In vitro cell culture infectivity assay for human noroviruses

B cell lines fail to support efficient rhesus enteric calicivirus and human norovirus replication

Analyses of intestinal biopsies of infected individuals and/or nonhuman primates (NHP) suggested the possible immune cell tropism of human noroviruses (HuNoV) and rhesus enteric caliciviruses (ReCV). Subsequently, the first HuNoV cell culture system using human B cell lines was reported. However, reproducibility issues raised questions about the validity and suitability of B cell cultures for HuNoV research. Histo-blood group antigens (HBGA) are known HuNoV susceptibility factors, but the full range of HuNoV susceptibility determinants remains unknown. In contrast, strain-specific ReCV susceptibility determinants have been recently characterized. Here, we evaluated NHP B cell lines and the human BJAB cell line for susceptibility to ReCV-FT285 infection, which is controlled by the Coxsackie and adenovirus receptor (CAR) and the type A or B HBGA. NHP B cell lines lacked CAR and HBGA expression and resisted infection. Inconsistent, low-level virus replication was detectable in BJAB cells, and expression of CAR and HBGAs was evident by Western blots. However, <1% of live, but >80% of fixed and permeabilized BJAB cells were CAR+, suggesting that CAR is mostly internalized. Co-transfection of BJAB cells with hCAR and A enzyme expression vectors led to substantial surface CAR and type A HBGA expression but not to an increase in ReCV titers. dsRNA staining revealed initial ReCV and HuNoV infection in a few cells that most likely became abortive. Based on both the similarities between ReCV and HuNoV replication profiles and the results obtained in the present study, considering BJAB cells an efficient culture system for HuNoV research is not justified.IMPORTANCERecently, two human norovirus (HuNoV) cell culture systems have been developed-the B cell culture system and the enteroid culture system. While the enteroid cell culture system became widely used in HuNoV research, mainly due to reproducibility issues, the B cell culture system did not. Here, we used HuNoV and rhesus enteric caliciviruses (ReCV) to evaluate enteric calicivirus B cell infections, in correlation to cell surface molecular determinants that control the susceptibility to infection. These are fully characterized for ReCVs, but not for HuNoVs. We found that only few BJAB cells express the cell surface molecules necessary for ReCV infection and support low-level, initial ReCV and HuNoV infection, but virus replication is most likely abortive, with minimal progeny virus release. Our findings and the poor reproducibility indicate that the B cell culture system in its current form is unsuitable for ReCV or HuNoV research and does not represent an efficient valid cell culture system.

A three-dimensional high throughput assay identifies novel antibacterial molecules with activity against intracellular Shigella

The Gram-negative bacterial species Shigella is the second leading cause of diarrhea among children in low and middle-income countries (LMICs) and is a World Health Organization (WHO) priority pathogen. Shigella infections are becoming increasing difficult to treat due to antimicrobial resistance (AMR), leading to an urgent need for new antimicrobial agents with novel modes of action. Shigella pathogenesis is largely intracellular and antibacterial chemicals that preferentially work inside cells may be desirable to limit collateral AMR and block key components of the Shigella infection cycle. Aiming to facilitate the process of identifying antibacterial chemicals that kill intracellular Shigella, we developed a high-throughput screening (HTS) cell-based chemical screening assay. The three-dimensional (3-D) assay, incorporating Shigella invasion into Caco-2 cells on Cytodex 3 beads, was scaled into a 384-well platform for screening chemical compound libraries. Using this assay, we evaluated >500,000 compounds, identifying 12 chemical hits that inhibit Shigella replication inside cells. This simple, efficient and HTS-compatible assays circumvents many of the limitations of traditional screening methods with cell monolayers and may be deployed for antibacterial compound screening for other intracellular pathogens.

Endoscopic findings among healthy adults with asymptomatic norovirus infection in Japan: A single-center cross-sectional study

INTRODUCTION

Norovirus infection, a major cause of acute viral gastroenteritis, is commonly reported during the winter season. Norovirus invades the upper intestinal tract, causing inflammation. In severe cases, endoscopic findings and complications, including duodenal perforation, have been reported. However endoscopic findings in patients with asymptomatic infections have rarely been reported. Therefore, this study aimed to investigate the upper endoscopic findings of patients with asymptomatic norovirus infection.

METHODS

Healthy adults (aged ≥18 years) who participated in voluntary health examinations between February 2017 and January 2018 were recruited twice a week. Only the individuals who had undergone esophagogastroduodenoscopy (EGD) were included. The primary outcome measure was the presence of any gross findings of EGD.

RESULTS

The norovirus genogroup I (GI)-positive group had more duodenal scarring than the norovirus negative group (16.3 % vs 5.9 %, respectively). After adjustment for age category, sex, and alcohol consumption status, duodenal ulcer scarring exhibited a significant association with GI-positive status (adjusted odds ratio: 3.11; 95 % confidence interval: 1.42-6.82; p = 0.005, Bonferroni-corrected, p = 0.015).

CONCLUSIONS

Healthy adults with asymptomatic norovirus (GI-positive) infection showed predominantly more duodenal ulcer scarring than the norovirus-negative group on EGD.

Progress and challenges in thermal inactivation of norovirus in oysters

Norovirus is the leading cause of viral foodborne illnesses worldwide, primarily due to its high infectivity, transmissibility, and environmental persistence. Oysters bioaccumulate norovirus particles through filter-feeding in sewage-contaminated waters and retain them for extended periods. Raw oysters are considered a significant high-risk food commody, as they can serve as vectors to transfer the pathogen to humans. Outbreaks associated with the consumption of cooked oysters indicate survival of virus particles in response to various cooking techniques. Undercooked oysters pose a substantial risk of norovirus infection, a risk that is suggested to be similar to raw oysters. Detecting human norovirus in food remains challenging due to the lack of a quantitative culture-based system that has hindered our understanding of norovirus response to heat. This article provides a critical review of the literature on mechanisms of heat inactivation and potential factors involved in the survival of norovirus in oysters during cooking. It also highlights challenges associated with norovirus detection, the necessity of risk-based research on norovirus in cooked oysters and understanding the impact of the virus-associated matrix on virus inactivation. Addressing these knowledge gaps is crucial for conducting a risk-based approach to determining cooking conditions sufficient to inactivate norovirus oysters to safe levels.

Insights into human norovirus cultivation in human intestinal enteroids

Human noroviruses (HuNoVs) are a significant cause of epidemic and sporadic acute gastroenteritis worldwide. The lack of a reproducible culture system hindered the study of HuNoV replication and pathogenesis for almost a half-century. This barrier was overcome with our successful cultivation of multiple HuNoV strains in human intestinal enteroids (HIEs), which has significantly advanced HuNoV research. We optimized culture media conditions and generated genetically modified HIE cultures to enhance HuNoV replication in HIEs. Building upon these achievements, we now present new insights into this culture system, which involve testing different media, unique HIE lines, and additional virus strains. HuNoV infectivity was evaluated and compared in new HIE models, including HIEs generated from different intestinal segments of individual adult organ donors, HIEs from human intestinal organoids produced from directed differentiation of human embryonic stem cells that were then transplanted and matured in mice before making enteroids (H9tHIEs), genetically engineered (J4FUT2 knock-in [KI], J2STAT1 knockout [KO]) HIEs, as well as HIEs derived from a patient with common variable immunodeficiency (CVID) and from infants. Our findings reveal that small intestinal HIEs, but not colonoids, from adults, H9tHIEs, HIEs from a CVID patient, and HIEs from infants support HuNoV replication with segment and strain-specific differences in viral infection. J4FUT2-KI HIEs exhibit the highest susceptibility to HuNoV infection, allowing the cultivation of a broader range of genogroup I and II HuNoV strains than previously reported. Overall, these results contribute to a deeper understanding of HuNoVs and highlight the transformative potential of HIE cultures in HuNoV research.IMPORTANCEHuman noroviruses (HuNoVs) cause global diarrheal illness and chronic infections in immunocompromised patients. This paper reports approaches for cultivating HuNoVs in secretor positive human intestinal enteroids (HIEs). HuNoV infectivity was compared in new HIE models, including ones from (i) different intestinal segments of single donors, (ii) human embryonic stem cell-derived organoids transplanted into mice, (iii) genetically modified lines, and (iv) a patient with common variable immunodeficiency disease. HIEs from small intestine, but not colon, support HuNoV replication with donor, segment, and strain-specific variations. Unexpectedly, HIEs from one donor are resistant to GII.3 infection. The genetically modified J4FUT2 knock-in (KI) HIEs enable cultivation of a broad range of GI and GII genotypes. New insights into strain-specific differences in HuNoV replication in HIEs support this platform for advancing understanding of HuNoV biology and developing potential therapeutics.

In Vitro Culture of Human Norovirus in the Last 20 Years

Human noroviruses (HuNoVs) are the main pathogens that cause acute gastroenteritis and lead to huge economic losses annually. Due to the lack of suitable culture systems, the pathogenesis of HuNoVs and the development of vaccines and drugs have progressed slowly. Although researchers have employed various methods to culture HuNoVs in vitro in the last century, problems relating to the irreducibility, low viral titer, and non-infectiousness of the progeny virus should not be ignored. In 2016, researchers achieved the cultivation and successive passaging of some HuNoV genotypes using human intestinal enteroids, initially demonstrating the potential use of organoids in overcoming this challenge. This paper reviews the efforts made in the last 20 years to culture HuNoVs in vitro and discusses the superiority and limitations of employing human intestinal enteroids/organoids as an in vitro culture model for HuNoVs.

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.

Current trends and new approaches for human norovirus replication in cell culture: a literature review

Human norovirus (HuNoV) is one of the world's leading causes of acute gastroenteritis. At present, effective reproduction of the virus in cell cultures remains a challenge for virologists, as there is a lack of a permissive cell line that allows the entire viral life cycle to be reproduced. This is a barrier to the study of the HuNoV life cycle, its tropism, and virus-host interactions. It is also a major hurdle for the development of viral detection platforms, and ultimately for the development of therapeutics. The lack of an inexpensive, technically simple, and easily implemented cultivation method also negatively affects our ability to evaluate the efficacy of a variety of control measures (disinfectants, food processes) for human norovirus. In the process of monitoring this pathogen, it is necessary to detect infectious viral particles in water, food, and other environmental samples. Therefore, improvement of in vitro replication of HuNoV is still needed. In this review, we discuss current trends and new approaches to HuNoV replication in cell culture. We highlight ways in which previous research on HuNoV and other noroviruses has guided and influenced the development of new HuNoV culture systems and discuss the improvement of in vitro replication of HuNoV.

Replication of Human Norovirus in Human Intestinal Enteroids Is Affected by Fecal Sample Processing

Human intestinal enteroids (HIEs) culture is an emerging model for assessing the infectivity of human noroviruses (HuNoVs). The model is based on detecting an increase in HuNoV RNA post-infection of HIEs. HuNoV fecal samples used for HIE infection are traditionally processed by serial filtration. Recently, processing HuNoV fecal samples by serial centrifugation was shown to retain vesicles containing HuNoV. The objective of this study was to investigate whether serially centrifuged fecal samples, RNA extraction kit (QIAamp versus MagMaX) and HIE age (newer versus older) affect HuNoV RNA fold increase in HIE. HuNoV GII.1, GII.4 and GII.6 fecal samples were prepared by serial centrifugation and filtration and the viral RNA in HIE was quantified at 1 and 72 h post-infection (hpi) following RNA extraction and RT-qPCR. The serially filtered GII.1, GII.4 and GII.6 showed successful replication in HIE, resulting in mean log increases of 2.2, 2 and 1.2, respectively, at 72 vs. 1 hpi. In contrast, only serially centrifuged GII.1 showed consistently successful replication. However, using newer HIE passages and the MagMAX kit resulted in mean log fold increases for serially centrifuged GII.1, GII.4 and GII.6 (1.6, 2.3 and 1.8 log, respectively) that were similar to serially filtered samples. Therefore, HuNoV fecal sample processing and HIE age can affect virus replication in the HIE model.

Biomanufacturing of 3D Tissue Constructs in Microgravity and their Applications in Human Pathophysiological Studies

The growing interest in bioengineering in-vivo-like 3D functional tissues has led to novel approaches to the biomanufacturing process as well as expanded applications for these unique tissue constructs. Microgravity, as seen in spaceflight, is a unique environment that may be beneficial to the tissue-engineering process but cannot be completely replicated on Earth. Additionally, the expense and practical challenges of conducting human and animal research in space make bioengineered microphysiological systems an attractive research model. In this review, published research that exploits real and simulated microgravity to improve the biomanufacturing of a wide range of tissue types as well as those studies that use microphysiological systems, such as organ/tissue chips and multicellular organoids, for modeling human diseases in space are summarized. This review discusses real and simulated microgravity platforms and applications in tissue-engineered microphysiological systems across three topics: 1) application of microgravity to improve the biomanufacturing of tissue constructs, 2) use of tissue constructs fabricated in microgravity as models for human diseases on Earth, and 3) investigating the effects of microgravity on human tissues using biofabricated in vitro models. These current achievements represent important progress in understanding the physiological effects of microgravity and exploiting their advantages for tissue biomanufacturing.

[In vitro propagation system for human norovirus]

Human norovirus (HuNoV) is an infectious virus that accounts for more than half of all cases of infectious gastroenteritis, but its mechanism of infection and multiplication within the host are largely unknown. Accordingly, there are no available vaccines or specific therapeutic agents　applicable to HuNoV infection. The primary reason for this is the absence of an established in vitro culture and growth system for HuNoV. Therefore, virological analysis of HuNoV has been conducted using murine norovirus, which is most closely related to HuNoV and can be cultured in some cell-lines. Recently, several laboratories have reported successful in vitro cultivation of HuNoV using human intestinal epithelial cells, raising expectations for further advancements in HuNoV research. In this paper, we present recent findings regarding the in vitro propagation system of HuNoV.  .

A split NanoLuc complementation-based human norovirus-like particle entry assay facilitates evaluation of anti-norovirus antibodies in live cells

Human noroviruses (NoVs) are the most common cause of acute gastroenteritis worldwide. One major obstacle in developing NoV vaccines is the lack of robust cell culture for efficacy evaluation. In this study, we successfully developed a NoV virus-like particle (VLP) entry assay based on split NanoLuc luciferase (LgBiT and HiBiT) complementation. HiBiT-tagged NoV GII.4 VLP (VLP-HiBiT) can be efficiently produced in Pichia pastoris and retain binding activity towards NoV receptor histo-blood group antigens (HBGAs). A 293T-FUT2-LgBiT cell line was established and was shown to stably express cell surface HBGAs and intracellular LgBiT. GII.4 VLP-HiBiT can bind and enter into the 293-FUT2-LgBiT cells, producing strong luminescence signals in live cells. Anti-GII.4 sera can inhibit VLP-HiBiT entry into the 293-FUT2-LgBiT cells in a dose-dependent manner, and neutralizing titers well correlate with their blocking titers measured by HBGAs-binding blockade assay. Moreover, such a surrogate infection/neutralization assay can be applied to other NoV genotypes such as GI.1 and GII.17. Together, the VLP-HiBiT entry assay can mimic both NoV attachment and internalization in live cells and thus facilitate reliable and comprehensive evaluation of NoV vaccine and antibodies.

Inactivation of Murine Norovirus Suspended in Organic Matter Simulating Actual Conditions of Viral Contamination

Foodborne viral illnesses are frequent worldwide and costly for the society. Human norovirus is one of the most common causal agents. Although some norovirus genotypes can now be cultured, surrogates are still used for inactivation studies. The aim of this study was to evaluate the effects of different organic loads individually (artificial feces, real fecal matter, ASTM tripartite organic load, fetal bovine serum) on the efficacy of three highly used sanitization treatments (thermal inactivation, peracetic acid and sodium hypochlorite treatment) using murine norovirus 3 in solutions and surfaces. Based on plaque-forming units, we show that organic matter protects murine norovirus 3 against thermal inactivation (viral reduction of ~ 1 log compared to 2.67 with PBS). However, there was a low-level but significant protection against peracetic acid (viral reduction of ~ 2 log compared to 2.85 with PBS) and none in the presence of sodium hypochlorite. Our study showed that the tested organic matters do not behave similarly depending on the treatments, especially with heat treatments, which showed a higher protection. Furthermore, Feclone ™ artificial feces mimicked some aspect of real fecal matter and may be used instead. Our results will be helpful to researchers undertaking viral inactivation studies in which an organic matrix is used to simulate actual conditions of human norovirus environment.

Mass Spectrometry-Based System for Identifying and Typing Norovirus Major Capsid Protein VP1

Norovirus-associated diseases are the most common foodborne illnesses worldwide. Polymerase chain reaction-based methods are the primary diagnostics for clinical samples; however, the high mutation rate of norovirus makes viral amplification and genotyping challenging. Technological advances in mass spectrometry (MS) make it a promising tool for identifying disease markers. Besides, the superior sensitivity of MS and proteomic approaches may enable the detection of all variants. Thus, this study aimed to establish an MS-based system for identifying and typing norovirus. We constructed three plasmids containing the major capsid protein VP1 of the norovirus GII.4 2006b, 2006a, and 2009a strains to produce virus-like particles for use as standards. Digested peptide signals were collected using a nano-flow ultra-performance liquid chromatography mass spectrometry (nano-UPLC/MS^E) system, and analyzed by ProteinLynx Global SERVER and TREE-PUZZLE software. Results revealed that the LC/MS^E system had an excellent coverage rate: the system detected more than 94% of amino acids of 3.61 femtomole norovirus VP1 structural protein. In the likelihood-mapping analysis, the proportions of unresolved quartets were 2.9% and 4.9% in the VP1 and S domains, respectively, which is superior to the 15.1% unresolved quartets in current PCR-based methodology. In summary, the use of LC/MS^E may efficiently monitor genotypes, and sensitively detect structural and functional mutations of noroviruses.

Current and Future Antiviral Strategies to Tackle Gastrointestinal Viral Infections

Acute gastroenteritis caused by virus has a major impact on public health worldwide in terms of morbidity, mortality, and economic burden. The main culprits are rotaviruses, noroviruses, sapoviruses, astroviruses, and enteric adenoviruses. Currently, there are no antiviral drugs available for the prevention or treatment of viral gastroenteritis. Here, we describe the antivirals that were identified as having in vitro and/or in vivo activity against these viruses, originating from in silico design or library screening, natural sources or being repurposed drugs. We also highlight recent advances in model systems available for this (hard to cultivate) group of viruses, such as organoid technologies, and that will facilitate antiviral studies as well as fill some of current knowledge gaps that hamper the development of highly efficient therapies against gastroenteric viruses.

Bile Goes Viral

Laboratory cultivation of viruses is critical for determining requirements for viral replication, developing detection methods, identifying drug targets, and developing antivirals. Several viruses have a history of recalcitrance towards robust replication in laboratory cell lines, including human noroviruses and hepatitis B and C viruses. These viruses have tropism for tissue components of the enterohepatic circulation system: the intestine and liver, respectively. The purpose of this review is to discuss how key enterohepatic signaling molecules, bile acids (BAs), and BA receptors are involved in the replication of these viruses and how manipulation of these factors was useful in the development and/or optimization of culture systems for these viruses. BAs have replication-promoting activities through several key mechanisms: (1) affecting cellular uptake, membrane lipid composition, and endocytic acidification; (2) directly interacting with viral capsids to influence binding to cells; and (3) modulating the innate immune response. Additionally, expression of the Na+-taurocholate cotransporting polypeptide BA receptor in continuous liver cell lines is critical for hepatitis B virus entry and robust replication in laboratory culture. Viruses are capable of hijacking normal cellular functions, and understanding the role of BAs and BA receptors, components of the enterohepatic system, is valuable for expanding our knowledge on the mechanisms of norovirus and hepatitis B and C virus replication.

Experimental Methods to Study the Pathogenesis of Human Enteric RNA Viruses

Every year, millions of children are infected with viruses that target the gastrointestinal tract, causing acute gastroenteritis and diarrheal illness. Indeed, approximately 700 million episodes of diarrhea occur in children under five annually, with RNA viruses norovirus, rotavirus, and astrovirus serving as major causative pathogens. Numerous methodological advancements in recent years, including the establishment of novel cultivation systems using enteroids as well as the development of murine and other animal models of infection, have helped provide insight into many features of viral pathogenesis. However, many aspects of enteric viral infections remain elusive, demanding further study. Here, we describe the different in vitro and in vivo tools available to explore different pathophysiological attributes of human enteric RNA viruses, highlighting their advantages and limitations depending upon the question being explored. In addition, we discuss key areas and opportunities that would benefit from further methodological progress.

3D culture models to study SARS-CoV-2 infectivity and antiviral candidates: From spheroids to bioprinting

The pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is receiving worldwide attention, due to the severity of the disease (COVID-19) that resulted in more than a million global deaths so far. The urgent need for vaccines and antiviral drugs is mobilizing the scientific community to develop strategies for studying the mechanisms of SARS-CoV-2 infection, replication kinetics, pathogenesis, host-virus interaction, and infection inhibition. In this work, we review the strategies of tissue engineering in the fabrication of three-dimensional (3D) models used in virology studies, which presented many advantages over conventional cell cultures, such as complex cytoarchitecture and a more physiological microenvironment. Scaffold-free (spheroids and organoids) and scaffold-based (3D scaffolding and 3D bioprinting) approach allow the biofabrication of more realistic models relevant to the pandemic, to be used as in vitro platforms for the development of new vaccines and therapies against COVID-19.

Exosomes Facilitate Transmission of Enterovirus A71 From Human Intestinal Epithelial Cells

BACKGROUND

Enterovirus A71 (EV-A71) has been noted for its tendency to lead to neurological manifestations in young children and infants. Although the alimentary tract has been identified as the primary replication site of this virus, how EV-A71 replicates in the gut and is transmitted to other organs remains unclear.

METHODS

By using differentiated C2BBe1 cells as a model, we observed that intestinal epithelial cells (IECs) were permissive to EV-A71 infection, and viral particles were released in a nonlytic manner.

RESULTS

The coexistence of active caspase 3 and EV-A71 protein was observed in the infected undifferentiated C2BBe1 and RD cells but not in the infected differentiated C2BBe1 cells. Furthermore, EV-A71 infection caused differentiated C2BBe1 and intestinal organoids to secrete exosomes containing viral components and have the ability to establish active infection. Inhibition of the exosome pathway decreased EV-A71 replication and release in IECs and increased the survival rates of infected animals.

CONCLUSIONS

Our findings showed that EV-A71 is able to be actively replicated in enterocytes, and that the exosome pathway is involved in the nonlytic release of viral particles, which may be useful for developing antiviral strategies.

Targeted Profiling of Immunological Genes during Norovirus Replication in Human Intestinal Enteroids

Norovirus is the leading cause of acute gastroenteritis worldwide. The pathogenesis of norovirus and the induced immune response remain poorly understood due to the lack of a robust virus culture system. The monolayers of two secretor-positive Chinese human intestinal enteroid (HIE) lines were challenged with two norovirus pandemic GII.4 Sydney strains. Norovirus RNA replication in supernatants and cell lysates were quantified by RT-qPCR. RNA expression levels of immune-related genes were profiled using PCR arrays. The secreted protein levels of shortlisted upregulated genes were measured in supernatants using analyte-specific enzyme-linked immunosorbent assay (ELISA). Productive norovirus replications were achieved in three (75%) out of four inoculations. The two most upregulated immune-related genes were CXCL10 (93-folds) and IFI44L (580-folds). Gene expressions of CXCL10 and IFI44L were positively correlated with the level of norovirus RNA replication (CXCL10: Spearman’s r = 0.779, p < 0.05; IFI44L: r = 0.881, p < 0.01). The higher level of secreted CXCL10 and IFI44L proteins confirmed their elevated gene expression. The two genes have been reported to be upregulated in norovirus volunteer challenges and natural human infections by other viruses. Our data suggested that HIE could mimic the innate immune response elicited in natural norovirus infection and, therefore, could serve as an experimental model for future virus-host interaction and antiviral studies.

Molecular Characterization of Norovirus Circulating in Northwest Mexico During 2013-2014

Norovirus (NoV) is an important etiological agent of diarrhea in children and adults. In Mexico, NoV screening is not routinely performed. NoV is highly infectious and is responsible for massive outbreaks due to the consumption of contaminated food. The study was a cross-sectional design. Samples of diarrheal stools were collected from (62) children and (38) adults with acute gastroenteritis during 2013-2014. The circulating genogroups of NoV were detected by amplifying the RdRp gene fragment, and for the genotyping, the capsid and polymerase fragments were sequenced. Seventy-seven percent of the analyzed samples were positive for NoV. Genotyping was possible for 51 samples; for polymerase GII.P2, GII.P31, GII.P4, GII.P7, GII.P40, and GI.P14 were identified, whereas for capsid, genotypes GI.3, GII.2, GII.4, GII.5, GII.14, and GII.17. In conclusion, there is a high prevalence of gastroenteritis due to NoV in the northwest of Mexico, including genotypes that have not been reported previously in Mexico.

Bioprinting for combating infectious diseases

Infectious diseases have the ability to impact health on a global scale, as is being demonstrated by the current coronavirus disease 2019 (COVID-19) pandemic. The strenuous circumstances related to this global health crisis have been highlighting the challenges faced by the biomedical field in combating infectious diseases. Notably, printing technologies have advanced rapidly over the last decades, allowing for the incorporation of living cells in the printing process (or bioprinting) to create constructs that are able to serve as in vitro tissue or virus-disease models in combating infectious diseases. This paper describes applications of bioprinting in addressing the challenges faced in combating infectious diseases, with a specific focus on in vitro modelling and on development of therapeutic agents and vaccines. Integration of these technologies may allow for a more efficient and effective response to current and future pandemics.

Put Some Guts into It: Intestinal Organoid Models to Study Viral Infection

The knowledge about enteric viral infection has vastly increased over the last eight years due to the development of intestinal organoids and enteroids that suppose a step forward from conventional studies using cell lines. Intestinal organoids and enteroids are three-dimensional (3D) models that closely mimic intestinal cellular heterogeneity and organization. The barrier function within these models has been adapted to facilitate viral studies. In this review, several adaptations (such as organoid-derived two-dimensional (2D) monolayers) and original intestinal 3D models are discussed. The specific advantages and applications, as well as improvements of each model are analyzed and an insight into the possible path for the field is given.

A three-dimensional A549 cell culture model to study respiratory syncytial virus infections

BACKGROUND

Respiratory syncytial virus (RSV) is a primary cause of morbidity and mortality worldwide, affecting infants, young children, and immune-compromised patients; however, currently no vaccine is available for prevention of RSV infections. The overwhelming majority of our knowledge of how RSV causes infection is based upon studies that have been carried out using traditional 2D methods, with cells cultured on flat plastic dishes. Although these simplified culture systems are essential to gain an insight into the fundamentals of host-pathogen interactions, cells in 2D are not exposed to the same conditions as cells in 3D tissues in the body and are therefore a poor representation of thein vivo microenvironment. In this study, we aim to develop the first 3D culture model for RSV infection using A549 cells to test its utility for RSV pathogenesis.

METHODS

To generate spheroids, A549 cells were cultured using ultra-low attachment plates to generate 25 × 10³ cell spheroids. The viability of the spheroids was assessed by trypan blue exclusion assay and flow cytometry showing prominent live cells throughout the spheroids confirming high viability over seven days of incubation.

RESULTS

Immunostaining of A549 spheroids inoculated with RSV, showed time-dependent dissemination of the viral antigen RSV-F within the spheroid, resulting in syncytia formation and a 3-fold increase in mucin secretion compared to the uninfected cells. Additionally, RSV successfully replicated in the spheroids producing infectious virus as early as day one post-inoculation and was sustained for up to 7 days post-inoculation.

CONCLUSIONS

Results show that A549 spheroids are susceptible and permissive for RSV since they exhibit the characteristics of RSV infection including syncytia formation and mucin overexpression, suggesting that A549 spheroids can be used a promising model for studying RSV in vitro.

Heat sensitization of hepatitis A virus and Tulane virus using grape seed extract, gingerol and curcumin

Human noroviruses (HNoV) and hepatitis A virus (HAV) are predominantly linked to foodborne outbreaks worldwide. As cell-culture systems to propagate HNoV in laboratories are not easily available, Tulane virus (TV) is used as a cultivable HNoV surrogate to determine inactivation. Heat-sensitization of HAV and TV by "generally recognized as safe'' (GRAS) substances can potentially reduce their time-temperature inactivation parameters during processing to ensure food safety. Curcumin, gingerol (from ginger), and grape seed extract (GSE) reportedly have anti-inflammatory, immune-modulating and antiviral properties. The objective of this study was to determine and compare the D-values and z-values of HAV and TV at 52-68 °C with or without curcumin (0.015 mg/ml), gingerol (0.1 mg/ml), or GSE (1 mg/ml) in 2-ml glass vials. HAV at ~7 log PFU/ml and TV at ~6 log PFU/ml were diluted in phosphate buffered saline (PBS) and added to two sets of six 2-mL sterile glass vials. One set served as the control and the second set had the three extracts individually added for thermal treatments in a circulating water bath for 0-10 min. The D-values for TV in PBS ranged from 4.55 ± 0.28 to 1.08 ± 0.16 min, and for HAV in PBS ranged from to 9.21 ± 0.24 to 0.67 ± 0.19 min at 52-68 °C. Decreased D-values (52-58 °C) for TV with curcumin ranging from 4.32 ± 0.25 to 0.62 ± 0.17 min, gingerol from 4.09 ± 0.18 to 0.72 ± 0.09 min and GSE from 3.82 ± 0.18 to 0.80 ± 0.07 min, with similar trends for HAV were observed. The linear model showed significant differences (p < 0.05) between the D-values of HAV and TV with and without plant extracts for most tested temperatures. This suggests that GRAS substances can potentially lower temperature and time regimens needed to inactivate HAV and TV.

Human Norovirus Cultivation in Nontransformed Stem Cell-Derived Human Intestinal Enteroid Cultures: Success and Challenges

Noroviruses, in the genus Norovirus, are a significant cause of viral gastroenteritis in humans and animals. For almost 50 years, the lack of a cultivation system for human noroviruses (HuNoVs) was a major barrier to understanding virus biology and the development of effective antiviral strategies. This review presents a historical perspective of the development of a cultivation system for HuNoVs in human intestinal epithelial cell cultures. Successful cultivation was based on the discovery of genetically-encoded host factors required for infection, knowledge of the site of infection in humans, and advances in the cultivation of human intestinal epithelial cells achieved by developmental and stem cell biologists. The human stem cell-derived enteroid cultivation system recapitulates the multicellular, physiologically active human intestinal epithelium, and allows studies of virus-specific replication requirements, evaluation of human host-pathogen interactions, and supports the pre-clinical assessment of methods to prevent and treat HuNoV infections.

Human Norovirus Replication in Human Intestinal Enteroids as Model to Evaluate Virus Inactivation

Human noroviruses are a leading cause of epidemic and endemic acute gastroenteritis worldwide and a leading cause of foodborne illness in the United States. Recently, human intestinal enteroids (HIEs) derived from human small intestinal tissue have been shown to support human norovirus replication. We implemented the HIE system in our laboratory and tested the effect of chlorine and alcohols on human norovirus infectivity. Successful replication was observed for 6 norovirus GII genotypes and was dependent on viral load and genotype of the inoculum. GII.4 viruses had higher replication levels than other genotypes. Regardless of concentration or exposure time, alcohols slightly reduced, but did not completely inactivate, human norovirus. In contrast, complete inactivation of the 3 GII.4 viruses occurred at concentrations as low as 50 ppm of chlorine. Taken together, our data confirm the successful replication of human noroviruses in HIEs and their utility as tools to study norovirus inactivation strategies.

Discovery of novel astrovirus and calicivirus identified in ruddy turnstones in Brazil

Birds are the natural reservoir of viruses with zoonotic potential, as well as contributing to the evolution, emergence, and dissemination of novel viruses. In this study, we applied a high-throughput screening approach to identify the diversity of viruses in 118 samples of birds captured between October 2006 to October 2010 in the North and Northeast regions of Brazil. We found nearly complete genomes of novel species of astrovirus and calicivirus in cloacal swabs of ruddy turnstones (Arenaria interpres) collected in Coroa do Avião islet, Pernambuco State. These viruses are positive-sense single-stranded RNA with a genome of ~7 to 8 kb, and were designated as Ruddy turnstone astrovirus (RtAstV) and Ruddy turnstone calicivirus (RTCV), respectively. Phylogenetic analysis showed that RtAstV and RTCV grouped in a monophyletic clade with viruses identified from poultry samples (i.e., chicken, goose, and turkey), including viruses associated with acute nephritis in chickens. Attempts of viral propagation in monkey and chicken cell lines for both viruses were unsuccessful. Also, we found genomes related with viral families that infect invertebrates and plants, suggesting that they might be ingested in the birds' diet. In sum, these findings shed new light on the diversity of viruses in migratory birds with the notable characterization of a novel astrovirus and calicivirus.

Critical issues in application of molecular methods to environmental virology

Waterborne diseases have significant public health and socioeconomic implications worldwide. Many viral pathogens are commonly associated with water-related diseases, namely enteric viruses. Also, novel recently discovered human-associated viruses have been shown to be a causative agent of gastroenteritis or other clinical symptoms. A wide range of analytical methods is available for virus detection in environmental water samples. Viral isolation is historically carried out via propagation on permissive cell lines; however, some enteric viruses are difficult or not able to propagate on existing cell lines. Real-time polymerase chain reaction (qPCR) screening of viral nucleic acid is routinely used to investigate virus contamination in water due to the high sensitivity and specificity. Additionally, the introduction of metagenomic approaches into environmental virology has facilitated the discovery of viruses that cannot be grown in cell culture. This review (i) highlights the applications of molecular techniques in environmental virology such as PCR and its modifications to overcome the critical issues associated with the inability to discriminate between infectious viruses and nonviable viruses, (ii) outlines the strengths and weaknesses of Nucleic Acid Sequence Based Amplification (NASBA) and microarray, (iii) discusses the role of digital PCR as an emerging water quality monitoring assay and its advantages over qPCR, (iv) addresses the viral metagenomics in terms of detecting emerging viral pathogens and diversity in aquatic environment. Indeed, there are many challenges for selecting methods to detect classic and emerging viruses in environmental samples. While the existing techniques have revealed the importance and diversity of viruses in the water environment, further developments are necessary to enable more rapid and accurate methodologies for viral water quality monitoring and regulation.

Key role of singlet oxygen and peroxynitrite in viral RNA damage during virucidal effect of plasma torch on feline calicivirus

A dielectric barrier discharge (DBD) plasma torch has been used to evaluate the mechanism underlying inactivation of feline calicivirus (FCV) by plasma treatment. Plasma treatment of cell lysate infected with FCV F9 strain reduced the viral titer of the median tissue culture infectious dose (TCID₅₀). The D value (treatment time required to lower the viral titer to 1/10) was 0.450 min, while the viral titer dropped below the detection limit within 2 min. FCV was not significantly inactivated by heat or UV applied at levels corresponding to those generated from the DBD plasma torch after 2 min (38.4 °C and 46.79 mJ/cm² UV, respectively). However, TCID₅₀ was reduced by 2.47 log after exposure to 4.62 mM ONOO⁻, corresponding to the concentration generated after 2 min of plasma treatment. Radical scavengers, including superoxide dismutase, dimethyl sulfoxide, and catalase, did not significantly affect viral titers; however, sodium azide, uric acid, and ascorbic acid, which are scavengers of ¹O₂ radicals, ONOO⁻, and peroxynitrous acid (ONOOH; produced from ONOO⁻ under acidic conditions), respectively, significantly increased TCID₅₀ and intact viral RNA. These findings suggest that ONOO⁻ and ¹O₂ play an important role in FCV inactivation by attacking viral RNA during DBD plasma torch treatment.

Modeling Host-Pathogen Interactions in the Context of the Microenvironment: Three-Dimensional Cell Culture Comes of Age

Tissues and organs provide the structural and biochemical landscapes upon which microbial pathogens and commensals function to regulate health and disease. While flat two-dimensional (2-D) monolayers composed of a single cell type have provided important insight into understanding host-pathogen interactions and infectious disease mechanisms, these reductionist models lack many essential features present in the native host microenvironment that are known to regulate infection, including three-dimensional (3-D) architecture, multicellular complexity, commensal microbiota, gas exchange and nutrient gradients, and physiologically relevant biomechanical forces (e.g., fluid shear, stretch, compression). A major challenge in tissue engineering for infectious disease research is recreating this dynamic 3-D microenvironment (biological, chemical, and physical/mechanical) to more accurately model the initiation and progression of host-pathogen interactions in the laboratory. Here we review selected 3-D models of human intestinal mucosa, which represent a major portal of entry for infectious pathogens and an important niche for commensal microbiota. We highlight seminal studies that have used these models to interrogate host-pathogen interactions and infectious disease mechanisms, and we present this literature in the appropriate historical context. Models discussed include 3-D organotypic cultures engineered in the rotating wall vessel (RWV) bioreactor, extracellular matrix (ECM)-embedded/organoid models, and organ-on-a-chip (OAC) models. Collectively, these technologies provide a more physiologically relevant and predictive framework for investigating infectious disease mechanisms and antimicrobial therapies at the intersection of the host, microbe, and their local microenvironments.

Modeling Tissue Polarity in Context

Polarity is critical for development and tissue-specific function. However, the acquisition and maintenance of tissue polarity is context dependent. Thus, cell and tissue polarity depend on cell adhesion which is regulated by the cytoskeleton and influenced by the biochemical composition of the extracellular microenvironment and modified by biomechanical cues within the tissue. These biomechanical cues include fluid flow induced shear stresses, cell-density and confinement-mediated compression, and cellular actomyosin tension intrinsic to the tissue or induced in response to morphogens or extracellular matrix stiffness. Here, we discuss how extracellular matrix stiffness and fluid flow influence cell-cell and cell-extracellular matrix adhesion and alter cytoskeletal organization to modulate cell and tissue polarity. We describe model systems that when combined with state of the art molecular screens and high-resolution imaging can be used to investigate how force modulates cell and tissue polarity.

Attempts to grow human noroviruses, a sapovirus, and a bovine norovirus in vitro

Noroviruses (NoVs) and Sapoviruses (SaVs) are enteric caliciviruses that have been detected in multiple mammalian species, including humans. Currently, efficient cell culture systems have been established only for murine NoVs and porcine SaV Cowden strain. Establishment of an efficient in vitro cell culture system for other NoVs and SaVs remains challenging; however, human NoV (HuNoV) replication in 3D cultured Caco-2 cells and a clone of Caco-2 cells, C2BBe1, human enteroids and in human B cells has been reported. In this study, we tested various cells and culture conditions to grow HuNoVs and a human SaV (HuSaV) to test the possibility of the propagation in different cells and culture conditions. We also attempted to grow a bovine NoV (BoNoV) in ex vivo organ cultures. We did not observe significant RNA level increases for HuSaV and BoNoV under our test conditions. HuNoV RNA levels increased to a maximum of ~600-fold in long-term Caco-2 cells that were cultured for 1–2 months in multi-well plates and inoculated with HuNoV-positive and bacteria-free human stool suspensions using serum-free medium supplemented with the bile acid, GCDCA. However, this positive result was inconsistent. Our results demonstrated that HuNoVs, BoNoV and HuSaV largely failed to grow in vitro under our test conditions. Our purpose is to share our findings with other researchers with the goal to develop efficient, reproducible simplified and cost-effective culture systems for human and animal NoVs and SaVs in the future.

Human intestinal organoids express histo-blood group antigens, bind norovirus VLPs, and support limited norovirus replication

Through pluripotent stem cell (PSC) technology, human intestinal organoids (HIOs) with remarkably similarity to the fetal intestine in cellular composition, architecture, and absorptive/secretory functions have been successfully developed, providing a useful in vitro model system to study the structure and function of human congenital gut and intestinally related diseases. We report here the usefulness of HIOs as a model system to study intestinal carbohydrate expression, virus-host interaction, and replication of human noroviruses (huNoVs). We found that fully developed HIOs express effectively various types 1 and 2 HBGAs, including Lewis, secretor, and nonsecretor antigens, distributing on the glycocalyx. Selected huNoV-like particles (VLPs) bound the glycocalyx of HIOs with matched HBGA phenotypes. Using GII.4 huNoV positive stool filtrates, we demonstrated limited huNoV replication in HIOs with corresponding HBGAs through detection of viral RNAs by RT-PCR and capsid antigens by immunostaining methods. Our data suggested that, after further improvements, HIOs can be a useful model to study intestinal glycan expression, huNoV-intestine interaction, and huNoV infection in the intestine.

Intranasal delivery of a bivalent norovirus vaccine formulated in an in situ gelling dry powder

The global health community is beginning to understand the burden of norovirus-associated disease, which has a significant impact in both developed and developing countries. Norovirus virus like particle (VLP)-based vaccines are currently under development and have been shown to elicit systemic and mucosal immune responses when delivered intranasally. In the present study, we describe the use of a dry powder formulation (GelVac™) with an in situ gelling polysaccharide (GelSite™) extracted from Aloe vera for nasal delivery of a bivalent vaccine formulation containing both GI and GII.4 norovirus VLPs. Dose-ranging studies were performed to identify the optimal antigen dosages based on systemic and mucosal immune responses in guinea pigs and determine any antigenic interference. A dose-dependent increase in systemic and mucosal immunogenicity against each of the VLPs were observed as well as a boosting effect for each VLP after the second dosing. A total antigen dose of ≥50 μg of each GI and GII.4 VLPs was determined to be the maximally immunogenic dose in guinea pigs. The immunogenicity results of this bivalent formulation, taken together with previous work on monovalent GelVac™ norovirus vaccine formulation, provides a basis for future development of this norovirus VLP vaccine.

Three-Dimensional Rotating Wall Vessel-Derived Cell Culture Models for Studying Virus-Host Interactions

The key to better understanding complex virus-host interactions is the utilization of robust three-dimensional (3D) human cell cultures that effectively recapitulate native tissue architecture and model the microenvironment. A lack of physiologically-relevant animal models for many viruses has limited the elucidation of factors that influence viral pathogenesis and of complex host immune mechanisms. Conventional monolayer cell cultures may support viral infection, but are unable to form the tissue structures and complex microenvironments that mimic host physiology and, therefore, limiting their translational utility. The rotating wall vessel (RWV) bioreactor was designed by the National Aeronautics and Space Administration (NASA) to model microgravity and was later found to more accurately reproduce features of human tissue in vivo. Cells grown in RWV bioreactors develop in a low fluid-shear environment, which enables cells to form complex 3D tissue-like aggregates. A wide variety of human tissues (from neuronal to vaginal tissue) have been grown in RWV bioreactors and have been shown to support productive viral infection and physiological meaningful host responses. The in vivo-like characteristics and cellular features of the human 3D RWV-derived aggregates make them ideal model systems to effectively recapitulate pathophysiology and host responses necessary to conduct rigorous basic science, preclinical and translational studies.

Three-dimensional cell culture models for investigating human viruses

Three-dimensional (3D) culture models are physiologically relevant, as they provide reproducible results, experimental flexibility and can be adapted for high-throughput experiments. Moreover, these models bridge the gap between traditional two-dimensional (2D) monolayer cultures and animal models. 3D culture systems have significantly advanced basic cell science and tissue engineering, especially in the fields of cell biology and physiology, stem cell research, regenerative medicine, cancer research, drug discovery, and gene and protein expression studies. In addition, 3D models can provide unique insight into bacteriology, virology, parasitology and host-pathogen interactions. This review summarizes and analyzes recent progress in human virological research with 3D cell culture models. We discuss viral growth, replication, proliferation, infection, virus-host interactions and antiviral drugs in 3D culture models.

Norovirus Dynamics in Wastewater Discharges and in the Recipient Drinking Water Source: Long-Term Monitoring and Hydrodynamic Modeling

Norovirus (NoV) that enters drinking water sources with wastewater discharges is a common cause of waterborne outbreaks. The impact of wastewater treatment plants (WWTPs) on the river Göta älv (Sweden) was studied using monitoring and hydrodynamic modeling. The concentrations of NoV genogroups (GG) I and II in samples collected at WWTPs and drinking water intakes (source water) during one year were quantified using duplex real-time reverse-transcription polymerase chain reaction. The mean (standard deviation) NoV GGI and GGII genome concentrations were 6.2 (1.4) and 6.8 (1.8) in incoming wastewater and 5.3 (1.4) and 5.9 (1.4) log₁₀ genome equivalents (g.e.) L^-1 in treated wastewater, respectively. The reduction at the WWTPs varied between 0.4 and 1.1 log₁₀ units. In source water, the concentration ranged from below the detection limit to 3.8 log₁₀ g.e. L^-1. NoV GGII was detected in both wastewater and source water more frequently during the cold than the warm period of the year. The spread of NoV in the river was simulated using a three-dimensional hydrodynamic model. The modeling results indicated that the NoV GGI and GGII genome concentrations in source water may occasionally be up to 2.8 and 1.9 log₁₀ units higher, respectively, than the concentrations measured during the monitoring project.

Survival of Enteric Viruses in the Environment and Food

Enteric viruses are those human viruses that are primarily transmitted by the fecal-oral route, either by person-to-person contact or by ingestion of contaminated food or water. The importance of viral foodborne diseases is increasingly being recognized, and several international organizations have found that there is an upward trend in their incidence. Thus, in this review, state-of-the-art information regarding virus persistence in food and the environment is compiled.

Replication of human noroviruses in stem cell-derived human enteroids

The major barrier to research and development of effective interventions for human noroviruses (HuNoVs) has been the lack of a robust and reproducible in vitro cultivation system. HuNoVs are the leading cause of gastroenteritis worldwide. We report the successful cultivation of multiple HuNoV strains in enterocytes in stem cell-derived, nontransformed human intestinal enteroid monolayer cultures. Bile, a critical factor of the intestinal milieu, is required for strain-dependent HuNoV replication. Lack of appropriate histoblood group antigen expression in intestinal cells restricts virus replication, and infectivity is abrogated by inactivation (e.g., irradiation, heating) and serum neutralization. This culture system recapitulates the human intestinal epithelium, permits human host-pathogen studies of previously noncultivatable pathogens, and allows the assessment of methods to prevent and treat HuNoV infections.

Development of a Multicellular Three-dimensional Organotypic Model of the Human Intestinal Mucosa Grown Under Microgravity

Because cells growing in a three-dimensional (3-D) environment have the potential to bridge many gaps of cell cultivation in 2-D environments (e.g., flasks or dishes). In fact, it is widely recognized that cells grown in flasks or dishes tend to de-differentiate and lose specialized features of the tissues from which they were derived. Currently, there are mainly two types of 3-D culture systems where the cells are seeded into scaffolds mimicking the native extracellular matrix (ECM): (a) static models and (b) models using bioreactors. The first breakthrough was the static 3-D models. 3-D models using bioreactors such as the rotating-wall-vessel (RWV) bioreactors are a more recent development. The original concept of the RWV bioreactors was developed at NASA's Johnson Space Center in the early 1990s and is believed to overcome the limitations of static models such as the development of hypoxic, necrotic cores. The RWV bioreactors might circumvent this problem by providing fluid dynamics that allow the efficient diffusion of nutrients and oxygen. These bioreactors consist of a rotator base that serves to support and rotate two different formats of culture vessels that differ by their aeration source type: (1) Slow Turning Lateral Vessels (STLVs) with a co-axial oxygenator in the center, or (2) High Aspect Ratio Vessels (HARVs) with oxygenation via a flat, silicone rubber gas transfer membrane. These vessels allow efficient gas transfer while avoiding bubble formation and consequent turbulence. These conditions result in laminar flow and minimal shear force that models reduced gravity (microgravity) inside the culture vessel. Here we describe the development of a multicellular 3-D organotypic model of the human intestinal mucosa composed of an intestinal epithelial cell line and primary human lymphocytes, endothelial cells and fibroblasts cultured under microgravity provided by the RWV bioreactor.

Detection of human norovirus in intestinal biopsies from immunocompromised transplant patients

Human noroviruses (HuNoVs) can often cause chronic infections in solid organ and haematopoietic stem cell transplant (HSCT) patients. Based on histopathological changes observed during HuNoV infections, the intestine is the presumed site of virus replication in patients; however, the cell types infected by HuNoVs remain unknown. The objective of this study was to characterize histopathological changes during HuNoV infection and to determine the cell types that may be permissive for HuNoV replication in transplant patients. We analysed biopsies from HuNoV-infected and non-infected (control) transplant patients to assess histopathological changes in conjunction with detection of HuNoV antigens to identify the infected cell types. HuNoV infection in immunocompromised patients was associated with histopathological changes such as disorganization and flattening of the intestinal epithelium. The HuNoV major capsid protein, VP1, was detected in all segments of the small intestine, in areas of biopsies that showed histopathological changes. Specifically, VP1 was detected in enterocytes, macrophages, T cells and dendritic cells. HuNoV replication was investigated by detecting the non-structural proteins, RdRp and VPg. We detected RdRp and VPg along with VP1 in duodenal and jejunal enterocytes. These results provide critical insights into histological changes due to HuNoV infection in immunocompromised patients and propose human enterocytes as a physiologically relevant cell type for HuNoV cultivation.