Isolation and Pathogenicity of a Novel Goose Astrovirus from Overfed Adult Landaise Geese in China.

Goose astrovirus (GAstV) is an important pathogen causing visceral gout and high mortality in goslings, which has broken out and spread across China. In 2021, a disease characterized by urate deposition on the visceral surface and 30% mortality occurred in commercial adult Landaise geese in Zhejiang Province, China. A systematic study identified an infecting astrovirus, designated ZJCX, that was efficiently isolated from a diseased goose with a chicken hepatocellular carcinoma cell line (LMH). In contrast to other GAstVs originating from goslings, ZJCX caused cytopathogenic effects in LMH cells, and the crystalline arrangement of viral particles was observed through transmission electron microscopy. Indeed, phylogenetic analysis and nucleotide homology comparison revealed that ZJCX isolate belongs to the genotype II cluster of GAstVs and displays 97.8-98.4% identity with other GAstV II strains. However, several specific mutations occurred in the polyprotein and capsid protein regions. Moreover, a pathogenicity assessment of ZJCX with a gosling model was conducted, and typical visceral gout was reproduced and led to 18% mortality. The viral loads of ZJCX in the blood, kidney, and liver were detected with specific primers after inoculation, which demonstrated that the kidney and liver presented viral loads peaking at seven days post-inoculation (dpi). Biochemical parameter examination showed that AST, ALT, γ-GT, UA, and BUN levels were significantly increased by GAstV, whereas body weight was reduced. Overall, this study indicated that the GAstV isolate could infect adult geese, and the results regarding the viral loads and biochemical parameters induced by ZJCX provide insight into GAstV pathogenicity.

Coinfection of parvovirus and astrovirus in gout-affected goslings.

Outbreaks of gosling gout have occurred in China since 2017 and caused a considerable economic impact on the poultry industry. While gosling astrovirus (GoAstV) is believed to be the main causal pathogen of gout, the full-blown disease of gout cannot be well reproduced by infecting the goslings with GoAstV, suggesting the possibility of other infectious agents being involved with the development of gosling gout. To assess other possible infectious agents, we collected tissues from gout-affected goslings in 12 goose farms in China, followed by PCR detection of GoAstV, goose reovirus (GRV), goose parvovirus (GPV), fowl adenovirus (FAdV), goose circovirus (GcoV), Tembusu virus (TMUV) and goose haemorrhagic polyomavirus (GHPV). Our data showed that all gout-affected goslings carried both of GoAstV and GPV determined by PCRs, and this was further confirmed by fluorescence multiplex immunohistochemical staining, and phylogenetic analysis of ORF2 gene of GoAstV and VP3 gene of GPV. In addition to the haemorrhage in the kidney, liver, spleen and lung of the gout-affected goslings, histological examinations showed also extensive infiltration of heterophil myelocytes in the kidney, liver, spleen, bursa of Fabricius, thymus, lungs and pancreas. Our findings strongly suggest that coinfection of GoAstV and GPV increases the severity of gout. While this is the first study to report GPV in gout-affected goslings, further studies including infection model are warranted to investigate the role of GPV and its coinfection with GoAstV in the development of gosling gout.

Astrovirus infects actively secreting goblet cells and alters the gut mucus barrier.

Astroviruses are a global cause of pediatric diarrhea, but they are largely understudied, and it is unclear how and where they replicate in the gut. Using an in vivo model, here we report that murine astrovirus preferentially infects actively secreting small intestinal goblet cells, specialized epithelial cells that maintain the mucus barrier. Consequently, virus infection alters mucus production, leading to an increase in mucus-associated bacteria and resistance to enteropathogenic E. coli colonization. These studies establish the main target cell type and region of the gut for productive murine astrovirus infection. They further define a mechanism by which an enteric virus can regulate the mucus barrier, induce functional changes to commensal microbial communities, and alter host susceptibility to pathogenic bacteria.

Experimental infection of conventional newly-weaned piglets with porcine astrovirus.

The presence of porcine astroviruses in diarrheic and healthy pigs has been reported, however, the consequences of the astrovirus infection during the weaning process have not been described. In this study, eight healthy conventional newly-weaned piglets were used to evaluate effects of astrovirus infection during the first five days. Four piglets were infected with the porcine astrovirus PoAstV/PUJP5 strain and the other four represented the control group. Body weight, rectal temperature, diarrhea and other clinical signs were monitored every 24 hours. The results showed that all animals gained body weight, the occurrence of mild diarrhea on the 3rd day post-infection, and the astroviral presence in diarrheic samples. On the 5th day post-infection all the piglets were euthanized and then intestinal and extra-intestinal tissues were analyzed for the presence of PoAstV/PUJP5. The cytoplasmic antigen of PoAstV/PUJP5 was observed in the enterocytes of infected piglets from jejunum, ileum, colon and in inflammatory cells from mesenteric lymph nodes. In addition, villi atrophy, fusion, epithelial hyperplasia and incipient virus detection in mesenteric lymph were observed. RNAemia could not be proved. This study shows for the first time the effects of porcine astrovirus infection on conventional newly-weaning piglets. Keywords: porcine astrovirus; newly-weaned piglets.

Chicken astrovirus as an aetiological agent of runting-stunting syndrome in broiler chickens.

Despite descriptions of runting-stunting syndrome (RSS) in broiler chickens dating back over 40 years, the aetiology has not yet been described. A novel chicken astrovirus (CkAstV) was isolated in an LMH liver cell line from the intestines of chickens affected with RSS. Clinical RSS is characterized by retarded growth and cystic crypt lesions in the small intestine. In 1-day-old broiler chickens infected with the CkAstV isolate, virus was only detected in the intestinal epithelial cells during the first few days after infection. Notably, the preferred host cells are the crypt epithelial cells following initial replication in the villous epithelial cells, thus implying viral preference for immature intestinal cells. Nevertheless, the CkAstV isolate did not induce remarkable pathological changes, despite the presence of the virus in situ. Serial chicken-to-chicken passages of the virus induced increased virulence, as displayed by decreased weight gain and the presence of cystic lesions in the small intestine reproducing clinical RSS in chickens. The analysis of the full-length genome sequences from the isolated CkAstV and the CkAstV from the bird-to-bird passages showed >99 % similarity. The data obtained in this study suggest that the CkAstV isolate is capable of inducing RSS following serial bird-to-bird passages in broilers and is as an aetiological agent of the disease.

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

UNLABELLED: 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-ß]) 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. IMPORTANCE: 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.

Astrovirus VA1/HMO-C: an increasingly recognized neurotropic pathogen in immunocompromised patients.

BACKGROUND: An 18-month-old boy developed encephalopathy, for which extensive investigation failed to identify an etiology, 6 weeks after stem cell transplant. To exclude a potential infectious cause, we performed high-throughput RNA sequencing on brain biopsy. METHODS: RNA-Seq was performed on an Illumina Miseq, generating 20 million paired-end reads. Nonhost data were checked for similarity to known organisms using BLASTx. The full viral genome was sequenced by primer walking. RESULTS: We identified an astrovirus, HAstV-VA1/HMO-C-UK1(a), which was highly divergent from human astrovirus (HAstV 1-8) genotypes, but closely related to VA1/HMO-C astroviruses, including one recovered from a case of fatal encephalitis in an immunosuppressed child. The virus was detected in stool and serum, with highest levels in brain and cerebrospinal fluid (CSF). Immunohistochemistry of the brain biopsy showed positive neuronal staining. A survey of 680 stool and 349 CSF samples identified a related virus in the stool of another immunosuppressed child. CONCLUSIONS: The discovery of HAstV-VA1/HMO-C-UK1(a) as the cause of encephalitis in this case provides further evidence that VA1/HMO-C viruses, unlike HAstV 1-8, are neuropathic, particularly in immunocompromised patients, and should be considered in the differential diagnosis of encephalopathy. With a turnaround from sample receipt to result of <1 week, we confirm that RNA-Seq presents a valuable diagnostic tool in unexplained encephalitis.

Increase in the detection rate of viral and parasitic enteric pathogens among Egyptian children with acute diarrhea.

INTRODUCTION: Acute diarrhea continues to be a major cause of morbidity and mortality in children from developing countries. Determination of the frequency of diarrhea in an area, along with the proportion of disease caused by specific enteric agents of different origins, is considered the first step in controlling diarrheal diseases. METHODOLOGY: From 2005 to 2007, a hospital-based surveillance was conducted in two locations in Egypt to determine the causes of acute diarrhea in children younger than 5-years seeking treatment. Five additional enteric viral and parasitic pathogens were tested using commercially-available enzyme immunoassays (EIA) to re-evaluate the prevalence of diarrheal pathogens in undiagnosed cases. RESULTS: Adenovirus, astrovirus, norovirus and G. lamblia were detected as the sole pathogen in 2% (n=34), 3% (n=56), 9% (n=191) and 7% (n=146) of the cases, respectively. E. histolytica was never detected as the sole pathogen. The percentage of diarrheal cases with a known cause increased significantly, from 48% (n=1,006) to 74% (n=1,568) (P < 0.0001). CONCLUSION: In our study, the incorporation of immunoassays yielded useful data in identifying pathogens in previously pathogen-negative diarrhea cases.

Pathology of astrovirus associated diarrhoea in a paediatric bone marrow transplant recipient.

Human astrovirus infection often causes outbreaks of self limiting diarrhoea, but may also infect patients who are immunodeficient or immunocompromised. Although there are previous publications relating to various aspects of astroviruses, there is a minimal amount of literature on the histopathological features of gastrointestinal astrovirus infection in humans. We report the histopathological findings, including immunohistochemical and electron microscopic features, of astrovirus infection in a bone marrow transplant recipient aged 4 years with diarrhoea. The appearance of a small intestinal biopsy did not suggest graft versus host disease, but demonstrated villous blunting, irregularity of surface epithelial cells, and an increase in lamina propria inflammatory cell density. Immunohistochemical staining with a murine astrovirus group specific monoclonal antibody demonstrated progressively more extensive staining in the duodenal and jejunal biopsies, predominantly restricted to the luminal surface and cytoplasm of surface epithelial cells, most marked at the villus tips. Electron microscopic examination demonstrated viral particles within the cytoplasm of enterocytes, focally forming paracrystalline arrays.

Characterization of a small round virus associated with the poult enteritis and mortality syndrome.

A small round virus (SRV) identified and isolated in our laboratory from intestinal samples of poults affected with the poult enteritis and mortality syndrome was further characterized. The SRV was propagated in turkey embryos and purified by differential and isopycnic ultracentrifugation. The size of the SRV was 30-32 nm in diameter. The buoyant density of the SRV in cesium chloride was between 1.34 and 1.36 g/cm3. It was resistant to chloroform treatment, stable at pH 3.0, and resistant to heat treatment. Attempts to propagate the SRV in turkey embryo kidney, turkey kidney, Caco-2, Vero, and BGM-70 cells were unsuccessful. Analysis of the SRV capsid proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed three polypeptides with molecular weights of 34.5, 31, and 28 kD. Genome analysis of the SRV showed that the SRV had a single-strand RNA genome about 7500 nucleotides in length. Reverse transcription-polymerase chain reactions (RT-PCRs) with primers specific to conserved sequences of enteroviruses yielded products with expected sizes. However, sequence analysis of the RT-PCR products showed that there was no similarity between the sequences and that of enteroviruses. RT-PCR with primers specific to the 3' end of a SRV RNA genome yielded products with expected sizes. These products were sequenced and found to contain 669 nucleotides, excluding the polyadenylated tail. Sequence analysis indicated that the SRV shared 38.18% amino acid identity in the C-terminal capsid precursor protein and 41.26% nucleotide identity of the 3' end of turkey astrovirus RNA genome (Genbank accession no. Y15936). We concluded that the SRV is a member of the astrovirus family.