Molecular characterization of astrovirus in stool samples from children in São Paulo, Brazil

Genetic Susceptibility to Astrovirus Diarrhea in Bangladeshi Infants

Background

Astroviral infections commonly cause acute nonbacterial gastroenteritis in children globally. However, these infections often go undiagnosed outside of research settings. There is no treatment available for astrovirus, and Astroviridae strain diversity presents a challenge to potential vaccine development.

Methods

To address our hypothesis that host genetic risk factors are associated with astrovirus disease susceptibility, we performed a genome-wide association study of astrovirus infection in the first year of life from children enrolled in 2 Bangladeshi birth cohorts.

Results

We identified a novel region on chromosome 1 near the loricrin gene (LOR) associated with astrovirus diarrheal infection (rs75437404; meta-analysis P = 8.82 × 10-9; A allele odds ratio, 2.71) and on chromosome 10 near the prolactin releasing hormone receptor gene (PRLHR) (rs75935441; meta-analysis P = 1.33 × 10-8; C allele odds ratio, 4.17). The prolactin-releasing peptide has been shown to influence feeding patterns and energy balance in mice. In addition, several single-nucleotide polymorphisms in the chromosome 1 locus have previously been associated with expression of innate immune system genes PGLYRP4, S100A9, and S100A12.

Conclusions

This study identified 2 significant host genetic regions that may influence astrovirus diarrhea susceptibility and should be considered in further studies.

Leveraging machine learning for taxonomic classification of emerging astroviruses

Astroviruses are a family of genetically diverse viruses associated with disease in humans and birds with significant health effects and economic burdens. Astrovirus taxonomic classification includes two genera, Avastrovirus and Mamastrovirus. However, with next-generation sequencing, broader interspecies transmission has been observed necessitating a reexamination of the current host-based taxonomic classification approach. In this study, a novel taxonomic classification method is presented for emergent and as yet unclassified astroviruses, based on whole genome sequence k-mer composition in addition to host information. An optional component responsible for identifying recombinant sequences was added to the method's pipeline, to counteract the impact of genetic recombination on viral classification. The proposed three-pronged classification method consists of a supervised machine learning method, an unsupervised machine learning method, and the consideration of host species. Using this three-pronged approach, we propose genus labels for 191 as yet unclassified astrovirus genomes. Genus labels are also suggested for an additional eight as yet unclassified astrovirus genomes for which incompatibility was observed with the host species, suggesting cross-species infection. Lastly, our machine learning-based approach augmented by a principal component analysis (PCA) analysis provides evidence supporting the hypothesis of the existence of human astrovirus (HAstV) subgenus of the genus Mamastrovirus, and a goose astrovirus (GoAstV) subgenus of the genus Avastrovirus. Overall, this multipronged machine learning approach provides a fast, reliable, and scalable prediction method of taxonomic labels, able to keep pace with emerging viruses and the exponential increase in the output of modern genome sequencing technologies.

Diversity of classic and novel human astrovirus in outpatient children with acute gastroenteritis in Shanghai, China

Introduction

Human astrovirus (HAstV) is an important pathogen of acute gastroenteritis (AGE) in children. This study was aimed at investigating the diversity and epidemiology of classic and novel HAstV in outpatient children aged 0-16 years old with AGE in Shanghai.

Methods

From May 2020 to December 2022, a total of 1,482 stool samples were collected from children diagnosed as AGE from the Children's Hospital of Fudan University. HAstV was identified using pan-astrovirus consensus primers by Reverse transcription PCR.

Results

During the study period, 3.3% (49/1,482) of specimens were identified as HAstV, with a detection rate of 2.5% (37/1,482) for classic HAstV and 0.8% (12/1,482) for novel HAstV. Among the 12 novel HAstV strains, 11 (91.7%) belonged to the HAstV-MLB and 1 (8.3%) was HAstV-VA. Genotyping revealed six circulating genotypes. Strain HAstV-1 was predominant in the study population with a detection rate of 1.8% (26/1,482) followed by HAstV-MLB1 (0.7%, 10/1,482) and HAstV-4 (0.6%, 9/1,482). Of note, all the HAstV-4 strains detected in this study were close to one astrovirus strain isolated from Bactrian camels with 99.0-100.0% amino acid sequences identity. In this study, HAstV was detected in all age groups with the highest detection rate of HAstV-positive specimens observed in children older than 73 months (5.7%, 12/209).

Discussion

This study provided useful information and contributed to the molecular epidemiology of both classic and novel HAstV, which were simultaneously characterized and reported for the first time in Shanghai.

Worldwide prevalence and genotype distribution of human astrovirus in gastroenteritis patients: A systematic review and meta-analysis

AIM

Human astrovirus (HAstV) is an important causative agent of gastroenteritis in humans, which mainly infects young children and the elderly. The goal of this study was to conduct a meta-analytic review of the prevalence of HAstV amongst patients with gastroenteritis, and to shed light on the connection between HAstV infection and gastroenteritis.

METHODS

Systematic literature searches were conducted to identify all potentially relevant studies recorded up to April 8th, 2022. For study weighting, the inverse variance method was employed and the random-effects model was applied to evaluate data. For case-control studies, the pooled odds ratio (OR) and 95% confidence interval (CI) were calculated to establish the relationship between HAstV infection and gastroenteritis.

RESULTS

Among 302423 gastroenteritis patients from 69 different countries, the overall pooled prevalence of HAstV infection was 3.48% (95% CI: 3.11%-3.89%). Case-control approach was used in 39 investigations, and the overall prevalence of HAstV infection among the 11342 healthy controls was 2.01% (95% CI: 1.40%-2.89%). Gastroenteritis and HAstV infection were associated with a pooled OR of 2.16 (95% CI: 1.72-2.71; P < 0.0001; I² = 33.7%). The most commonly found HAstV genotypes in gastroenteritis patients were HAstV1 (62.18%), HAstV7 (33.33%), and HAstV-MLB1 (17.43%).

CONCLUSION

The frequency of HAstV infection was the highest in children under the age of five, and in developing countries. The prevalence rate of HAstV was not influenced by gender. Semi-nested and nested RT-PCR were highly sensitive assays for detecting HAstV infections.

Human astrovirus types 1, 4 and 5 circulating among children with acute gastroenteritis in a rural Brazilian state, 2010-2016

This study combined conventional epidemiology of human astroviruses. From 2010 to 2016, 232 stool samples from children under 5 years of age were screened using NGS and conventional RT-PCR followed by genetic analysis in order to investigate the genotypic diversity of classical human astrovirus (HAstV) circulating in Tocantins State, Brazil. HAstV was detected in 16 cases (6.9%). Seven specimens (43.7%; 7/16) were positive according RT-PCR and next-generation sequencing (NGS) to investigate the molecular to both NGS and RT-PCR. NGS and RT-PCR individually revealed six (37.5%; 6/16) and three (18.8%; 3/16) additional positive samples, respectively. Sequencing of the HAstV-positive samples revealed HAstV-1a (9/16), HAstV-4c (3/16), and HAstV-5c (4/16) lineages.

An outbreak of gastroenteritis associated with a novel GII.8 sapovirus variant-transmitted by vomit in Shenzhen, China, 2019

Background

Human Sapoviruses (SaVs) has been reported as one of the causative agents of acute gastroenteritis (AGE) worldwide. An outbreak of SaVs affected 482 primary school students during spring activities from February 24 to March 11, 2019 in Shenzhen City, China. Our study was aimed at determining the epidemiology of the outbreak, investigating its origins, and making a clear identification of the SaVs genetic diversity.

Methods

Epidemiological investigation was conducted for this AGE outbreak. Stool samples were collected for laboratory tests of causative agents. Real-time reverse-transcription polymerase chain reaction (rRT-PCR) and conventional RT-PCR were used for detecting and genotyping of SaVs. The nearly complete genome of GII.8 SaV strains were amplified and sequenced by using several primer sets designed in this study. Phylogenetic analysis was performed to characterize the genome of GII.8 SaV strains.

Results

The single factor analysis showed that the students who were less than 1.5 m away from the vomitus in classroom or playgroundwere susceptible (P < 0.05). Seven of 11 fecal samples from patients were positive for GII.8 SaV genotype. In this study, we obtained the genome sequence of a SaV GII.8 strain Hu/SaV/2019008Shenzhen/2019 /CHN (SZ08) and comprehensively analyzed the genetic diversity. The phylogenetic analysis showed that the GII.8 strain SZ08 formed an independent branch and became a novel variant of GII.8 genotype. Strain SZ08 harbored 11 specific amino acid variations compared with cluster A-D in full-length VP1.

Conclusions

This study identified SaVs as the causative agents for the AGE outbreak. Strain Hu SZ08 was clustered as independent branch and there was no recombination occurred in this strain SZ08. Further, it might become the predominant strain in diarrhea cases in the near future. Constant surveillance is required to monitor the emerging variants which will improve our knowledge of the evolution of SaVs among humans.

Molecular Epidemiology of Human Astrovirus in Stool Samples From Patients With Acute Gastroenteritis in Korea, 2013-2017

Background

Human astroviruses (HAstVs) are one of the major causes of acute gastroenteritis. Classic HAstVs can be classified into eight genotypes. We investigated the positive rate of HAstVs and the distribution of HAstV genotypes in strains isolated from patients with acute gastroenteritis in Hwaseong, Korea, in 2013–2017.

Methods

Between November 2013 and December 2017, 3,519 stool samples were collected from patients with symptoms of acute gastroenteritis and tested for HAstV using multiplex PCR. For HAstV-positive samples, the ORF2 gene, which encodes a capsid protein, was genotyped by reverse-transcription PCR and sequencing. Phylogenetic analysis was performed to determine whether the sequences of the HAstVs differed by year.

Results

The positive rate of HAstV was 1.9% (67 samples). HAstV Type 1 was the most prevalent genotype (82.4%), and Types 4, 5, and 8 were also detected. Infection occurred year-round, with no distinct seasonal variation. Infection occurred at nearly all ages (55 days–81 years; median: 3 years), and the positive rate was substantially higher in children younger than five years. Phylogenetic analysis revealed three distinct clades of HAstV Type 1 according to the collection time.

Conclusions

Our results provide recent epidemiological data on HAstVs in Korea between 2013 and 2017. The finding of three distinct clades of HAstV Type 1 according to collection time suggests genetic evolution of HAstVs. These findings can enhance our knowledge on HAstV infection and viral evolution.

Epidemiological and molecular investigation of norovirus and astrovirus infections in Rio Branco, Acre, Northern Brazil: A retrospective study

Norovirus (NoV) is a major cause of nonbacterial acute gastroenteritis (AGE) outbreaks worldwide, with infections reported in semiclosed environments, particularly in hospitals and nursing homes. Astrovirus (HAstV) is prevalent worldwide, especially in developing countries. We aimed to determine the prevalence, spatial distribution, and genetic diversity of NoV and HAstV in children under 5 years of age in Rio Branco city, Acre State, Amazon Region, Brazil. Stool samples from children with (n = 240) and without (n = 248) AGE were collected from January to December 2012 from seven neighborhoods. The overall NoV prevalence was 12.3% (60 of 488); representing 15.8% (38 of 240) of the symptomatic samples and 8.9% (22 of 248) of the controls. HAstVs infection was observed in 4.7% (23 of 488) of the samples tested, 6.2% (15 of 240) of AGE cases, and 2.4% (6 of 248) of the controls (plus two without information about feces consistency). Infections were found in all age groups with higher frequency in children less than two years of age, for both viruses. NoV was detected in all neighborhoods, with a higher concentration in the fourth (30%; 18 of 60). NoV nucleotide sequencing performed in 86.7% (52 of 60) of the positive samples showed the circulation of the strains GII.4 (57.7%; 30 of 52), GIIPe/GII.4 (19.2%; 10 of 52), GII.7, GII.Pg/GII.1, and GII.Pc (3.8%; 2 of 52 for each), GII.6 and GII.Pg (1.9%; 1 of 52 for each), and GI.3 (7.7%; 4 of 52). Three GII.4 variants were detected: Den Haag_2006b (n = 1), New Orleans_2009 (n = 1), and Sydney_2012 (n = 14). HAstV types HAstV-1a (81.8%; 9 of 11) and HAstV-2c (18.2%; 2 of 11) were observed in the 47.8% (11 of 23) of characterized samples. This is the first data obtained in Acre State regarding the prevalence of these viruses and provides epidemiological and molecular information for a better understanding of their role among children with and without AGE.

Quito's virome: Metagenomic analysis of viral diversity in urban streams of Ecuador's capital city

In Quito, the microbiological contamination of surface water represents a public health problem, mainly due to the lack of sewage treatment from urban wastewater. Contaminated water contributes to the transmission of many enteric pathogens through direct consumption, agricultural and recreational use. Among the different pathogens present in urban discharges, viruses play an important role on disease, being causes of gastroenteritis, hepatitis, meningitis, respiratory infections, among others. This study analyzes the presence of viruses in highly impacted surface waters of urban rivers using next-generation sequencing techniques. Three representative locations of urban rivers, receiving the main discharges from Quito sewerage system, were selected. Water samples of 500 mL were concentrated by skimmed-milk flocculation method and the viral nucleic acid was extracted and processed for high throughput sequencing using Illumina MiSeq. The results yielded very relevant data of circulating viruses in the capital of Ecuador. A total of 29 viral families were obtained, of which 26 species were associated with infections in humans. Among the 26 species identified, several were related to gastroenteritis: Human Mastadenovirus F, Bufavirus, Sapporovirus, Norwalk virus and Mamastrovirus 1. Also detected were: Gammapapillomavirus associated with skin infections, Polyomavirus 1 related to cases of kidney damage, Parechovirus A described as cause of neonatal sepsis with neurological affectations and Hepatovirus A, the etiologic agent of Hepatitis A. Other emergent viruses identified, of which its pathogenicity remains to be fully clarified, were: Bocavirus, Circovirus, Aichi Virus and Cosavirus. The wide diversity of species detected through metagenomics gives us key information about the public health risks present in the urban rivers of Quito. In addition, this study describes for the first time the presence of important infectious agents not previously reported in Ecuador and with very little reports in Latin America.

Epidemiology and genetic diversity of classic human astrovirus among hospitalized children with acute gastroenteritis in Uruguay

Classic Human Astrovirus (Classic HAstV) are one of the most important causes of pediatric acute gastroenteritis (AGE), after rotaviruses and arguably caliciviruses. The aim of this study was to determine the molecular epidemiology of Classic HAstV from 175 clinical samples, being 153 stools and 22 vomits, collected from pediatric hospitalized patients with AGE in Salto city, Uruguay, from January 2011 to December 2012. Classic HAstV were detected and genotyped by using a qualitative Retro Transcription-Polimerase Chain Reaction (RT-PCR) directed to the Open Reading Frame-2 (ORF2) region C. Amplicons were sequenced and phylogenetic analyses were carried out in order to determine genotypes and lineages. Classic HAstV were detected in 18 out of 175 analyzed samples (10.3%) and 14 of them (78.0%) were successfully sequenced being 6 (42.8%) classified as HAstV-1 (1a lineage), 4 (28.6%) as HAstV-2 (2c lineage), and 4 (28.6%) as HAstV-3 (3c lineage). A higher detection of Classic HAstV infections was observed in autumn for both years of surveillance, and the majority of the positive cases were observed in 2011. The group of children between 2 and 5 years old presented the higher percentage of infections. To our knowledge, the present study represents the first report of astrovirus from acute gastroenteritis cases in Uruguay, evidencing its role as a relevant etiologic agent in severe cases of this disease.

Epidemiology of Classic and Novel Human Astrovirus: Gastroenteritis and Beyond

Since they were identified in 1975, human astroviruses have been considered one of the most important agents of viral acute gastroenteritis in children. However, highly divergent astroviruses infecting humans have been recently discovered and associated with extra-intestinal infections. The report of cases of fatal meningitis and encephalitis, especially in immunocompromised individuals, has broadened their disease spectrum. Although zoonotic transmission among animal and human astroviruses has not been clearly recognized, the genetic similarity between some human and animal viruses makes it likely to occur. This review provides an update on the epidemiology of both classic and novel human astroviruses, and a comprehensive view on confirmed or potential association between astrovirus and human disease.

Impact of co-infections with enteric pathogens on children suffering from acute diarrhea in southwest China

Background

Acute diarrhea is a global health problem, resulting in high morbidity and mortality in children. It has been suggested that enteric pathogen co-infections play an important role in gastroenteritis, but most research efforts have only focused on a small range of species belonging to a few pathogen groups. This study aimed to assess the impact of co-infections with a broad range of enteric pathogens on children aged below five years who suffer from acute diarrhea in southwest China.

Method

A total of 1020 subjects (850 diarrhea cases and 170 healthy controls) were selected from four sentinel hospitals in Kunming, Yunnan province, southwest China, from June 2014 to July 2015. Stool specimens were collected to detect five virus (rotavirus group A, RVA; norovirus, NoV; Sapovirus, SaV; astrovirus, As; and adenovirus, Ad), seven bacterial (diarrheagenic Escherichia coli, DEC; non-typhoidal Salmonella, NTS; Shigella spp.; Vibrio cholera; Vibrio parahaemolyticus; Aeromonas spp.; and Plesiomonas spp.), and three protozoan (Cryptosporidium spp., Giardia lamblia, and Blastocystis hominis, B. hominis) species using standard microbiologic and molecular methods. Data were analyzed using the partial least square regression technique and chi-square test.

Results

At least one enteric pathogen was detected in 46.7 % (n = 397) of acute gastroenteritis cases and 13.5 % (n = 23) of healthy controls (χ² = 64.4, P < 0.05). Single infection with RVA was associated with acute diarrhea (26.5 % vs. 5.8 %, P < 0.05). The prevalence of a single infection with B. hominis in diarrhea cases was higher than in healthy controls (3.1 % vs. 0.5 %, OR = 4.7, 95 % CI: 1.01–112.0). Single infection with NoV GII was not associated with diarrhea (4.4 % vs. 3.5 %, OR = 1.2, 95 % CI: 0.5–3.3). Single infections with bacterial species were not observed. The prevalence of co-infections with two enteric pathogens in diarrhea cases was higher than in asymptomatic children (20.1 % vs. 5.3 %, P < 0.05). RVA-NoV GII was the most common co-infection in symptomatic children (4.4 %), with it aggravating the severity of diarrhea.

Conclusions

Although it is clear that RVA has an overwhelming impact on diarrhea illnesses in children, co-infection with other enteric pathogens appears to also aggravate diarrhea severity. These findings should serve as evidence for public health services when planning and developing intervention programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0157-2) contains supplementary material, which is available to authorized users.

Complete genome sequencing of a recombinant strain between human astrovirus antigen types 2 and 8 isolated from South Korea

Human astroviruses (HAstVs) occur worldwide and are known to the causative agents of diarrhea in infants and elderly patients with immune dysfunction. This study aimed to identify recombinant HAstV strains and characterize rare genotypes. The full-length genome of a recombinant HAstV strain isolated from the stool sample of a patient with acute gastroenteritis from South Korea was amplified using three pairs of previously designed primers and seven newly designed primers. The recombinant HAstV was 6757-bp long and contained three sequential open reading frames (ORFs), designated as ORF1a (2781 bp), ORF1b (1548 bp), and ORF2 (2349 bp). Our findings suggested that a recombination event had occurred between ORF1b and ORF2 of the isolated strain, with a recombination breakpoint at 4081 bp. To our knowledge, this is the first study to reveal the complete nucleotide sequence of a recombinant HAstV strain from South Korea. Our study findings might be useful for identifying other recombinant HAstV strains and for developing vaccines against this pathogenic virus.

Deciphering the Diversities of Astroviruses and Noroviruses in Wastewater Treatment Plant Effluents by a High-Throughput Sequencing Method

Although clinical epidemiology lists human enteric viruses to be among the primary causes of acute gastroenteritis in the human population, their circulation in the environment remains poorly investigated. These viruses are excreted by the human population into sewers and may be released into rivers through the effluents of wastewater treatment plants (WWTPs). In order to evaluate the viral diversity and loads in WWTP effluents of the Paris, France, urban area, which includes about 9 million inhabitants (approximately 15% of the French population), the seasonal occurrence of astroviruses and noroviruses in 100 WWTP effluent samples was investigated over 1 year. The coupling of these measurements with a high-throughput sequencing approach allowed the specific estimation of the diversity of human astroviruses (human astrovirus genotype 1 [HAstV-1], HAstV-2, HAstV-5, and HAstV-6), 7 genotypes of noroviruses (NoVs) of genogroup I (NoV GI.1 to NoV GI.6 and NoV GI.8), and 16 genotypes of NoVs of genogroup II (NoV GII.1 to NoV GII.7, NoV GII.9, NoV GII.12 to NoV GII.17, NoV GII.20, and NoV GII.21) in effluent samples. Comparison of the viral diversity in WWTP effluents to the viral diversity found by analysis of clinical data obtained throughout France underlined the consistency between the identified genotypes. However, some genotypes were locally present in effluents and were not found in the analysis of the clinical data. These findings could highlight an underestimation of the diversity of enteric viruses circulating in the human population. Consequently, analysis of WWTP effluents could allow the exploration of viral diversity not only in environmental waters but also in a human population linked to a sewerage network in order to better comprehend viral epidemiology and to forecast seasonal outbreaks.

Novel human astroviruses: challenges for developing countries

Astroviruses have been gaining widespread importance over the past few decades owing to their detection through advanced molecular techniques. The association of astrovirus-associated enteric infections have been reported from various settings among different age groups. The tremendous efforts of scientists from different countries to detect and characterize these star-like viruses in the course of surveillance has shown the emergence of novel astroviruses from varied host species, necessitating changes in the classification to update their taxonomy. The public health importance of these viruses implies new control measures are essential to reduce disease burden in developing countries.

Astrovirus infection in children in lagos, Nigeria

A preliminary investigation was conducted to screen for astrovirus in Lagos. Two hundred and fifteen (215) faecal samples collected from children under 5 years old with diarrhoea (161) and without diarrhoea (54) admitted at paediatric clinics in Lagos State were studied. The stool specimens were examined for the presence of human astrovirus antigen using a monoclonal antibody-based ELISA (Astrovirus RIDASCREEN(®) r-Biopharm, Germany) technique. Astrovirus was detected in 40.4 percent (65/161) of the diarrhoeal stools compared to 11.1 percent (6/54) of the control specimens. Astrovirus was found to infect younger children and about three quarter of the children infected was under 12 months of age. The prevalence of infection decreases with age group and was statistically significant (P = 0.0470). Although, prevalence of infection is more in males than females but this is not significant. This study shows that astrovirus is an important agent of acute gastroenteritis among children in Lagos state.

Molecular characterization of astrovirus infection in children with diarrhea in Beijing, 2005-2007

Human astroviruses (HAstVs) have been recognized as one of the major causes of acute gastroenteritis in children. To provide more insight into the prevalence of HAstV gastroenteritis in China, 664 fecal samples were collected from children affected with acute gastroenteritis in Beijing from March 2005 to November 2007. The samples were analyzed genetically. All eight serotypes (genotypes) of HAstVs were screened using RT-PCR assays targeting the ORF2 region in the study. The assays detected HAstVs in 52 (7.8%) of the patients, with HAstV-1 (50/52) being the dominant genotype during the study period. Two minor genotypes, HAstV-6 and HAstV-3, were also detected. Partial sequencing of the 50 HAstV-1 strains showed that the homology of the nucleotide sequence of the ORF1a region between these strains was 88.4-100%, whereas the homology of the amino acid sequences was 95.6-100%. In the ORF2 partial region, the nucleotide identities ranged from 91.5% to 100%, and amino acid identities ranged from 97.3% to 100%. The identity of the whole genome sequence between four randomly examined HAstV-1 strains was 91-99%. No recombination events were observed in HAstVs in this study. The findings of this study will provide baseline data for HAstVs surveillance and control. J. Med. Virol. 82:415-423, 2010. (c) 2010 Wiley-Liss, Inc.