Molecular characterization and sequence analysis of human astroviruses circulating in Hungary

Molecular characterization of human astrovirus infection in children under 5 years of age with acute gastroenteritis in Tehran, Iran, 2021-2022: co-infection with rotavirus

Human astroviruses (HAstVs) are considered important causative pathogens of acute gastroenteritis (AGE) in children under 5 years of age worldwide, along with group A rotavirus (RVA), norovirus (NoV), and enteric adenovirus (EAdV). The present study was aimed to both detect HAstV and its co-infections and investigate genetic analysis of circulating HAstV and co-infected virus in hospitalized children under 5 years of age with AGE in Iran. Accordingly, a sum of 200 stool specimens were screened by PCR for HAstV during 2021-2022. The HAstV was found in 0.5% of 200 specimens (n = 1) while was co-infected with RVA. The genetic and phylogenetic analysis indicated HAstV1 genotype, which clustered with viruses from lineage 1b, which has not been previously reported in Iran. The detected RVA strain belonged to G1 lineage II/P[8]-lineage III, which has been reported previously in Iran as the most common strain. The further genetic analysis of RVA VP6 and NSP4 demonstrated an atypical genotype pattern G1P[8]-I1-E2, as a mono-reassortant of a Wa-like genogroup, which appeared to be reassorted with the NSP4 gene of E2 genotype of the G2P[4] DS-1 genogroup. Although the clinical outcomes of the AGE-causing viruses co-infection is not yet entirely clear, it seems that future studies will be helpful to merge clinical and epidemiological data of co-infecting viruses for a more accurate medical and clinical relevance in symptomatic children.

Clinical surveillance for human astrovirus in Monastir region, Tunisia

Background/aims

Astroviruses (AstVs) are enteric viruses that can cause gastroenteritis in children. This study is part of monitoring the circulation of astroviruses in children hospitalized and/or outpatients for acute gastroenteritis at the primary care center of Ouerdanine or at the Pediatric Department of the University Hospital Fattouma-Bourguiba (Monastir, Tunisia). The aims of our study were to know the prevalence of human astrovirus in clinical samples of children, characterize the strains and evaluate the infectivity of isolated strains on cell culture.

Methods

Fifty stool samples were collected from children under five years old in the region of Monastir (Tunisia) from October 2010 to June 2011. All specimens were subjected to RT-PCR amplification followed by sequencing and phylogenetic analysis.

Results

The study shows a low prevalence of astrovirus (4 %) in children. The two positive samples obtained were HAstV type 3. Samples that were RT-PCR positive were cultured in CaCO-2 cells and the presence of infectious viral particles was confirmed. The phylogenetic analysis shows that the different HAstV-3 strains isolated in Tunisia are grouped into two clusters. The first cluster includes strains obtained in 2004, which belong to lineage HAstV-3a, while strains isolated in 2010 belong to lineage HAstV-3c.

Conclusions

This study is part of monitoring the circulation of astroviruses in children younger than five years old from Monastir region, Tunisia. The results show low prevalence (4 %). All genotyped samples belonged to lineage HAstV-3c, which could be presently emerging. Two different lineages have been isolated in Tunisia: HAstV-3a in 2004 and HAstV-3c in 2010.

Human astroviruses

Human astroviruses (HAtVs) are positive-sense single-stranded RNA viruses that were discovered in 1975. Astroviruses infecting other species, particularly mammalian and avian, were identified and classified into the genera Mamastrovirus and Avastrovirus. Through next-generation sequencing, many new astroviruses infecting different species, including humans, have been described, and the Astroviridae family shows a high diversity and zoonotic potential. Three divergent groups of HAstVs are recognized: the classic (MAstV 1), HAstV-MLB (MAstV 6), and HAstV-VA/HMO (MAstV 8 and MAstV 9) groups. Classic HAstVs contain 8 serotypes and account for 2 to 9% of all acute nonbacterial gastroenteritis in children worldwide. Infections are usually self-limiting but can also spread systemically and cause severe infections in immunocompromised patients. The other groups have also been identified in children with gastroenteritis, but extraintestinal pathologies have been suggested for them as well. Classic HAstVs may be grown in cells, allowing the study of their cell cycle, which is similar to that of caliciviruses. The continuous emergence of new astroviruses with a potential zoonotic transmission highlights the need to gain insights on their biology in order to prevent future health threats. This review focuses on the basic virology, pathogenesis, host response, epidemiology, diagnostic assays, and prevention strategies for HAstVs.

Astrovirus infections in humans and animals - molecular biology, genetic diversity, and interspecies transmissions

Astroviruses are small, non-enveloped, positive sense, single-stranded RNA viruses first identified in 1975 in children suffering from diarrhea and then described in a wide variety of animals. To date, the list of animal species susceptible to astrovirus infection has expanded to 22 animal species or families, including domestic, synantropic and wild animals, avian, and mammalian species in the terrestrial and aquatic environments. Astrovirus infections are considered among the most common cause of gastroenteritis in children, second only to rotavirus infections, but in animals their association with enteric diseases is not well documented, with the exception of turkey and mink astrovirus infection. Genetic variability has been described in almost all astrovirus species sufficiently examined infecting mammals and birds; however, antigenic variability has been demonstrated for human astroviruses but is far less investigated in animal viruses. Interestingly, there is an increasing evidence of recombination events occurring in astroviruses, which contributes to increase the genetic variability of this group of viruses. A wide variety of species infected, the evident virus genetic diversity and the occurrence of recombination events indicate or imply either cross-species transmission and subsequent virus adaptation to new hosts or the co-infection of the same host with different astroviruses. This can also favor the emergence of novel astroviruses infecting animals or with a zoonotic potential. After more than 30 years from their first description in humans, there are many exciting streams of research to be explored and intriguing questions that remain to be answered about the relatively under-studied Astroviridae family. In the present work, we will review the existing knowledge concerning astrovirus infections in humans and animals, with particular focus on the molecular biology, interspecies transmission and zoonotic potential of this group of viruses.

Astrovirus infection induces sodium malabsorption and redistributes sodium hydrogen exchanger expression

Astroviruses are known to be a leading cause of diarrhea in infants and the immunocompromised; however, our understanding of this endemic pathogen is limited. Histological analyses of astrovirus pathogenesis demonstrate clinical disease is not associated with changes to intestinal architecture, inflammation, or cell death. Recent studies in vitro have suggested that astroviruses induce actin rearrangement leading to loss of barrier function. The current study used the type-2 turkey astrovirus (TAstV-2) and turkey poult model of astrovirus disease to examine how astrovirus infection affects the ultrastructure and electrophysiology of the intestinal epithelium. These data demonstrate that infection results in changes to the epithelial ultrastructure, rearrangement of F-actin, decreased absorption of sodium, as well as redistribution of the sodium/hydrogen exchanger 3 (NHE3) from the membrane to the cytoplasm. Collectively, these data suggest astrovirus infection induces sodium malabsorption, possibly through redistribution of specific sodium transporters, which results in the development of an osmotic diarrhea.

Identification of new subtype of astrovirus type 3 from an infant with diarrhea in Wuhan, China

Human astrovirus is one of the important causes for viral gastroenteritis in young children. In previous study where we examined the molecular epidemiology of human astrovirus (HAstV) infection in infants in Wuhan City, we isolated and identified a new subtype (WH1859) of HAstV genotype 3 from an infant with diarrhea. The sequence analysis of this strain showed that the complete region of ORF2 of WH1859 contains 2385-bp of nucleotides that encode 795 amino acids. Because WH1859 strain has the identity of less than 95% with the distance of more than 0.05 to the reference strains of HAstV-3, WH1859 represents a distinct subtype within HAstV-3 strains. Further studies are needed to determine the role of this new subtype strain of HAstV in viral gastroenteritis among young children.

Human astroviruses in raw sewage samples in Hungary

AIMS

Routine procedures for monitoring viruses in water samples have not been drawn up for the water-microbiology screening panel. Enteric viruses, including astroviruses, are able to persist under environmental conditions and may cause public health problems by contaminating natural and drinking water resources. The aim of this study was to detect human astroviruses (HAstVs) from raw wastewater samples.

METHODS AND RESULTS

To obtain data on whether human astroviruses are shed in the environment, 35 raw sewage samples from 22 sewage plants in different regions of Baranya County, Hungary were tested for astrovirus using a polyethylene glycol method for concentration and a guanidinium thiocyanate-silica procedure for extraction of viral RNA. Reverse transcription-polymerase chain reaction (RT-PCR) with HAstV-specific primer pairs was used for amplification and the specificity of amplicons was confirmed by nucleotide sequencing and phylogenetic analysis. Among the 35 raw sewage samples, 15 (43%) contained HAstV and by sequence analysis, 10 genotype HAstV-1 and one genotype HAstV-2 were identified.

CONCLUSIONS

The high detection rate of astroviruses we encountered in this study provide convincing evidence that HAstVs circulate at a relatively high frequency in the Hungarian population. No correlation between the standard indicators of faecal pollution and the presence of HAstVs was found.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study is the first report on detection of HAstV in sewage in Hungary and suggests that HAstV might be potent indicators of viral pollution in environmental specimens.

Molecular characterization of human astroviruses isolated in Brazil, including the complete sequences of astrovirus genotypes 4 and 5

Human astroviruses (HAstV) are recognized as an important cause of gastroenteritis in young children worldwide. This study describes the molecular characteristics of astroviruses isolated in Brazil, using RT-PCR and molecular sequencing of segments of all three viral ORFs. Genetic analysis of a 348-nucleotide segment from ORF 2 demonstrated that the Brazilian isolates belong to HAstV genotypes 1 to 5 and 8. ORF 1b sequences displayed a high degree of nucleotide identity even between different genotypes, which disfavours HAstV genotyping in this region. ORF 1a sequence analysis classified all Brazilian samples as genogroup A. The complete sequences of HAstV genotype 4 (putative serotype 4) and genotype 5 (putative serotype 5) were determined for the first time.

Human astrovirus diagnosis and typing: current and future prospects

Human astroviruses (HAstV) are important human pathogens causing gastroenteritis worldwide. The increased recognition of astroviruses as the cause of sporadic outbreaks of disease is due to the recent availability of improved diagnostic methods. During the last decade, most epidemiological surveys have chosen astrovirus-specific RT-PCR as screening methods. In addition to serotyping by molecular techniques, new typing methods are being developed that may also identify other viral properties related to virulence. The information provided by different typing assays is required for a better understanding of both the antigenic diversity and the molecular mechanisms of pathogenicity.

Comparison of clinical characteristics between astrovirus and rotavirus infections diagnosed in 1997 to 2002 in Hungary

AIM

To determine the severity and clinical characteristics of human astrovirus (HAstV) infections among hospitalized children and compare them with children infected by rotavirus.

METHODS

Retrospective, case-control study of astrovirus-infected and rotavirus-infected children. Astroviruses were detected in stool samples by enzyme immunoassay and/or reverse transcriptase-polymerase chain reaction. All stool samples were tested for rotavirus and bacterial pathogens, and all negative samples were further tested for human astrovirus. Children with astrovirus-positive stool samples and complete clinical data were included in this study.

RESULTS

Astrovirus was detected in 29 (1.8%) children, and 63 rotavirus-infected children were included as controls. Astrovirus-infected children had shorter duration of diarrhea than rotavirus-infected children (median 4 and 6 d, respectively; p<0.05), and 79% of the astrovirus infections were associated with a short duration of vomiting (median 1 and 4 d, respectively; p<0.0001). Rotavirus-infected children had longer hospitalization (p<0.050) than astrovirus-infected children.

CONCLUSION

HAstV-infected children had similar symptoms to those occurring in rotavirus infection. However, astrovirus-infected patients had a significantly shorter duration of diarrhea and vomiting, and they required a shorter hospitalization. On the basis of the clinical data and severity scores, children with rotavirus infection had more severe illness.

A review of viral gastroenteritis

PURPOSE OF REVIEW

Since Kapakian first identified a virus in the stool of a patient with diarrhoea in 1972, many viruses have been described that cause diarrhoea directly or indirectly. It is now appreciated that viruses are the most common cause of diarrhoeal illness worldwide. Although bacteria and other pathogens cause significant numbers of gastroenteritis, it is the viruses that are dealt with in this review. The viruses responsible will be discussed individually.

RECENT FINDINGS

Rotavirus remains the leading cause of diarrhoeal disease overall, with the newly designated calicivirus family causing the most outbreaks in the industrialized nations. As diagnostic techniques improve, however, the importance of astrovirus and other previously under-reported pathogens is becoming more apparent and the number of viruses associated with gastroenteritis continues to increase. The emergence of severe acute respiratory syndrome coronavirus, arguably the most important emerging infection of recent years and a cause of significant gastrointestinal disease, is also discussed.

SUMMARY

No effective treatments have been developed for viral gastroenteritis. Current efforts are targeted at the development of suitable vaccines and the implementation of infection control measures.

One-year survey of astrovirus infection in children with gastroenteritis in a large hospital in Hungary: Occurrence and genetic analysis of astroviruses

Human astroviruses (HAstV) are the causative agents of viral gastroenteritis mainly in children worldwide. This study investigated the epidemiology and genotype diversity of HAstVs detected in children admitted to hospital with gastroenteritis in Hungary. Stool samples were collected from children with diarrhea at the Municipal "Szent László" Hospital, Budapest, Hungary, between January 2002 and December 2002. Of 2,758 samples, 607 were negative for both rotaviruses and bacterial pathogens and were tested for astroviruses using a reverse transcriptase-polymerase chain reaction (RT-PCR) targeting the open reading frame (ORF2), capsid region. Astrovirus was detected in 10 samples (1.6%) by RT-PCR. Astrovirus infection was more frequent among children 49 to 60 months of age. Genotyping of positive samples was performed by type-specific RT-PCR and confirmed by sequence analysis. Phylogenetic analysis was performed using a 203 nucleotide consensus length of the 3'-end of the capsid gene. Type-specific RT-PCR and sequence analysis detected genotypes 1 (50%), 4 (30%), 3 (10%), and 8 (10%) among the children admitted to hospital. Genotype 1 was the predominant genotype, but genotypes 3, 4, and 8 were also present indicating the importance of emerging genotype 8 infections. Two distinct genotype 4 variants were observed during this study. Sequence analysis confirmed type-specific RT-PCR results in the capsid region. This is the first comprehensive report on the occurrence of HAstV infections in Central/Eastern Europe.