Astrovirus Infection Research Articles

Astrovirus Diagnostics.

Various methods exist to detect an astrovirus infection. Current methods include electron microscopy (EM), cell culture, immunoassays, polymerase chain reaction (PCR) and various other molecular approaches that can be applied in the context of diagnostic or in surveillance studies. With the advent of metagenomics, novel human astrovirus (HAstV) strains have been found in immunocompromised individuals in association with central nervous system (CNS) infections. This work reviews the past and current methods for astrovirus detection and their uses in both research laboratories and for medical diagnostic purposes.

Astroviruses in poultry

Astroviruses are small, round, nonenveloped viruses with star-like morphology and a diameter of 25-35 nm, and their genome constitutes linear, positive-sense ssRNA of about 7 kb of size. Astroviruses are known to cause enteritis in humans, as well as in different animal species, including sheep, cattle, swine, dogs, cats and mice. In poultry, they cause enteritis combined with growth depression and higher mortality, but may also cause other pathological conditions. Duck astrovirus (DAstV) infections trigger hepatitis with a high morbidity and mortality of ducklings. Infections of chickens with avian nephritis virus (ANV) cause diarrhea, growth retardation, kidney damage and gout, resulting in increased mortality. Recently, another member of this group, chicken astrovirus (CAstV), has been described as the etiological factor of “white chicks” condition. Astroviruses have also been detected in domestic geese, guinea fowl, pigeons and different species of wild aquatic birds, and all of them belong to the Astroviridae family, the Avastrovirus genus. Initially, they were further divided into separate species, depending on their host of origin. According to these criteria, six different astroviruses were identified in avian species – in turkeys: turkey astrovirus type 1 (TAstV-1) and type 2 (TAstV-2), in chickens: ANV and chicken astrovirus, and in ducks: DAstV type 1 (DAstV-1) and type 2 (DAstV-2). However, since astroviruses can be transmitted between different species, this classification was replaced with one based on the amino acid structure of viral capsid protein. Currently, astroviruses detected in avian species are classified into three official avastrovirus species: 1, 2, and 3. This review presents data on the replication, pathogenesis, and diagnosis of astroviruses, as well as on the control and prevention of astrovirus infection.

The Immune Response to Astrovirus Infection.

Astroviruses are one of the leading causes of pediatric gastroenteritis worldwide and are clinically importantly pathogens in the elderly and immunocompromised populations. Although the use of cell culture systems and small animal models have enhanced our understanding of astrovirus infection and pathogenesis, little is known about the immune response to astrovirus infection. Studies from humans and animals suggest that adaptive immunity is important in restricting classic and novel astrovirus infections, while studies from animal models and cell culture systems suggest that an innate immune system plays a role in limiting astrovirus replication. The relative contribution of each arm of the immune system in restricting astrovirus infection remains unknown. This review summarizes our current understanding of the immune response to astrovirus infection and highlights some of the key questions that stem from these studies. A full understanding of the immune response to astrovirus infection is required to be able to treat and control astrovirus-induced gastroenteritis.

Complete genome sequence analysis of chicken astrovirus isolate from India.

ObjectiveChicken astroviruses have been known to cause severe disease in chickens leading to increased mortality and “white chicks” condition. Here we aim to characterize the causative agent of visceral gout suspected for astrovirus infection in broiler breeder chickens.MethodsTotal RNA isolated from allantoic fluid of SPF embryo passaged with infected chicken sample was sequenced by whole genome shotgun sequencing using ion-torrent PGM platform. The sequence was analysed for the presence of coding and non-coding features, its similarity with reported isolates and epitope analysis of capsid structural protein.ResultsThe consensus length of 7513 bp genome sequence of Indian isolate of chicken astrovirus was obtained after assembly of 14,121 high quality reads. The genome was comprised of 13 bp 5′-UTR, three open reading frames (ORFs) including ORF1a encoding serine protease, ORF1b encoding RNA dependent RNA polymerase (RdRp) and ORF2 encoding capsid protein, and 298 bp of 3′-UTR which harboured two corona virus stem loop II like “s2m” motifs and a poly A stretch of 19 nucleotides. The genetic analysis of CAstV/INDIA/ANAND/2016 suggested highest sequence similarity of 86.94% with the chicken astrovirus isolate CAstV/GA2011 followed by 84.76% with CAstV/4175 and 74.48%% with CAstV/Poland/G059/2014 isolates. The capsid structural protein of CAstV/INDIA/ANAND/2016 showed 84.67% similarity with chicken astrovirus isolate CAstV/GA2011, 81.06% with CAstV/4175 and 41.18% with CAstV/Poland/G059/2014 isolates. However, the capsid protein sequence showed high degree of sequence identity at nucleotide level (98.64-99.32%) and at amino acids level (97.74–98.69%) with reported sequences of Indian isolates suggesting their common origin and limited sequence divergence. The epitope analysis by SVMTriP identified two unique epitopes in our isolate, seven shared epitopes among Indian isolates and two shared epitopes among all isolates except Poland isolate which carried all distinct epitopes.Electronic supplementary materialThe online version of this article (doi:10.1007/s11259-016-9673-6) contains supplementary material, which is available to authorized users.

Oral Administration of Astrovirus Capsid Protein Is Sufficient To Induce Acute Diarrhea In Vivo.

ABSTRACTThe disease mechanisms associated with the onset of astrovirus diarrhea are unknown. Unlike other enteric virus infections, astrovirus infection is not associated with an inflammatory response or cellular damage. In vitro studies in differentiated Caco-2 cells demonstrated that human astrovirus serotype 1 (HAstV-1) capsid protein alone disrupts the actin cytoskeleton and tight junction complex, leading to increased epithelial barrier permeability. In this study, we show that oral administration of purified recombinant turkey astrovirus 2 (TAstV-2) capsid protein results in acute diarrhea in a dose- and time-dependent manner in turkey poults. Similarly to that induced by infectious virus, TAstV-2 capsid-induced diarrhea was independent of inflammation or histological changes but was associated with increased intestinal barrier permeability, as well as redistribution of sodium hydrogen exchanger 3 (NHE3) from the membrane to the cytoplasm of the intestinal epithelium. Unlike other viral enterotoxins that have been identified, astrovirus capsid induces diarrhea after oral administration, reproducing the natural route of infection and demonstrating that ingestion of intact noninfectious capsid protein may be sufficient to provoke acute diarrhea. Based on these data, we hypothesize that the astrovirus capsid acts like an enterotoxin and induces intestinal epithelial barrier dysfunction.

English

This is a case-control study design that aims to determine the prevalence of norovirus and astrovirus infections in diarrheic children in Northeast region of Nigeria. Six hundred diarrheic stools (which were neither mucoid nor blood tinged) of children of 5 years or below were collected between May 2013 – April 2014. They were screened according to the manufacturer’s instruction, using a 3rd generation Ridascreen ELISA kit (R-Biopharm AG, Germany). The control group comprised thirty five non-diarrheic stools. Demographic data were collected via questionnaire administered to parents/guardians of the subjects and analysis was done using online Easy-Chi-square (p<0.05) statistical package. An overall norovirus and astrovirus prevalence of 6.7% (40/600) and 5.0% (30/600) respectively across the Northeast region was obtained. The prevalence of norovirus in Taraba, Bauchi and Borno states was 7 (14/200), 5 (10/200) and 8% (16/200), while that of astrovirus was 5.5 (11/200) 4.5 (9/200) and 5% (10/200), respectively. The sex distribution of number of male relative to female children sampled reveals a preponderance of male (336/600) over female (264/600). Prevalence of norovirus and astrovirus antigen was high in children aged 1 to 2 years across the region. Source of drinking water, nearness of toilet to source of drinking water, hand washing after toilet use, playing with toys, attendance of day care center and educational status of parents were statistically (p<0.05) and significantly contributory factors to infection. The prevalence of norovirus (6.7%) and astrovirus (5.0%) in diarrhea in Northeast Nigeria has shown that both viruses contribute to childhood diarrhea, with most of the children infected below age 2. Key words: Prevalence, predisposing factors, norovirus, astrovirus, diarrhea, north-east, Nigeria.

Epidemiology of Astrovirus infection in infants in Tehran, Iran

Epidemiology of Astrovirus infection in infants in Tehran, Iran

Full-genome based molecular characterization of encephalitis-associated bovine astroviruses

Novel types of astrovirus have been identified recently in association with neurological disease in cattle. Among those viruses is bovine astrovirus CH13 (BoAstV CH13) that has been identified in Switzerland in a cow with encephalitis. Molecular testing by a combination of reverse transcription (RT-) PCR and in situ hybridization (ISH) indicated that astrovirus infection accounts for around one quarter of viral encephalitis cases of unknown etiology in cattle. Yet, it remained to be explored whether these animals were infected by BoAstV CH13 or other astrovirus species. In the present study we sequenced the entire astrovirus genome in brain tissues of eight RT-PCR and/or ISH positive cattle. Phylogenetic comparison of the genomic RNA and the encoded non-structural and structural proteins revealed that all these astrovirus strains were very similar to BoAstV CH13 as well as to a bovine encephalitis strain reported from the USA (BoAstV NeuroS1), and clearly distinct from other previously reported astroviruses. Conserved 5′ and 3′ untranslated regions (UTRs) were predicted to display distinct secondary RNA structures, which likely play a role in viral RNA replication and/or protein translation. Based on these data we propose that BoAstV CH13/NeuroS1 represents a new genotype species within the genus Mammastrovirus. The high degree of similarity between the strains and their relative distance to other genotype species suggest that during evolution some astroviruses acquired factors that specifically contribute to neuroinvasion.

Type I Interferon Response Limits Astrovirus Replication and Protects against Increased Barrier Permeability In Vitro and In Vivo.

Little is known about intrinsic epithelial cell responses against astrovirus infection. Here we show that human astrovirus type 1 (HAstV-1) infection induces type I interferon (beta interferon [IFN-β]) production in differentiated Caco2 cells, which not only inhibits viral replication by blocking positive-strand viral RNA and capsid protein synthesis but also protects against HAstV-1-increased barrier permeability. Excitingly, we found similar results in vivo using a murine astrovirus (MuAstV) model, providing new evidence that virus-induced type I IFNs may protect against astrovirus replication and pathogenesis in vivo. Human astroviruses are a major cause of pediatric diarrhea, yet little is known about the immune response. Here we show that type I interferon limits astrovirus infection and preserves barrier permeability both in vitro and in vivo. Importantly, we characterized a new mouse model for studying astrovirus replication and pathogenesis.

In vitro antiviral activity against rotavirus and astrovirus infection exerted by substances obtained from Achyrocline bogotensis (Kunth) DC. (Compositae).

BackgroundAchyrocline bogotensis has been traditionally used to treat infections of skin, respiratory, tract urinary and other infections, but not to treat viral gastrointestinal disease. In this study, this Colombian native medicinal plant was investigated by its in vitro anti-rotavirus and anti-astrovirus activity.MethodsSeveral extracts and fractions phytochemically obtained from A. bogotensis were evaluated initially for their cell toxicity on MA104 and Caco2 cells and then for their anti-rotavirus (RRV) and anti-astrovirus (Yuc8) activity following three strategies: pre-treatment of cells (blocking effect), direct viral activity (virucidal effect) and post-treatment of infected cells (reduction of viral yield post-infection). In addition qualitative chemical studies were developed for the active compounds.ResultsNon-toxic concentrations of a fraction obtained exhibited antiviral activity against both viruses characterized by a virucidal effect and by the reduction of the infectious particles produced post-infection. Steroids, sterols, terpenes, phenols, flavonoids and sesquiterpenlactones were identified qualitatively in the active fraction.ConclusionsA. bogotensis contains substances with in vitro antiviral activity against rotavirus and astrovirus. This study confirms their anti-microbial properties and describes by the first time its antiviral activity in vitro.

Non-Human Primates Harbor Diverse Mammalian and Avian Astroviruses Including Those Associated with Human Infections.

Astroviruses (AstVs) are positive sense, single-stranded RNA viruses transmitted to a wide range of hosts via the fecal-oral route. The number of AstV-infected animal hosts has rapidly expanded in recent years with many more likely to be discovered because of the advances in viral surveillance and next generation sequencing. Yet no study to date has identified human AstV genotypes in animals, although diverse AstV genotypes similar to animal-origin viruses have been found in children with diarrhea and in one instance of encephalitis. Here we provide important new evidence that non-human primates (NHP) can harbor a wide variety of mammalian and avian AstV genotypes, including those only associated with human infection. Serological analyses confirmed that >25% of the NHP tested had antibodies to human AstVs. Further, we identified a recombinant AstV with parental relationships to known human AstVs. Phylogenetic analysis suggests AstVs in NHP are on average evolutionarily much closer to AstVs from other animals than are AstVs from bats, a frequently proposed reservoir. Our studies not only demonstrate that human astroviruses can be detected in NHP but also suggest that NHP are unique in their ability to support diverse AstV genotypes, further challenging the paradigm that astrovirus infection is species-specific.

Development of an indirect enzyme-linked immunosorbent assay test for detecting antibodies to chicken astrovirus in chicken sera

The development of an indirect enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of Group B chicken astrovirus (CAstV) infections is described. The test was based on the use of an affinity-purified capsid antigen, specific to CAstV isolate 11672, produced as a glutathione-S-transferase N-terminal fusion protein by a recombinant baculovirus. Strongly positive ELISA signals were elicited against experimentally produced antisera raised to CAstVs from Group B (subgroups i and ii) but were negative for antisera raised to a Group A CAstV. Using a panel of 240 selected serum samples, 99% agreement was observed when the results obtained by ELISA were compared to those from an indirect immunofluorescence test for CAstV 11672. The ELISA test was applied to 68 serum sets comprising 1864 samples, which were obtained from parent and grandparent flocks originating mainly in the UK. Of the 52 sets containing ELISA-positive samples, 24 sets had >75% samples positive and nine sets had <25% samples positive and were regarded as having high and low seropositivities, respectively. Of the 1864 serum samples tested 1090 (58.5%) were ELISA positive and of these, 234 sera (21.5%) produced strongly positive signals, whereas moderately positive and weakly positive signals were produced by 562 (51.5%) and 294 (27%) sera. When used for flock screening purposes, this ELISA test can be used to (i) investigate the occurrence of first-time CAstV infections of parent flocks during lay and the possible adverse effects caused by vertically transmitted CAstV infections on broiler hatchability and performance and (ii) diagnose Group B CAstV infections within specific pathogen free flocks.

Surveillance of Human Astrovirus Infection in Brazil: The First Report of MLB1 Astrovirus.

Human astrovirus (HAstV) represents the third most common virus associated with acute diarrhea (AD). This study aimed to estimate the prevalence of HAstV infection in Brazilian children under 5 years of age with AD, investigate the presence of recently described HAstV strains, through extensive laboratory-based surveillance of enteric viral agents in three Brazilian coastal regions between 2005 and 2011. Using reverse transcription-polymerase chain reaction (RT-PCR), the overall HAstV detection rate reached 7.1% (207/2.913) with percentage varying according to the geographic region: 3.9% (36/921) in the northeast, 7.9% in the south (71/903) and 9.2% in the southeast (100/1.089) (p < 0.001). HAstV were detected in cases of all age groups. Detection rates were slightly higher during the spring. Nucleotide sequence analysis of a 320-bp ORF2 fragment revealed that HAstV-1 was the predominant genotype throughout the seven years of the study. The novel AstV-MLB1 was detected in two children with AD from a subset of 200 samples tested, demonstrating the circulation of this virus both the in northeastern and southeastern regions of Brazil. These results provide additional epidemiological and molecular data on HAstV circulation in three Brazilian coastal regions, highlighting its potential to cause infantile AD.

Clinical and Epidemiologic Features of Severe Viral Gastroenteritis in Children: A 3-Year Surveillance, Multicentered Study in Taiwan With Partial Rotavirus Immunization.

The global epidemiological landscape of childhood acute gastroenteritis (AGE) is changing after the introduction of 2 effective rotavirus vaccines in 2006. A comprehensive evaluation for viral etiology of childhood AGE in Taiwan, where rotavirus vaccination was provided by the private sector since 2006, is lacking.From 2009 to 2011, children younger than 5 years of age with AGE who were hospitalized at 3 sentinel hospitals were enrolled in this surveillance study. Stool specimens were tested for rotavirus, norovirus, enteric adenovirus, and astrovirus. The epidemiologic and clinical information was collected by questionnaire-based interviews and chart reviews.Viral agents were detected in 1055 (37.5%) of 2810 subjects, with rotavirus (21.2%) being the leading cause of disease, followed by norovirus (14.9%), enteric adenovirus (3.74%), astrovirus (2.10%), and a mixture of at least 2 of 4 above-mentioned viruses (4.06%). The majority (56%) of the viral AGE occurred in children <2 years of age. Rotavirus and norovirus were detected more frequently in cool seasons (P < 0.0001 for both), whereas no seasonal variation was observed for adenovirus and astrovirus. Adult households with diarrhea and a Vesikari score >10 were independent factors respectively associated with an increased risk of norovirus (adjusted odds ratio [aOR] 9.034, P = 0.0003) and rotavirus (aOR, 3.284, P < 0.0001) infections. Rotavirus immunization and female gender were protective factors against rotavirus (aOR, 0.198, P < 0.0001) and astrovirus (aOR, 0.382, P = 0.0299) infections, respectively.Rotavirus and norovirus are the 2 most important viral agents of childhood AGE in Taiwan with partial rotavirus immunization. In addition, different enteric viruses are associated with distinct epidemiologic and clinical features.

Bovine astrovirus associated with encephalitis in cattle

Bovine astrovirus infection identified in a three-year-old Limousin bullBotulism in lambs causes dramatic lossesSummary of small ruminant diagnostic submissions for the first quarter of 2015Clostridial enteritis in neonatal pigletsMultiple diagnoses...

Type I interferon response is delayed in human astrovirus infections.

Type I interferon (IFN) activation and its subsequent effects are important in the response to viral infections. Here we show that human astroviruses (HAstVs), which are important agents of acute gastroenteritis in children, induce a mild and delayed IFN response upon infecting CaCo-2 cells. Although IFN-β mRNA is detected within infected cells and supernatant from infected cells show antiviral activity against the replication of other well-known IFN-sensitive viruses, these responses occur at late stages of infection once genome replication has taken place. On the other hand, HAstV replication can be partially reduced by the addition of exogenous IFN, and inhibition of IFN activation by BX795 enhances viral replication, indicating that HAstVs are IFN-sensitive viruses. Finally, different levels of IFN response were observed in cells infected with different HAstV mutants with changes in the hypervariable region of nsP1a/4, suggesting that nsP1a/4 genotype may potentially have clinical implications due to its correlation with the viral replication phenotype and the antiviral responses induced within infected cells.

The prevalence of norovirus, astrovirus and adenovirus infections among hospitalised children with acute gastroenteritis in Porto Velho, state of Rondônia, western Brazilian Amazon.

Although viruses are well-established causes of acute gastroenteritis, few data on the circulation of these pathogens in Porto Velho, state of Rondônia, Brazil, are available. Thus, faecal samples from hospitalised diarrhoeic children, under six years of age, were collected and tested for the presence of norovirus (NoV), adenovirus (AdV) and astrovirus (AstV) from February 2010-February 2012. Specimens were screened by reverse-transcription polymerase chain reaction and viruses were found in 10.7% (63/591) of the cases. NoV, AdV and AstV were detected in 7.8%, 2% and 0.8% of the samples, respectively. NoV infection was observed at all ages and was most prevalent in zero-18-month-old children (84.7%; p = 0.002). A higher incidence of NoV was detected from February-April 2010, when it was found in 52.2% of the cases. Co-infections involving these viruses, rotavirus and enteropathogenic bacteria were detected in 44.4% (28/63) of the children with viral diarrhoea. Nosocomial infections were demonstrated in 28.6% (18/63) of the cases in which viruses were detected. The present paper reports, for the first time, the circulation of NoV and AstV among the paediatric population of Porto Velho and it contributes to our understanding of the roles of these pathogens in gastrointestinal infections.

Diagnosis of Neuroinvasive Astrovirus Infection in an Immunocompromised Adult With Encephalitis by Unbiased Next-Generation Sequencing

Metagenomic next-generation sequencing (NGS) was used to diagnose an unusual and fatal case of progressive encephalitis in an immunocompromised adult presenting at disease onset as bilateral hearing loss. The sequencing and confirmatory studies revealed neuroinvasive infection of the brain by an astrovirus belonging to a recently discovered VA/HMO clade.

Outbreak of Astrovirus in Adults with Acute Gastroenteritis in Korea

Astrovirus is generally known for inducing mild diarrhea in infants. However, an outbreak of astrovirus infection occurred in adults on February 14, 2014, in Korea. Astrovirus type 1a is the predominant strain worldwide but was not detected in this study. By contrast, type 5 was detected in all specimens, although type 5 is relatively uncommon in Korea.

Human astrovirus among hospitalized children under five years of age with acute diarrhea in Basrah, Iraq

Background: Human astrovirus are considered as a common cause of infantile gastroenteritis worldwide. The importance of astrovirus in the area is not well recognized. Objectives: The study is designed to determine the frequency and importance of astrovirus in childhood gastroenteritis and to investigate the most affected age group, the predominant clinical symptoms associated with astrovirus infection. Subjects and methods: A total of 400 stool specimens (200 from symptomatic and 200 from asymptomatic healthy children) were collected during 2011-2012 and the relevant informations were obtained on special questionnaire form. Astrovirus nucleic acid was extracted from stool specimens using a spin column technique according to the instruction given by QIAamp-Mini-Elute virus spin kit for purification of virus-RNA (Qiagen-Germany). Astrovirus was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) using specific primers; Mono269-F and Mono270-R of human astrovirus. Results: Astrovirus was detected in 2.6% of acute diarrheal cases, while asymptomatic control group were all negative for astrovirus. Age group analysis revealed that astrovirus infection was more frequent among children with age of 1- < 3 years (P < 0.05). Most of astrovirus cases were observed during winter months (January and February). The dominant clinical symptoms among astrovirus infected cases were vomiting (80%), fever (60%) and dehydration and abdominal pain was found in 40% for both respectively. Conclusion: Astrovirus is frequent among children with acute diarrhea and should be taken in consideration as a causative agent in childhood gastroenteritis.