharged home. Within 30 days of discharge, 1.0% were hospitalized, and 2.8% had another outpatient visit due to AGE. The mean cost of the index visit plus 30-day AGE-related follow-up was $1,338 per patient, amounting to $333,060,182 for the total study population. Among patients with microbiology data available (n = 12,469), common pathogens detected were Clostridioides difficile (32.2%), norovirus (6.3%), and Campylobacter spp. (4.0%).

DISCUSSION

AGE is a common and costly disease affecting adults of all ages and more females than males, including individuals with or without baseline conditions in a hospital-based outpatient setting. C. difficile was the most common pathogen detected.

High yield production of norovirus GII.4 virus-like particles using silkworm pupae and evaluation of their protective immunogenicity

Noroviruses (NoVs) are one of the major causes of acute viral gastroenteritis in humans. Virus-like particles (VLPs) without genomes that mimic the capsid structure of viruses are promising vaccine candidates for the prevention of NoVs infection. To produce large amounts of recombinant protein, including VLPs, the silkworm-expression vector system (silkworm-BEVS) is an efficient and powerful tool. In this study, we constructed a recombinant baculovirus that expresses VP1 protein, the major structural protein of NoV GII.4. Expression analysis showed that the baculovirus-infected silkworm pupae expressed NoV VP1 protein more efficiently than silkworm larval fat bodies. We obtained about 4.9 mg of purified NoV VP1 protein from only five silkworm pupae. The purified VP1 protein was confirmed by dynamic light scattering and electron microscopy to form VLPs of approximately 40 nm in diameter. Antisera from mice immunized with the antigen blocked NoV VLPs binding to histo-blood group antigens of pig gastric mucin and also blocked NoV infection in intestinal epithelial cells derived from human induced pluripotent stem (iPS) cells. Our findings demonstrated that NoV VLP eliciting protective antibodies could be obtained in milligram quantities from a few silkworm pupae using the silkworm-BEVS.

Norovirus: An Overview of Virology and Preventative Measures

Norovirus (NoV) is an enteric non-enveloped virus which is the leading cause of gastroenteritis across all age groups. It is responsible for around 200,000 deaths annually and outbreaks are common in small communities such as educational and care facilities. 40% of all NoV outbreaks occur in long-term and acute-care facilities, forming the majority of outbreaks. Nosocomial settings set ideal environments for ease of transmission, especially due to the presence of immunocompromised groups. It is estimated to cost global economies around £48 billion a year, making it a global issue. NoV is transmitted via the faecal-oral route and infection with it results in asymptomatic cases or gastrointestinal disease. It has high mutational rates and this allows for new variants to emerge and be more resistant. The classification system available divides NoV into 10 genogroups and 49 genotypes based on whole amino acid sequencing of VP1 capsid protein and partial sequencing of RdRp, respectively. The most predominant genotypes which cause gastroenteritis in humans include GI.1 and GII.4, where GII.4 is responsible for more extreme clinical implications such as hospitalisation. In addition, GII.4 has been responsible for 6 pandemic strains, the last of which is the GII.4 Sydney (2012) variant. In recent years, the successful cultivation of HuNoV was reported in stem cell-derived human intestinal enteroids (HIEs), which promises to assist in giving a deeper understanding of its underlying mechanisms of infection and the development of more personalized control measures. There are no specific control measures against NoV, therefore common practices are used against it such as hand washing. No vaccine is available, but the HIL-214 candidate passed clinical phase 2b and shows promise.

Genetic characteristics of archival noroviruses detected from the 1970s to the 1990s

The genetic characterization of archival specimens is important for evaluating the evolutionary processes of noroviruses. Complete viral genome sequences, GVIII.1[GII.P28] and GIX.1[GII.P15], were determined from two archival specimens collected in Tokyo, Japan, in 1986 and 1995. In addition, complete VP1 and partial RdRp sequences of four samples collected between 1975 and 1983 were determined. Two viruses were classified as GI.5[P5] and GI.9[P9]; however, the viruses from the other two samples could not be assigned to any known genotypes using norovirus typing tools and phylogenetic analysis, suggesting that they might be untypable genotypes. Further evolutionary analysis of these viruses is warranted.

A randomized, double-blind, placebo-controlled, dose-escalating phase I trial to evaluate safety and immunogenicity of a plant-produced, bivalent, recombinant norovirus-like particle vaccine

Noroviruses (NoV) are the leading cause of epidemic acute gastroenteritis in humans worldwide and a safe and effective vaccine is needed. Here, a phase I, double-blind, placebo-controlled clinical trial was performed in 60 healthy adults, 18 to 40 years old. Safety (primary objective) and immunogenicity (secondary and exploratory objectives) of a bivalent (GI.4 and GII.4), plant-produced, virus-like particle (VLP), NoV vaccine candidate formulation were investigated at two dose levels (50 µg + 50 µg and 150 µg + 150 µg) without adjuvant. Overall, 13 subjects (65.0%) in the 50 µg group, 16 subjects (80.0%) in the 150 µg group, and 14 subjects (70.0%) in the placebo group reported at least 1 solicited local or general symptom during the 7-day post-vaccination periods following each dose. Severe solicited adverse events (AEs) were rare (2 events in the 50 µg group). A total of 8 subjects (40.0%) in each group reported at least one unsolicited AE during the 28-day post-vaccination periods. Immunogenicity was assessed on days 1, 8, 29, 57, 183 and 365. All subjects were pre-exposed to norovirus as indicated by baseline levels of the different immunological parameters examined. Vaccine-specific humoral and cellular immune responses increased after the first dose but did not rise further after the second vaccination. Increased GI.4- and GII.4-specific IgG titers persisted until day 365. The vaccine elicited cross-reactive IgG antibodies against non-vaccine NoV VLPs, which was more pronounced for NoV strains of the same genotype as the GII.4 vaccine strain than for non-vaccine genotypes. Significant blocking anti-GI.4 and anti-GII.4 VLP titers were triggered in both dose groups. Lymphoproliferation assays revealed strong cell-mediated immune responses that persisted until day 365. In conclusion, both dose levels were safe and well-tolerated, and no higher incidence of AEs was observed in the higher dose group. The data show that a single dose of the vaccine formulated at 50 µg of each VLP is sufficient to reach a peak immune response after 8 to 28 days. The results of this Phase I study warrant further evaluation of the non-adjuvanted vaccine candidate.

Gut as an Alternative Entry Route for SARS-CoV-2: Current Evidence and Uncertainties of Productive Enteric Infection in COVID-19

The gut has been proposed as a potential alternative entry route for SARS-CoV-2. This was mainly based on the high levels of SARS-CoV-2 receptor expressed in the gastrointestinal (GI) tract, the observations of GI disorders (such as diarrhea) in some COVID-19 patients and the detection of SARS-CoV-2 RNA in feces. However, the underlying mechanisms remain poorly understood. It has been proposed that SARS-CoV-2 can productively infect enterocytes, damaging the intestinal barrier and contributing to inflammatory response, which might lead to GI manifestations, including diarrhea. Here, we report a methodological approach to assess the evidence supporting the sequence of events driving SARS-CoV-2 enteric infection up to gut adverse outcomes. Exploring evidence permits to highlight knowledge gaps and current inconsistencies in the literature and to guide further research. Based on the current insights on SARS-CoV-2 intestinal infection and transmission, we then discuss the potential implication on clinical practice, including on long COVID. A better understanding of the GI implication in COVID-19 is still needed to improve disease management and could help identify innovative therapies or preventive actions targeting the GI tract.

Ultrasensitive and visual detection of human norovirus genotype GII.4 or GII.17 using CRISPR-Cas12a assay

Background

Integrating CRISPR-Cas12a sensors with isothermal signal amplification can be exploited to develop low-cost, disposable, and ultrasensitive assays for the diagnostics of human pathogens.

Methods

RT-RAA-Cas12a-mediated real-time or end-point fluorescent and lateral flow strip (LFS) assays for direct detection of norovirus (NOV) genotype GII.4 or GII.17 were explored.

Results

The results showed that our RT-RAA-Cas12a-mediated fluorescent and LFS assay could detect NOV GII.4 or GII.17 by targeting the viral protein 1 gene. Our RT-RAA-Cas12a-mediated fluorescent and LFS assay can specifically detect NOV GII.4 or GII.17 with no cross-reactivity for other related viruses. The low limit of detection could reach 0.1 copies/μL within approximately 30–40 min, and the results were visualized using an ultraviolet light illuminator or on a LFS without complex equipment. In addition, our RT-RAA-Cas12a-mediated fluorescent and LFS assay provided a visual and faster alternative to real-time RT-PCR assay, with 95.7% and 94.3% positive predictive agreement and 100% negative predictive agreement.

Conclusions

Together, our RT-RAA-Cas12a-mediated approach would have a great potential for point-of-care diagnostics of NOV GII.4 and/or GII.17 in resource-limited settings.

Selective Polyprotein Processing Determines Norovirus Sensitivity to Trim7

Noroviruses are a leading cause of gastroenteritis worldwide, yet the molecular mechanisms of how host antiviral factors restrict norovirus infection are poorly understood. Here, we present a CRISPR activation screen that identifies mouse genes which inhibit murine norovirus (MNV) replication. Detailed analysis of the major hit Trim7 demonstrates a potent inhibition of the early stages of MNV replication. Leveraging in vitro evolution, we identified MNV mutants that escape Trim7 restriction by altering the cleavage of the viral NS6-7 polyprotein precursor. NS6, but not the NS6-7 precursor, directly binds the substrate-binding domain of Trim7. Surprisingly, the selective polyprotein processing that enables Trim7 evasion inflicts a significant evolutionary burden, as viruses with decreased NS6-7 cleavage are strongly attenuated in viral replication and pathogenesis. Our data provide an unappreciated mechanism of viral evasion of cellular antiviral factors through selective polyprotein processing and highlight the evolutionary tradeoffs in acquiring resistance to host restriction factors. IMPORTANCE To maximize a limited genetic capacity, viruses encode polyproteins that can be subsequently separated into individual components by viral proteases. While classically viewed as a means of economy, recent findings have indicated that polyprotein processing can spatially and temporally coordinate the distinct phases of the viral life cycle. Here, we present a function for alternative polyprotein processing centered on immune defense. We discovered that selective polyprotein processing of the murine norovirus polyprotein shields MNV from restriction by the host antiviral protein Trim7. Trim7 can bind the viral protein NS6 but not the viral precursor protein NS6-7. Our findings provide insight into the evolutionary pressures that define patterns of viral polyprotein processing and uncover a trade-off between viral replication and immune evasion.

Norovirus outbreaks in China, 2000-2018: A systematic review

To understand epidemiological characteristics of norovirus outbreaks in China from 2000 to 2018 the literature on norovirus outbreaks was identified by searching WANFANG, CNKI, PubMed, and Web of Science databases before 31 December 2018. Statistical analyses were performed using Statistical Product Service Solutions software. RStudio1.4.1717 and ArcGIS trial version were used for plotting bar graphs and maps. A total of 419 norovirus outbreaks were reported in the 394 included articles, which occurred between June 2000 and October 2018, showing an overall increasing trend. The majority of outbreaks occurred in schools (52.28%, 218/417) and kindergartens (55/417, 13.19%). Person-to-person transmission (41.64%, 137/329) was most common, followed by food-borne transmission (75/329, 22.80%) and water-borne transmission (72/329, 21.88%). GII was the most predominant norovirus genogroup, with GII.4, GII.17 and GII.2 being the dominant genotypes in 2007-2013, 2014-2015, 2016-2017, respectively. Increased outbreaks were associated with the prevalence of new variants. Most norovirus outbreaks were reported in the southeast of the country. The number of norovirus outbreaks was positively associated with the per capita gross domestic product and the year-end resident population. Norovirus outbreaks have become an important public health problem in China. It is necessary to establish surveillance in hospitals and nursing homes. Genotyping of noroviruses is important for monitoring the circulating strains and improving the vaccine design, so it should be carried out in more regions.

Can cases and outbreaks of norovirus in children provide an early warning of seasonal norovirus infection: an analysis of nine seasons of surveillance data in England UK

Background

Children are important transmitters of norovirus infection and there is evidence that laboratory reports in children increase earlier in the norovirus season than in adults. This raises the question as to whether cases and outbreaks in children could provide an early warning of seasonal norovirus before cases start increasing in older, more vulnerable age groups.

Methods

This study uses weekly national surveillance data on reported outbreaks within schools, care homes and hospitals, general practice (GP) consultations for infectious intestinal disease (IID), telehealth calls for diarrhoea and/or vomiting and laboratory norovirus reports from across England, UK for nine norovirus seasons (2010/11–2018/19). Lagged correlation analysis was undertaken to identify lead or lag times between cases in children and those in adults for each surveillance dataset. A partial correlation analysis explored whether school outbreaks provided a lead time ahead of other surveillance indicators, controlling for breaks in the data due to school holidays. A breakpoint analysis was used to identify which surveillance indicator and age group provided the earliest warning of the norovirus season each year.

Results

School outbreaks occurred 3-weeks before care home and hospital outbreaks, norovirus laboratory reports and NHS 111 calls for diarrhoea, and provided a 2-week lead time ahead of NHS 111 calls for vomiting. Children provided a lead time ahead of adults for norovirus laboratory reports (+ 1–2 weeks), NHS 111 calls for vomiting (+ 1 week) and NHS 111 calls for diarrhoea (+ 1 week) but occurred concurrently with adults for GP consultations. Breakpoint analysis revealed an earlier seasonal increase in cases among children compared to adults for laboratory, GP and NHS 111 data, with school outbreaks increasing earlier than other surveillance indicators in five out of nine surveillance years.

Conclusion

These findings suggest that monitoring cases and outbreaks of norovirus in children could provide an early warning of seasonal norovirus infection. However, both school outbreak data and syndromic surveillance data are not norovirus specific and will also capture other causes of IID. The use of school outbreak data as an early warning indicator may be improved by enhancing sampling in community outbreaks to confirm the causative organism.

Recent Advances in Early Diagnosis of Viruses Associated with Gastroenteritis by Biosensors

Gastroenteritis, as one of the main worldwide health challenges, especially in children, leads to 3–6 million deaths annually and causes nearly 20% of the total deaths of children aged ˂5 years, of which ~1.5 million gastroenteritis deaths occur in developing nations. Viruses are the main causative agent (~70%) of gastroenteritis episodes and their specific and early diagnosis via laboratory assays is very helpful for having successful antiviral therapy and reduction in infection burden. Regarding this importance, the present literature is the first review of updated improvements in the employing of different types of biosensors such as electrochemical, optical, and piezoelectric for sensitive, simple, cheap, rapid, and specific diagnosis of human gastroenteritis viruses. The Introduction section is a general discussion about the importance of viral gastroenteritis, types of viruses that cause gastroenteritis, and reasons for the combination of conventional diagnostic tests with biosensors for fast detection of viruses associated with gastroenteritis. Following the current laboratory detection tests for human gastroenteritis viruses and their limitations (with subsections: Electron Microscope (EM), Cell Culture, Immunoassay, and Molecular Techniques), structural features and significant aspects of various biosensing methods are discussed in the Biosensor section. In the next sections, basic information on viruses causing gastroenteritis and recent developments for fabrication and testing of different biosensors for each virus detection are covered, and the prospect of future developments in designing different biosensing platforms for gastroenteritis virus detection is discussed in the Conclusion and Future Directions section as well.

Inanimate Surfaces as a Source of Hospital Infections Caused by Fungi, Bacteria and Viruses with Particular Emphasis on SARS-CoV-2

The carriers of nosocomial infections are the hands of medical personnel and inanimate surfaces. Both hands and surfaces may be contaminated as a result of contact with the patient, their body fluids, and touching contaminated surfaces in the patient’s surroundings. Visually clean inanimate surfaces are an important source of pathogens. Microorganisms have properties thanks to which they can survive in unfavorable conditions, from a few days to several months. Bacteria, viruses and fungi are able to transmit from inanimate surfaces to the skin of the patient and the medical staff. These pathogens include SARS-CoV-2, which can survive on various types of inanimate surfaces, being a potential source of infection. By following the recommendations related to washing and disinfecting hands and surfaces, and using appropriate washing and disinfecting agents with a broad biocidal spectrum, high material compatibility and the shortest duration of action, we contribute to breaking the chain of nosocomial infections.

Immunodominant B-Cell Linear Epitope on the VP1 P Domain of a Feline Norovirus Cat Model

Norovirus (NoV) infection remains a major public health concern worldwide. Appropriate animal models are essential for the development of effective NoV vaccines. We previously established the feline NoV (FNoV)-cat model as a surrogate animal model for human NoV infection. In the present study, we analyzed the B-cell linear epitope in the P domain of FNoV to confirm the basic immunological features of the FNoV-cat model. B-cell linear epitopes were present in the P2 subdomain. We compared antibody levels to peptides containing the B-cell linear epitope (P-10) in three FNoV-infected cats with time-course changes in viral load and symptom scoring. After FNoV infection, viral shedding and clinical symptoms were shown to improve by elevated levels of antibodies against P-10 in the plasma. This report provides important information for understanding NoV infections in humans and cats.

The role of gastrointestinal pathogen PCR testing in liver transplant recipients hospitalized with diarrhea

BACKGROUND

Diarrhea is a common symptom among liver transplant (LT) recipients and can result in significant morbidity. The utility of PCR-based multiplex gastrointestinal (GI) pathogen panels in this population is unknown.

METHODS

We assessed incidence, predictors, and outcomes of GI PCR positivity among inpatients who underwent stool pathogen testing with the FilmArray multiplex GI PCR panel at our institution within 1 year following LT from April 2015 to December 2019.

RESULTS

112 patients were identified. 14 (12.5%) had a positive PCR for any pathogen. Escherichia coli (n = 9) and Norovirus (n = 5) were the most common pathogens detected. Recipients with a positive PCR were significantly further from LT (median 74.5 vs 15.5 days, p < 0.01) and tested earlier during hospitalization (median 1.0 vs 9.0 days, p < 0.01). C. difficile was positive in 20.0% of patients with a positive PCR and 11.4% with a negative PCR. CMV viremia was observed in 11.6% of patients, all in the negative PCR group. Following a positive PCR, patients were more likely to have a change in antimicrobial regimen (71.4% vs 28.6%, p = 0.02), a shorter length of stay (median 7.5 vs. 17.5 days, p < 0.01), and a trend toward lower rates of readmission and colonoscopy within 30 days.

CONCLUSIONS

In hospitalized LT recipients with diarrhea, GI PCR pathogen identification was associated with the use of targeted antimicrobial therapy and a shorter length of stay. GI PCR testing should be considered early during admission and later in the post-LT period. This article is protected by copyright. All rights reserved.