Norovirus gastroenteritis causes severe and lethal complications after chemotherapy and hematopoietic stem cell transplantation

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

The Inhibitory Effect of Resveratrol from Reynoutria japonica on MNV-1, a Human Norovirus Surrogate

As a natural nonflavonoid polyphenol compound, resveratrol is the main functional component of Reynoutria japonica and has anti-inflammatory, antioxidant, antiviral, and other physiological activities. In this study, the effect of resveratrol on the viability of RAW264.7 cells was examined, and murine norovirus (MNV-1) was used as a surrogate for human norovirus to evaluate the inhibitory effect of resveratrol. The concentrations of resveratrol resulting in 50% cytotoxicity (CC50) for RAW264.7 cells were 21.32 and 24.97 μg/mL after 24 and 48 h of incubation, respectively, and resveratrol at a concentration lower than the half-effective inhibitory concentration (EC50) could not damage cell DNA. The EC50 of resveratrol on MNV-1 in infected RAW264.7 cells was determined to equal 5.496 μg/mL. After RAW264.7 cells, virus, and a fresh mixture of virus and RAW264.7 cells were treated with resveratrol solution for 1 h (denoted cell pre-treatment, virus pre-treatment, and mixture coprocessing), the RAW264.7 cells obtained after cell pre-treatment exhibited lower virus infection, and MNV-1 obtained after virus pre-treatment and mixture coprocessing showed a decreased infectious capacity. The inhibition ratio of resveratrol on MNV-1 did not significantly differ between the treatments at 4 and 25 °C or among the various pH values except for the lower acidic condition (pH 2). TEM revealed significant changes in the morphology of MNV-1 after treatment with resveratrol, and molecular docking indicated that resveratrol strongly binds to the viral capsid protein of MNV-1. In addition, resveratrol regulated the expression of cytokine that protects against MNV-1 infection. Therefore, at a lower concentration, resveratrol, a natural component from Reynoutria japonica, exerts an inhibitory effect on MNV-1 growth and could be used as a safe additive in food products to improve the nutritional status and control norovirus.

Using molecular methods to delineate norovirus outbreaks: a systematic review

Noroviruses are among the major causative agents of human acute gastroenteritis, and the nature of norovirus outbreaks can differ considerably. The number of single-nucleotide polymorphisms (SNPs) between strains is used to assess their relationships. There is currently no universally accepted cutoff value for clustering strains that define an outbreak or linking the individuals involved. This study was conducted to estimate the threshold value of genomic variations among related strains within norovirus outbreaks. We carried out a literature search in the PubMed and Web of Science databases. SNP rates were defined as the number of SNPs/sequence length (bp) × 100%. The Mann-Whitney U-test was used in comparisons of the distribution of SNP rates for different sequence regions, genogroups (GI and GII), transmission routes, and sequencing methods. A total of 25 articles reporting on 108 norovirus outbreaks were included. In 99.1% of the outbreaks, the SNP rates were below 0.50%, and in 89.8%, the SNP rates were under 0.20%. Outbreak strains showed higher SNP rates when the P2 domain was used for sequence analysis (Z = -2.652, p = 0.008) and when an NGS method was used (Z = -3.686, p < 0.001). Outbreaks caused by different norovirus genotypes showed no significant difference in SNP rates. Compared with person-to-person outbreaks, SNP rates were lower in common-source outbreaks, but no significant difference was found when differences in sequencing methods were taken into consideraton. SNP rates under 0.20% and 0.50% could be considered as the rigorous and relaxed threshold, respectively, of strain similarity within a norovirus outbreak. More data are needed to evaluate differences within and between various norovirus outbreaks.

Therapeutic potential of salicylamide derivatives for combating viral infections

Since time immemorial human beings have constantly been fighting against viral infections. The ongoing and devastating coronavirus disease 2019 pandemic represents one of the most severe and most significant public health emergencies in human history, highlighting an urgent need to develop broad-spectrum antiviral agents. Salicylamide (2-hydroxybenzamide) derivatives, represented by niclosamide and nitazoxanide, inhibit the replication of a broad range of RNA and DNA viruses such as flavivirus, influenza A virus, and coronavirus. Moreover, nitazoxanide was effective in clinical trials against different viral infections including diarrhea caused by rotavirus and norovirus, uncomplicated influenza A and B, hepatitis B, and hepatitis C. In this review, we summarize the broad antiviral activities of salicylamide derivatives, the clinical progress, and the potential targets or mechanisms against different viral infections and highlight their therapeutic potential in combating the circulating and emerging viral infections in the future.

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

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

Point-of-Care Testing for Norovirus Typing Using CRISPR/Cas12a Combined with Reverse Transcription Recombinase Polymerase Amplification

Noroviruses (NoVs) are one of the leading causes of acute gastroenteritis in humans. This study combined reverse transcription recombinase polymerase amplification (RT-RPA) with a clustered regularly interspaced short palindromic repeat/CRISPR-associated protein (CRISPR/Cas) nucleic acid detection system to develop a point-of-care testing (POCT) technology for typing NoVs. The detection can be completed within 35 min at 37 °C, covering each genotype of genogroup I (GI) and II (GII) NoVs. The sensitivity of this method is 10 copies/μL for GI and 1 copy/μL for GII NoV plasmids. For the detection of clinical samples, the detection results of this method for NoV infected samples are consistent with the RT-qPCR detection method in the laboratory, and this detection method has no cross-reactivity with rotavirus and adenovirus. Therefore, the detection method established in this study enables the diagnosis and screening of suspected patients and close contacts by POCT, which is important for the timely identification and control of NoV outbreaks. In addition, the typing detection of GI and GII NoVs can achieve a precise diagnosis and treatment of patients infected with NoVs.

A large cohort study of the effects of Lewis, ABO, 13 other blood groups, and secretor status on COVID-19 susceptibility, severity, and long COVID-19

BACKGROUND

Previous studies have reported Blood type O to confer a lower risk of SARS-CoV-2 infection, while secretor status and other blood groups have been suspected to have a similar effect as well.

STUDY DESIGN AND METHODS

To determine whether any other blood groups influence testing positive for SARS-CoV-2, COVID-19 severity, or prolonged COVID-19, we used a large cohort of 650,156 Danish blood donors with varying available data for secretor status and blood groups ABO, Rh, Colton, Duffy, Diego, Dombrock, Kell, Kidd, Knops, Lewis, Lutheran, MNS, P1PK, Vel, and Yt. Of these, 36,068 tested positive for SARS-CoV-2 whereas 614,088 tested negative between 2020-02-17 and 2021-08-04. Associations between infection and blood groups were assessed using logistic regression models with sex and age as covariates.

RESULTS

The Lewis blood group antigen Le^a displayed strongly reduced SARS-CoV-2 susceptibility OR 0.85 CI[0.79-0.93] p < .001. Compared to blood type O, the blood types B, A, and AB were found more susceptible toward infection with ORs 1.1 CI[1.06-1.14] p < .001, 1.17 CI[1.14-1.2] p < .001, and 1.2 CI[1.14-1.26] p < .001, respectively. No susceptibility associations were found for the other 13 blood groups investigated. There was no association between any blood groups and COVID-19 hospitalization or long COVID-19. No secretor status associations were found.

DISCUSSION

This study uncovers a new association to reduced SARS-CoV-2 susceptibility for Lewis type Le^a and confirms the previous link to blood group O. The new association to Le^a could be explained by a link between mucosal microbiome and SARS-CoV-2.

Norovirus: An Overview of Virology and Preventative Measures

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

Phenol Derivatives Obtained from Grape Seed Extract Show Virucidal Activity against Murine Norovirus

Human noroviruses are the most common pathogens known to cause acute gastroenteritis, a condition that can lead to severe illness among immunocompromised individuals such as organ transplant recipients and the elderly. To date, no safe and effective vaccines or therapeutic agents have been approved for treating norovirus infections. Therefore, we aimed to demonstrate the virucidal activity of grape seed extract (GSE), which contains >83% proanthocyanidins, against murine norovirus (MNV), a surrogate for human norovirus. GSE showed virucidal activity against MNV in a dose- and time-dependent manner. Atomic force microscopic analysis showed viral particle aggregates after treatment of MNV with GSE. MNV treated with 50 µg/mL of GSE for 10 min resulted in the absence of pathogenicity in an animal model of infection, indicating that GSE has irreversible virucidal activity against MNV particles. Thus, GSE may aid in the development of treatments for norovirus infections.

Selective Polyprotein Processing Determines Norovirus Sensitivity to Trim7

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

The Importance of Secretor-Status in Norovirus Infection Following Allogeneic Hematopoietic Stem Cell Transplantation

Background. Human secretor-status is a strong susceptibility factor for norovirus infection in immunocompetent people. The predominant norovirus genotype GII.4 almost exclusively infects secretors and is also associated with more severe symptoms. However, it is not known to what extent this also applies to immunocompromised individuals. Our objective was to determine the importance of secretor-status and norovirus genotype for the susceptibility and/or the clinical course of norovirus infection in allogeneic hematopoietic stem cell transplant (HCT) patients. Methods: This was a retrospective study of 89 HCT patients diagnosed with norovirus infection. Secretor-status and norovirus genotype were determined using stored extracted DNA or blood (n = 89) and fecal samples (n = 22), respectively. Results: Seven of eighty-nine (8%) of the patients were secretor-negative, a small proportion compared to the expected rate of at least 20% non-secretors in the general Swedish population. Among the genotyped samples, norovirus genotype GII.4 was predominant (n = 12) and only detected in secretor-positive individuals. Patients with norovirus GII.4 had a median symptom duration of 36 (3–681) days compared to 15 (1–94) days in patients infected with other norovirus genotypes (n = 10, p = 0.1). Conclusions: The results suggest that secretor-status affects the susceptibility to norovirus infection even when the immune system is severely compromised. The norovirus genotype may also be a risk factor for chronic norovirus symptoms in immunocompromised patients.

Virucidal and Immunostimulating Activities of Monogalactosyl Diacylglyceride from Coccomyxa sp. KJ, a Green Microalga, against Murine Norovirus and Feline Calicivirus

Human noroviruses are the most common pathogens causing acute gastroenteritis and may lead to more severe illnesses among immunosuppressed people, including elderly and organ transplant recipients. To date, there are no safe and effective vaccines or antiviral agents for norovirus infections. In the present study, we aimed to demonstrate the antiviral activity of monogalactosyl diacylglyceride (MGDG) isolated from a microalga, Coccomyxa sp. KJ, against murine norovirus (MNV) and feline calicivirus (FCV), the surrogates for human norovirus. MGDG showed virucidal activities against these viruses in a dose- and time-dependent manner—MGDG at 100 μg/mL reduced the infectivity of MNV and FCV to approximately 10% after 60 min incubation. In the animal experiments of MNV infection, intraoral administration of MGDG (1 mg/day) exerted a therapeutic effect by suppressing viral shedding in the feces and produced high neutralizing antibody titers in sera and feces. When MGDG was orally administered to immunocompromised mice treated with 5-fluorouracil, the compound exhibited earlier stopping of viral shedding and higher neutralizing antibody titers of sera than those in the control mice administered with distilled water. Thus, MGDG may offer a new therapeutic and prophylactic alternative against norovirus infections.

Norovirus Protease Structure and Antivirals Development

Human norovirus (HuNoV) infection is a global health and economic burden. Currently, there are no licensed HuNoV vaccines or antiviral drugs available. The protease encoded by the HuNoV genome plays a critical role in virus replication by cleaving the polyprotein and is an excellent target for developing small-molecule inhibitors. The current strategy for developing HuNoV protease inhibitors is by targeting the enzyme’s active site and designing inhibitors that bind to the substrate-binding pockets located near the active site. However, subtle differential conformational flexibility in response to the different substrates in the polyprotein and structural differences in the active site and substrate-binding pockets across different genogroups, hamper the development of effective broad-spectrum inhibitors. A comparative analysis of the available HuNoV protease structures may provide valuable insight for identifying novel strategies for the design and development of such inhibitors. The goal of this review is to provide such analysis together with an overview of the current status of the design and development of HuNoV protease inhibitors.

Protective effect of pogostone on murine norovirus infected-RAW264.7 macrophages through inhibition of NF-κB/NLRP3-dependent pyroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Pogostemon cablin, the dry overground parts of Pogostemon cablin (Blanco) Benth, has been widely used in the treatment of gastrointestinal dysfunction, such as nausea, diarrhea, headaches and fever. Pogostone (PO) is a major component of Pogostemon cablin which has a variety of pharmacological properties, including antiinflammatory, and immunosuppressive activities, and antioxidant. However, the effect of PO on norovirus gastroenteritis and the underlying molecular mechanism remain unclear.

AIM OF THE STUDY

The purpose of our study is to investigate the effects of PO against MNV infection using RAW264.7 cells and to elucidate its active mechanisms.

MATERIALS AND METHODS

The cell viability was assessed using Cell Counting Kit-8 (CCK-8) assay and Fluorescein diacetate (FDA) staining. The activation of nuclear factor kappa B (NF-κB) signaling and NOD-like receptor 3 (NLRP3) inflammasome was evaluated by assessing the level of phospho-NF-κB p65, interleukin (IL)-6, TNF-α, NLRP3, cleaved caspase-1, IL-18, IL-1β using Western blot and quantitative real-time PCR (qPCR), respectively. The number of infected cells were determined by immunofluorescence microscopic assay.

RESULTS

PO did not possess a cytotoxic effect toward RAW264.7 cells. The cytotoxic damage caused by MNV infection in RAW264.7 cells decreased significantly in the presence of PO. Cell viability assays showed that pyroptosis is the major mechanism of death in MNV-infected RAW264.7 cells. PO could decreased the expression levels of p-p65, IL-6, TNF-α, NLRP3, cleaved caspase-1, IL-1β, and IL-18.

CONCLUSIONS

These results demonstrate that PO decreases MNV-induced RAW264.7 macrophages death and MNV replication through repressing NF-κB/NLRP3-dependent pyroptosis. Therefore PO may be considered as a potential therapeutic agent for preventing and treating norovirus gastroenteritis.

Risk factors for norovirus infection in healthcare workers during nosocomial outbreaks: a cross-sectional study

Background

Norovirus outbreaks cause severe medico-socio-economic problems affecting healthcare workers and patients. The aim of the study was to investigate prevalence of norovirus infection and risk factors for infection in healthcare workers during nosocomial outbreaks.

Methods

A cross-sectional study of norovirus infections in healthcare workers was performed in seven outbreak wards in a large university hospital. Packs (swab for rectal sampling, and questionnaire) were posted to healthcare workers on notification of a ward outbreak. Rectal samples were examined with norovirus-specific real-time PCR. Replies from questionnaires were analysed using logistic regression models with norovirus genogroup (G)II positive findings as dependent variable. The results are expressed as odds ratios (OR) with 95% confidence intervals (CI). Sequencing and phylogenetic analyses (1040 nucleotides) were used to characterize norovirus strains from healthcare workers. Cluster analyses included norovirus GII.4 strains detected in ward patients during the ongoing outbreaks.

Results

Of 308 packs issued to healthcare workers, 129 (42%) were returned. norovirus GII was detected in 26 healthcare workers (20.2%). Work in cohort care (OR 4.8, 95% CI 1.4–16.3), work in wards for patients with dementia (OR 13.2, 95% CI 1.01–170.7), and having diarrhoea, loose stools or other gastrointestinal symptoms the last week (OR 7.7, 95% CI 2.5–27.2) were associated with increased norovirus prevalence in healthcare workers. Sequencing revealed norovirus GII.4 in healthcare workers samples, and strains detected in healthcare workers and ward patients during a given ward outbreak showed ≥ 99% similarity.

Conclusion

Norovirus positive findings in healthcare workers were strongly associated with symptomatic infection, close contact with sick patients, and dementia nursing.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-00979-8.

Norovirus in Cancer Patients: A Review

Norovirus (NoV) is the leading cause of viral-related diarrhea in cancer patients, in whom it can be chronic, contributing to decreased quality of life, interruption of cancer care, malnutrition, and altered mucosal barrier function. Immunosuppressed cancer patients shed NoV for longer periods of time than immunocompetent hosts, favoring quasispecies development and emergence of novel NoV variants. While nucleic acid amplification tests (NAATs) for NoV diagnosis have revolutionized our understanding of NoV burden of disease, not all NAATs provide information on viral load or infecting genotype. There is currently no effective antiviral or vaccine for chronic NoV infections. Screening for inhibitors of NoV replication in intestinal organoid culture models and creation of NoV-specific adoptive T cells are promising new strategies to develop treatments for chronic NoV in immunosuppressed patients. Herein we summarize data on the epidemiology, clinical manifestations, diagnostic challenges, and treatment of NoV infection in patients with cancer.

Impact of a Multiplexed Polymerase Chain Reaction Panel on Identifying Diarrheal Pathogens in Hematopoietic Cell Transplant Recipients

BACKGROUND

Diarrhea is common and associated with substantial morbidity among hematopoietic cell transplant (HCT) recipients, but the etiology is often not identified. Multiplexed polymerase chain reaction (PCR) assays increase the detection of diarrheal pathogens, but the impact of this technology in this population has not been evaluated.

METHODS

Our center replaced stool cultures and other conventional microbiologic methods with the FilmArray Gastrointestinal Panel (GI PCR) in June 2016. We reviewed all adult patients who received an HCT from June 2014-May 2015 (pre-GI PCR, n = 163) and from June 2016-May 2017 (post-GI PCR, n = 182) and followed them for 1 year after transplantation. Clostridioides difficile infection was diagnosed by an independent PCR test in both cohorts.

RESULTS

The proportion of patients with ≥1 identified infectious diarrheal pathogen increased from 25% to 37% after implementation of GI PCR (P = .01). Eight patients (5%) in the pre-GI PCR cohort tested positive for a pathogen other than C. difficile versus 49 patients (27%) in the post-GI PCR cohort (P < .001). The most common non-C. difficile diarrheal pathogens in the post-GI PCR cohort were enteropathogenic Escherichia coli (n = 14, 8%), norovirus (n = 14, 8%), and Yersinia enterocolitica (n = 7, 4%). The percentage of diarrheal episodes with an identified infectious etiology increased from 14% to 23% (P = .001). Median total costs of stool testing per patient did not increase (pre: $473; post: $425; P = .25).

CONCLUSIONS

Infectious etiologies of diarrhea were identified in a higher proportion of HCT recipients after replacing conventional stool testing with a multiplexed PCR assay, without an increase in testing costs.

Norovirus evolution in immunodeficient mice reveals potentiated pathogenicity via a single nucleotide change in the viral capsid

Interferons (IFNs) are key controllers of viral replication, with intact IFN responses suppressing virus growth and spread. Using the murine norovirus (MNoV) system, we show that IFNs exert selective pressure to limit the pathogenic evolutionary potential of this enteric virus. In animals lacking type I IFN signaling, the nonlethal MNoV strain CR6 rapidly acquired enhanced virulence via conversion of a single nucleotide. This nucleotide change resulted in amino acid substitution F514I in the viral capsid, which led to >10,000-fold higher replication in systemic organs including the brain. Pathogenicity was mediated by enhanced recruitment and infection of intestinal myeloid cells and increased extraintestinal dissemination of virus. Interestingly, the trade-off for this mutation was reduced fitness in an IFN-competent host, in which CR6 bearing F514I exhibited decreased intestinal replication and shedding. In an immunodeficient context, a spontaneous amino acid change can thus convert a relatively avirulent viral strain into a lethal pathogen.

Infectious Disease Complications in Patients with Cancer

Critically ill patients with cancer are vulnerable to infections because of the underlying malignancy, tumor-directed therapy, immunosuppression, breaches in mucosa or skin, malnutrition, and other factors. Neutropenia remains the most important risk factor for infection. Infectious complications occurring in critically ill patients with cancer can affect the bloodstream, lungs, gastrointestinal tract, central nervous system, urinary tract, and the skin. Pneumonias are the leading cause of infection in patients with cancer admitted to the intensive care unit. Consideration of opportunistic pathogens in the differential diagnosis is important in patients with impaired cellular and/or humoral immunity or compromised splenic function.

Broad Virus Detection and Variant Discovery in Fecal Samples of Hematopoietic Transplant Recipients Using Targeted Sequence Capture Metagenomics

Pediatric allogeneic hematopoietic stem cell transplantation (HSCT) patients often suffer from gastro-intestinal (GI) disease caused by viruses, Graft-versus-Host Disease (GVHD) or a combination of the two. Currently, the GI eukaryotic virome of HSCT recipients remains relatively understudied, which complicates the understanding of its role in GVHD pathogenicity. As decisions regarding immunosuppressive therapy in the treatment of virus infection or GVHD, respectively, can be completely contradicting, it is crucial to better understand the prevalence and relevance of viruses in the GI tract in the HSCT setting. A real time PCR panel for a set of specific viruses widely used to diagnose the most common causes of GI viral gastroenteritis is possibly insufficient to grasp the full extent of viruses present. Therefore, we applied the targeted sequence capture method ViroCap to residual fecal samples of 11 pediatric allogeneic HSCT recipients with GI symptoms and a suspicion of GVHD, to enrich for nucleic acids of viruses that are known to infect vertebrate hosts. After enrichment, NGS was applied to broadly detect viral sequences. Using ViroCap, we were able to detect viruses such as norovirus and adenovirus (ADV), that had been previously detected using clinical diagnostic PCR on the same sample. In addition, multiple, some of which clinically relevant viruses were detected, including ADV, human rhinovirus (HRV) and BK polyomavirus (BKV). Interestingly, in samples in which specific PCR testing for regular viral GI pathogens did not result in a diagnosis, the ViroCap pipeline led to the detection of viral sequences of human herpesvirus (HHV)-7, BKV, HRV, KI polyomavirus and astrovirus. The latter was an only recently described variant and showed extensive sequence mismatches with the applied real time PCR primers and would therefore not have been detected if tested. Our results indicate that target enrichment of viral nucleic acids through ViroCap leads to sensitive and broad possibly clinically relevant virus detection, including the detection of newer variants in clinical HSCT recipient samples. As such, ViroCap could be a useful detection tool clinically, but also in studying the associations between viral presence and GVHD.

Infectious Causes of Acute Gastroenteritis in US Children Undergoing Allogeneic Hematopoietic Cell Transplant: A Longitudinal, Multicenter Study

BACKGROUND

Acute gastroenteritis (AGE) in hematopoietic cell transplant (HCT) patients causes significant morbidity and mortality. Data regarding the longitudinal assessment of infectious pathogens during symptomatic AGE and asymptomatic periods, particularly in children, are limited. We investigated the prevalence of AGE-associated infectious pathogens in children undergoing allogeneic HCT.

METHODS

From March 2015 through May 2016, 31 pediatric patients at 4 US children's hospitals were enrolled and had stool collected weekly from pre-HCT through 100 days post-HCT for infectious AGE pathogens by molecular testing. Demographics, clinical symptoms, antimicrobials, vaccination history, and outcomes were manually abstracted from the medical record into a standardized case report form.

RESULTS

We identified a pathogen in 18% (38/206) of samples, with many detections occurring during asymptomatic periods. Clostridioides difficile was the most commonly detected pathogen in 39% (15/38) of positive specimens, although only 20% (3/15) of C. difficile-positive specimens were obtained from children with diarrhea. Detection of sapovirus, in 21% (8/38) of pathogen-positive specimens, was commonly associated with AGE, with 87.5% of specimens obtained during symptomatic periods. Norovirus was not detected, and rotavirus was detected infrequently. Prolonged shedding of infectious pathogens was rare.

CONCLUSIONS

This multicenter, prospective, longitudinal study suggests that the epidemiology of AGE pathogens identified from allogeneic HCT patients may be changing. Previously reported viruses, such as rotavirus and norovirus, may be less common due to widespread vaccination and institution of infection control precautions, and emerging viruses such as sapoviruses may be increasingly recognized due to the use of molecular diagnostics.

The Butyrogenic and Lactic Bacteria of the Gut Microbiota Determine the Outcome of Allogenic Hematopoietic Cell Transplant

Graft versus host disease (GVHD) is a post-transplant pathology in which donor-derived T cells present in the Peyer's patches target the cell-surface alloantigens of the recipient, causing host tissue damages. Therefore, the GVHD has long been considered only a purely immunological process whose prevention requires an immunosuppressive treatment. However, since the early 2010s, the impact of gut microbiota on GVHD has received increased attention. Both a surprising fall in gut microbiota diversity and a shift toward Enterobacteriaceae were described in this disease. Recently, unexpected results were reported that further link GVHD with changes in bacterial composition in the gut and disruption of intestinal epithelial tight junctions leading to abnormal intestinal barrier permeability. Patients receiving allogenic hematopoietic stem cell transplant (allo-HCT) as treatment of hematologic malignancies showed a decrease of the overall diversity of the gut microbiota that affects Clostridia and Blautia spp. and a predominance of lactic acid bacteria (LAB) of the Enterococcus genus, in particular the lactose auxotroph Enterococcus faecium. The reduced microbiota diversity (likely including Actinobacteria, such as Bifidobacterium adolescentis that cross feed butyrogenic bacteria) deprives the butyrogenic bacteria (such as Roseburia intestinalis or Eubacterium) of their capacity to metabolize acetate to butyrate. Indeed, administration of butyrate protects against the GVHD. Here, we review the data highlighting the possible link between GVHD and lactase defect, accumulation of lactose in the gut lumen, reduction of Reg3 antimicrobial peptides, narrower enzyme equipment of bacteria that predominate post-transplant, proliferation of En. faecium that use lactose as metabolic fuels, induction of innate and adaptive immune response against these bacteria which maintains an inflammatory process, elevated expression of myosin light chain kinase 210 (MLCK210) and subsequent disruption of intestinal barrier, and translocation of microbial products (lactate) or transmigration of LAB within the liver. The analysis of data from the literature confirms that the gut microbiota plays a major role in the GVHD. Moreover, the most recent publications uncover that the LAB, butyrogenic bacteria and bacterial cross feeding were the missing pieces in the puzzle. This opens new bacteria-based strategies in the treatment of GVHD.

Attach Me If You Can: Murine Norovirus Binds to Commensal Bacteria and Fungi

The presence of commensal bacteria enhances both acute and persistent infection of murine noroviruses. For several enteric viral pathogens, mechanisms by which these bacteria enhance infection involve direct interactions between the virus and bacteria. While it has been demonstrated that human noroviruses bind to a variety of commensal bacteria, it is not known if this is also true for murine noroviruses. The goal of this study was to characterize interactions between murine noroviruses and commensal bacteria and determine the impact of bacterial growth conditions, incubation temperature and time, on murine norovirus attachment to microbes that comprise the mammalian microbiome. We show that murine noroviruses bind directly to commensal bacteria and show similar patterns of attachment as human norovirus VLPs examined under the same conditions. Furthermore, while binding levels are not impacted by the growth phase of the bacteria, they do change with time and incubation temperature. We also found that murine norovirus can bind to a commensal fungal species, Candidaalbicans.

Significance of norovirus in occupational health: a review of published norovirus outbreaks in Central and Northern Europe

Objectives

Globally, norovirus (NoV) is the leading cause of gastroenteritis infection among all ages. The development of prevention strategies in the field of occupational health requires a detailed knowledge about the impact of the disease on employees. This review article aims not only at evaluating the burden of NoV outbreaks on staff but also at discussing implications for future prevention strategies.

Methods

Published NoV outbreaks in Central and Northern Europe were identified via a systematic literature search. Additionally, published NoV outbreaks in Germany were detected via a manual literature search. Key epidemiological data, as the number of symptomatic staff, was then extracted. The proportion of affected employees was calculated for each dataset (single NoV outbreaks or aggregated data of multiple outbreaks).

Results

Overall, 116 datasets were extracted from 72 relevant articles. 144,852 persons were affected by NoV gastroenteritis, 25,408 out of them (17.5%) were employees. 23,874 (94.0%) of them fell sick during outbreaks in hospitals and related settings. NoV cases among personnel in food establishments were reported only sporadically (mean ratio: 0.01).

Conclusions

Employees in hospitals and community facilities seem quantitatively to be most vulnerable towards NoV epidemics. Therefore, high quality of prevention measures in these settings, respective compliance with prevention strategies should have the highest priority. The disease can be considered as an occupational disease, even regularly without long-term consequences. Following work safety rules, a vaccination for vulnerable groups should be recommended if the vaccine development turns out to be successful.

Electronic supplementary material

The online version of this article (10.1007/s00420-020-01543-4) contains supplementary material, which is available to authorized users.

Identification of a norovirus outbreak on a hematopoietic stem cell transplant unit and development and implementation of a novel infection prevention algorithm for controlling transmission

Controlling norovirus transmission in units with immunocompromised patients is challenging. We present a cluster of norovirus cases that occurred on a stem-cell transplant unit and the prevention efforts that were implemented to limit the outbreak. Protocols developed to control this cluster may provide a model for other facilities.

Generation of Norovirus-Specific T Cells From Human Donors With Extensive Cross-Reactivity to Variant Sequences: Implications for Immunotherapy

BACKGROUND

Chronic norovirus infection in immunocompromised patients can be severe, and presently there is no effective treatment. Adoptive transfer of virus-specific T cells has proven to be safe and effective for the treatment of many viral infections, and this could represent a novel treatment approach for chronic norovirus infection. Hence, we sought to generate human norovirus-specific T cells (NSTs) that can recognize different viral sequences.

METHODS

Norovirus-specific T cells were generated from peripheral blood of healthy donors by stimulation with overlapping peptide libraries spanning the entire coding sequence of the norovirus genome.

RESULTS

We successfully generated T cells targeting multiple norovirus antigens with a mean 4.2 ± 0.5-fold expansion after 10 days. Norovirus-specific T cells comprised both CD4+ and CD8+ T cells that expressed markers for central memory and effector memory phenotype with minimal expression of coinhibitory molecules, and they were polyfunctional based on cytokine production. We identified novel CD4- and CD8-restricted immunodominant epitopes within NS6 and VP1 antigens. Furthermore, NSTs showed a high degree of cross-reactivity to multiple variant epitopes from clinical isolates.

CONCLUSIONS

Our findings identify immunodominant human norovirus T-cell epitopes and demonstrate that it is feasible to generate potent NSTs from third-party donors for use in antiviral immunotherapy.

[On Statistical Underreporting of Norovirus-Infections: Insights from Register Data of Two Local Public Health Authorities]

BACKGROUND

Only laboratory-confirmed norovirus (NoV) cases have to be notified to the Robert Koch Institute (RKI) since 2011, but not other, e. g. clinical-epidemiological cases. It can be assumed that the extent of underreporting of NoV cases in Germany has significantly increased since then.

OBJECTIVES

To discuss the extent of underreporting, we wanted to find out how many laboratory tests were carried out during gastroenteritis outbreaks. Furthermore, the significance of NoV outbreaks in occupational health is discussed.

MATERIALS AND METHODS

Of all pseudonymized gastroenteritis outbreak data reported to 2 local health authorities between 2011 and 2015, the proportion of NoV outbreaks and reported cases of infection among employees in hospitals and community facilities (nursing homes for the elderly, day-care centers, schools) confirmed by laboratory tests was calculated retrospectively.

RESULTS

Only a few gastroenteritis outbreaks in day-care centers were etiologically diagnosed, so that only 6% and less could be classified as NoV outbreaks. In nursing homes for the elderly, about half of the outbreaks were classified as NoV, in hospitals almost all of them. Employees accounted for up to 23% of those affected in NoV outbreaks.

CONCLUSIONS

The low level of laboratory diagnostics carried out during gastroenteritis outbreaks in day-care centers suggests a considerable number of hidden NoV cases. The significant proportion of staff relative to the total number of infected persons during the outbreaks highlights the importance of the burden of NoV outbreaks as a topic in occupational health. Further, large-scale prospective studies are needed to empirically substantiate these initial findings.

Norovirus infection results in eIF2α independent host translation shut-off and remodels the G3BP1 interactome evading stress granule formation

Viral infections impose major stress on the host cell. In response, stress pathways can rapidly deploy defence mechanisms by shutting off the protein synthesis machinery and triggering the accumulation of mRNAs into stress granules to limit the use of energy and nutrients. Because this threatens viral gene expression, viruses need to evade these pathways to propagate. Human norovirus is responsible for gastroenteritis outbreaks worldwide. Here we examined how norovirus interacts with the eIF2α signaling axis controlling translation and stress granules. While norovirus infection represses host cell translation, our mechanistic analyses revealed that eIF2α signaling mediated by the stress kinase GCN2 is uncoupled from translational stalling. Moreover, infection results in a redistribution of the RNA-binding protein G3BP1 to replication complexes and remodelling of its interacting partners, allowing the avoidance from canonical stress granules. These results define novel strategies by which norovirus undergo efficient replication whilst avoiding the host stress response and manipulating the G3BP1 interactome.

Viruses have evolved elegant strategies to evade host responses that restrict viral propagation by targeting the protein synthesis machinery and stress granules, which are membrane-less RNA granules with antiviral properties. Previous studies have unravelled how viruses, including norovirus the leading cause of gastroenteritis, regulate the activity of translation factors to affect the antiviral response. Furthermore, stress granules evasion strategies have been linked to targeting the scaffolding protein G3BP1. Here we dissect how murine norovirus, the main model for norovirus, evades the cellular stress responses. Our work challenges the dogma that translational control during infection is mainly mediated by eIF2α and demonstrate that norovirus evades this stress pathway. We further show that norovirus evades the stress granule response in a novel way by isolating and characterising the G3BP1 interactome for the first time in the context of a viral infection. We conclude that norovirus infection results in a redistribution of G3BP1 and its cellular partners to replication complexes, thereby preventing the assembly of stress granules. Overall, we define a novel evasion strategy by which norovirus escapes stress granule formation by rewiring the G3BP1 interactome.

Challenges in Infection Epidemiology: On the Underreporting of Norovirus Gastroenteritis Cases in Germany

It is commonly accepted that the number of officially reported incidences of norovirus (NoV) according to the German Protection against Infection Act (Infektionsschutzgesetz) does not reflect the ‘true’ incidence of NoV in Germany. This study aims to reveal the reasons for the underreporting of NoV cases by comparing secondary data. Methods: NoV incidence (cases per 100,000 reference persons) in the age group 18–65 was derived from register data of four different sources in the German public health system (2011–2015): Statutory health insurance in the federal state of Lower Saxony (AOK; in- and outpatient cases), the Research Institute of Ambulatory Health Care in Germany (ZI; outpatient cases), the German Federal Statistical Office (inpatient cases; DESTATIS), and the Robert Koch Institute (RKI SurvStat; health reporting data). Results: the incidence derived from the AOK in Lower Saxony varied between 49 and 66 NoV cases per 100,000 persons and was thus lower than at the federal level. Incidences of all inpatient and outpatient data were lower than the incidence according to the RKI in the last 2–3 years of the observation period. Conclusions: the disagreement between NoV incidences calculated from secondary inpatient and outpatient data and the respective numbers published by the RKI can be regarded as an indication that not all NoV cases were reported to public health authorities. This might be due to missed cases during the notification procedure or misclassification of gastroenteritis cases by general practitioners. Considering the limitations associated with analyzing secondary data, the appropriateness of these assumptions should be verified in future studies.

Norovirus encounters in the gut: multifaceted interactions and disease outcomes

Noroviruses are major causes of gastroenteritis, with epidemic outbreaks occurring frequently. They are an important global health concern, especially for pediatric and immunocompromised populations, and are challenging pathogens to target immunologically due to their rapid rates of genetic and antigenic evolution and failure to stimulate durable protective immunity. In this Review, we summarize our current understanding of norovirus pathogenesis, noting the prominent role of murine norovirus as a small animal model for norovirus research. We highlight intriguing data supporting the possible involvement of norovirus in sequelae including irritable bowel syndrome and inflammatory bowel diseases, and describe the innate and adaptive immune mechanisms involved in control of both human and murine norovirus infection. Furthermore, we discuss the potential implications of recent discoveries regarding norovirus interactions with the gut microbiota, and briefly detail current understanding of noroviral evolution and its influence on viral pathogenesis. Our mechanistic understanding of norovirus pathogenesis continues to improve with increasing availability of powerful model systems, which will ultimately facilitate development of effective preventive and therapeutic approaches for this pathogen.

The Intestinal Virome and Immunity

The composition of the human microbiome is considered a major source of interindividual variation in immunity and, by extension, susceptibility to diseases. Intestinal bacteria have been the major focus of research. However, diverse communities of viruses that infect microbes and the animal host cohabitate the gastrointestinal tract and collectively constitute the gut virome. Although viruses are typically investigated as pathogens, recent studies highlight a relationship between the host and animal viruses in the gut that is more akin to host-microbiome interactions and includes both beneficial and detrimental outcomes for the host. These viruses are likely sources of immune variation, both locally and extraintestinally. In this review, we describe the components of the gut virome, in particular mammalian viruses, and their ability to modulate host responses during homeostasis and disease.

Calicivirus RNA-Dependent RNA Polymerases: Evolution, Structure, Protein Dynamics, and Function

The Caliciviridae are viruses with a positive-sense, single-stranded RNA genome that is packaged into an icosahedral, environmentally stable protein capsid. The family contains five genera (Norovirus, Nebovirus, Sapovirus, Lagovirus, and Vesivirus) that infect vertebrates including amphibians, reptiles, birds, and mammals. The RNA-dependent RNA polymerase (RdRp) replicates the genome of RNA viruses and can speed up evolution due to its error-prone nature. Studying calicivirus RdRps in the context of genuine virus replication is often hampered by a lack of suitable model systems. Enteric caliciviruses and RHDV in particular are notoriously difficult to propagate in cell culture; therefore, molecular studies of replication mechanisms are challenging. Nevertheless, research on recombinant proteins has revealed several unexpected characteristics of calicivirus RdRps. For example, the RdRps of RHDV and related lagoviruses possess the ability to expose a hydrophobic motif, to rearrange Golgi membranes, and to copy RNA at unusually high temperatures. This review is focused on the structural dynamics, biochemical properties, kinetics, and putative interaction partners of these RdRps. In addition, we discuss the possible existence of a conserved but as yet undescribed structural element that is shared amongst the RdRps of all caliciviruses.

Genetic Susceptibility to Human Norovirus Infection: An Update

Noroviruses are the most common etiological agent of acute gastroenteritis worldwide. Despite their high infectivity, a subpopulation of individuals is resistant to infection and disease. This susceptibility is norovirus genotype-dependent and is largely mediated by the presence or absence of human histo-blood group antigens (HBGAs) on gut epithelial surfaces. The synthesis of these HBGAs is mediated by fucosyl- and glycosyltransferases under the genetic control of the FUT2 (secretor), FUT3 (Lewis) and ABO(H) genes. The so-called non-secretors, having an inactivated FUT2 enzyme, do not express blood group antigens and are resistant to several norovirus genotypes, including the predominant GII.4. Significant genotypic and phenotypic diversity of HBGA expression exists between different human populations. Here, we review previous in vivo studies on genetic susceptibility to norovirus infection. These are discussed in relation to population susceptibility, vaccines, norovirus epidemiology and the impact on public health.

Discontinuation and Nonadherence to Medications for Chronic Conditions after Hematopoietic Cell Transplantation: A 6-Year Propensity Score-Matched Cohort Study

INTRODUCTION

Hematopoietic cell transplantation (HCT) is an established curative option for patients with hematological malignancies and other life-threatening conditions. Evidence on nonpersistence and nonadherence to oral medications for chronic conditions among patients following HCT is lacking.

OBJECTIVES

This study aims to examine patterns of oral medication use for chronic conditions following HCT in the U.S.

POPULATION

METHODS

Nonpersistence and nonadherence to oral medications for diabetes, hypertension, and dyslipidemia among HCT recipients were assessed in a cohort that included 1382 autologous and 650 allogeneic HCT recipients with hematological malignancies using the Truven Health MarketScan Research Database between 2009 and 2014. Recipients of HCT were compared to propensity score-matched cancer patients receiving chemotherapy without transplantation. Multivariable Cox proportional hazards models and generalized estimating equations were used to determine characteristics associated with nonpersistence and nonadherence to oral chronic medications, respectively.

RESULTS

Recipients of HCT had higher risks of discontinuing medication for diabetes mellitus (allogeneic HCT hazard ratio [HR] = 1.93, 95% confidence interval [CI] 1.10-3.39; autologous HCT HR = 1.49, 95% CI 1.04-2.15); hypertension (allogeneic HCT HR = 1.75, 95% CI 1.21-2.53; autologous HCT HR = 1.32, 95% CI 1.07-1.62), and dyslipidemia (allogeneic HCT HR = 2.02, 95% CI 1.39-2.93; autologous HCT, HR = 1.26, 95% CI 0.98-1.61) compared to patients treated with only chemotherapy. Lower odds of adherence to antihypertensive medications (odds ratio [OR] = 0.58, 95% CI 0.38-0.89) and to lipid-lowering medications (OR = 0.38, 95% CI 0.22-0.65) were observed in allogeneic HCT recipients compared with propensity score-matched patients who underwent chemotherapy only.

CONCLUSIONS

Poor medication persistence and adherence to chronic disease medications are common after HCT. Further research to improve long-term outcomes following HCT should include management of medication therapy for chronic comorbid conditions.

Nitazoxanide Inhibits Human Norovirus Replication and Synergizes with Ribavirin by Activation of Cellular Antiviral Response

Norovirus is the main cause of viral gastroenteritis worldwide. Although norovirus gastroenteritis is self-limiting in immunocompetent individuals, chronic infections with debilitating and life-threatening complications occur in immunocompromised patients. Nitazoxanide (NTZ) has been used empirically in the clinic and has demonstrated effectiveness against norovirus gastroenteritis. In this study, we aimed at uncovering the antiviral potential and mechanisms of action of NTZ and its active metabolite, tizoxanide (TIZ), using a human norovirus (HuNV) replicon. NTZ and TIZ, collectively referred to as thiazolides (TZD), potently inhibited replication of HuNV and a norovirus surrogate, feline calicivirus. Mechanistic studies revealed that TZD activated cellular antiviral response and stimulated the expression of a subset of interferon-stimulated genes (ISGs), particularly interferon regulatory factor 1 (IRF-1), not only in a Huh7 cell-based HuNV replicon, but also in naive Huh7 and Caco-2 cells and novel human intestinal organoids. Overexpression of exogenous IRF-1 inhibited HuNV replication, whereas knockdown of IRF-1 largely attenuated the antiviral activity of TZD, suggesting that IRF-1 mediated TZD inhibition of HuNV. By using a Janus kinase (JAK) inhibitor, CP-690550, and a STAT1 knockout approach, we found that TZD induced antiviral response independently of the classical JAK-signal transducers and activators of transcription (JAK-STAT) pathway. Furthermore, TZD and ribavirin synergized to inhibit HuNV replication and completely depleted the replicons from host cells after long-term treatment. In summary, our results demonstrated that TZD combated HuNV replication through activation of cellular antiviral response, in particular by inducing a prominent antiviral effector, IRF-1. NTZ monotherapy or combination with ribavirin represent promising options for treating norovirus gastroenteritis, especially in immunocompromised patients.

Within-host evolution of virus variants during chronic infection with novel GII.P26-GII.26 norovirus

BACKGROUND

Noroviruses are a leading cause of acute gastroenteritis in all age groups. They generally cause a rapidly self-limiting illness. However, chronic norovirus diarrheal disease occurs in immunocompromised individuals, and is accompanied by persistent shedding of infectious norovirus in stool.

OBJECTIVES

The study aims to characterize a novel GII.P26-GII.26 norovirus strain. Furthermore, it analyses viral mutations arising during chronic infection of an immunocompromised host.

STUDY DESIGN

Over the course of more than three years, stool samples were obtained from an immunocompromised patient and screened for the presence of norovirus RNA by real-time PCR and norovirus antigen by immunoassay. Viral population kinetics was analyzed by conventional and high-throughput-sequencing.

RESULTS

Real-time PCR yielded high amounts of norovirus RNA in the stool, but antigen immunoassays failed to detect the virus. The near complete norovirus genome was assigned as novel GII.P26-GII.26 genotype. Conventional as well as high-throughput sequencing pointed to a heterogeneous viral population with low rates of non-synonymous substitutions. Within-host evolution was enhanced in non-structural protein p22 and the N-terminal arm of the capsid protein VP1 but reduced in the viral polymerase RdRp. Intermittent non-synonymous substitutions in the protruding domain of the VP1 reverted fully over time.

CONCLUSIONS

Confirmation of novel GII.P26-GII.26 norovirus genotypes provides insight into norovirus genetic diversity. The study further illustrates norovirus infection as an important differential diagnosis of recurrent persistent diarrhea in immunocompromised patients. The provided data on within-host evolution contribute to the insight of the mechanisms of viral persistence and pathogenesis in chronic norovirus infections.

Incidence of household transmission of acute gastroenteritis (AGE) in a primary care sentinel network (1992-2017): cross-sectional and retrospective cohort study protocol

INTRODUCTION

Acute gastroenteritis (AGE) is a highly transmissible condition. Determining characteristics of household transmission will facilitate development of prevention strategies and reduce the burden of this disease.We are carrying out this study to describe household transmission of medically attended AGE, and explore whether there is an increased incidence in households with young children.

METHODS AND ANALYSIS

This study used the Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) primary care sentinel network, comprising data from 1 750 167 registered patients (August 2017 database). We conducted a novel analysis using a 'household key', to identify patients within the same household (n=811 027, mean 2.16 people). A 25-year repeated cross-sectional study will explore the incidence of medically attended AGE overall and then a 5-year retrospective cohort study will describe household transmission of AGE. The cross-sectional study will include clinical data for a 25-year period-1 January 1992 until the 31 December 2017. We will describe the incidence of AGE by age-band and gender, and trends in incidence. The 5-year study will use Poisson and quasi-Poisson regression to identify characteristics of individuals and households to predict medically attended AGE transmitted in the household. This will include whether the household contained a child under 5 years and the age category of the first index case (whether adult or child under 5 years). If there is overdispersion and zero-inflation we will compare results with negative binomial to handle these issues.

ETHICS AND DISSEMINATION

All RCGP RSC data are pseudonymised at the point of data extraction. No personally identifiable data are required for this investigation. The protocol follows STrengthening the Reporting of OBservational studies in Epidemiology guidelines (STROBE). The study results will be published in a peer-review journal, the dataset will be available to other researchers.

Chronic norovirus infection in primary immune deficiency disorders: an international case series

OBJECTIVE

Predictive factors associated with clinical outcomes of chronic norovirus infection (CNI) in primary immunodeficiency diseases (PIDD) are lacking.

METHOD

We sought to characterize CNI using a multi-institutional cohort of patients with PIDD and CNI using the Clinical Immunology Society's CIS-PIDD Listserv e-mail group.

RESULTS

Thirty-four subjects (21 males and 13 females) were reported from centers across North America, Europe, and Asia. All subjects were receiving high doses (median IgG dose: 1200 mg/kg/month) of supplemental immunoglobulin therapy. Fifty-three percent had a complete absence of B cells (median B-cell count 0; range 0-139 cells/μL). Common Variable Immune Deficiency (CVID) subjects manifested a unique phenotype with B-cell lymphopenia, non O+ blood type, and villous atrophy (logistic regression model, P = 0.01). Five subjects died, all of whom had no evidence of villous atrophy.

CONCLUSION

While Norovirus (NoV) is thought to replicate in B cells, in this PIDD cohort of CNI, B-cell lymphopenia was common, indicating that the presence of B lymphocytes is not essential for CNI.

The evaluation of critically ill transplant patients with infectious diarrhea

PURPOSE OF REVIEW

The review summarizes the epidemiology, risk factors, clinical presentation, diagnosis and management of the most important etiologic agents of infectious diarrhea in critically ill transplant recipients.

RECENT FINDINGS

Diarrhea, frequently caused by infectious pathogens, can cause significant morbidity and mortality in transplant recipients. Diarrhea can lead to severe dehydration, acute renal failure, medication toxicity, rejection, graft-versus-host disease and impairs patients' quality of life. Opportunistic infectious pathogens can pose significant diagnostic and therapeutic challenges in immunocompromised hosts.

SUMMARY

In transplant recipients, it is vital to differentiate infectious from noninfectious diarrhea to adequately manage their therapeutic approach. Supportive measures and reduction in immunosuppression are essential for the treatment management.

Successful treatment of chronic norovirus gastroenteritis with nitazoxanide in a pediatric kidney transplant recipient

Uncontrolled studies suggest a benefit of nitazoxanide for the treatment of norovirus gastroenteritis in immunocompromised individuals. Here, we report the use of nitazoxanide in a 13-year-old male kidney transplant recipient who developed intractable norovirus gastroenteritis. Reduction of immunosuppression was not possible due to refractory TCMR. Administration of oral immunoglobulin and switching from tacrolimus to sirolimus failed to produce a meaningful clinical response. Treatment with a 14-day course of nitazoxanide resulted in prompt resolution of diarrhea as well as clearance of norovirus from the stool despite intense immunosuppression. Nitazoxanide may be considered as an option for the treatment of intractable norovirus gastroenteritis in pediatric transplant patients when reduced immunosuppression is not feasible or other treatment options have failed. Further studies to evaluate the safety and effectiveness of nitazoxanide in immunocompromised children are needed.

Severe infections in critically ill solid organ transplant recipients

BACKGROUND

Severe infections are among the most common causes of death in immunocompromised patients admitted to the intensive care unit. The epidemiology, diagnosis and treatment of these infections has evolved in the last decade.

AIMS

We aim to provide a comprehensive review of these severe infections in this population.

SOURCES

Review of the literature pertaining to severe infections in critically ill solid organ transplant recipients. PubMed and Embase databases were searched for documents published since database inception until November 2017.

CONTENT

The epidemiology of severe infections has changed in the immunocompromised patients. This population is presenting to the intensive care unit with specific transplantation procedure-related infections, device-associated infections, a multitude of opportunistic viral infections, an increasing number of nosocomial infections and bacterial diseases with a more limited therapeutic armamentarium. Both molecular diagnostics and imaging techniques have had substantial progress in the last decade, which will, we hope, translate into faster and more precise diagnoses, as well as more optimal empirical treatment de-escalation.

IMPLICATIONS

The key clinical elements to improve the outcome of critically ill solid organ transplant recipients depend on the knowledge of geographic epidemiology, specific surgical procedures, net state of immunosuppression, hospital microbial ecology, aggressive diagnostic strategy and search for source control, rapid initiation of antimicrobials and minimization of iatrogenic immunosuppression.

Norovirus Illnesses in Children and Adolescents

Norovirus is a leading cause of childhood vomiting and diarrhea in the United States and globally. Although most illnesses caused by norovirus are self-resolving, severe outcomes may occur from dehydration, including hospitalization and death. A vast majority of deaths from norovirus occur in developing countries. Immunocompromised children are at risk for more severe outcomes. Treatment of norovirus illness is focused on early correction of dehydration and maintenance of fluid status and nutrition. Hand hygiene, exclusion of ill individuals, and environmental cleaning are important for norovirus outbreak prevention and control, and vaccines to prevent norovirus illness are currently under development.

Norovirus causing severe gastrointestinal disease following allogeneic hematopoietic stem cell transplantation: A retrospective analysis

BACKGROUND

Norovirus (NV) can cause chronic and severe gastroenteritis with possible lethal outcome in immunocompromised patients. The knowledge of NV infections in allogeneic hematopoietic stem cell transplantation (HSCT) recipients is limited. The aim of this study was to clarify the clinical importance of NV in a large cohort of HSCT recipients.

METHODS

All patients undergoing HSCT and diagnosed with NV at Karolinska University Hospital from 2006-2012 were included in the study (63 patients). Clinical data were collected from medical records, and statistics were performed using the logistic regression method.

RESULTS

The majority of patients (70%) had short-term symptoms (≤14 days). However, 54% of all patients required admission or prolonged hospitalization owing to the infection. In 16% of the patients the symptoms were chronic (>30 days), and in all but one of these patients the clinical picture also was severe, with malnutrition requiring long-term TPN, or serious dehydration. Severe combined immune deficiency (SCID) diagnosis was associated with chronic symptoms of NV infection (OR 30.3, CI 2.5-368).

CONCLUSION

NV is an important pathogen in the HSCT setting, although the infection seems to be mild in most patients. Increased knowledge is needed to further identify risk factors for a severe course of NV infection in HSCT patients.

Diagnosis and management of gastrointestinal complications in adult cancer patients: 2017 updated evidence-based guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO)

Cancer patients frequently suffer from gastrointestinal complications. In this manuscript, we update our 2013 guideline on the diagnosis and management of gastrointestinal complications in adult cancer patients by the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO). An expert group was put together by the AGIHO to update the existing guideline. For each sub-topic, a literature search was performed in PubMed, Medline, and Cochrane databases, and strengths of recommendation and the quality of the published evidence for major therapeutic strategies were categorized using the 2015 European Society for Clinical Microbiology and Infectious Diseases (ESCMID) criteria. Final recommendations were approved by the AGIHO plenary conference. Recommendations were made with respect to non-infectious and infectious gastrointestinal complications. Strengths of recommendation and levels of evidence are presented. A multidisciplinary approach to the diagnosis and management of gastrointestinal complications in cancer patients is mandatory. Evidence-based recommendations are provided in this updated guideline.

Acute graft-versus-host disease of the gut: considerations for the gastroenterologist

Haematopoietic stem cell transplantation (HSCT) is central to the management of many haematological disorders. A frequent complication of HSCT is acute graft-versus-host disease (GVHD), a condition in which immune cells from the donor attack healthy recipient tissues. The gastrointestinal system is among the most common sites affected by acute GVHD, and severe manifestations of acute GVHD of the gut portends a poor prognosis in patients after HSCT. Acute GVHD of the gastrointestinal tract presents both diagnostic and therapeutic challenges. Although the clinical manifestations are nonspecific and overlap with those of infection and drug toxicity, diagnosis is ultimately based on clinical criteria. As reliable serum biomarkers have not yet been validated outside of clinical trials, endoscopic and histopathological evaluation continue to be utilized in diagnosis. Once a diagnosis of gastrointestinal acute GVHD is established, therapy with systemic corticosteroids is typically initiated, and non-responders can be treated with a wide range of second-line therapies. In addition to treating the underlying disease, the management of complications including profuse diarrhoea, severe malnutrition and gastrointestinal bleeding is paramount. In this Review, we discuss strategies for the diagnosis and management of acute GVHD of the gastrointestinal tract as they pertain to the practising gastroenterologist.

Norovirus Infection in Older Adults: Epidemiology, Risk Factors, and Opportunities for Prevention and Control

Norovirus is the leading cause of acute gastroenteritis. In older adults, it is responsible for an estimated 3.7 million illnesses; 320,000 outpatient visits; 69,000 emergency department visits; 39,000 hospitalizations; and 960 deaths annually in the United States. Older adults are particularly at risk for severe outcomes, including prolonged symptoms and death. Long-term care facilities and hospitals are the most common settings for norovirus outbreaks in developed countries. Diagnostic platforms are expanding. Several norovirus vaccines in clinical trials have the potential to reap benefits. This review summarizes current knowledge on norovirus infection in older adults.

Norovirus Loads in Stool Specimens of Cancer Patients with Norovirus Gastroenteritis

In immunocompromised patients with norovirus (NoV) gastroenteritis, the relationship between fecal NoV load and clinical complications has not been examined. In this study, a validated real-time quantitative PCR assay was used to determine viral loads for NoV genogroup I and II (GI and GII) in NoV-positive stool specimens of cancer patients. A total of 234 specimens from 152 patients were positive for NoV, including 201 of GII and 33 of GI. Geometric mean of logarithmic copies per gram of stool (w/w) of NoV-GII were 9.03 ± 1.71 (means ± SD), which was significantly higher than that of NoV-GI [7.87 ± 1.49; odd ratio (OR), 3.22; 95% CI, 1.33-7.76; P = 0.009]. Among 152 patients with gastroenteritis, the fecal NoV geometric mean of logarithmic copy was correlated with mild (n = 85; 7.97 ± 1.55), moderate (n = 23; 9.09 ± 1.38), and severe (n = 44; 10.39 ± 0.91) episodes of severity by modified Vesikari scoring system, respectively. Multivariate analysis revealed that high level of NoV load was correlated with GII infections (OR, 4.13; 95% CI, 1.62-10.55; P = 0.003) and associated with development of severe clinical symptom (OR, 5.53; 95% CI, 2.00-7.24; P = 0.001) at the time of diagnosis. Infection with GII strains was more common than GI infection in cancer patients with viral gastroenteritis.

Severity and outcome of the norovirus infection in children after intestinal transplantation

In immunocompromised patients, the NoV infection is prolonged and severe. We retrospectively studied the severity of the NoV infection in children after an ITx, the treatment, and the long-term evolution. Norovirus PCR in stools was positive for 19 children in 21 separate episodes. The infection was symptomatic in 18 cases. At diagnosis, the median weight loss was 5% (0-11) and the creatinine clearance was 75 mL/min/1.73 m² (19-142). On 14 digestive biopsies, the pathological findings were non-specific with a constant mononuclear infiltration, showing signs of rejection in one case. Fifteen children in 17 cases were hospitalized for a median duration of 41 days (0-119) with IV infusions for 33 days (0-120). The viral shedding lasted 78 days (20-360). Nine children with severe or prolonged diarrhea received intravenous IGs and four of them additional NTZ. On follow-up, five other children developed a rejection 12 months (1-33) after NoV infection. Four uncontrolled rejections led to graft removal. Children mostly needed hospital admission and IV rehydration, but the symptoms upon presentation were moderate. Symptoms and shedding durations are prolonged as expected. The treatment efficacy cannot be assessed. The rejection induction by the NoV cannot be excluded.

The eukaryotic gut virome in hematopoietic stem cell transplantation: new clues in enteric graft-versus-host disease

Much attention has been focused on the role of the bacterial microbiome in human health, but the virome is understudied. Although previously investigated in individuals with inflammatory bowel diseases or solid-organ transplants, virome dynamics in allogeneic hematopoietic stem cell transplantation (HSCT) and enteric graft-versus-host disease (GVHD) remain unexplored. Here we characterize the longitudinal gut virome in 44 recipients of HSCT using metagenomics. A viral 'bloom' was identified, and significant increases were demonstrated in the overall proportion of vertebrate viral sequences following transplantation (P = 0.02). Increases in both the rates of detection (P < 0.0001) and number of sequences (P = 0.047) of persistent DNA viruses (anelloviruses, herpesviruses, papillomaviruses and polyomaviruses) over time were observed in individuals with enteric GVHD relative to those without, a finding accompanied by a reduced phage richness (P = 0.01). Picobirnaviruses were detected in 18 individuals (40.9%), more frequently before or within a week after transplant than at later time points (P = 0.008). In a time-dependent Cox proportional-hazards model, picobirnaviruses were predictive of the occurrence of severe enteric GVHD (hazard ratio, 2.66; 95% confidence interval (CI) = 1.46-4.86; P = 0.001), and correlated with higher fecal levels of two GVHD severity markers, calprotectin and α1-antitrypsin. These results reveal a progressive expansion of vertebrate viral infections over time following HSCT, and they suggest an unexpected association of picobirnaviruses with early post-transplant GVHD.

Clinical-associated characteristics and microbiological features of bloodstream nontyphoidal salmonella infection in adult patients receiving allogeneic hematopoietic stem cell transplantation

Bloodstream nontyphoidal salmonella (NTS) infection is rare, but its associated characteristics and microbiological features in immunocompromised patients are worth paying attention to, particularly for those receiving allogeneic hematopoietic stem cell transplantation (SCT). No studies so far have analyzed post-transplant bloodstream NTS infection. Therefore, we reviewed 423 adult patients undergoing allogeneic hematopoietic SCT from 2003 to 2014. Nine out of four hundred twenty-three patients (2.13%) developed post-transplant bloodstream NTS infection, including two patients who had subsequent or combined metastatic infections. The median age at SCT was 35 years (interquartile range, 29-46) among the nine patients with bloodstream NTS infection. Male patients were predominant (78%). The median onset of bloodstream NTS infection was at 315 days after SCT (range, 207-629). Multivariate analysis revealed that extensive chronic graft-versus-host disease (GVHD) (OR 8.054, p = 0.003) and nonmyeloablative transplant conditioning (OR 4.604, p = 0.037) were significant associated characteristics for NTS infection. Currently, there are no published data analyzing and exploring post-transplant bloodstream NTS infections in adult allogeneic hematopoietic SCT. Our study determined the associated characteristics and microbiological features for this infection.