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

Sepsis and Challenging Infections in the Immunosuppressed Patient in the Intensive Care Unit

In 2017, most intensive care units (ICUs) worldwide are admitting a growing population of immunosuppressed patients. The most common causes of pre-ICU immunosuppression are solid organ transplantation, hematopoietic stem cell transplantation, and infection due to human immunodeficiency virus. In this article, the authors review the most frequent infections that cause critical care illness in each of these 3 immunosuppressed patient populations.

Hospital-Associated Infections

Hospital-associated infection (HAI) in immunocompromised patients can result in high rates of morbidity and mortality. Infections caused by multidrug-resistant organisms (MDROs) are especially worrisome because of the limited choice of remaining antibiotics available when a patient becomes colonized or infected with an MDRO. It is therefore important that immunocompromised patients be cared for in an environment that limits the risk for acquiring infections. However, with healthcare being increasingly delivered in settings other than the traditional inpatient hospital wards, a bigger effort will need to be set forth to prevent or rapidly diagnose HAI. The last few years have seen a significant increase in the number of singleplex and multiplex molecular assays for the detection of many of the organisms responsible for HAI, but more is needed as infections caused by organisms like Legionella pneumophila and Aspergillus species are still diagnosed with methods that have relatively low yield and are slow to provide actionable results. Finally, the use of novel techniques for outbreak investigations will provide new information on transmission of infectious agents in healthcare settings and allow stronger, evidence-based recommendations to be developed for prevention of HAIs in the immunocompromised host.

Severe chronic norovirus diarrheal disease in transplant recipients: Clinical features of an under-recognized syndrome

BACKGROUND

Norovirus (NV) infection has been reported as a cause of severe chronic diarrhea in transplant recipients, but this entity remains under-recognized in clinical practice, leading to diagnostic delays. Transplant clinicians should become familiar with this syndrome in order to facilitate early detection and management.

METHODS

Demographic, clinical, and outcomes variables were summarized from a series of transplant recipients with positive stool NV reverse transcription polymerase chain reaction (RT-PCR) assays at Johns Hopkins in 2013-2014. Factors associated with longer duration of symptoms were compared using random forest analysis.

RESULTS

Thirty-one of 193 (16%) transplant recipients who were tested for NV had positive stool RT-PCRs. Symptoms included diarrhea (100%), nausea/vomiting (58%), abdominal pain (52%), and wasting (35%). Acute kidney injury occurred in 23%, and persisted in 21% after 6 months. Median duration of diarrheal symptoms was 4 months (range, <1-20) and 11/31 (35.4%) patients had relapses after improvement. Wasting, incompatible kidney transplant status, and plasmapheresis were associated with longer diarrhea durations. Treatments included nitazoxanide (in 74%), reduction of immunosuppression (58%), and intravenous immunoglobulin (32%). Six patients died, but no deaths were attributed to NV.

CONCLUSIONS

It is important for clinicians to recognize that NV can cause severe chronic diarrhea in transplant recipients. In this series, receipt of a human leukocyte antigen- and/or blood type-incompatible kidney transplant, and plasmapheresis were associated with longer symptom duration.

Structure(s), function(s), and inhibition of the RNA-dependent RNA polymerase of noroviruses

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This review summarizes current knowledge on the norovirus RdRp.

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Multiple X-ray structures of norovirus RdRp show important conformational changes.

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Norovirus RdRp recognizes specific promotor sequences to initiate RNA synthesis.

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Anti-HCV nucleoside analogs such as 2CM-C also inhibit Norovirus RdRp.

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Suramin and its analogs act as allosteric non-nucleoside polymerase inhibitors.

Noroviruses belong to the Caliciviridae family of single-stranded positive-sense RNA viruses. The genus Norovirus includes seven genogroups (designated GI-GVII), of which GI, GII and GIV infect humans. Human noroviruses are responsible for widespread outbreaks of acute gastroenteritis and represent one of the most common causes of foodborne illness. No vaccine or antiviral treatment options are available for norovirus infection. The RNA-dependent RNA polymerase (RdRp) of noroviruses is a key enzyme responsible for transcription and replication of the viral genome. Here, we review the progress made in understanding the structures and functions of norovirus RdRp and its use as a target for small molecule inhibitors. Crystal structures of the RdRp at different stages of substrate interaction have been determined, which shed light on its multi-step catalytic cycle. The in vitro assays and in vivo animal models that have been developed to identify and characterize inhibitors of norovirus RdRp are also summarized, followed by an update on the current antiviral research targeting different regions of norovirus RdRp. In the future, structure-based drug design and rational optimization of known nucleoside and non-nucleoside inhibitors of norovirus RdRp may pave the way towards the next generation of direct-acting antivirals.

Chronic Norovirus Infections in Cardiac Transplant Patients

Norovirus is a common self-limiting gastrointestinal infection, but in transplant recipients, symptoms can last for months and result in serious health complications. As there is currently no established treatment for chronic norovirus infection in transplant patients, management has been directed at symptom control, trial of various antivirals, and ultimately reductions in immunosuppression. We present 3 cases of chronic norovirus infection in cardiac transplant patients to illustrate various approaches to diagnosis, the prolonged nature of disease symptoms, and treatment options. When managing a transplant recipient with chronic diarrhea, considering a broad differential as well as maintaining a high suspicion for infectious etiologies is key. A stepwise approach to management includes termination of diarrhea-causing medications, trials of nitazoxanide and immunoglobulin, and reductions in immunosuppressive therapies. Although brief discontinuation of immunosuppression is often required to achieve symptom, graft rejection is often a complication.

Norovirus infection in solid organ transplant recipients: a single-center retrospective study

BACKGROUND

Norovirus (NoV) is gaining recognition as an important cause of diarrhea among solid organ transplant (SOT) recipients, but existing studies have been limited by a small sample size.

METHODS

We conducted a retrospective study of all adult SOT recipients diagnosed with NoV between 2006 and 2013 and compared their data to that of adult SOT recipients with diarrhea who tested negative for NoV during that time.

RESULTS

A total of 192 patients with diarrhea had stool NoV testing as part of their work-up during the study period; of these patients, 35% (67) tested positive for NoV. Of patients with diarrhea without NoV, Clostridium difficile (25%) and cytomegalovirus (12%) were the most commonly identified infectious cause of diarrhea. Diarrheal duration was significantly protracted in NoV patients, with an average of 241 days vs 75 days in the control group (P=.0007). One patient death and 2 graft failures were related to the NoV illness within the first month after the onset of diarrhea, and 30% of NoV patients had a ≥20% increase in creatinine within 1 year of diagnosis. These outcomes did not differ significantly from those of SOT patients with diarrhea in the non-NoV group.

CONCLUSIONS

NoV is a common cause of diarrhea among SOT recipients at our institution and is responsible for a very prolonged course of chronic diarrhea.

Viral associated diarrhea in immunocompromised and cancer patients at a large comprehensive cancer center: a 10-year retrospective study

BACKGROUND

Viral associated diarrhea (VAD) due to Norovirus (NV), Rotavirus (RV) and Adenovirus (AV) is common in immunocompromised and cancer patients. We sought to determine if the clinical characteristics, morbidity and seasonality of infection differed according to the type of enteric virus identified.

METHODS

Cases of NV, RV and AV were identified in stool specimens submitted to the clinical microbiology laboratory between November 2005 and February 2015. Clinical characteristics of patients, potential risk factors and outcomes were compared.

RESULTS

A total of 97 VAD cases were identified: NV (n = 49), RV (n = 34) and AV (n = 14). The majority of cases were in patients with leukemia and lymphoma. NV (59%), RV (74%) and AV (78%) were identified in hematopoietic stem cell transplant (HSCT) recipients; and in patients with graft versus host disease (GVHD): NV (34%), RV (46%) and AV (57%). Nine cases of NV were genotyped; all were due to genotype II. Nine of 49 (18%) cases of NV, 7 of 34 (20%) cases of RV and 2 of 14 (14%) cases of AV were considered to be health care acquired (HCA). In multivariate analysis, immunosuppression (OR 2.8 95% CI 1.26-6.60, p = .01) and neutropenia (OR 4.8 95% CI 1.27-18.5, p = .01) were identified as risk factors for NV diarrhea compared to RV and AV.

CONCLUSIONS

In our study, agents responsible for VAD occurred year round but predominated in the winter time; caused prolonged illness and were frequently health care associated. Presentations were atypical in many cases without upper gastrointestinal symptoms such as nausea and vomiting.

Viral gastrointestinal infections and norovirus genotypes in a paediatric UK hospital, 2014-2015

BACKGROUND

Diarrhoea in children is a common disease; understanding the incidence of causative viruses can aid infection control and vaccine development.

OBJECTIVES

Describe the incidence and characteristics of gastroenteric viruses including norovirus genotypes in a paediatric hospital cohort.

STUDY DESIGN

Norovirus, adenovirus, sapovirus, astrovirus, rotavirus qPCR and norovirus genotyping results for all stool specimens (n=4786; 1393 patients) at a UK paediatric tertiary referral hospital June 2014-July 2015.

RESULTS AND DISCUSSION

24% (329/1393) of patients were positive for a GI virus; the majority were positive for norovirus (44%, 144/329) or adenovirus (44%, 146/329). The overall incidence of rotavirus (2%) is reduced compared to pre-vaccination studies; however the incidence of other GI viruses has not increased. Norovirus infections had a significantly higher virus burden compared to other GI viruses (P ≤0.03); sapovirus infections had the lowest viral burden. The number of norovirus cases per month did not follow the typical winter seasonal trend of nationally reported outbreaks. The number of cases per month correlates with the number of hospital admissions (R=0.703, P=0.011); the number of admissions accounts for 50% of the variability in number of cases per month. The breadth of genotypes seen (48% non-GII.4), suggests a community source for many norovirus infections and has implications for vaccine development. All GI viruses caused chronic infections, with the majority (50-100%) in immunocompromised patients. Incidence or duration of infection in chronic norovirus infections did not differ between genotypes, suggesting host-mediated susceptibility.

Feline Calicivirus Infection Disrupts Assembly of Cytoplasmic Stress Granules and Induces G3BP1 Cleavage

In response to stress such as virus infection, cells can stall translation by storing mRNAs away in cellular compartments called stress granules (SGs). This defense mechanism favors cell survival by limiting the use of energy and nutrients until the stress is resolved. In some cases it may also block viral propagation as viruses are dependent on the host cell resources to produce viral proteins. Human norovirus is a member of the Caliciviridae family responsible for gastroenteritis outbreaks worldwide. Previous studies on caliciviruses have identified mechanisms by which they can usurp the host translational machinery, using the viral protein genome-linked VPg, or regulate host protein synthesis through the mitogen-activated protein kinase (MAPK) pathway. Here, we examined the effect of feline calicivirus (FCV) infection on SG accumulation. We show that FCV infection impairs the assembly of SGs despite an increased phosphorylation of eukaryotic initiation factor eIF2α, a hallmark of stress pathway activation. Furthermore, SGs did not accumulate in FCV-infected cells that were stressed with arsenite or hydrogen peroxide. FCV infection resulted in the cleavage of the SG-nucleating protein Ras-GTPase activating SH3 domain-binding protein (G3BP1), which is mediated by the viral 3C-like proteinase NS6(Pro) Using mutational analysis, we identified the FCV-induced cleavage site within G3BP1, which differs from the poliovirus 3C proteinase cleavage site previously identified. Finally, we showed that NS6(Pro)-mediated G3BP1 cleavage impairs SG assembly. In contrast, murine norovirus (MNV) infection did not impact arsenite-induced SG assembly or G3BP1 integrity, suggesting that related caliciviruses have distinct effects on the stress response pathway.

IMPORTANCE

Human noroviruses are a major cause of viral gastroenteritis, and it is important to understand how they interact with the infected host cell. Feline calicivirus (FCV) and murine norovirus (MNV) are used as models to understand norovirus biology. Recent studies have suggested that the assembly of stress granules is central in orchestrating stress and antiviral responses to restrict viral replication. Overall, our study provides the first insight on how caliciviruses impair stress granule assembly by targeting the nucleating factor G3BP1 via the viral proteinase NS6(Pro) This work provides new insights into host-pathogen interactions that regulate stress pathways during FCV infection.

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.

Laboratory Diagnosis of Infections in Cancer Patients: Challenges and Opportunities

Infections remain a significant cause of morbidity and mortality in cancer patients. The differential diagnosis for these patients is often wide, and the timely selection of the right clinical tests can have a significant impact on their survival. However, laboratory findings with current methodologies are often negative, challenging clinicians and laboratorians to continue the search for the responsible pathogen. Novel methodologies are providing increased sensitivity and rapid turnaround time to results but also challenging our interpretation of what is a clinically significant pathogen in cancer patients. This minireview provides an overview of the most common infections in cancer patients and discusses some of the challenges and opportunities for the clinical microbiologist supporting the care of cancer patients.

Norovirus in Transplantation

Noroviruses are among the most common cause of diarrhea in transplant recipients. The clinical spectrum of norovirus infection after transplant is increasingly being recognized. As substantial morbidity is now associated with norovirus infections in this population; the quest for rapid diagnostic modalities and newer therapies has expanded. Transplant recipients with norovirus infection are at risk for several complications, including protracted illness with malnutrition, organ failure, and chronic viral shedding. This review summarizes the current knowledge on the epidemiology, complications, diagnosis, and treatment of norovirus infection in the transplant setting.

Norovirus Infection: Replication, Manipulation of Host, and Interaction with the Host Immune Response

Noroviruses (NoVs) belong to the Caliciviridae family of viruses and are responsible for causing the majority of gastroenteritis outbreaks worldwide. In the past decade, research on NoV biology has intensified because of the discovery of murine NoV and subsequently the first cell culture system and small animal model for NoV replication and pathogenesis. In this review, we discuss the current literature on NoV biology, focusing particularly on NoV replication and the interaction between NoV and the host immune response. Understanding the NoV replication cycle and its interaction with cellular processes and innate immune immunity will help develop molecular targets to control human NoV infection and prevent outbreaks. In addition to the innate immune response, we have documented the current efforts to develop NoV vaccines to control outbreaks.

Emerging and Rare Viral Infections in Transplantation

Immunocompromised patients such as those undergoing solid organ or hematopoietic stem cell transplantation are at substantial risk for infection with numerous pathogens. Infections with cytomegalovirus (CMV), herpes simplex virus (HSV), Epstein–Barr virus (EBV), and human herpesvirus-6 (HHV-6) are well-described complications of transplantation. As viruses previously believed to be quiescent through widespread vaccination (e.g., measles and mumps) reemerge and molecular diagnostic techniques are refined, rare and emerging viral infections are increasingly diagnosed in transplant recipients. This chapter will review the clinical manifestations, diagnosis, and potential antiviral therapies for these viruses in the transplant population.

Treatment with a Nucleoside Polymerase Inhibitor Reduces Shedding of Murine Norovirus in Stool to Undetectable Levels without Emergence of Drug-Resistant Variants

Prolonged norovirus shedding may occur in certain patients, such as organ transplant recipients. We established a mouse model for persistent norovirus infection (using the mouse norovirus MNV.CR6 strain). The nucleoside viral polymerase inhibitor 2'-C-methylcytidine (2CMC), but not favipiravir (T-705), reduced viral shedding to undetectable levels. Viral rebound was observed after stopping treatment, which was again effectively controlled by treatment with 2CMC. No drug-resistant variants emerged.

Norovirus infections and seroprevalence of genotype GII.4-specific antibodies in a Spanish population

Genotype II.4 noroviruses (NoVs) are a leading cause of epidemic acute gastroenteritis in children and adults worldwide. The prevalence of different NoV genotypes causing outbreaks and sporadic cases of acute gastroenteritis in the region of Valencia, Spain, during a 4-year period (2008-11) was investigated. NoVs were detected in 42 out of 55 (76.3%) outbreaks and in 26 out of 332 (7.8%) sporadic cases of acute gastroenteritis. Genogroup GII strains were predominant in outbreaks and sporadic cases. Different genotype GII.4 variants were found (Yerseke_2006a, Den Haag_2006b, Apeldoorn_2007, and New Orleans_2009), with the latter variant detected most frequently (35.3%). A recombinant P domain of the NoV GII.4 Apeldoorn_2007 variant was produced in Escherichia coli and used as the coating antigen in an enzyme immunoassay to survey the IgG antibody seroprevalence against NoV GII.4 in a Spanish population. Baculovirus-expressed virus-like particles (VLPs) of NoV GII.4 Den Haag_2006b variant were also produced and used as antigen to compare seroreactivity. Of the 434 serum specimens analyzed, 429 (98.6%) had antibodies against the P domain. The comparison of reactivities of 30 serum samples to the NoV GII.4 P polypeptide and VLP showed reproducible results with a correlation coefficient of r = 0.794. Titers of antibodies to the P domain increased gradually and significantly with age, reaching the highest levels at the age group of 41-50 years. These results confirm the high prevalence of NoV GII.4 infections in Valencia from early childhood.

Control of norovirus outbreak on a pediatric oncology unit

BACKGROUND

Patients undergoing treatment for cancer with chemotherapy and hematopoietic stem cell recipients are at risk for severe morbidity caused by norovirus (NV).

METHODS

We describe a NV outbreak on the Memorial Sloan Kettering Cancer Center's pediatric oncology unit. Stool testing for diagnosis of NV was performed by real-time polymerase chain reaction (PCR).

RESULTS

Twelve NV cases occurred; 7 were hospital acquired. Twenty-five health care workers reported NV compatible illness. Patient-to-patient transmission occurred once. The practices of the Centers for Disease Control and Prevention were supplemented with electronic surveillance, surrogate screening for NV, and heightened cleaning. Two additional cases occurred after implementation of interventions. Long-term shedding was detected in 2 patients.

CONCLUSION

We describe interventions for controlling NV on a pediatric oncology unit. High-risk chronic shedders pose ongoing transmission risks. PCR is a valuable diagnostic tool but may be overly sensitive. Surrogate markers to assess NV burden in stool and studies on NV screening are needed to develop guidelines for high-risk chronic shedders.

GII.4 Sydney_2012 norovirus infection in immunocompromised patients in Beijing and its rapid evolution in vivo

To study the epidemiology and evolution of norovirus (NoV) in immunocompromised patients in a tertiary hospital in China. Stool specimens were collected from 131 hospitalized patients presenting with diarrhea from July 1, 2012, to June 30, 2013, and were tested for NoV using RT-PCR. RT-PCR was performed to amplify the complete capsid genome for a series of samples from chronic diarrhea patients, and nucleotide and amino acid changes were analyzed. There were nine NoV-positive patients among 124 immunocompromised patients (7.3%); all nine were infected with GII.4 Sydney_2012 strain. In three chronic diarrhea patients, the GII.4 Sydney_2012 strains accumulated 19, 18, and eight nucleotide mutations within 110, 113, and 22 days, respectively, most were non-synonymous. The greatest number of stable amino acid mutations was 10 in patient 2; eight stable mutations (including three in antigenic sites) occurred while the patient was asymptomatic and shedding the virus. GII.4 Sydney_2012 strain tends to undergo stable mutations during the asymptomatic shedding phase and may generate new variants in chronic diarrhea patients.

Norovirus immunology: Of mice and mechanisms

Noroviruses (NoVs) are the most common cause of sporadic and epidemic gastroenteritis in the United States and Europe and are responsible for 20% of acute gastroenteritis worldwide. Over the past decade, the understanding of NoV immunology has grown immensely. Studies of the natural immune response to NoV in humans and animal models have laid the foundation for innovations in cell culture systems for NoV and development of new therapeutics. Evidence from animal models, NoV surrogates, observational human research, and human challenge studies suggest that the innate immune response is critical for limiting NoV infection but is insufficient for viral clearance. NoV may antagonize the innate immune response to establish or prolong infection. However, once a robust adaptive immune response is initiated, the immune system clears the infection through the action of T and B cells, simultaneously generating highly specific protective immunologic memory. We review here both the current knowledge on NoV immunity and exciting new developments, with a focus on ongoing vaccine development work, novel cell culture systems, and advances in understanding the role of the gut microbiome. These changes reinforce the need for a better understanding of the human immune response to NoV and suggest novel hypotheses.

Noroviruses: epidemiology, immunity and prospects for prevention

In recent years, noroviruses have become recognized as an important cause of both sporadic and epidemic acute gastroenteritis (AGE), largely due to the improved availability of broadly reactive real-time RT-PCR (TaqMan-based RT-PCR) assays. While there is substantial diversity among noroviruses, one specific genotype, GII.4, is the most common etiology in sporadic and epidemic AGE. Outbreaks of norovirus AGE most commonly occur in healthcare facilities and restaurants and result in significant morbidity and mortality and substantial healthcare costs. Norovirus vaccine development is progressing, and Phase I and II human trials have shown proof-of-principle that norovirus vaccines can reduce illness and infection.

Noroviruses as a Cause of Diarrhea in Immunocompromised Pediatric Hematopoietic Stem Cell and Solid Organ Transplant Recipients

Case reports describe significant norovirus gastroenteritis morbidity in immunocompromised patients. We evaluated norovirus pathogenesis in prospectively enrolled solid organ (SOT) and hematopoietic stem cell transplant (HSCT) patients with diarrhea who presented to Texas Children's Hospital and submitted stool for enteric testing. Noroviruses were detected by real-time reverse transcription polymerase chain reaction. Clinical outcomes of norovirus diarrhea and non-norovirus diarrhea patients, matched by transplanted organ type, were compared. Norovirus infection was identified in 25 (22%) of 116 patients, more frequently than other enteropathogens. Fifty percent of norovirus patients experienced diarrhea lasting ≥14 days, with median duration of 12.5 days (range 1-324 days); 29% developed diarrhea recurrence. Fifty-five percent of norovirus patients were hospitalized for diarrhea, with 27% requiring intensive care unit (ICU) admission. One HSCT recipient developed pneumatosis intestinalis. Three HSCT patients expired ≤6 months of norovirus diarrhea onset. Compared to non-norovirus diarrhea patients, norovirus patients experienced significantly more frequent ICU admission (27% vs. 0%, p = 0.02), greater serum creatinine rise (median 0.3 vs. 0.2 mg/dL, p = 0.01), and more weight loss (median 1.6 vs. 0.6 kg, p < 0.01). Noroviruses are an important cause of diarrhea in pediatric transplant patients and are associated with significant clinical complications.

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.

Viral gastroenteritis in children in Colorado 2006-2009

Acute gastroenteritis accounts for a significant burden of medically attended illness in children under the age of five. For this study, four multiplex reverse transcription PCR assays were used to determine the incidence of adenovirus, astrovirus, coronavirus, norovirus GI and GII, rotavirus, and sapovirus in stool samples submitted for viral electron microscopy (EM) to the Children's Hospital Colorado. Of 1105 stool samples available, viral RNA/DNA was detected in 247 (26.2%) of 941 pediatric samples (median age = 2.97 years, 54% male) with 28 (3.0%) positive for more than one virus. Adenovirus, astrovirus, norovirus GI, norovirus GII, rotavirus, and sapovirus were detected in 95 (10.0%), 33 (3.5%), 8 (0.9%), 90 (9.6%), 49 (5.2%), and 2 (0.2%) of the pediatric samples, respectively. No coronaviruses were identified. Sequencing of norovirus positive samples indicated an outbreak of norovirus strain GII.4 in 2006 with evidence of numerous circulating strains. Multiple samples from the same immunocompromised patients demonstrated symptomatic shedding of norovirus for up to 32 weeks and astrovirus for 12 weeks. RT-PCR detected 99 of 111 (89%) adenovirus-positive samples versus 12 (11%) by EM, and 186 of 192 (97%) sapovirus/astrovirus/norovirus-positive samples versus 21 (11%) by EM. Noroviruses and adenoviruses are common causes of gastroenteritis in children. Immunocompromised patients can be infected with multiple viruses and shed viruses in their stools for prolonged periods. This data support the superiority of RT-PCR compared to EM for diagnosis of viral gastroenteritis.

Characteristics and outcomes of patients diagnosed with norovirus gastroenteritis after allogeneic hematopoietic stem cell transplantation based on immunochromatography

Norovirus gastroenteritis (NV-GE) is a highly transmittable disease that can lead to fatal outcomes in vulnerable populations including patients after hematopoietic stem cell transplantation (HSCT). Prompt detection of NV is therefore important for HSCT recipients. Immunochromatography (IC) can be used to easily and rapidly diagnose NV-GE by detecting NV antigens. In this study, we examined 642 stool specimens in patients who developed diarrhea after allogeneic HSCT between January 2007 and June 2011. NV was detected in 10 of 350 (2.9 %) HSCT recipients. The median onset of symptoms was 36 days (range 3-93) after HSCT. The median duration of symptoms was 42 days (3-135). A second or subsequent allogeneic HSCT was associated with a higher incidence of NV-GE (P = 0.034). Of four patients who underwent colonoscopy, two showed intestinal graft-versus-host disease (GVHD) histopathology, whereas the other two showed no evidence of GVHD, and thus no need for intensified immunosuppression. None of the patients died of NV-GE. In conclusion, IC may be useful in the differential diagnosis of diarrhea after allogeneic HSCT, and could enable the appropriate adjustment of immunosuppressive drugs and prompt preventive measures.

Antigenic Relatedness of Norovirus GII.4 Variants Determined by Human Challenge Sera

The GII.4 noroviruses (NoVs) are a single genotype that is responsible for over 50% of NoV gastroenteritis epidemics worldwide. However, GII.4 NoVs have been found to undergo antigenic drifts, likely selected by host herd immunity, which raises an issue for vaccine strategies against NoVs. We previously characterized GII.4 NoV antigenic variations and found significant levels of antigenic relatedness among different GII.4 variants. Further characterization of the genetic and antigenic relatedness of recent GII.4 variants (2008b and 2010 cluster) was performed in this study. The amino acid sequences of the receptor binding interfaces were highly conserved among all GII.4 variants from the past two decades. Using serum samples from patients enrolled in a GII.4 virus challenge study, significant cross-reactivity between major GII.4 variants from 1998 to 2012 was observed using enzyme-linked immunosorbent assays and HBGA receptor blocking assays. The overall abilities of GII.4 NoVs to bind to the A/B/H HBGAs were maintained while their binding affinities to individual ABH antigens varied. These results highlight the importance of human HBGAs in NoV evolution and how conserved antigenic types impact vaccine development against GII.4 variants.

The burden of norovirus gastroenteritis: an important foodborne and healthcare-related infection

Human norovirus (NoV) is now recognized as one of the most important causative agents of gastroenteritis in all age groups worldwide. During the course of NoV infection, symptoms are usually mild and disappear within 48 h after onset. The incidence of NoV infection is high, with hundreds of cases per 10 000 of the population, although the number of infections is still underestimated. Epidemiological surveys conducted in Europe and North America have shown that NoV infections constitute a major disease burden, especially for young children and the elderly, in whom NoV infection leads to high rates of hospitalization and mortality. NoV infections are also of concern in hospitals, where viral infections can be persistent in immunocompromised patients. Although the cost of NoV infection in the hospital community has not yet been clearly established, it appears that NoV infections could cost hundreds of thousands of euros in terms of unit closure, and NoV-related sickness in patients and health workers. Besides their clinical burden, NoVs, as foodborne pathogens, also cause to millions of dollars of losses for the healthcare system and the food industry. Recent estimates in the USA showed that, annually, NoV illness cost $2 billion and led to a loss of approximately 5000 quality-adjusted life-years, making NoV one of the top five pathogens causing enteric illnesses. The highest cost among 14 foodborne pathogens is also attributed to human NoV in The Netherlands. This accumulation of evidence underlines the enormous impact of NoV on populations.

The role of type I interferons in intestinal infection, homeostasis, and inflammation

Type I interferons are a widely expressed family of effector cytokines that promote innate antiviral and antibacterial immunity. Paradoxically, they can also suppress immune responses by driving production of anti-inflammatory cytokines, and dysregulation of these cytokines can contribute to host-mediated immunopathology and disease progression. Recent studies describe their anti-inflammatory role in intestinal inflammation and the locus containing IFNAR, a heterodimeric receptor for the type I interferons has been identified as a susceptibility region for human inflammatory bowel disease. This review focuses on the role of type I IFNs in the intestine in health and disease and their emerging role as immune modulators. Clear understanding of type I IFN-mediated immune responses may provide avenues for fine-tuning existing IFN treatment for infection and intestinal inflammation.

Murine norovirus 1 (MNV1) replication induces translational control of the host by regulating eIF4E activity during infection

Protein synthesis is a tightly controlled process responding to several stimuli, including viral infection. As obligate intracellular parasites, viruses depend on the translation machinery of the host and can manipulate it by affecting the availability and function of specific eukaryotic initiation factors (eIFs). Human norovirus is a member of the Caliciviridae family and is responsible for gastroenteritis outbreaks. Previous studies on feline calicivirus and murine norovirus 1 (MNV1) demonstrated that the viral protein, genome-linked (VPg), acts to direct translation by hijacking the host protein synthesis machinery. Here we report that MNV1 infection modulates the MAPK pathway to activate eIF4E phosphorylation. Our results show that the activation of p38 and Mnk during MNV1 infection is important for MNV1 replication. Furthermore, phosphorylated eIF4E relocates to the polysomes, and this contributes to changes in the translational state of specific host mRNAs. We propose that global translational control of the host by eIF4E phosphorylation is a key component of the host-pathogen interaction.

Norovirus

Norovirus, an RNA virus of the family Caliciviridae, is a human enteric pathogen that causes substantial morbidity across both health care and community settings. Several factors enhance the transmissibility of norovirus, including the small inoculum required to produce infection (<100 viral particles), prolonged viral shedding, and its ability to survive in the environment. In this review, we describe the basic virology and immunology of noroviruses, the clinical disease resulting from infection and its diagnosis and management, as well as host and pathogen factors that complicate vaccine development. Additionally, we discuss overall epidemiology, infection control strategies, and global reporting efforts aimed at controlling this worldwide cause of acute gastroenteritis. Prompt implementation of infection control measures remains the mainstay of norovirus outbreak management.

Diarrhea after kidney transplantation: a new look at a frequent symptom

Diarrhea is a frequent but overlooked complication of kidney transplantation. Diarrhea is repeatedly neglected, often considered by patients and clinicians an unavoidable side effect of immunosuppressive regimens. It is, however, associated with a significant impairment in life quality. Severe and chronic posttransplant diarrhea may lead to dehydration, malabsorption, rehospitalization, immunosuppression, noncompliance, and a greater risk of graft loss and death. There is thus a need to optimize and standardize the management of posttransplant diarrhea with consistent diagnostic and therapeutic strategies. A recent study has suggested that the increased sensitivity of molecular tools might help in early pathogen identification and guidance of antimicrobial treatment. Most bacterial and protozoan infections are readily curable with appropriate antimicrobial agents; cryptosporidiosis and C. difficile infections may however be complicated by relapsing courses. In addition, identification of enteric viral genomes in stool has further reduced posttransplant diarrhea of unknown origin. Chronic norovirus-related posttransplant diarrhea, arising from the interplay of the virus and immunosuppressive drugs, has emerged as a new challenge in the field. Prospective and controlled studies are necessary to evaluate the efficacy and safety of innovative anti-norovirus therapeutics, as well as optimal immunosuppressive regimens, to enable viral clearance while preventing rejection and donor-specific antibody formation. This review seeks to provide a basis for the design of future clinical prospective studies.

Prospective study on Norovirus infection among allogeneic stem cell transplant recipients: prolonged viral excretion and viral RNA in the blood

BACKGROUND

Human caliciviruses (Norovirus and Sapovirus) are important acute gastroenteritis agents. The Norovirus (NoV) disease is usually self-limited; however, prolonged viral excretion and complications have been reported, mainly in immunosuppressed individuals.

OBJECTIVES

In this prospective study, we have monitored allogeneic stem cell transplant (ASCT) patients for human calicivirus infection.

STUDY DESIGN

Ten ASCT patients were monitored for NoV and sapoviruses (SaV) infection, for a period of five months to a maximum of one year. Prolonged NoV excretion and long term viral RNA in the blood were assessed by multiplex RT-PCR targeting region C of the viral capsid. Secretor status of the patients was determined by enzyme immunoassay using Ulex Europaeus agglutinin. Partial genomic sequencing and phylogenetic analysis were performed to characterize the viral genotypes.

RESULTS

NoV was detected in six out of ten patients (60%). Prolonged viral excretion in feces (mean of 61.6 days) and long term presence of NoV RNA in the sera (mean of 33.6 days) of the patients were observed. SaV was not detected in any of the samples. All patients had diarrhea, vomiting and fever during NoV positivity. All NoV-positive samples were characterized as GI.3 NoV. Three Nov-infected patients presented with acute intestinal graft versus host disease.

CONCLUSIONS

This study brings important information on NoV course of infection in ASCT patients. It also provides evidence for long term viral RNA in the blood highlighting the importance of the inclusion of NoV screening in the routine testing performed before transplantation and during follow-up of these patients.

Norovirus infection in immunocompromised hosts

Acute gastroenteritis caused by noroviruses often has a duration of 2-3 days and is characteristically self-limiting. In contrast, chronic infection caused by noroviruses in immunocompromised individuals can last from weeks to years, making clinical management difficult. The mechanisms by which noroviruses establish persistent infection, and the role of immunocompromised hosts as a reservoir for noroviruses in the general human population, are not known. However, study of this patient cohort may lead to new insights into norovirus biology and approaches to treatment.

Bacterial foodborne infections after hematopoietic cell transplantation

Diarrhea, abdominal pain, and fever are common among patients undergoing hematopoietic cell transplantation (HCT), but such symptoms are also typical with foodborne infections. The burden of disease caused by foodborne infections in patients undergoing HCT is unknown. We sought to describe bacterial foodborne infection incidence after transplantation within a single-center population of HCT recipients. All HCT recipients who underwent transplantation from 2001 through 2011 at the Fred Hutchinson Cancer Research Center in Seattle, Washington were followed for 1 year after transplantation. Data were collected retrospectively using center databases, which include information from transplantation, on-site examinations, outside records, and collected laboratory data. Patients were considered to have a bacterial foodborne infection if Campylobacter jejuni/coli, Listeria monocytogenes, E. coli O157:H7, Salmonella species, Shigella species, Vibrio species, or Yersinia species were isolated in culture within 1 year after transplantation. Nonfoodborne infections with these agents and patients with pre-existing bacterial foodborne infection (within 30 days of transplantation) were excluded from analyses. A total of 12 of 4069 (.3%) patients developed a bacterial foodborne infection within 1 year after transplantation. Patients with infections had a median age at transplantation of 50.5 years (interquartile range [IQR], 35 to 57), and the majority were adults ≥18 years of age (9 of 12 [75%]), male gender (8 of 12 [67%]) and had allogeneic transplantation (8 of 12 [67%]). Infectious episodes occurred at an incidence rate of 1.0 per 100,000 patient-days (95% confidence interval, .5 to 1.7) and at a median of 50.5 days after transplantation (IQR, 26 to 58.5). The most frequent pathogen detected was C. jejuni/coli (5 of 12 [42%]) followed by Yersinia (3 of 12 [25%]), although Salmonella (2 of 12 [17%]) and Listeria (2 of 12 [17%]) showed equal frequencies; no cases of Shigella, Vibrio, or E. coli O157:H7 were detected. Most patients were diagnosed via stool (8 of 12 [67%]), fewer through blood (2 of 12 [17%]), 1 via both stool and blood simultaneously, and 1 through urine. Mortality due to bacterial foodborne infection was not observed during follow-up. Our large single-center study indicates that common bacterial foodborne infections were a rare complication after HCT, and the few cases that did occur resolved without complications. These data provide important baseline incidence for future studies evaluating dietary interventions for HCT patients.

Norovirus: targets and tools in antiviral drug discovery

The development of antiviral strategies to treat or prevent norovirus infections is a pressing matter. Noroviruses are the number 1 cause of acute gastroenteritis, of foodborne illness, of sporadic gastroenteritis in all age groups and of severe acute gastroenteritis in children less than 5 years old seeking medical assistance [USA/CDC]. In developing countries, noroviruses are linked to significant mortality (~200,000 children <5 years old). Noroviruses are a major culprit for the closure of hospital wards, and associated with increased hospitalization and mortality among the elderly. Transplant patients have significant risk of acquiring persistent norovirus gastroenteritis. Control and prevention strategies are limited to the use of disinfectants and hand sanitizers, whose efficacy is frequently insufficient. Hence, there is an ample need for antiviral treatment and prophylaxis of norovirus infections. The fact that only a handful of inhibitors of norovirus replication have been reported can largely be attributable to the hampering inability to cultivate human noroviruses in cell culture. The Norwalk replicon-bearing cells and the murine norovirus-infected cell lines are the available models to assess in vitro antiviral activity of compounds. Human noroviruses have been shown to replicate (to some extent) in mice, calves, gnotobiotic pigs, and chimpanzees. Infection of interferon-deficient mice with the murine norovirus results in virus-induced diarrhea. Here we review recent developments in understanding which norovirus proteins or host cell factors may serve as targets for inhibition of viral replication. Given the recent advances, significant progress in the search for antiviral strategies against norovirus infections is expected in the upcoming years.

Treatment of norovirus infections: moving antivirals from the bench to the bedside

Noroviruses (NV) are the most common cause of acute gastrointestinal illness in the United States and worldwide. The development of specific antiviral countermeasures has lagged behind that of other viral pathogens, primarily because norovirus disease has been perceived as brief and self-limiting and robust assays suitable for drug discovery have been lacking. The increasing recognition that NV illness can be life-threatening, especially in immunocompromised patients who often require prolonged hospitalization and intensive supportive care, has stimulated new research to develop an effective antiviral therapy. Here, we propose a path forward for evaluating drug therapy in norovirus-infected immunocompromised individuals, a population at high risk for serious and prolonged illness. The clinical and laboratory features of norovirus illness in immunocompromised patients are reviewed, and potential markers of drug efficacy are defined. We discuss the potential design of clinical trials in these patients and how an antiviral therapy that proves effective in immunocompromised patients might also be used in the setting of acute outbreaks, especially in confined settings such as nursing homes, to block the spread of infection and reduce the severity of illness. We conclude by reviewing the current status of approved and experimental compounds that might be evaluated in a hospital setting.

Gastrointestinal infections after transplantation

PURPOSE OF REVIEW

Recipients of both solid organ transplant and hematopoietic stem cell transplantation are at increased risk for infectious morbidity and mortality after transplantation due to on-going immunosuppression. Gastrointestinal infections have been increasingly reported in these populations.

RECENT FINDINGS

Increased reports of gastrointestinal infections including bacterial infection with Clostridium difficile, viral infection with norovirus and parasitic pathogens like cryptosporidium are emerging. Risk factors identified have focused on type of transplant, transplant immunosuppression regimens and exposures. Although many events are self-limiting, significant morbidity and rare mortality are reported.

SUMMARY

Improved diagnostic techniques have increased the reporting of several gastrointestinal infections after transplantation, affording improved understanding of the epidemiology of these diseases. Armed with this emerging data, prevention, recognition of infection and treatment strategies can be more thoroughly assessed in these at-risk populations.

Viral gastroenteritis in the adult population: the GI peril

Viral gastroenteritis is extremely common, causing millions of cases of diarrhea in all age groups worldwide. Norovirus has been identified as the leading cause of viral gastroenteritis in the adult population. The combination of a low infectious dose, viral shedding before and for weeks after illness, and resistance to temperatures from freezing to 60°C and to many common household cleaners makes norovirus a winter peril. Mild disease requires symptomatic treatment alone. Complicated cases develop severe dehydration and hypovolemia, requiring the skills of critical care nurses to meet the challenges of care. This article addresses diagnosis and prevention strategies.

Norovirus and FRNA bacteriophage determined by RT-qPCR and infectious FRNA bacteriophage in wastewater and oysters

Norovirus (NoV), the leading cause of adult non-bacterial gastroenteritis can be commonly detected in wastewater but the extent of NoV removal provided by wastewater treatment plants (WWTPs) is unclear. We monitored a newly commissioned WWTP with UV disinfection on a weekly basis over a six month period for NoV using RT-qPCR and for FRNA bacteriophage GA using both RT-qPCR (total concentration) and a plaque assay (infectious concentration). Mean concentrations of NoV GI and GII in influent wastewater were reduced by 0.25 and 0.41 log10 genome copies 100 ml(-1), respectively by the WWTP. The mean concentration of total FRNA bacteriophage GA was reduced by 0.35 log genome copies 100 ml(-1) compared to a reduction of infectious FRNA bacteriophage GA of 2.13 log PFU 100 ml(-1). A significant difference between concentrations of infectious and total FRNA bacteriophage GA was observed in treated, but not in untreated wastewaters. We conclude that RT-qPCR in isolation underestimates the reduction of infectious virus during wastewater treatment. We further compared the concentrations of infectious virus in combined sewer overflow (CSO) and UV treated effluents using FRNA bacteriophage GA. A greater percentage (98%) of infectious virus is released in CSO discharges than UV treated effluent (44%). Following a CSO discharge, concentrations of NoV GII and infectious FRNA bacteriophage GA in oysters from less than the limit of detection to 3150 genome copies 100 g(-1) and 1050 PFU 100 g(-1) respectively.

An outbreak of norovirus infection in a bone marrow transplant unit

BACKGROUND

Norovirus is a single-stranded RNA virus belonging to the Caliciviridae family.

METHODS

Our observational cohort study aimed to describe a nosocomial outbreak of norovirus on a bone marrow transplant (BMT) unit.

RESULTS

Six of 8 BMT patients with increased liquid stools tested positive for norovirus: 4 had new onset diarrhea; 2 had acute exacerbations of chronic diarrhea caused by graft versus host disease. Eight non-BMT inpatients had norovirus infection, but 7 of these were community acquired; cumulative incidence rates in BMT and non-BMT units were 26% and 0.16%, respectively. In BMT patients, diarrhea (increased or new onset) lasted 6 to 33 days-durations shorter than those reported in sporadic BMT cases. All patients had private rooms and bathrooms. Five of 6 patients were on the BMT unit during their presumed incubation periods. Three were in adjacent rooms. Three nurses and 1 physician had symptoms compatible with norovirus infection, and all 4 worked while ill. The outbreak ended coincident with implementation of stricter infection control practices.

CONCLUSION

Norovirus appeared to spread in a BMT unit more avidly than it did among general medical patients. Explanations include prolonged diarrhea and viral excretion, long hospital stays of infected patients, rarity of empiric contact isolation for diarrhea, routine handling of liquid stool, and a closed community of health care workers.

Hemophagocytic lymphohistiocytosis after allogeneic bone marrow transplantation during chronic norovirus infection

Hemophagocytic lymphohistiocytosis (HLH) is a macrophage activating syndrome that is known to develop in patients with autoimmune disease, malignancies or infection, for example with Epstein-Barr virus, cytomegalovirus or varicella zoster virus. We describe a 24-month old boy with acute myelogenous leukaemia relapse and allogeneic bone marrow transplantation, who developed HLH on day +40 during chronic infection with norovirus. Here, we report for the first time the development of HLH in combination with chronic norovirus infection after allogeneic bone marrow transplantation in a hematopoietic malignancy.

Microbiological diagnosis of severe diarrhea in kidney transplant recipients by use of multiplex PCR assays

Diarrhea is a frequent complication after kidney transplantation, ascribed to adverse effects of the immunosuppressive therapy in case of negative microbiological examination of the stools. The aim of this study was to improve the microbiological diagnosis by implementing molecular tests. Fifty-four severe diarrhea events that occurred in 49 adult kidney transplant recipients from September 2010 to November 2011 were investigated. One or several enteric pathogens were detected in 13 (23%) stool samples using classical microbiological methods versus 39 (72%) for the seven commercially available multiplex PCR assays used retrospectively (P = 0.006). Interestingly, molecular diagnosis identified 15 multiple infections compared to none using classical techniques. The primary pathogens detected were enteropathogenic Escherichia coli (EPEC) (n = 15; 38%), Campylobacter spp. (n = 15; 38%), and Norovirus (n = 14; 36%). Specificities for Campylobacter and Norovirus infection diagnosis were 75 and 100%, respectively, by comparison to reference methods. Based on molecular findings, a cyclosporine-mycophenolate mofetil combination was identified as a risk factor for developing Norovirus-induced diarrhea. Norovirus infections were also responsible for higher weight loss than all the other causes of diarrhea. In samples from asymptomatic immunocompromised and immunocompetent patients, EPEC but not Norovirus and Campylobacter infections were detected at a frequency similar to that observed in symptomatic kidney transplant recipients. In conclusion, molecular tools significantly improved the detection of single and multiple enteric infections by comparison to classical techniques and could quickly become the key element in the management of severe acute diarrhea in transplant recipients.

High pressure processing and its application to the challenge of virus-contaminated foods

High pressure processing (HPP) is an increasingly popular non-thermal food processing technology. Study of HPP's potential to inactivate foodborne viruses has defined general pressure levels required to inactivate hepatitis A virus, norovirus surrogates, and human norovirus itself within foods such as shellfish and produce. The sensitivity of a number of different picornaviruses to HPP is variable. Experiments suggest that HPP inactivates viruses via denaturation of capsid proteins which render the virus incapable of binding to its receptor on the surface of its host cell. Beyond the primary consideration of treatment pressure level, the effects of extending treatment times, temperature of initial pressure application, and matrix composition have been identified as critical parameters for designing HPP inactivation strategies. Research described here can serve as a preliminary guide to whether a current commercial process could be effective against HuNoV or HAV.

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

BACKGROUND

Cancer patients frequently suffer from gastrointestinal complications. However, a comprehensive, practical and evidence-based guideline on this issue is not yet available.

PATIENTS AND METHODS

An expert group was put together by the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO) to develop a guideline on gastrointestinal complications in cancer patients. For each subtopic, a literature search was carried out in PubMed, Medline and Cochrane databases and the strength of recommendation and the quality of the published evidence for major therapeutic strategies were categorized using a modification of the 'Infectious Diseases Society of America' criteria. Consensus discussions were held on each of the topics.

RESULTS

Recommendations were made with respect to non-infectious and infectious gastrointestinal complications. For all recommendations, the strength of the recommendation and the level of evidence are presented.

CONCLUSION

This guideline is an evidence-based approach to the diagnosis and management of gastrointestinal complications in cancer patients.