Norovirus Vaccine: Priorities for Future Research and Development

CRISPR/Cas12-mediated detection of GI and GII Norovirus in different food samples

Norovirus is one of the leading causes of infectious diarrhea, occurring in about 18% of diarrhea cases worldwide. Norovirus is characterized by a low infectious dose, rapid onset, and strong transmission capacity. Given the lack of specific drugs and vaccines, developing efficient and accurate detection technologies is of great significance to prevent and control the spread of diseases. This study combined the reverse transcription loop-mediated isothermal amplification (RT-LAMP) technology with the clustered regularly interspaced short palindromic repeats (CRISPR) technology to develop a sensitive and rapid detection method, which can reduce the reliance on temperature control and expensive real-time fluorescent polymerase chain reaction (PCR) devices. The RT-LAMP/CRISPR Cas12a method demonstrated good specificity and sensitivity, testing food samples of three different substrates with 100% positive qualitative accuracy. The detection sensitivity is 32.8 copies/reaction for Norovirus GI and 22.8 copies/reaction for Norovirus GII. This method helps to effectively identify food products contaminated with Norovirus, thereby preventing human infections and economic losses due to disease outbreaks.

Plant-Made Vaccines Targeting Enteric Pathogens-Safe Alternatives for Vaccination in Developing Countries

Enteric diseases by pathogenic organisms are one of the leading causes of death worldwide, particularly in low-income countries. Despite antibiotics, access to clean water and vaccination are the most economically affordable options to prevent those infections and their health consequences. Vaccines, such as those approved for rotavirus and cholera, have played a key role in preventing several enteric diseases. However, vaccines for other pathogens are still in clinical trials. Distribution and cost remain significant barriers to vaccine access in developing regions due to poor healthcare infrastructure, cold-chain requirements, and high production costs. Plant-made vaccines offer a promising alternative to address these challenges. Plants can be easily grown, lowering production costs, and can be administered in oral forms, potentially eliminating cold-chain dependency. Although there are some promising prototypes of vaccines produced in plants, challenges remain, including yields and achieving sufficient immunogenicity. This review aims to describe common enteric pathogens and available vaccines, followed by a strategic summary of plant-made vaccine development and a discussion of plant-made enteric vaccine prototypes. Trends to overcome the key challenges for plant-made vaccines are identified and placed in perspective for the development of affordable and effective vaccines for populations at the highest risk of enteric diseases.

Norovirus Surveillance and Outbreak Investigations in Peru: 25 Years of Experience at NAMRU SOUTH

Norovirus is the worldwide leading cause of gastroenteric diseases. It affects mainly infants and older adults, but the findings are mainly derived from outbreak investigations rather than population-based cohorts. The U. S. Naval Medical Research Unit SOUTH (NAMRU SOUTH) developed and conducted research studies in the last 20 years focusing on the military and general populations afflicted by this pathogen. For the latter, studies included all age groups in 2 main communities in Peru, representing people from the highlands and tropical areas. The results helped elucidate the incidence of norovirus infection among different age groups as well as identifying risk factors, seasonality, and economic burden on the patient. The collected data demonstrate an increase of norovirus cases, not only in the previously reported age groups but also in adults. Consequently, this increase of norovirus cases in adults may impair the occupational productivity in civilian populations and operational readiness among service members.

Replication-deficient Sendai virus expressing human norovirus capsid protein elicits robust NoV-specific antibody and T-cell responses in mice

Human norovirus (HuNoV) is a major global cause of acute gastroenteritis, with vaccine development facing several challenges. Despite years of research, there are currently no licensed vaccines available for controlling HuNoVs. Here, we describe the construction and testing of a replication-deficient Sendai virus (SeV) vector as a potential vaccine candidate against the HuNoV GII.4 genotype. SeV was chosen as the vaccine backbone due to its non-pathogenic nature in humans, its capability for long-term antigen expression in mammalian cells, and its suitability for mucosal administration. By inserting the HuNoV GII.4 capsid gene, VP1, into the SeV genome, we generated a replication-deficient SeV (SeV/dP.VP1) vector. The resultant SeV/dP.VP1 virus were observed to successfully express the inserted NoV VP1 gene upon infection. Inoculating the vaccine into wild-type mice elicited NoV-specific IgG antibodies, along with INF-γ and IL-2-producing T cells, through both intranasal (i.n.) and intramuscular (i.m.) immunization. Furthermore, a significant level of NoV-specific IgA was detected in lung homogenates after i.n. immunization, particularly using a high dose of the viral vector. Additionally, a synergistic effect was observed with heterologous prime-boost regimens using SeV/dP.VP1 and MVA.VP1 vectors, indicating the potential for more robust immune responses when the vaccine design is optimized. Our study demonstrates the potential of a SeV vaccine candidate in eliciting a broad immune response and lays the foundation for further exploration of the SeV vector platform's potential as a HuNoV vaccine. Additionally, the results emphasize the importance of vaccine dosage and administration route, highlighting the need for tailored immunization strategies.

Production of norovirus VLPs of the nine representative genotypes widely distributed in Japan using the silkworm-baculovirus expression vector system

Norovirus (NoV) is one of the major causes of acute viral gastroenteritis in humans. Genetic variation is abundant, and prevalent genotypes vary from year to year and region to region. Since NoVs are difficult to amplify in cultured cells, genome RNA-free virus-like particles (VLPs) that mimic the capsid structure of the virus are promising vaccine candidates for the prevention of NoVs infection, and the development of multivalent VLP vaccines is required to prevent NoV infection in a wide range of genotypes. In this study, we attempted to produce NoV VLPs of the top nine genotypes that have a history of epidemics in Japan using the silkworm-baculovirus expression vector system (silkworm-BEVS), which has a proven track record in the mass production of recombinant proteins. In silkworm pupae infected with recombinant baculoviruses constructed to express VP1s, the major protein that forms VLP, the NoV VP1 protein was expressed in large amounts. Most genotypes of VP1 accumulated in the cytoplasm as soluble proteins, but solubility was reduced for that of two genotypes. VP1s of five genotypes could be purified in large quantities (>0.9 mg per pupa) by a two-step purification process, and gel filtration chromatography analysis confirmed the formation of VLPs. This study demonstrates the utility of silkworm-BEVS in producing NoV VLPs of multiple genotypes and provides the basis for the development of a multivalent vaccine against genetically diverse NoV infections.

Lipid nanoparticles as adjuvant of norovirus VLP vaccine augment cellular and humoral immune responses in a TLR9- and type I IFN-dependent pathway

Norovirus (NoV) virus-like particles (VLPs) adjuvanted with aluminum hydroxide (Alum) are common vaccine candidates in clinical studies. Alum adjuvants usually inefficiently assist recombinant proteins to induce cellular immune responses. Thus, novel adjuvants are required to develop NoV vaccines that could induce both efficient humoral and robust cellular immune responses. Lipid nanoparticles (LNPs) are well-known mRNA delivery vehicles. Increasing evidence suggests that LNPs may have intrinsic adjuvant activity and can be used as adjuvants for recombinant protein vaccines; however, the underlying mechanism remains poorly understood. In this study, we compared the adjuvant effect of LNPs and Alum for a bivalent GI.1/GII.4 NoV VLP vaccine. Compared with Alum, LNP-adjuvanted vaccines induced earlier production of binding, blocking, and neutralizing antibodies and promoted a more balanced IgG2a/IgG1 ratio. It is crucial that LNP-adjuvanted vaccines induced stronger Th1-type cytokine-producing CD4+ T cell and CD8+ T cell responses than Alum. The adjuvant activity of LNPs depended on the ionizable lipid components. Mechanistically, LNPs activated innate immune responses in a type I IFN-dependent manner and were partially dependent on Toll-like receptor (TLR) 9, thus affecting the adaptive immune responses of the vaccine. This conclusion was supported by RNA-seq analysis and in vitro cell experiments and by the deeply blunted T cell responses in IFNαR1-/- mice immunized with LNP-adjuvanted vaccines. This study not only identified LNPs as a high quality adjuvant for NoV VLP vaccines, but also clarified the underlying mechanism of LNPs as a potent immunostimulatory component for improving protein subunit vaccines.IMPORTANCEWith the rapid development of mRNA vaccines, recurrent studies show that lipid nanoparticles (LNPs) have adjuvant activity. However, the mechanism of its adjuvant effect in protein vaccines remains unknown. In this study, we found that the LNP-adjuvanted norovirus bivalent virus-like particle vaccines led to durable antibody responses as well as Th1-type cytokine-producing CD4+ T cell and CD8+ T cell responses, which exceeded the efficiency of the conventional adjuvant aluminum hydroxide. Mechanistically, LNPs activated innate immune responses in a type I IFN-dependent manner and were partially dependent on Toll-like receptor 9, thus affecting the adaptive immune responses of the vaccine. This work unveils that LNPs as a potent immunostimulatory component may be ideal for generating CD8+ T cell and B cell responses for recombinant protein vaccines.

Characteristics of Norovirus capsid protein-specific CD8+ T-Cell responses in previously infected individuals

Norovirus (NV) infection causes acute gastroenteritis in children and adults. Upon infection with NV, specific CD8+ T cells, which play an important role in anti-infective immunity, are activated in the host. Owing to the NV's wide genotypic variability, it is challenging to develop vaccines with cross-protective abilities against infection. To aid effective vaccine development, we examined specific CD8+ T-cell responses towards viral-structural protein (VP) epitopes, which enable binding to host susceptibility receptors. We isolated peripheral blood mononuclear cells from 196 participants to screen and identify predominant core peptides towards NV main and small envelope proteins using ex vivo and in vitro intracellular cytokine staining assays. Human leukocyte antigen (HLA) restriction characteristics were detected using next-generation sequencing. Three conservative immunodominant VP-derived CD8+ T-cell epitopes, VP294-102 (TDAARGAIN), VP2153-161 (RGPSNKSSN), and VP1141-148 (FPHIIVDV), were identified and restrictively presented by HLA-Cw * 0102, HLA-Cw * 0702, and HLA-A *1101 alleles, separately. Our findings provide useful insights into the development of future vaccines and treatments for NV infection.

Human norovirus cultivation models, immune response and vaccine landscape

Norovirus infections are a leading cause of gastroenteritis worldwide. Despite the substantial global health burden and economic impact, there are currently no approved antiviral therapeutics or vaccines. Additionally, much of our knowledge of norovirus comes from experiments using surrogate viruses, such as murine norovirus and feline calicivirus. The challenge surrounding human norovirus research arises from a lack of robust cell culture systems and efficient animal models. In this review, we explore recent advances in the in vitro cultivation of human norovirus and reverse genetics systems and discuss commonly used in vivo models. We summarize the current understanding of both innate and adaptive immune responses to norovirus infection and provide an overview of vaccine strategies and the current clinical trial landscape, with a focus on the only vaccine candidate that has reached phase III clinical development stage.

Evaluation of the detection of diarrhoea-associated RNA viruses in immunocompromised children in Iran

Background

Gastroenteritis accounts for about 10% of the deaths among children, especially in immunocompromised children. Few studies on the prevalence of gastrointestinal infections caused by RNA viruses have been done in Iran. The aim of the study was to evaluate the detection of RNA viruses causing diarrhoea using a multiplex PCR.

Methods

Stool samples were collected from 130 paediatric patients with diarrhoea who had acute lymphocytic leukaemia, non-Hodgkin lymphoma, and retinoblastoma. After RNA extraction and synthesis of cDNA, multiplex PCR was done to evaluate the presence of rotavirus, norovirus, astrovirus, and enterovirus.

Results

There were 9 (6.9%), 7 (5.4%), 3 (2.3%), and 6 (4.6%) cases of rotavirus, norovirus, astrovirus, and enterovirus detected, respectively. One case of co-infection with astrovirus and norovirus was observed.

Conclusions

This is the first report from Iran which identified the presence of common RNA viruses causing diarrhoea in immunocompromised children. Increased awareness of these viruses will enable healthcare professionals to improve strategies and policies to control spread and infection caused by these viruses.

Signal-amplified surface-enhanced Raman scattering using core/shell satellite nanoparticles for norovirus detection

The development of an innovative approach is explored to amplify the signal of a surface-enhanced Raman scattering (SERS)-based detection system using a novel nanotag: Au@Ag NPs covered by satellite AuNPs and conjugated by 4-mercaptbenzoic acid (4-MBA) as a Raman tag (Au@Ag-MBA-AuNPs). The Au@Ag-MBA-AuNPs nanotags showed strong SERS activities with an enhancement factor in the 108 order of magnitude. This indicates the formation of many hot spots due to the combination of core-shell nanoparticles and satellite AuNPs on the surface of Au@Ag-MBA NPs. The newly fabricated nanotags were employed in a small-sized Palmtop Raman spectrometer. A concentration-dependent increase in SERS intensity was observed in the norovirus-like particle (NoV-LP) concentration range 10 fg/mL to 100 pg/mL with a detection limit of 0.76 fg/mL. Even in the severe interfering matrices, this detection method's coefficient of variation was less than 10%. This detection system was approximately 107 times more sensitive than commercially available ELISA kits. Norovirus in clinical samples was detected over a wide concentration range of 1.0 × 101 - 1.0 × 106 RNA copy number/mL with a detection limit of 7.8 RNA copy number/mL, indicating sensitivity comparable to real-time PCR. These results suggest that this detection system is stable in a complex matrix and has the potential for detecting norovirus in clinical samples with a small Palmtop Raman spectrometer.

CX-6258 hydrochloride hydrate: A potential non-nucleoside inhibitor targeting the RNA-dependent RNA polymerase of norovirus

Human norovirus (HuNoV), a primary cause of non-bacterial gastroenteritis, currently lacks approved treatment. RdRp is vital for virus replication, making it an attractive target for therapeutic intervention. By application of structure-based virtual screening procedure, we present CX-6258 hydrochloride hydrate as a potent RdRp non-nucleoside inhibitor, effectively inhibiting HuNoV RdRp activity with an IC50 of 3.61 μM. Importantly, this compound inhibits viral replication in cell culture, with an EC50 of 0.88 μM. In vitro binding assay validate that CX-6258 hydrochloride hydrate binds to RdRp through interaction with the "B-site" binding pocket. Interestingly, CX-6258-contacting residues such as R392, Q439, and Q414 are highly conserved among major norovirus GI and GII variants, suggesting that it may be a general inhibitor of norovirus RdRp. Given that CX-6258 hydrochloride hydrate is already utilized as an orally efficacious pan-Pim kinase inhibitor, it may serve as a potential lead compound in the effort to control HuNoV infections.

Epidemiology of norovirus infection in Nigeria: a systematic review and meta-analysis

Human norovirus (HuNoV) is responsible for most cases of gastroenteritis worldwide, but information about the prevalence and diversity of HuNoV infections in lower-income settings is lacking. In order to provide more information about the burden and distribution of norovirus in Nigeria, we systematically reviewed original published research articles on the prevalence of HuNoV in Nigeria by accessing databases, including PubMed, Web of Science, ScienceDirect, Google Scholar, and African Journals Online (AJOL). The protocol for the review was registered on PROSPERO (registration number CRD42022308857). Thirteen relevant articles were included in the review, and 10 of them were used for meta-analysis. The pooled prevalence of HuNoV-associated gastroenteritis among children below 5 years of age in Nigeria, determined using the random-effects model, was 10.9% (95% CI, 6.7-16.7%). Among children below the age of 5 presenting with HuNoV infections, the highest prevalence was in children ≤2 years old (n = 127, 83%). The prevalence of HuNoV infections was seen to decrease with increasing age. In addition, HuNoV was detected in asymptomatic food handlers, bats, and seafoods. A total of 85 sequences of HuNoV isolates from Nigeria have been determined, and based on those sequences, the most prevalent norovirus genogroup was GII (84%). Genotypes GII.4 and GI.3 were the most frequently identified genotypes, with GII.4 constituting 46% of all of the HuNoVs identified in Nigeria. These results suggest a risk associated with cocirculation of emerging variants with known genotypes because of their recombination potential. Larger molecular epidemiological studies are still needed to fully understand the extent and pattern of circulation of HuNoVs in Nigeria.

Rotavirus vaccines in Africa and Norovirus genetic diversity in children aged 0 to 5 years old: a systematic review and meta-analysis : Rotavirus vaccines in Africa and Norovirus genetic diversity

Noroviruses are the second leading cause of death in children under the age of 5 years old. They are responsible for 200 million cases of diarrhoea and 50,000 deaths in children through the word, mainly in low-income countries. The objective of this review was to assess how the prevalence and genetic diversity of noroviruses have been affected by the introduction of rotavirus vaccines in Africa. PubMed, Web of Science and Science Direct databases were searched for articles. All included studies were conducted in Africa in children aged 0 to 5 years old with gastroenteritis. STATA version 16.0 software was used to perform the meta-analysis. The method of Dersimonian and Laird, based on the random effects model, was used for the statistical analyses in order to estimate the pooled prevalence's at a 95% confidence interval (CI). Heterogeneity was assessed by Cochran's Q test using the I2 index. The funnel plot was used to assess study publication bias. A total of 521 studies were retrieved from the databases, and 19 were included in the meta-analysis. The pooled norovirus prevalence's for pre- and post-vaccination rotavirus studies were 15% (95 CI, 15-18) and 13% (95 CI, 09-17) respectively. GII was the predominant genogroup, with prevalence of 87.64% and 91.20% respectively for the pre- and post-vaccination studies. GII.4 was the most frequently detected genotype, with rates of 66.84% and 51.24% respectively for the pre- and post-vaccination studies. This meta-analysis indicates that rotavirus vaccination has not resulted in a decrease in norovirus infections in Africa.

Noroviruses: Evolutionary Dynamics, Epidemiology, Pathogenesis, and Vaccine Advances-A Comprehensive Review

Noroviruses constitute a significant aetiology of sporadic and epidemic gastroenteritis in human hosts worldwide, especially among young children, the elderly, and immunocompromised patients. The low infectious dose of the virus, protracted shedding in faeces, and the ability to persist in the environment promote viral transmission in different socioeconomic settings. Considering the substantial disease burden across healthcare and community settings and the difficulty in controlling the disease, we review aspects related to current knowledge about norovirus biology, mechanisms driving the evolutionary trends, epidemiology and molecular diversity, pathogenic mechanism, and immunity to viral infection. Additionally, we discuss the reservoir hosts, intra-inter host dynamics, and potential eco-evolutionary significance. Finally, we review norovirus vaccines in the development pipeline and further discuss the various host and pathogen factors that may complicate vaccine development.

Seasonality of respiratory, enteric, and urinary viruses revealed by wastewater genomic surveillance

Wastewater surveillance can reveal population-level infectious disease burden and emergent public health threats can be reliably assessed through wastewater surveillance. While molecular methods for wastewater monitoring of microorganisms have traditionally relied on PCR-based approaches, next-generation sequencing (NGS) can provide deeper insights via genomic analyses of multiple diverse pathogens. We conducted a year-long sequencing surveillance of 1,408 composite wastewater samples collected from 12 neighborhood-level access points in the greater Tempe area, Arizona, USA, and show that variation in wastewater viruses is driven by seasonal time and location. The temporal dynamics of viruses in wastewater were influenced cyclically, with the most dissimilarity between samples 23 weeks apart (i.e., winter vs summer, spring vs fall). We identified diverse urinary and enteric viruses including polyomaviruses, astroviruses, and noroviruses, and showed that their genotypes/subtypes shifted across seasons. We show that while wastewater data of certain respiratory viruses like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strongly correlate with clinical case rates, laboratory-reported case incidences were discordant with surges of high viral load in wastewater for other viruses like human coronavirus 229E. These results demonstrate the utility of wastewater sequencing for informing decision-making in public health.IMPORTANCEWastewater surveillance can provide insights into the spread of pathogens in communities. Advances in next-generation sequencing (NGS) methodologies allow for more precise detection of viruses in wastewater. Long-term wastewater surveillance of viruses is an important tool for public health preparedness. This system can act as a public health observatory that gives real-time early warning for infectious disease outbreaks and improved response times.

A Bivalent Human Norovirus Vaccine Induces Homotypic and Heterotypic Neutralizing Antibodies

A GII.2 outbreak in an efficacy study of a bivalent virus-like particle norovirus vaccine, TAK-214, in healthy US adults provided an opportunity to examine GII.4 homotypic vs GII.2 heterotypic responses to vaccination and infection. Three serologic assays-virus-like particle binding, histoblood group antigen blocking, and neutralizing-were performed for each genotype. Results were highly correlated within a genotype but not between genotypes. Although the vaccine provided protection from GII.2-associated disease, little GII.2-specific neutralization occurred after vaccination. Choice of antibody assay can affect assessments of human norovirus vaccine immunogenicity.

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.

Gastrointestinal Infection in South African Children under the Age of 5 years: A Mini Review

Objective

To estimate gastroenteritis disease and its etiological agents in children under the age of 5 years living in South Africa.

Methods

A mini literature review of pertinent articles published in ScienceDirect, PubMed, GoogleScholar, and Scopus was conducted using search terms: "Gastroenteritis in children," "Gastroenteritis in the world," Gastroenteritis in South Africa," "Prevalence of gastroenteritis," "Epidemiological surveillance of gastroenteritis in the world," and "Causes of gastroenteritis".

Results

A total of 174 published articles were included in this mini review. In the last 20 years, the mortality rate resulting from diarrhea in children under the age of 5 years has declined and this is influenced by improved hygiene practices, awareness programs, an improved water and sanitation supply, and the availability of vaccines. More modern genomic amplification techniques were used to re-analyze stool specimens collected from children in eight low-resource settings in Asia, South America, and Africa reported improved sensitivity of pathogen detection to about 65%, that viruses were the main etiological agents in patients with diarrhea aged from 0 to 11 months but that Shigella, followed by sapovirus and enterotoxigenic Escherichia coli had a high incidence in children aged 12-24 months. In addition, co-infections were noted in nearly 10% of diarrhea cases, with rotavirus and Shigella being the main co-infecting agents together with adenovirus, enteropathogenic E. coli, Clostridium jejuni, or Clostridium coli.

Conclusions

This mini review outlines the epidemiology and trends relating to parasitic, viral, and bacterial agents responsible for gastroenteritis in children in South Africa. An increase in sequence-independent diagnostic approaches will improve the identification of pathogens to resolve undiagnosed cases of gastroenteritis. Emerging state and national surveillance systems should focus on improving the identification of gastrointestinal pathogens in children and the development of further vaccines against gastrointestinal pathogens.

Predicting Dominant Genotypes in Norovirus Seasons in Japan

Human noroviruses are an etiological agent of acute gastroenteritis. Since multiple genotypes co-circulate every season changing their proportions, it may be desirable to develop multivalent vaccines by formulating genotype composition of seed strains to match that of dominant strains. Here, performances of the models for predicting dominant genotypes, defined as the two most prevalent genotypes, were evaluated using observed genotype frequencies in Japan and genomic sequences for GI and GII strains. In the null model, genotype proportions in the target season were predicted to be the same as those in the immediately preceding season. In the fitness model, genotype proportions were predicted taking into account the acquisition of novel P-types through recombination and genotype-specific proliferation efficiency, as well as herd immunity to VP1 assuming the duration (d) of 0-10 years. The null model performed better in GII than in GI, apparently because dominant genotypes were more stable in the former than in the latter. Performance of the fitness model was similar to that of the null model irrespective of the assumed value of d. However, performance was improved when dominant genotypes were predicted as the union of those predicted with d = 0-10, suggesting that d may vary among individuals.

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.

The Upper Nasal Space: Option for Systemic Drug Delivery, Mucosal Vaccines and "Nose-to-Brain"

Sino-nasal disease is appropriately treated with topical treatment, where the nasal mucosa acts as a barrier to systemic absorption. Non-invasive nasal delivery of drugs has produced some small molecule products with good bioavailability. With the recent COVID pandemic and the need for nasal mucosal immunity becoming more appreciated, more interest has become focused on the nasal cavity for vaccine delivery. In parallel, it has been recognized that drug delivery to different parts of the nose can have different results and for "nose-to-brain" delivery, deposition on the olfactory epithelium of the upper nasal space is desirable. Here the non-motile cilia and reduced mucociliary clearance lead to longer residence time that permits enhanced absorption, either into the systemic circulation or directly into the CNS. Many of the developments in nasal delivery have been to add bioadhesives and absorption/permeation enhancers, creating more complicated formulations and development pathways, but other projects have shown that the delivery device itself may allow more differential targeting of the upper nasal space without these additions and that could allow faster and more efficient programs to bring a wider range of drugs-and vaccines-to market.

Linear epitopes on the capsid protein of norovirus commonly elicit high antibody response among past-infected individuals

BACKGROUND

Human norovirus (HuNoV) is the leading cause of acute nonbacterial gastroenteritis globally, and its infection is usually self-limited, so most people become past Norovirus (NoV)-infected individuals. It is known that some antibody responses may play a critical role in preventing viral infection and alleviating disease; however, the characteristics and functions of particular antibody responses in persons with previous infections are not fully understood. Capsid proteins, including VP1 and VP2, are crucial antigenic components of NoV and may regulate antibody immune responses, while epitope-specific antibody responses to capsid proteins have not been comprehensively characterized.

METHODS

We prepared purified VP1 and VP2 proteins by ion exchange chromatography and measured serum antigen-specific IgG levels in 398 individuals by ELISA. Overlapping 18-mer peptides covering the full length of VP1 and VP2 were synthesized, and then we identified linear antigenic epitopes from 20 subjects with strong IgG positivity. Subsequently, specific antibody responses to these epitopes were validated in 185 past infected individuals, and the conservation of epitopes was analyzed. Finally, we obtained epitope-specific antiserum by immunizing mice and expressed virus-like particles (VLPs) in an insect expression system for a blockade antibody assay to evaluate the receptor-blocking ability of epitope-specific antibodies.

RESULTS

The IgG responses of VP1 were significantly stronger than those of VP2, both of which had high positive rates of over 80%. The overall positive rate of VP1-IgG and/or VP2-IgG was approximately 94%, which may be past NoV-infected individuals. Four linear antigenic B-cell epitopes of capsid proteins were identified, namely, VP1_199-216, VP1_469-492, VP2_97-120, and VP2_241-264, all of which were conserved. The IgG response rates of the above epitopes in past NoV-infected individuals were 38.92%, 22.16%, 8.11% and 28.11%, respectively. In addition, VP1_199-216- and VP1_469-492-specific antibodies can partially block the binding of VLPs to the receptor histo-blood group antigen (HBGA).

CONCLUSION

This is the first study to describe specific antibody responses of VP2 and to identify its B-cell epitopes. Our findings offer data for a more thorough understanding of norovirus capsid protein-specific IgG responses and could provide useful information for designing and developing vaccines.

Immunogenicity and Blocking Efficacy of Norovirus GII.4 Recombinant P Protein Vaccine

Noroviruses (NoVs) are the main cause of acute gastroenteritis in all ages worldwide. The aim of this study was to produce the recombinant P protein of norovirus and to demonstrate its blocking effect. In this study, the engineered strains were induced to express the P protein of NoVs GII.4, which was identified using SDS-PAGE and ELISA as having the capacity to bind to histo-blood group antigens (HBGAs). Rabbits were immunized to obtain neutralizing antibodies. ELISA and ISC-RT-qPCR were used to determine the blocking efficacy of the neutralizing antibody to human norovirus (HuNoV) and murine norovirus (MNV). The recombinant P protein (35 KD) was obtained, and the neutralizing antibody was successfully prepared. The neutralizing antibody could block the binding of the P protein and HuNoV to HBGAs. Neutralizing antibodies can also block MNV invasion into host cells RAW264.7. The recombinant P protein expressed in E. coli can induce antibodies to block HuNoV and MNV. The recombinant P protein of NoVs GII.4 has the value of vaccine development.

Immunoinformatics-guided design of a multi-valent vaccine against Rotavirus and Norovirus (ChRNV22)

Rotavirus (RV) and Norovirus (NV) are the main viral etiologic agents of acute gastroenteritis (AG), a serious pediatric condition associated with significant death rates and long-term complications. Anti-RV vaccination has been proved efficient in the reduction of severe AG worldwide, however, the available vaccines are all attenuated and have suboptimal efficiencies in developing countries, where AG leads to substantial disease burden. On the other hand, no NV vaccine has been licensed so far. Therefore, we used immunoinformatics tools to develop a multi-epitope vaccine (ChRNV22) to prevent severe AG by RV and NV. Epitopes were predicted against 17 prevalent genotypes of four structural proteins (NV's VP1, RV's VP4, VP6 and VP7), and then assembled in a chimeric protein, with two small adjuvant sequences (tetanus toxin P2 epitope and a conserved sequence of RV's enterotoxin, NSP4). Simulations of the immune response and interactions with immune receptors indicated the immunogenic properties of ChRNV22, including a Th1-biased response. In silico search for putative host-homologous, allergenic and toxic regions also indicated the vaccine safety. In summary, we developed a multi-epitope vaccine against different NV and RV genotypes that seems promising for the prevention of severe AG, which will be further assessed by in vivo tests.

The Role of Lactoferrin in Intestinal Health

The intestine represents one of the first barriers where microorganisms and environmental antigens come into tight contact with the host immune system. A healthy intestine is essential for the well-being of humans and animals. The period after birth is a very important phase of development, as the infant moves from a protected environment in the uterus to one with many of unknown antigens and pathogens. In that period, mother's milk plays an important role, as it contains an abundance of biologically active components. Among these components, the iron-binding glycoprotein, lactoferrin (LF), has demonstrated a variety of important benefits in infants and adults, including the promotion of intestinal health. This review article aims to provide a compilation of all the information related to LF and intestinal health, in infants and adults.

Predicting Norovirus in England Using Existing and Emerging Syndromic Data: Infodemiology Study

BACKGROUND

Norovirus is associated with approximately 18% of the global burden of gastroenteritis and affects all age groups. There is currently no licensed vaccine or available antiviral treatment. However, well-designed early warning systems and forecasting can guide nonpharmaceutical approaches to norovirus infection prevention and control.

OBJECTIVE

This study evaluates the predictive power of existing syndromic surveillance data and emerging data sources, such as internet searches and Wikipedia page views, to predict norovirus activity across a range of age groups across England.

METHODS

We used existing syndromic surveillance and emerging syndromic data to predict laboratory data indicating norovirus activity. Two methods are used to evaluate the predictive potential of syndromic variables. First, the Granger causality framework was used to assess whether individual variables precede changes in norovirus laboratory reports in a given region or an age group. Then, we used random forest modeling to estimate the importance of each variable in the context of others with two methods: (1) change in the mean square error and (2) node purity. Finally, these results were combined into a visualization indicating the most influential predictors for norovirus laboratory reports in a specific age group and region.

RESULTS

Our results suggest that syndromic surveillance data include valuable predictors for norovirus laboratory reports in England. However, Wikipedia page views are less likely to provide prediction improvements on top of Google Trends and Existing Syndromic Data. Predictors displayed varying relevance across age groups and regions. For example, the random forest modeling based on selected existing and emerging syndromic variables explained 60% variance in the ≥65 years age group, 42% in the East of England, but only 13% in the South West region. Emerging data sets highlighted relative search volumes, including "flu symptoms," "norovirus in pregnancy," and norovirus activity in specific years, such as "norovirus 2016." Symptoms of vomiting and gastroenteritis in multiple age groups were identified as important predictors within existing data sources.

CONCLUSIONS

Existing and emerging data sources can help predict norovirus activity in England in some age groups and geographic regions, particularly, predictors concerning vomiting, gastroenteritis, and norovirus in the vulnerable populations and historical terms such as stomach flu. However, syndromic predictors were less relevant in some age groups and regions likely due to contrasting public health practices between regions and health information-seeking behavior between age groups. Additionally, predictors relevant to one norovirus season may not contribute to other seasons. Data biases, such as low spatial granularity in Google Trends and especially in Wikipedia data, also play a role in the results. Moreover, internet searches can provide insight into mental models, that is, an individual's conceptual understanding of norovirus infection and transmission, which could be used in public health communication strategies.

An oral NoV-rAd5 vaccine with built-in dsRNA adjuvant elicits systemic immune responses in mice

Norovirus (NoV) is an enteric pathogen notorious for causing epidemics of acute gastroenteritis. An effective vaccine against NoV is therefore urgently needed. A short double-stranded RNA (dsRNA) has been described that acts as a retinoic-acid-inducible gene-I agonist to induce the production of type I interferon; it also exhibits adjuvant activity. Using built-in dsRNA of different lengths (DS1 and DS2), we developed a recombinant adenovirus 5 (rAd5) expressing NoV VP1, and evaluated its immunogenicity following oral administration in a mouse model. An in vitro study demonstrated that the dsRNA adjuvants significantly enhanced VP1 protein expression in infected cells. The oral administration of both rAd5-VP1-DS vaccines elicited high serum levels of VP1-specific IgG and blocking antibodies, as well as strong and long-lasting mucosal immunity. There was no apparent difference in immunostimulatory effects in immunised mice between the two dsRNA adjuvants. This study indicates that an oral NoV-rAd5 vaccine with a built-in dsRNA adjuvant may be developed to prevent NoV infection in humans.

Vaccine mandates for healthcare workers beyond COVID-19

We provide ethical criteria to establish when vaccine mandates for healthcare workers are ethically justifiable. The relevant criteria are the utility of the vaccine for healthcare workers, the utility for patients (both in terms of prevention of transmission of infection and reduction in staff shortage), and the existence of less restrictive alternatives that can achieve comparable benefits. Healthcare workers have professional obligations to promote the interests of patients that entail exposure to greater risks or infringement of autonomy than ordinary members of the public. Thus, we argue that when vaccine mandates are justified on the basis of these criteria, they are not unfairly discriminatory and the level of coercion they involve is ethically acceptable-and indeed comparable to that already accepted in healthcare employment contracts. Such mandates might be justified even when general population mandates are not. Our conclusion is that, given current evidence, those ethical criteria justify mandates for influenza vaccination, but not COVID-19 vaccination, for healthcare workers. We extend our arguments to other vaccines.

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.

Engineered Norovirus-Derived Nanoparticles as a Plug-and-Play Cancer Vaccine Platform

In recent years, virus-derived self-assembled protein nanoparticles (NPs) have emerged as attractive antigen delivery platforms for developing both preventive and therapeutic vaccines. In this study, we exploited the genetically engineered Norovirus S domain (Nov-S) with SpyCatcher003 fused to the C-terminus to develop a robust, modular, and versatile NP-based carrier platform (Nov-S-Catcher003). The NPs can be conveniently armed in a plug-and-play pattern with SpyTag003-linked antigens. Nov-S-Catcher003 was efficiently expressed in Escherichia coli and self-assembled into highly uniform NPs with a purified protein yield of 97.8 mg/L. The NPs presented high stability at different maintained temperatures and after undergoing differing numbers of freeze-thaw cycles. Tumor vaccine candidates were easily obtained by modifying Nov-S-Catcher003 NPs with SpyTag003-linked tumor antigens. Nov-S-Catcher003-antigen NPs significantly promoted the maturation of bone marrow-derived dendritic cells in vitro and were capable of efficiently migrating to lymph nodes in vivo. In TC-1 and B16F10 tumor-bearing mice, the subcutaneous immunization of NPs elicited robust tumor-specific T-cell immunity, reshaped the tumor microenvironment, and inhibited tumor growth. In the TC-1 model, the NPs even completely abolished established tumors. In conclusion, the Nov-S-Catcher003 system is a promising delivery platform for facilitating the development of NP-based cancer vaccines.

Long-time scale simulations of virus-like particles from three human-norovirus strains

The dynamics of the virus like particles (VLPs) corresponding to the GII.4 Houston, GII.2 SMV, and GI.1 Norwalk strains of human noroviruses (HuNoV) that cause gastroenteritis was investigated by means of long-time (about 30 μs in the laboratory timescale) molecular dynamics simulations with the coarse-grained UNRES force field. The main motion of VLP units turned out to be the bending at the junction between the P1 subdomain (that sits in the VLP shell) and the P2 subdomain (that protrudes outside) of the major VP1 protein, this resulting in a correlated wagging motion of the P2 subdomains with respect to the VLP surface. The fluctuations of the P2 subdomain were found to be more pronounced and the P2 domain made a greater angle with the normal to the VLP surface for the GII.2 strain, which could explain the inability of this strain to bind the histo-blood group antigens (HBGAs).

Jatrorrhizine Suppresses Murine-Norovirus-Triggered N-GSDMD-Dependent Pyroptosis in RAW264.7 Macrophages

Human norovirus (HNV) is one of the emerging and rapidly spreading groups of pathogens and the main cause of epidemic viral gastroenteritis globally. Due to a lack of in vitro culture systems and suitable animal models for HNV infection, murine norovirus (MNV) has become a common model. A recent study showed that MNV activates NLRP3 inflammasome leading to pyroptosis. Jatrorrhizine (JAT) is a natural isoquinoline alkaloid isolated from Coptis Chinensis, which has been proven to have antibacterial, anti-inflammatory, and antitumor effects. However, whether JAT has an effect on norovirus gastroenteritis and the underlying molecular mechanism remain unclear. Here, we found that JAT could ameliorate NLRP3-N-GSDMD-dependent pyroptosis induced by MNV infection through inhibiting the MAPKs/NF-κB signaling pathways and decrease MNV replication in RAW264.7 macrophages, suggesting that JAT has the potential to be a therapeutic agent for treating norovirus gastroenteritis.

Generation of Recombinant Rotaviruses Expressing Human Norovirus Capsid Proteins

Rotavirus, a segmented double-stranded RNA virus of the Reoviridae family, is a primary cause of acute gastroenteritis in young children. In countries where rotavirus vaccines are widely used, norovirus (NoV) has emerged as the major cause of acute gastroenteritis. Towards the goal of creating a combined rotavirus-NoV vaccine, we explored the possibility of generating recombinant rotaviruses (rRVs) expressing all or portions of the NoV GII.4 VP1 capsid protein. This was accomplished by replacing the segment 7 NSP3 open reading frame with a cassette encoding, sequentially, NSP3, a 2A stop-restart translation element, and all or portions (P, P2) of NoV VP1. In addition to successfully recovering rRVs with modified SA11 segment 7 RNAs encoding NoV capsid proteins, analogous rRVs were recovered through modification of the segment 7 RNA of the RIX4414 vaccine strain. An immunoblot assay confirmed that rRVs expressed NoV capsid proteins as independent products. Moreover, VP1 expressed by rRVs underwent dimerization and was recognized by conformational-dependent anti-VP1 antibodies. Serially passaged rRVs that expressed the NoV P and P2 were genetically stable, retaining additional sequences of up to 1.1 kbp without change. However, serially passaged rRVs containing the longer 1.6-kb VP1 sequence were less stable and gave rise to virus populations with segment 7 RNAs lacking VP1 coding sequences. Together, these studies suggest that it may be possible to develop combined rotavirus-NoV vaccines using modified segment 7 RNA to express NoV P or P2. In contrast, development of potential rotavirus-NoV vaccines expressing NoV VP1 will need additional efforts to improve genetic stability. IMPORTANCE Rotavirus (RV) and norovirus (NoV) are the two most important causes of acute viral gastroenteritis (AGE) in infants and young children. While the incidence of RV AGE has been brought under control in many countries through the introduction of universal mass vaccination with live attenuated RV vaccines, similar highly effective NoV vaccines are not available. To pursue the development of a combined RV-NoV vaccine, we examined the potential of using RV as an expression vector of all or portions of the NoV capsid protein VP1. Our results showed that by replacing the NSP3 open reading frame in RV genome segment 7 RNA with a coding cassette for NSP3, a 2A stop-restart translation element, and VP1, recombinant RVs can be generated that express NoV capsid proteins. These findings raise the possibility of developing new generations of RV-based combination vaccines that provide protection against a second enteric pathogen, such as NoV.

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.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/record/NCT05508178, identifier (NCT05508178).

Controlled Human Infection Models To Accelerate Vaccine Development

The timelines for developing vaccines against infectious diseases are lengthy, and often vaccines that reach the stage of large phase 3 field trials fail to provide the desired level of protective efficacy. The application of controlled human challenge models of infection and disease at the appropriate stages of development could accelerate development of candidate vaccines and, in fact, has done so successfully in some limited cases. Human challenge models could potentially be used to gather critical information on pathogenesis, inform strain selection for vaccines, explore cross-protective immunity, identify immune correlates of protection and mechanisms of protection induced by infection or evoked by candidate vaccines, guide decisions on appropriate trial endpoints, and evaluate vaccine efficacy. We prepared this report to motivate fellow scientists to exploit the potential capacity of controlled human challenge experiments to advance vaccine development. In this review, we considered available challenge models for 17 infectious diseases in the context of the public health importance of each disease, the diversity and pathogenesis of the causative organisms, the vaccine candidates under development, and each model's capacity to evaluate them and identify correlates of protective immunity. Our broad assessment indicated that human challenge models have not yet reached their full potential to support the development of vaccines against infectious diseases. On the basis of our review, however, we believe that describing an ideal challenge model is possible, as is further developing existing and future challenge models.

The Efficacy of Commercial Surface Sanitizers against Norovirus on Formica Surfaces with and without Inclusion of a Wiping Step

Commonly used surface sanitizers often lack activity against human noroviruses (hNoVs). The impact of inactivation versus removal when these products are applied via wiping is poorly characterized. The purpose of this work was to assess the anti-hNoV efficacy of various surface sanitizer chemistries, as applied to a laminate material commonly used for restaurant tabletops, using standard surface assays (ASTM E1053-11) and a newly developed wiping protocol. Four commercially available products with different active ingredient(s) (i.e., ethanol [EtOH], acid + anionic surfactant [AAS], quaternary ammonium compound [QAC], and sodium hypochlorite [NaOCl]) and a water control were evaluated against hNoV GII.4 Sydney, hNoV GI.6, and the cultivable surrogate Tulane virus (TuV). Virus concentration was evaluated using RNase-reverse transcriptase (RT)-quantitative PCR (qPCR) (hNoV) and infectivity assay (TuV). Only the EtOH-based product significantly reduced virus concentration (>3.5 log10 reduction [LR]) by surface assay, with all other products producing ≤0.5 LR. The inclusion of a wiping step enhanced the efficacy of all products, producing complete virus elimination for the EtOH-based product and 1.6 to 3.8 LR for the other chemistries. For hNoVs, no detectable residual virus could be recovered from paper towels used to wipe the EtOH-based product, while high concentrations of virus could be recovered from the used paper towel and the wiped coupon (1.5 to 2.5 log10 lower genome equivalent copies [GEC] compared to control) for the QAC- and AAS-based products and for water. These results illustrate the variability in anti-hNoV activity of representative surface sanitizers and highlights the value of wiping, the efficacy of which appears to be driven by a combination of virus inactivation and removal. IMPORTANCE Human noroviruses (hNoVs) are the leading cause of acute gastroenteritis and food-borne disease worldwide. Noroviruses are difficult to inactivate, being recalcitrant to sanitizers and disinfectants commonly used by the retail food sector. This comparative study demonstrates the variability in anti-hNoV activity of representative surface sanitizers, even those allowed to make label claims based on the cultivable surrogate, feline calicivirus (FCV). It also highlights the importance of wiping in the process of sanitization, which significantly improves product efficacy through the action of physical removal of surface microbes. There is a need for more and better product formulations with demonstrated efficacy against hNoVs, which will likely necessitate the use of alternative cultivable surrogates, such as Tulane virus (TuV). These findings help food safety professionals make informed decisions on sanitizing product selection and application methods in order to reduce the risk of hNoV contamination and transmission in their facilities.

In silico based multi-epitope vaccine design against norovirus

Norovirus (NoV) belongs to the Calciviridae family that causes diarrhoea, vomiting, and stomach pain in people who have acute gastroenteritis (AGE). Identifying multi-epitope dependent vaccines for single stranded positive sense viruses such as NoV has been a long due. Although efforts have been in place to look into the candidate epitopes, understanding molecular mimicry and finding new epitopes for inducing immune responses against the T/B-cells which play an important role for the cell-mediated and humoral immunity was not dealt with in great detail. The current study focuses on identifying new epitopes from various databases that were filtered for antigenicity, allergenicity, and toxicity. The adjuvant β-defensin along with different linkers were used for vaccine construction. Further, the binding relationship between the vaccine construct and toll-like immune receptor (TLR3) complex was determined using a molecular docking analysis, followed by molecular dynamics simulation of 100 ns. The vaccine candidate developed expresses good solubility with a score of 0.530, Z-score of -4.39 and molecular docking score of -140.4 ± 12.1. The MD trajectories reveal that there is a stability between TLR3 and the developed vaccine candidate with an average of 0.91 nm RMSD value and also the system highest occupancy H-bond formed between GLU127 of TLR3 and TYR10 of vaccine candidate (61.55%). Four more H-bonds exist with an occupancy of more than 32% between TLR3 and the vaccine candidates which makes it stable. Thus, the multi-epitope based vaccine developed in the present study forms the basis for further experimental investigations to develop a potentially good vaccine against NoV.Communicated by Ramaswamy H. Sarma.

Potentially Pathogenic Organisms in Stools and Their Association With Acute Diarrheal Illness in Children Aged <2 Years

BACKGROUND

Acute diarrheal illness (ADI) causes a substantial disease burden in high-income countries. We investigated associations between potentially pathogenic organisms in stools and ADI by polymerase chain reaction (PCR) in Australian children aged <2 years.

METHODS

Children in a community-based birth cohort had gastrointestinal symptoms recorded daily and stool samples collected weekly until their second birthday. Diarrhea was defined as ≥3 liquid or looser than normal stools within a 24-hour period. PCR assays tested for 11 viruses, 5 bacteria, and 4 protozoa. Detections of a new organism or of the same following at least 2 negative tests were linked to ADIs, and incidence rates and estimates of association with ADI were calculated.

RESULTS

One hundred fifty-four children provided 11 111 stool samples during 240 child-years of observation, and 228 ADIs were linked to samples. Overall, 6105 (55%) samples tested positive for a target organism. The incidence rate of 2967 new detections was 11.9 (95% confidence interval 11.4-12.3) per child-year, with 2561 (92%) new detections unrelated to an ADI. The relative risk of an ADI was 1.5-6.4 times greater for new detections of adenovirus, enterovirus, norovirus GII, parechovirus A, wild-type rotavirus, sapovirus GI/II/IV/V, Salmonella, Blastocystis, and Cryptosporidium, compared to when these were absent.

CONCLUSIONS

Wild-type rotavirus, norovirus GII, sapovirus GI/II/IV/V, adenovirus 40/41, and Salmonella were associated with ADI in this age group and setting. However, high levels of asymptomatic shedding of potential pathogens in stools from children may contribute to diagnostic confusion when children present with an episode of ADI.

6-Valent Virus-Like Particle-Based Vaccine Induced Potent and Sustained Immunity Against Noroviruses in Mice

Norovirus is a major cause of acute gastroenteritis worldwide, and no vaccine is currently available. The genetic and antigenic diversity of Norovirus presents challenges for providing broad immune protection, which calls for a multivalent vaccine application. In this study, we investigated the possibility of developing a virus-like particle (VLP)-based 6-valent Norovirus vaccine candidate (Hexa-VLPs) that covers GI.1, GII.2, GII.3, GII.4, GII.6, and GII.17 genotypes. Hexa-VLPs (30 µg) adjuvanted with 500 µg of aluminum hydroxide (alum) were selected as the optimal immunization dose after a dose-escalation study. Potent and long-lasting blockade antibody responses were induced by 2-or 3-shot Hexa-VLPs, especially for the emerging GII.P16-GII.2 and GII.17 (Kawasaki 2014) genotypes. Hexa-VLPs plus alum elicited Th1/Th2 mixed yet Th2-skewed immune responses, characterized by an IgG1-biased subclass profile and significant IL-4⁺ T-cell activation. Notably, simultaneous immunization with a mixture of six VLPs revealed no immunological interference among the component antigens. These results demonstrate that Hexa-VLPs are promising broad-spectrum vaccines to provide immunoprotection against major GI/GII epidemic strains in the future.

Immunogenicity of a bivalent virus-like particle norovirus vaccine in children from 1 to 8 years of age: A phase 2 randomized, double-blind study

BACKGROUND

Young children can suffer severe consequences of norovirus gastroenteritis. We performed a dose-finding study of a bivalent virus-like particle (VLP) vaccine candidate (TAK-214) in healthy 1-8-year-old children.

METHODS

In this phase 2 study two age cohorts (1-3 and 4-8 years of age inclusive, N = 120 per cohort) of children enrolled from Finland, Panama and Colombia were initially randomized 1:1:1:1 to four groups which were further split into two equal subgroups, to receive one or two intramuscular doses of four TAK-214 formulations containing 15/15, 15/50, 50/50 or 50/150 μg of GI.1/GII.4c genotype VLPs and 0.5 mg Al(OH)₃ at 28 days interval. ELISA Pan-Ig and histoblood group antigen-blocking (HBGA) antibodies against each VLP were measured on days 1, 29, 57 and 210. Parents/guardians recorded solicited local and systemic adverse events (AE) and any unsolicited or serious AEs (SAE).

RESULTS

All formulations were well-tolerated across both age cohorts and dosage groups with no vaccine-related SAEs reported. Solicited AEs were mostly mild-to-moderate, resolved quickly, and did not increase after the second dose. Pan-Ig and HBGA responses induced after one dose were only slightly increased by the second dose. Across dose groups at Day 29 after one dose GI.1 Pan Ig seroresponse rates (SRR) were 82-97% and 81-96% and GII.4c SRR were 79-97% and 80-91% in 1-3 and 4-8 year-olds, respectively. Respective rates were to 92-93% and 73-92% for GI.1, and 77-100% and 62-83% for GII.4c at Day 57 following two doses. HBGA responses had similar profiles. Both Pan Ig and HBGA geometric mean titers persisted above baseline up to Day 210.

CONCLUSIONS

All dosages of TAK-214 displayed acceptable reactogenicity in 1-8-year-old children and induced robust, durable immune responses after one dose which are further increased after two doses.

Human Norovirus Triggers Primary B Cell Immune Activation In Vitro

Human norovirus (HNoV) is a global health and socioeconomic burden, estimated to infect every individual at least five times during their lifetime. The underlying mechanism for the potential lack of long-term immune protection from HNoV infections is not understood and prompted us to investigate HNoV susceptibility of primary human B cells and its functional impact. Primary B cells isolated from whole blood were infected with HNoV-positive stool samples and harvested at 3 days postinfection (dpi) to assess the viral RNA yield by reverse transcriptase quantitative PCR (RT-qPCR). A 3- to 18-fold increase in the HNoV RNA yield was observed in 50 to 60% of donors. Infection was further confirmed in B cells derived from splenic and lymph node biopsy specimens. Next, we characterized infection of whole-blood-derived B cells by flow cytometry in specific functional B cell subsets (naive CD27- IgD+, memory-switched CD27+ IgD-, memory-unswitched CD27+ IgD+, and double-negative CD27- IgD- cells). While the susceptibilities of the subsets were similar, changes in the B cell subset distribution upon infection were observed, which were also noted after treatment with HNoV virus-like particles and the predicted recombinant NS1 protein. Importantly, primary B cell stimulation with the predicted recombinant NS1 protein triggered B cell activation and induced metabolic changes. These data demonstrate that primary B cells are susceptible to HNoV infection and suggest that the NS1 protein can alter B cell activation and metabolism in vitro, which could have implications for viral pathogenesis and immune responses in vivo. IMPORTANCE Human norovirus (HNoV) is the most prevalent causative agent of gastroenteritis worldwide. Infection results in a self-limiting disease that can become chronic and severe in the immunocompromised, the elderly, and infants. There are currently no approved therapeutic and preventative strategies to limit the health and socioeconomic burdens associated with HNoV infections. Moreover, HNoV does not elicit lifelong immunity as repeat infections are common, presenting a challenge for vaccine development. Given the importance of B cells for humoral immunity, we investigated the susceptibility and impact of HNoV infection on human B cells. We found that HNoV replicates in human primary B cells derived from blood, spleen, and lymph node specimens, while the nonstructural protein NS1 can activate B cells. Because of the secreted nature of NS1, we put forward the hypothesis that HNoV infection can modulate bystander B cell function with potential impacts on systemic immune responses.

Safety and immunogenicity studies in animal models support clinical development of a bivalent norovirus-like particle vaccine produced in plants

Noroviruses (NoV) are the leading cause of epidemic acute gastroenteritis in humans worldwide. A safe and effective vaccine that prevents NoV infection or minimizes NoV disease burden is needed, especially for children and the elderly who are particularly susceptible to NoV disease. A plant-based expression system (magnICON®) was used to manufacture two different virus-like particle (VLP) immunogens derived from human NoV genogroups I and II, genotype 4 (GI.4 and GII.4), which were subsequently blended 1:1 (w/w) into a bivalent vaccine composition (rNV-2v). Here, we report on the safety and immunogenicity of rNV-2v from one pilot and two GLP-compliant toxicity studies in New Zealand White rabbits administered the vaccine subcutaneously (SC) or intramuscularly (IM). Strong genogroup-specific immune responses were induced by vaccination without adjuvant at various doses (200 to 400 μg VLP/administration) and administration schedules (Days 1 and 7; or Days 1, 15 and 29). The results showed sporadic local irritation at the injection site, which resolved over time, and was non-adverse and consistent with expected reactogenicity. There were no signs of systemic toxicity related to vaccine administration relative to vehicle-treated controls with respect to clinical chemistry, haematology, organ weights, macroscopic examinations, or histopathology. In a 3-administration regimen (n + 1 the clinical regimen), the NOAEL for rNV-2v via the SC or IM route was initially determined to be 200 μg. An improved GI.4 VLP variant mixed 1:1 (w/w) with the wild-type GII.4 VLP was subsequently evaluated via the IM route at a higher dose in the same 3-administration model, and the NOAEL was raised to 300 µg. Serology performed in samples of both toxicity studies showed significant and substantial anti-VLP-specific antibody titers for rNV-2v vaccines administered via the IM or SC route, as well as relevant NoV blocking antibody responses. These results support initiation of clinical development of the plant-made NoV vaccine.

Illuminating Human Norovirus: A Perspective on Disinfection of Water and Surfaces Using UVC, Norovirus Model Organisms, and Radiation Safety Considerations

Human noroviruses (HuNoVs) are a major cause of gastroenteritis and are associated with high morbidity because of their ability to survive in the environment and small inoculum size required for infection. Norovirus is transmitted through water, food, high touch-surfaces, and human-to-human contact. Ultraviolet Subtype C (UVC) light-emitting diodes (LEDs) can disrupt the norovirus transmission chain for water, food, and surfaces. Here, we illuminate considerations to be adhered to when picking norovirus surrogates for disinfection studies and shine light on effective use of UVC for norovirus infection control in water and air and validation for such systems and explore the blind spot of radiation safety considerations when using UVC disinfection strategies. This perspective also discusses the promise of UVC for norovirus mitigation to save and ease life.

The Initial Timing and Burden of Viral Gastrointestinal Infections in Australian Infants: A Birth Cohort Study

ABSTRACT

The timing and nature of initial infections by potentially vaccine-preventable gastrointestinal viruses (group-F adenoviruses, classic human astrovirus, norovirus I/II, and sapovirus I/II/IV/V) was investigated in a community-based birth cohort. Weekly stool samples were collected from 158 children aged <2 years in an Australian subtropical city. Median age at initial infection was lowest for norovirus II (13.8 months) followed by sapovirus (14.3 months) and classic human astrovirus (17.6 months), and was >24 months for the remaining viruses. Norovirus II and sapovirus were most often associated with acute gastroenteritis symptoms (57% and 44%, respectively). Overall, healthcare was sought for 45% of symptomatic initial infections, which varied between 17% for norovirus I to 55% for norovirus II. Age at initial infection was lower when participants were exposed to other children. Norovirus II and sapovirus were the most important pathogens in this cohort, providing further evidence for them being priority targets for vaccine development.

Norovirus Vaccines: Current Clinical Development and Challenges

Noroviruses are the major viral pathogens causing epidemic and endemic acute gastroenteritis with significant morbidity and mortality. While vaccines against norovirus diseases have been shown to be of high significance, the development of a broadly effective norovirus vaccine remains difficult, owing to the wide genetic and antigenic diversity of noroviruses with multiple co-circulated variants of various genotypes. In addition, the absence of a robust cell culture system, an efficient animal model, and reliable immune markers of norovirus protection for vaccine evaluation further hinders the developmental process. Among the vaccine candidates that are currently under clinical studies, recombinant VP1-based virus-like particles (VLPs) that mimic major antigenic features of noroviruses are the common ones, with proven safety, immunogenicity, and protective efficacy, supporting a high success likelihood of a useful norovirus vaccine. This short article reviews the recent progress in norovirus vaccine development, focusing on those from recent clinical studies, as well as summarizes the barriers that are being encountered in this developmental process and discusses issues of future perspective.

Norovirus strains among children aged 0-18 years hospitalized with acute gastroenteritis in Estonia 2015-2016

Norovirus (NoV) is the leading cause of acute gastroenteritis (AGE) in many countries that have introduced universal rotavirus mass vaccination. This is the first study to report data on NoV strains in Estonia. We recruited 2249 children aged 0-18 years hospitalized for AGE in Estonian hospitals from February 1, 2015 to August 31, 2016. Norovirus gastroenteritis (NoVGE) was diagnosed in 14.5% (n = 325) cases. Stool sample for RNA extraction and genotyping was available in 86% (n = 280) of NoVGE cases (2015, n = 91; 2016, n = 189). Dominant capsid types detected in 75% (n = 210) samples were, GII.4 (63.8%, n = 134), GII.3 (15.2%, n = 32), GII.17 (6.7%, n = 14), and GII.6 (5.2%, n = 11). Prevailing RNA polymerase types found in 77% (n = 215) samples were GII.P31 (51.1%, n = 110), GII.P21 (17.7%, n = 38), GII.P4 (11.2%, n = 24), and GII.P7 (6.5%, n = 14). Both regions were typeable for 67% (n = 189) of samples. Most prevalent strains were GII.4Sydney_2012[P31] (48.7%, n = 92), GII.3[P21] (15.3%, n = 29), GII.4Sydney_2012[P4] (5.8%, n = 11) and GII.17[P17] (5.8%, n = 11). Simpson's diversity index showed a significant difference between the age groups 1-4 and 5-9 years: D 0.64 (95% confidence interval [CI]: 0.55-0.73) versus 0.83 (95% CI: 0.81-0.86), respectively (p = 0.03). An accurate understanding of NoV strain diversity is important for control and preventive measures, especially in the postrotavirus vaccine era.

Predicted norovirus resurgence in 2021-2022 due to the relaxation of nonpharmaceutical interventions associated with COVID-19 restrictions in England: a mathematical modeling study

BACKGROUND

To reduce the coronavirus disease burden in England, along with many other countries, the government implemented a package of non-pharmaceutical interventions (NPIs) that have also impacted other transmissible infectious diseases such as norovirus. It is unclear what future norovirus disease incidence is likely to look like upon lifting these restrictions.

METHODS

Here we use a mathematical model of norovirus fitted to community incidence data in England to project forward expected incidence based on contact surveys that have been collected throughout 2020-2021.

RESULTS

We report that susceptibility to norovirus infection has likely increased between March 2020 and mid-2021. Depending upon assumptions of future contact patterns incidence of norovirus that is similar to pre-pandemic levels or an increase beyond what has been previously reported is likely to occur once restrictions are lifted. Should adult contact patterns return to 80% of pre-pandemic levels, the incidence of norovirus will be similar to previous years. If contact patterns return to pre-pandemic levels, there is a potential for the expected annual incidence to be up to 2-fold larger than in a typical year. The age-specific incidence is similar across all ages.

CONCLUSIONS

Continued national surveillance for endemic diseases such as norovirus will be essential after NPIs are lifted to allow healthcare services to adequately prepare for a potential increase in cases and hospital pressures beyond what is typically experienced.

Two-step purification of tag-free norovirus-like particles from silkworm larvae (Bombyx mori)

Recombinantly expressed VP1 of norovirus self-assembled and formed norovirus-like particles (NoV-LPs). This native VP1 was expressed using the Bombyx mori nucleopolyhedrovirus (BmNPV) expression system in silkworm larva. NoV-LPs were collected from silkworm fat body lysate by density gradient centrifugation. To improve the purity of the NoV-LP, the proteins were further purified using immobilized metal affinity chromatography based on the surface exposed side chain of histidine residues. The additional purification led to a highly purified virus-like particle (VLP). The morphology and size of the purified VLPs were examined using a transmission electron microscope, and dynamic light scattering revealed a monodispersed spherical morphology with a diameter of 34 nm. The purified product had a purity of >90% with a recovery yield of 48.7% (equivalent to 930 μg) from crude lysate, obtained from seven silkworm larvae. In addition, the purified VLP could be recognized by antibodies against GII norovirus in sandwich enzyme-linked immunosorbent assay, which indicated that the silkworm-derived VLP is biologically functional as a NoV-LP in its native state, is structurally correct, and exerts its biological function. Our results suggest that the silkworm-derived NoV-LP may be useful for subsequent applications, such as in a vaccine platform. Moreover, the silkworm-based expression system is known for its robustness, facile up-scalability, and relatively low expense compared to insect cell systems.