Restriction of Viral Replication, Rather than T Cell Immunopathology, Drives Lethality in Murine Norovirus CR6-Infected STAT1-Deficient Mice.

Recent evidence indicates that viral components of the microbiota can contribute to intestinal homeostasis and protection from local inflammatory or infectious insults. However, host-derived mechanisms that regulate the virome remain largely unknown. In this study, we used colonization with the model commensal murine norovirus (MNV; strain CR6) to interrogate host-directed mechanisms of viral regulation, and we show that STAT1 is a central coordinator of both viral replication and antiviral T cell responses. In addition to restricting CR6 replication to the intestinal tract, we show that STAT1 regulates antiviral CD4+ and CD8+ T cell responses and prevents systemic viral-induced tissue damage and disease. Despite altered T cell responses that resemble those that mediate lethal immunopathology in systemic viral infections in STAT1-deficient mice, depletion of adaptive immune cells and their associated effector functions had no effect on CR6-induced disease. However, therapeutic administration of an antiviral compound limited viral replication, preventing virus-induced tissue damage and death without impacting the generation of inflammatory antiviral T cell responses. Collectively, our data show that STAT1 restricts MNV CR6 replication within the intestinal mucosa and that uncontrolled viral replication mediates disease rather than the concomitant development of dysregulated antiviral T cell responses in STAT1-deficient mice. IMPORTANCE The intestinal microbiota is a collection of bacteria, archaea, fungi, and viruses that colonize the mammalian gut. Coevolution of the host and microbiota has required development of immunological tolerance to prevent ongoing inflammatory responses against intestinal microbes. Breakdown of tolerance to bacterial components of the microbiota can contribute to immune activation and inflammatory disease. However, the mechanisms that are necessary to maintain tolerance to viral components of the microbiome, and the consequences of loss of tolerance, are less well understood. Here, we show that STAT1 is integral for preventing escape of a commensal-like virus, murine norovirus CR6 (MNV CR6), from the gut and that in the absence of STAT1, mice succumb to infection-induced disease. In contrast to the case with other systemic viral infections, mortality of STAT1-deficient mice is not driven by immune-mediated pathology. Our data demonstrate the importance of host-mediated geographical restriction of commensal-like viruses.

Molecular epidemiology of norovirus infections in children with acute gastroenteritis in 2017-2019 in Tianjin, China.

Norovirus (NoV) is the leading cause of acute gastroenteritis (AGE) worldwide. Globally, the GII.4 Sydney 2012 strain has predominated since 2012, although GII.4 variant strains have caused AGE outbreaks in China. Recent patterns of NoV genotype distributions in 6011 children with AGE in Tianjin, China were investigated. NoV was detected using real-time reverse-transcriptase polymerase chain reaction and sequencing of partial sequences of the viral capsid gene. NoV genotypes were determined, and phylogenetic analysis was conducted. Epidemiological and clinical data were compared between children infected with different NoV genotypes. NoV was detected in 27.6% of the specimens tested. GII.4 strains comprised 49.4% infections, followed by GII.3 at 39.9%. Genotypes GII.2, GII.13, GII.17, GII.1, GII.6, and GII.14 were also detected. NoV was detected during most of the year, with a peak season of cases in the winter. Diarrhea, vomiting, fever, abdominal pain, and dehydration were present in patients with NoV infection. The main genotypes were GII.4 and GII.3, with a slight increase in GII.2, beginning in March 2017. Among the GII.4 strains, GII.4 Sydney 2012 was the only epidemic strain in Tianjin. Patients with GII.4 genotypes were more likely to present with diarrhea and vomiting than those with GII.3. Children with GII. Others were prone to suffered from dehydration and abdominal pain than those with GII.3. NoV GII has become the main cause of viral AGE in Tianjin, China. The predominant genotypes of NoV were GII.4 and GII.3. Identification of emerging genotypes is crucial for the prevention and control of NoV-caused AGE.

Molecular epidemiology and genetic diversity of norovirus among hospitalized children with acute gastroenteritis in Tianjin, China, 2018-2020.

BACKGROUND: Norovirus (NoV) is a major cause of viral acute gastroenteritis (AGE) in children worldwide. Epidemiological analysis with respect to the virus strains is limited in China. This study aimed to investigate the prevalence, patterns, and molecular characteristics of NoV infection among children with AGE in China. METHODS: A total 4848 stool samples were collected from children who were admitted with AGE in Tianjin Children's Hospital from August 2018 to July 2020. NoV was preliminarily detected using real-time reverse transcription polymerase chain reaction (RT-PCR). Partial sequences of the RNA-dependent RNA polymerase (RdRp) and capsid genes of positive samples were amplified by conventional RT-PCR and then sequenced. The NoV genotype was determined by online Norovirus Typing Tool Version 2.0, and phylogenetic analysis was conducted using MEGA 6.0. RESULTS: The prevalence of NoV was 26.4% (1280/4848). NoV was detected in all age groups, with the 7-12 months group having the highest detection rate (655/2014, 32.5%). NoV was detected during most part of the year with higher frequency in winter than other seasons. Based on the genetic analysis of RdRp, GII. Pe was the most predominant genotype detected at 70.7% (381/539) followed by GII.P12 at 25.4% (137/539). GII.4 was the most predominant capsid genotype detected at 65.3% (338/518) followed by GII.3 at 26.8% (139/518). Based on the genetic analysis of RdRp and capsid sequences, the strains were clustered into 10 RdRp-capsid genotypes: GII.Pe-GII.4 Sydney 2012 (65.5%), GII.P12-GII.3 (27.2%), GII.P16-GII.2 (1.8%), GII.P12-GII.2 (0.2%), GII.P17-GII.17 (1.1%), GII.Pe-GII.3 (1.8%), GII.Pe-GII.2 (1.1%), GII.Pe-GII.1 (0.4%), GII.16-GII.4 Sydney 2012 (0.7%), and GII.P7-GII.6 (0.2%). The predominant NoV genotypes changed from GII.Pe-GII.4 Sydney 2012 and GII.P12-GII.3 between August 2018 and July 2019 to GII.Pe-GII.4 Sydney 2012 and GII.P16-GII.2 between August 2019 and July 2020. The patients with GII.Pe-GII.4 Sydney 2012 genotype were more likely to suffer from vomiting symptom than those with GII.P12-GII.3. CONCLUSIONS: NoV is an important pathogen responsible for viral AGE among children in China. GII.Pe-GII.4 Sydney 2012 and GII.P12-GII.3 were major recombinant genotypes. Knowledge of circulating genotypes and seasonal trends is of great importance for disease prevention and surveillance.

Contrasting Results from Two Commercial Kits Testing for the Presence of Clostridium perfringens Enterotoxin in Feces from Norovirus-Infected Human Patients.

BACKGROUND: Detection of Clostridium perfringens enterotoxin (CPE) is critical for disease surveillance; however, commercial testing kits produce contrasting results. METHODS: We examined the cause of the differing results from a reversed passive latex agglutination (RPLA) assay (PET-RPLA Toxin Detection Kit) and an enzyme-linked immunosorbent assay (C. perfringens Enterotoxin ELISA Kit) using 73 human norovirus-positive fecal samples from gastroenteritis patients across 22 episodes in Japan. RESULTS: CPE was detected in 39/73 samples using the RPLA method; however, ELISA-based examination of 10 RPLA-positive samples produced negative results. Moreover, cpe was not detected in any of the RPLA-positive (n = 32) or -negative (n = 5) samples, and C. perfringens was only isolated from one RPLA-positive sample. CONCLUSIONS: An ELISA-based testing approach may be more reliable than RPLA assays for CPE detection from human fecal samples. These findings may also be applicable to the detection of other foodborne diseases.

Emerging Novel GII.P16 Noroviruses Associated with Multiple Capsid Genotypes.

Noroviruses evolve by antigenic drift and recombination, which occurs most frequently at the junction between the non-structural and structural protein coding genomic regions. In 2015, a novel GII.P16-GII.4 Sydney recombinant strain emerged, replacing the predominance of GII.Pe-GII.4 Sydney among US outbreaks. Distinct from GII.P16 polymerases detected since 2010, this novel GII.P16 was subsequently detected among GII.1, GII.2, GII.3, GII.10 and GII.12 viruses, prompting an investigation on the unique characteristics of these viruses. Norovirus positive samples (n = 1807) were dual-typed, of which a subset (n = 124) was sequenced to yield near-complete genomes. CaliciNet and National Outbreak Reporting System (NORS) records were matched to link outbreak characteristics and case outcomes to molecular data and GenBank was mined for contextualization. Recombination with the novel GII.P16 polymerase extended GII.4 Sydney predominance and increased the number of GII.2 outbreaks in the US. Introduction of the novel GII.P16 noroviruses occurred without unique amino acid changes in VP1, more severe case outcomes, or differences in affected population. However, unique changes were found among NS1/2, NS4 and VP2 proteins, which have immune antagonistic functions, and the RdRp. Multiple polymerase-capsid combinations were detected among GII viruses including 11 involving GII.P16. Molecular surveillance of protein sequences from norovirus genomes can inform the functional importance of amino acid changes in emerging recombinant viruses and aid in vaccine and antiviral formulation.

Feline calicivirus infection in cats with virulent systemic disease, Italy.

Feline calicivirus (FCV) is a contagious viral pathogen that usually causes a mild, self-limiting respiratory disease. More recently, highly virulent FCV strains have emerged and have been associated with severe systemic infection, referred to as virulent systemic disease (VSD). The objective of this study is to report VSD cases in Italian cats along with the molecular characterization of two detected FCV strains. Three client-owned cats showed clinical signs resembling to those described for VSD cases. The cats were subjected to molecular investigations for detection of FCV and other feline pathogens. Histopathology and immunohistochemistry were performed on internal organs of one cat; molecular characterization of two detected FCV strains was obtained through sequence and phylogenetic analyses. Putative VS-FCV strains were detected in all three cats, which were co-infected with feline panleukopenia virus. The cat submitted to histopathology and immunohistochemistry displayed severe histological changes and FCV antigens in internal organs. Two Italian FCV strains, for which amplification of ORF2 was successful, were strictly related and formed a unique phylogenetic cluster. These viruses did not show consistent changes in the amino acid sequences with respect to reference VS-FCVs. The results of our study confirm that VS-FCV strains are circulating in Italy and that VSD diagnosis is complicated since both genetic and clinical markers have not been identified so far.

Genetic Diversity of Norovirus Infections, Coinfections, and Undernutrition in Children From Brazilian Semiarid Region.

BACKGROUND AND OBJECTIVE: Norovirus (NoV) infections are known to have high-morbidity and mortality rates and are a major health problem globally. The impact of NoV on child development is, however, poorly understood. We evaluated the distribution of NoV genotypes in children from a low-income Brazilian semiarid region, in relation with their clinical symptoms, nutritional status, and co-pathogens. METHODS: The test population included children aged 2 to 36 months from 6 cities of the Brazilian semiarid region. Fecal samples were collected from each child, along with the information regarding their socioeconomic/clinical conditions using a standardized questionnaire. Detection and quantification of NoV were performed by reverse-transcription quantitative polymerase chain reaction, followed by molecular and phylogenetic analyses. RESULTS: The NoV detection rate was 45.2%. Presence of NoV was associated with lower z scores for weight-for-age (P = 0.03), weight-for-height (P = 0.03), and body mass index-for-age (P = 0.03). NoV infection was associated with more frequent respiratory illnesses (P < 0.01). GII.P7 (polymerase) and GII.3 (capsid) were the most frequent NoV genotypes. Analysis of the open reading frame (ORF)1-2 junction identified recombinant NoV strains in 80% of the sequenced samples. Enteroaggregative Escherichia coli coinfection was the major predictor for diarrhea in NoV-positive samples (P < 0.02). Moreover, Shigella spp was also associated with NoV-positive diagnosis (P = 0.02). CONCLUSIONS: This study highlights the genetic variability of NoV and, associated co-infections and undernutrition in infants from low-income Brazilian semiarid region.

Incidence and characteristics of norovirus-associated benign convulsions with mild gastroenteritis, in comparison with rotavirus ones.

BACKGROUND AND PURPOSE: Rotavirus was detected in 40-50% of patients with benign convulsions with mild gastroenteritis (CwG) before the rotavirus vaccine was introduced in late 2000. However, the rate of rotavirus positivity has decreased since 2010 while the prevalence of norovirus has gradually increased. We investigated the incidence of norovirus-associated CwG during a recent 3-year period and additionally compared the characteristics of norovirus-associated CwG with those of rotavirus-associated CwG. METHODS: The medical records of CwG patients admitted to our hospital between March 2014 and February 2017 were reviewed, including the results of stool virus tests. For comparing norovirus- and rotavirus-associated CwG, data obtained between March 2005 and February 2014 that included sufficient numbers of patients with rotavirus-associated CwG were additionally reviewed. Data were collected on clinical characteristics (age, sex, seasonal distribution, enteric symptoms, and the interval to seizure onset), seizure characteristics (frequency, duration, type, and electroencephalographic findings), and laboratory findings. RESULTS: CwG was diagnosed in 42 patients during the 3-year study period. Stool viruses were checked in 40 (95.2%) patients and were detected in 32 (80.0%) patients. Norovirus genogroup II was detected in 27 (67.5%) of the 40 patients, rotavirus was detected in 3 patients, and adenovirus was detected in 2 patients. In total, 140 CwG patients were enrolled between March 2005 and February 2017. The patients with norovirus-associated CwG (N = 44) and rotavirus-associated CwG (N = 26) were aged 18.66 ±â€¯5.57 and 19.31 ±â€¯7.37 months (mean ±â€¯standard deviation), respectively (P > 0.05). Norovirus-associated CwG was less prevalent than rotavirus-associated CwG during spring (13.6% vs. 34.6%, P = 0.04), while the prevalence of both types of CwG peaked during winter (63.6% and 46.2%, respectively). Vomiting was more prevalent in norovirus- than rotavirus-associated CwG (97.7% vs. 80.8%, P = 0.02) and the interval between enteric symptom onset and seizure onset was shorter in norovirus-associated CwG (2.00 ±â€¯1.06 vs. 2.58 ±â€¯1.21 days, P = 0.04). Most cases in both groups had seizures that lasted for less than 5 min (95.5% vs. 92.3%). Clustered seizures seemed to occur more frequently in the norovirus group (79.5% vs. 57.7%), although with borderline significance (P = 0.05). Posterior slowing was observed more frequently in norovirus-associated CwG (34.9% vs. 11.5%, P = 0.03). CONCLUSION: The most common viral pathogen of CwG was norovirus during the analyzed 3-year period, with an incidence of 67.5%. In comparison with rotavirus-associated CwG, norovirus-associated CwG was less frequent during spring, more frequently seen with vomiting, had a shorter interval from enteric symptom onset to seizure onset, and more frequently showed posterior slowing in electroencephalography.

Viral shedding and clinical status of feline-norovirus-infected cats after reinfection with the same strain.

Norovirus (NoV) infection is the most common cause of acute gastroenteritis in humans of all ages worldwide. When cats are experimentally infected with feline norovirus (FNoV), they develop symptoms of acute gastroenteritis. Therefore, FNoV infection may serve as an animal model for the disease caused by human norovirus infection. In this study, we examined whether FNoV of cats infected with genogroup GVI are protected from reinfection with the same strain. The blood anti-FNoV IgG level was inversely correlated with the viral load in stool samples and the clinical score of FNoV-infected cats, but complete prevention of reinfection was not observed. These findings were similar to the results of a reinfection experiment with NoV in human volunteers.

Norovirus and Rotavirus Disease Severity in Children: Systematic Review and Meta-analysis.

BACKGROUND: Rotaviruses (RVs) and noroviruses (NoVs) are the most common causes of severe acute gastroenteritis in children. It is generally accepted that RVs cause severe acute gastroenteritis in a higher proportion of cases compared with NoVs. To our knowledge, there are no systematic reviews and meta-analyses comparing the severity of NoV and RV disease. METHODS: We searched MEDLINE for studies reporting data for NoV and RV medically attended disease severity in children. We included studies where all children had been tested for both NoV (reverse transcription polymerase chain reaction) and RV (enzyme-linked immunosorbent assay or reverse transcription polymerase chain reaction) and that reported disease severity using the Vesikari or modified Vesikari score, or provided clinical information on severity. We generated pooled estimates of the mean with 95% confidence intervals using random effects meta-analysis. RESULTS: We identified 266 publications, of which 31 were retained for qualitative analysis and 26 for quantitative analysis. Fourteen studies provided data on severity score for the meta-analysis. The pooled mean severity scores (95% confidence interval) among outpatients were 10 (8-12) and 11 (8-14) for NoV and RV, respectively. Among inpatients, they were 11 (9-13) for NoV and 12 (10-14) for RV. The difference was statistically significant among inpatients, but relatively small (1 point in a 20-point scale). About 20% more children with RV required rehydration when compared with children with NoV. CONCLUSIONS: NoV causes moderate to severe disease similar to RV in young children. This information should be useful for future evaluations of an eventual introduction of NoV vaccines in national immunization programs.

Genotypic and Epidemiological Trends of Acute Gastroenteritis Associated with Noroviruses in China from 2006 to 2016.

There are periodical norovirus-associated acute gastroenteritis outbreaks around the world. This study aimed to analyze the molecular and epidemiological features of norovirus infections in China during 2006-2016. We extracted epidemiological data from 132 norovirus outbreaks and the norovirus genotyping for 1291 sequences in China over the past ten years. A total of 132 norovirus outbreaks (8133 cases) were reported in China, where the east and south regions were most affected [47.7% (63/132)]. The highest number of outbreaks occurred in 2015. A seasonal pattern has been observed, with a peak from November to the following March. Most of the outbreaks occurred in middle and primary schools, accounting for 28.8% (38/132), and 28.0% (37/132) of outbreaks, respectively. The dominant age group was 10 to 19 years old, responsible for 75.7% (933/1232) of cases. Generally, the dominant genotypes was GII, for 81.9% (1058/1291) of sequences. G II.4 was the predominant genotype in China from 2004 to 2014. However, the GII.17 became more prevalent starting in 2014. Norovirus-associated acute gastroenteritis increased sharply in recent years caused by the emergence of GII.17, but epidemiological features have not changed during 2006-2016. Vigilant surveillance should be strengthened to promptly detect any variation.

Clinical Characteristics and Risk Factors for Seizures Associated With Norovirus Gastroenteritis in Childhood.

Norovirus has become increasingly recognized as causing viral gastroenteritis in children. Few data are available on the characteristics of children admitted to pediatric emergency departments with norovirus gastroenteritis and accompanying seizures. Our aim in this study was to describe the clinical features of, and risk factors for, seizures accompanying norovirus gastroenteritis. We collected 6359 stool samples from patients with gastroenteritis, of whom 1444 (22.71%) had laboratory-confirmed norovirus gastroenteritis. Of all patients, 108 (7.48%) children exhibited norovirus gastroenteritis and seizures; 49 (45.4%) were febrile, and 59 (54.6%) afebrile. The mean patient age was 2.31 ± 2.12 years; most were <5 years of age (92.6%). The afebrile group had a significantly higher incidence of 2 or more seizures than the febrile subjects ( P = .004). Early recognition and prompt treatment of convulsions associated with norovirus gastroenteritis in children are important. Future studies might explore the long-term prognoses of these patients.

Expression of IL-1ß, IL-2, IL-10, TNF-ß and GM-CSF in peripheral blood leukocytes of rabbits experimentally infected with rabbit haemorrhagic disease virus.

Rabbit haemorrhagic disease (RHD) is a highly morbid and mortal viral infection of European rabbits. This disease is one of the main causes of death in wild rabbits, and results in large economic losses in farms of rabbits worldwide. Although the first outbreak of this disease was noted in 1984, the pathogenesis of RHD and mechanisms of RHDV (rabbit haemorrhagic disease virus) pathogenecity have still not been fully elucidated. Recent studies indicate a role of the immune response, especially peripheral blood leukocytes (PBL), in the pathogenesis of this disease. Thus, in the present study we investigated the expression of IL-1ß, IL-2, IL-10, TNF-ß and GM-CSF genes in PBL of RHDV-infected rabbits. We also compared the expression of genes encoding these cytokines in rabbits with different course of RHDV infection (in animals that died 36h postinfection or survived until 60th h after infection). The study revealed that three (IL-10, TNF-ß and GM-CSF) out of five investigated genes encoding cytokines showed increased expression in PBL of RHDV-infected rabbits, and the level of expression depended on the course of RHD. The results indicate the potential role of these cytokines in RHDV infection and their influence on the survival time of infected rabbits.

Characteristics of norovirus infection in Serbia.

BACKGROUND/AIM: Norovirus (NoV), formerly Norwalk-like virus is the most common cause of acute gastroenteritis in humans of all ages. It is known that 90% of viral gastroenteritis and about 60-85% of all outbreaks of gastroenteritis, especially in the territory of United States of America, Europe and Japan are caused by this virus. For the countries of the northern hemisphere, individual cases and outbreaks of acute NoV gastroen teritis appear in seasonal pattern, mainly during the winter months. The aim of this study as to describe characteristics of acute gastroenteritis with the established NoV etiology in Serbia. METHODS: The study group included 88 patients with the symp toms of acute gastroenteritis, throughout the year 2010 and 2011. From all the patients, stool samples were taken less than three days from the onset of symptoms. Detection of NoV in stool samples was performed by commercial qualitative immunochromatography assay. Statistical analysis included application of x2 test, Mann-Whitney U-test, Kruskal-Wallis's test, Spearman's rank correlation test and logistic regression analysis. RESULTS: Outbreaks of acute gastroenteritis caused by NoV were recorded to be the most common in children with the incidence of infection of 50% in the age group 0-15 years. Analysis of individual symptoms in the NoV proven infection, showed that diarrhea was the most common symptom, followed by vomiting espe cially in small children, while abdominal pain was most common in elderly (> 65 years). The presence of frequent vomiting, more than 4 times/day, indicated NoV infection in the women, while for men the infection was always presented with diarrhea. CONCLUSION: The obtained results confirmed that small children and elderly are,the most susceptible to NoV infection and that outbreaks are more frequent in the winter months. Those who consumed food in restaurants and other public facilities were not at higher risk for NoV infection.

Epidemiology of norovirus infections among diarrhea outpatients in a diarrhea surveillance system in Shanghai, China: a cross-sectional study.

BACKGROUND: Norovirus is an important cause of gastroenteritis both in children and adults. In China, few studies have been conducted on adult populations. This study aimed to determine the contribution of norovirus to gastroenteritis, characterize the features of norovirus infections, compare them with other pathogens, and test the effectiveness of the surveillance system. METHODS: A citywide surveillance network on diarrhea patients was established. Samples were collected with intervals from both children and adults among diarrhea outpatients in hospitals and tested for viruses using rRT-PCR and for bacteria in CDCs. Patient information was acquired through interviews and recorded into a dedicated online system. The Pearson χ2 test, multivariate logistic regression models and discriminant models were fitted into its comparisons with the non-norovirus group and other pathogens. RESULTS: Norovirus was detected in 22.91% of sampled diarrhea patients. The seasonal distribution of norovirus infections was different from non-norovirus patients (p<0.001), with a half-year peak. Higher proportions of males (p=0.001, OR=1.303, 95% CI=1.110-1.529), local citizens (p<0.001) and officials/clerks (p=0.001, OR=1.348, 95% CI=1.124-1.618) were affected with norovirus when compared with non-norovirus patients. Diarrhea patients affected with norovirus featured nausea (p<0.001, OR=1.418, 95% CI=1.176-1.709) and vomiting (p<0.001, OR=1.969, 95% CI=1.618-2.398), while fewer manifested fever (p=0.046, OR=0.758, 95% CI=0.577-0.996) and abdominal pain (p=0.018, OR=0.815, 95% CI=0.689-0.965). Children were more vulnerable to rotavirus (p=0.008, OR=1.637, 95% CI=1.136-2.358) and bacteria (p=0.027, OR=1.511, 95% CI=1.053-2.169) than norovirus. There was a seasonal difference between the GI and GII genotypes (p<0.001). Officials or clerks were more easily affected with GI than GII (p=0.006, OR=1.888, 95% CI=1.205-2.958). CONCLUSIONS: This study was based on a citywide hospital-sentinel surveillance system with multiple enteric pathogens included. Norovirus was recognized as the most prevalent enteric pathogen in Shanghai. The seasonal peak was from October to April. Males had a higher prevalence than females. Local citizens and officials/clerks were more vulnerable to norovirus than other pathogens. Compared with rotavirus and bacteria, children were less frequently affected by norovirus. Nausea and vomiting were typical of norovirus, whereas fever and abdominal pain were uncommon symptoms of this pathogen. GI and GII infections were centered in different seasons. Officials and clerks were more easily affected by GI than GII.

The importance of liver lesions and changes to biochemical and coagulation factors in the pathogenesis of RHD.

RHDV (rabbit haemorrhagic disease virus) is an etiologic factor of RHD (rabbit haemorrhagic disease), which is highly morbid and mortal viral infection of an adult European rabbit. Although three decades have passed since the first outbreak of rabbit haemorrhagic disease, the pathogenesis of RHD has still not been fully elucidated. It is known that RHDV replicates in the liver within the first hours following infection, causing necrotic and apoptotic cell death of hepatocytes. Anatomopathological changes are also observed in other organs of infected rabbits, i.e. lungs, spleen, kidneys, heart, as well as central nerve system. These changes leading to animals death are predominantly caused by systemic hemorrhagic diathesis with disseminated intravascular coagulation (DIC), appearing most likely as a consequence of liver cell loss through RHDV-induced apoptosis. In this paper, we presented previously described changes in biochemical and coagulation factors in RHDV infection.

Seroepidemiology of Norovirus GII.3 and GII.4 Infections in Children with Diarrhea in Xi'an, China.

OBJECTIVE: The objective of this study was to investigate the seroepidemiology of immunoglobulin G (IgG) antibodies against Norovirus (NoV) GII.3 and GII.4 genotypes among children younger than 5 years with acute diarrhea in Xi'an, China. MATERIALS AND METHODS: A total of 362 serum samples were collected from diarrheal children in the Department of Digestive Diseases of Xi'an Children's Hospital between March 2009 and October 2012. Recombinant capsid proteins of NoV genotypes GII.3 and GII.4 were expressed using the baculovirus expression system. The viruslike particles (VLPs) were examined by electron microscopy and Western blot, and VLPs were used as antigens for serological IgG tests using enzyme-linked immunosorbent assays. RESULTS: The overall seroprevalence for GII.4 (86.2%) was significantly higher (p<0.01) than for GII.3 (67.9%). The seroprevalence remained in a high and stable level (70.9% for GII.3 and 88.7% for GII.4) in children under 1 year of age, then dropped in the age group 12-17 months (49.3% for GII.3 and 68.1% for GII.4), and finally increased to 77.8% for GII.3 and 96.8% for GII.4 in the group >18 months. The seroprevalence in the age group 12-17 months showed more statistically significant differences than the other age groups for both GII.3 and GII.4 (p<0.05). CONCLUSIONS: In conclusion, seroprevalence of NoV GII.3 and GII.4 was high in young children in Xi'an, China, and the anti-GII.4-positive rates were statistically higher than GII.3 across all the age groups.

Association of host, agent and environment characteristics and the duration of incubation and symptomatic periods of norovirus gastroenteritis.

We analysed the reported duration of incubation and symptomatic periods of norovirus for a dataset of 1022 outbreaks, 64 of which reported data on the average incubation period and 87 on the average symptomatic period. We found the mean and median incubation periods for norovirus to be 32·8 [95% confidence interval (CI) 30·9-34·6] hours and 33·5 (95% CI 32·0-34·0) hours, respectively. For the symptomatic period we found the mean and median to be 44·2 (95% CI 38·9-50·7) hours and 43·0 (95% CI 36·0-48·0) hours, respectively. We further investigated how these average periods were associated with several reported host, agent and environmental characteristics. We did not find any strong, biologically meaningful associations between the duration of incubation or symptomatic periods and the reported host, pathogen and environmental characteristics. Overall, we found that the distributions of incubation and symptomatic periods for norovirus infections are fairly constant and showed little differences with regard to the host, pathogen and environmental characteristics we analysed.

Autophagic response in the Rabbit Hemorrhagic Disease, an animal model of virally-induced fulminant hepatic failure.

The Rabbit Hemorrhagic Disease Virus (RHDV) induces a severe disease that fulfils many requirements of an animal model of fulminant hepatic failure. However, a better knowledge of molecular mechanisms contributing to liver damage is required, and it is unknown whether the RHDV induces liver autophagy and how it relates to apoptosis. In this study, we attempted to explore which signalling pathways were involved in the autophagic response induced by the RHDV and to characterize their role in the context of RHDV pathogenesis. Rabbits were infected with 2 × 104 hemmaglutination units of a RHDV isolate. The autophagic response was measured as presence of autophagic vesicles, LC3 staining, conversion of LC3-I to autophagosome-associated LC3-II and changes in expression of beclin-1, UVRAG, Atg5, Atg12, Atg16L1 and p62/SQSTM1. RHDV-triggered autophagy reached a maximum at 24 hours post-infection (hpi) and declined at 30 and 36 hpi. Phosphorylation of mTOR also augmented in early periods of infection and there was an increase in the expression of the endoplasmic reticulum chaperones BiP/GRP78, CHOP and GRP94. Apoptosis, measured as caspase-3 activity and expression of PARP-1, increased significantly at 30 and 36 hpi in parallel to the maximal expression of the RHDV capsid protein VP60. These data indicate that RHDV infection initiates a rapid autophagic response, perhaps in an attempt to protect liver, which associates to ER stress development and is independent from downregulation of the major autophagy suppressor mTOR. As the infection continues and the autophagic response declines, cells begin to exhibit apoptosis.

Melatonin modulates the autophagic response in acute liver failure induced by the rabbit hemorrhagic disease virus.

Autophagy is an important survival pathway and participates in the host response to infection. Beneficial effects of melatonin have been previously reported in an animal model of acute liver failure (ALF) induced by the rabbit hemorrhagic disease virus (RHDV). This study was aimed to investigate whether melatonin protection against liver injury induced by the RHDV associates to modulation of autophagy. Rabbits were infected with 2 × 10(4) hemagglutination units of a RHDV isolate and received 20 mg/kg melatonin at 0, 12, and 24 hr postinfection. RHDV induced autophagy, with increased expression of beclin-1, ubiquitin-like autophagy-related (Atg)5, Atg12, Atg16L1 and sequestrosome 1 (p62/SQSTM1), protein 1 light chain 3 (LC3) staining, and conversion of LC3-I to autophagosome-associated LC3-II. These effects reached a maximum at 24 hr postinfection, in parallel to extensive colocalization of LC3 and lysosome-associated membrane protein (LAMP)-1. The autophagic response induced by RHDV infection was significantly inhibited by melatonin administration. Melatonin treatment also resulted in decreased immunoreactivity for RHDV viral VP60 antigen and a significantly reduction in RHDV VP60 mRNA levels, oxidized to reduced glutathione ratio (GSSG/GSH), caspase-3 activity, and immunoglobulin-heavy-chain-binding protein (BiP) and CCAAT/enhancer-binding protein homologous protein (CHOP) expression. Results indicate that, in addition to its antioxidant and antiapoptotic effects, and the suppression of ER stress, melatonin induces a decrease in autophagy associated with RHDV infection and inhibits RHDV RNA replication. Results obtained reveal novel molecular pathways accounting for the protective effect of melatonin in this animal model of ALF.