Propagating and banking genetically diverse human sapovirus strains using a human duodenal cell line: investigating antigenic differences between strains.

There are four genogroups and 18 genotypes of human sapoviruses (HuSaVs) responsible for acute gastroenteritis. To comprehend their antigenic and virological differences, it is crucial to obtain viral stocks of the different strains. Previously, we utilized the human duodenum-derived cell line HuTu80, and glycocholate, a conjugated bile acid, to replicate and propagate GI.1, GI.2, and GII.3 HuSaVs (H. Takagi et al., Proc Natl Acad Sci U S A 117:32078-32085, 2020, https://10.1073/pnas.2007310117). First, we investigated the impact of HuTu80 passage number on HuSaV propagation. Second, we demonstrated that taurocholate improved the initial replication success rate and viral RNA levels in fecal specimens relative to glycocholate. By propagating 15 HuSaV genotypes (GI.1-7, GII.1-5, -8, and GV.1-2) and accomplishing preparation of viral stocks containing 1.0 × 109 to 3.4 × 1011 viral genomic copies/mL, we found that all strains required bile acids for replication, with GII.4 showing strict requirements for taurocholate. The deduced VP1 sequences of the viruses during the scale-up of serial passaged virus cultures were either identical or differed by only two amino acids from the original sequences in feces. In addition, we purified virions from nine strains of different genotypes and used them as immunogens for antiserum production. Enzyme-linked immunosorbent assays (ELISAs) using rabbit and guinea pig antisera for each of the 15 strains of different genotypes revealed distinct antigenicity among the propagating viruses across genogroups and differences between genotypes. Acquisition of biobanked viral resources and determination of key culture conditions will be valuable to gain insights into the common mechanisms of HuSaV infection. IMPORTANCE: The control of human sapovirus, which causes acute gastroenteritis in individuals of all ages, is challenging because of its association with outbreaks similar to those caused by human norovirus. The establishment of conditions for efficient viral propagation of various viral strains is essential for understanding the infection mechanism and identifying potential control methods. In this study, two critical factors for human sapovirus propagation in a conventional human duodenal cell line were identified, and 15 strains of different genotypes that differed at the genetic and antigenic levels were isolated and used to prepare virus stocks. The preparation of virus stocks has not been successful for noroviruses, which belong to the same family as sapoviruses. Securing virus stocks of multiple human sapovirus strains represents a significant advance toward establishing a reliable experimental system that does not depend on limited virus-positive fecal material.

Prevalence and Genetic Diversity of Adenovirus 40/41, Astrovirus, and Sapovirus in Children with Acute Gastroenteritis in Kansas City 2011-2016.

BACKGROUND: Most U.S. acute gastroenteritis (AGE) episodes in children are attributed to norovirus, whereas very little information is available on adenovirus 40/41 (AdV40/41), astrovirus or sapovirus. The New Vaccine Surveillance Network (NVSN) conducted prospective, active, population-based AGE surveillance in young children. METHODS: We tested and typed stool specimens collected between December 2011 to June 2016 from one NVSN site in Kansas City for the three viruses, and calculated hospitalization and emergency department (ED) detection rate. RESULTS: Of 3,205 collected specimens, 2,453 (76.5%) were from AGE patients (339 inpatients and 2,114 ED patients) and 752 (23.5%) were from healthy controls (HC). In AGE patients, astrovirus was detected in 94 (3.8%), sapovirus in 252 (10.3%) and AdV40/41 in 101 (4.5%) of 2249 patients. In HC, astrovirus was detected in 13 (1.7%) and sapovirus in 15 (2.0%) specimens. Astrovirus type 1 (37.7%) and genogroup I sapoviruses (59.3%) were most prevalent.Hospitalization rates were 5 (AdV40/41), 4 (astrovirus) and 8 (sapovirus) per 100,000 children <11 years old, whereas ED rates were 2.4 (AdV40/41), 1.9 (astrovirus) and 5.3 (sapovirus) per 1000 children <5 years old. CONCLUSIONS: Overall, AdV40/41, astrovirus, and sapovirus were detected in 18.6% of AGE in a large pediatric hospital in Kansas City.

Charting the impact of maternal antibodies and repeat exposures on sapovirus immunity in early childhood from a Nicaraguan birth cohort.

BACKGROUND: Sapovirus is an important cause of acute gastroenteritis in childhood. While vaccines against sapovirus may reduce gastroenteritis burden, a major challenge to their development is a lack of information about natural immunity. METHODS: We measured sapovirus-specific IgG in serum collected, between 2017 and 2020, of mothers soon after delivery and at 6 time points in Nicaraguan children until 3 years of age (n=112 dyads) using virus-like particles representing three sapovirus genotypes (GI.1, GI.2, GV.1). RESULTS: Sixteen (14.3%) of the 112 children experienced at least one sapovirus gastroenteritis episode, of which GI.1 was the most common genotype. Seroconversion to GI.1 and GI.2 was most common between 5 and 12 months of age, while seroconversion to GV.1 peaked at 18 to 24 months of age. All children who experienced sapovirus GI.1 gastroenteritis seroconverted and developed genotype-specific IgG. The impact of sapovirus exposure on population immunity was determined using antigenic cartography: newborns share their mothers' broadly binding IgG responses, which declined at 5 months of age and then increased as infants experienced natural sapovirus infections. CONCLUSION: By tracking humoral immunity to sapovirus over the first 3 years of life, this study provides important insights for the design and timing of future pediatric sapovirus vaccines.

Strong evolutionary constraints against amino acid changes in the P2 subdomain of sapovirus GI.1 capsid protein VP1.

Sapovirus (SaV) is a nonenveloped RNA virus that causes acute gastroenteritis in humans. Although SaV is a clinically important pathogen in children, an effective vaccine is currently unavailable. The capsid protein VP1 of SaVs forms the outer shell of the virion and is highly diverse, as often seen in the virion-surface proteins of RNA viruses, creating an obstacle for vaccine development. We here report a unique phenomenon pertaining to the variation of SaV VP1. Phylogenetic and information entropy analyses using full-length VP1 sequences from a public database consistently showed that the amino acid sequences of the VP1 protein have been highly conserved over more than 40 years in the major epidemic genotype GI.1 but not in GI.2. Structural modeling showed that even the VP1 P2 subdomain, which is arranged on the outermost shell of the virion and presumably exposed to anti-SaV antibodies, remained highly homogeneous in GI.1 but not in GI.2. These results suggest strong evolutionary constraints against amino acid changes in the P2 subdomain of the SaV GI.1 capsid and illustrate a hitherto unappreciated mechanism, i.e., preservation of the VP1 P2 subdomain, involved in SaV survival. Our findings could have important implications for the development of an anti-SaV vaccine.

Human Sapovirus Replication in Human Intestinal Enteroids.

Human sapoviruses (HuSaVs), like human noroviruses (HuNoV), belong to the Caliciviridae family and cause acute gastroenteritis in humans. Since their discovery in 1976, numerous attempts to grow HuSaVs in vitro were unsuccessful until 2020, when these viruses were reported to replicate in a duodenal cancer cell-derived line. Physiological cellular models allowing viral replication are essential to investigate HuSaV biology and replication mechanisms such as genetic susceptibility, restriction factors, and immune responses to infection. In this study, we demonstrate replication of two HuSaV strains in human intestinal enteroids (HIEs) known to support the replication of HuNoV and other human enteric viruses. HuSaVs replicated in differentiated HIEs originating from jejunum, duodenum and ileum, but not from the colon, and bile acids were required. Between 2h and 3 to 6 days postinfection, viral RNA levels increased up from 0.5 to 1.8 log10-fold. Importantly, HuSaVs were able to replicate in HIEs independent of their secretor status and histo-blood group antigen expression. The HIE model supports HuSaV replication and allows a better understanding of host-pathogen mechanisms such as cellular tropism and mechanisms of viral replication. IMPORTANCE Human sapoviruses (HuSaVs) are a frequent but overlooked cause of acute gastroenteritis, especially in children. Little is known about this pathogen, whose successful in vitro cultivation was reported only recently, in a cancer cell-derived line. Here, we assessed the replication of HuSaV in human intestinal enteroids (HIEs), which are nontransformed cultures originally derived from human intestinal stem cells that can be grown in vitro and are known to allow the replication of other enteric viruses. Successful infection of HIEs with two strains belonging to different genotypes of the virus allowed discovery that the tropism of these HuSaVs is restricted to the small intestine, does not occur in the colon, and replication requires bile acid but is independent of the expression of histo-blood group antigens. Thus, HIEs represent a physiologically relevant model to further investigate HuSaV biology and a suitable platform for the future development of vaccines and antivirals.

Sapovirus infection as another cause of persistent viral diarrhea: case series and review of the literature.

Human sapovirus (HuSaV) is a common cause of gastroenteritis worldwide and is responsible for approximately 4% of acute gastroenteritis episodes in Europe. As reported with norovirus, patients with immunocompromised states are at increased risk of developing HuSaV infection, which can lead to persistent diarrhea and chronic viral shedding in some individuals. Chronic infections are incompletely investigated in these patients, and, due to the lack of specific treatment for HuSaV infection, different clinical approaches were carried out in order to provide further evidence on clinical evolution of these patients with different treatments. In this retrospective study, we report five immunocompromised pediatric patients with recurrent diarrhea caused by HuSaV and long-term viral shedding. Stool samples were analyzed by real-time PCR and tested for enteropathogenic viruses and bacteria and protozoa. Among transplant recipients, reduction of immunosuppressant therapy led to clinical improvement and relief of symptoms, maintaining a balance between managing the infection and preventing graft rejection. Nitazoxanide for 14 days was only used in one of these patients, showing to be an effective therapy to achieve reduction in time to resolution of symptoms. Neither nitazoxanide nor modification of immunosuppressant therapy could avoid recurrences. Further investigations are needed to develop new approaches that can both clear the infection and avoid persistent diarrhea in these patients.

Prevalence of astrovirus and sapovirus among adult oncology patients with acute gastroenteritis using a multiplexed gastrointestinal pathogen PCR panel.

BACKGROUND: Multiplex syndromic gastrointestinal panels (GIPCR) have streamlined the diagnosis of infectious diarrhea. Additionally, they have expanded the number of pathogens that can be routinely evaluated, allowing further understanding of the prevalence of enteric pathogens in various patient populations. The goal of this study was to investigate the prevalence and clinical presentation of astrovirus and sapovirus gastroenteritis in adult oncology patients as detected by the FilmArray GIPCR. METHODS: All GIPCR panel results from December 2017 to June 2021 were retrospectively reviewed to determine the prevalence of astrovirus and sapovirus in adult oncology patients. Medical records were also reviewed to obtain clinical information. Repeat GIPCR positivity and symptom duration were used to estimate prolonged viral shedding. RESULTS: A total of 18,014 panels were performed on samples collected from 9303 adults. Overall, astrovirus and sapovirus were detected in 0.35% (33/9303) and 0.45% (42/9303) GIPCRs respectively. At least one viral target was detected in 424 (4.4%) patients. Astrovirus accounted for 7.8% (33/424) and sapovirus 9.9% (42/424) of patients. Diarrhea was the most common symptom documented. A subset of transplant patients had protracted viral detection with a median of ~27 days (range 23-43 days) for astrovirus and 97 days (range 11-495) for sapovirus. No clusters or outbreaks were identified during the study period. CONCLUSION: In oncology patients with viral gastroenteritis, astrovirus and sapovirus were the causative agents in 18% of the cases. Both viruses were associated with mild disease. Prolonged diarrhea and viral shedding were observed in a few transplant patients.

Sapovirus: an emerging pathogen in kidney transplant recipients?

PURPOSE: Diarrhea is an important cause of morbidity and mortality in immunocompromised patients. After including sapovirus to the viral gastroenteritis screening of our institution's laboratory, we noticed an increase in sapovirus infections among kidney transplant recipients. Therefore, we assumed former gastrointestinal tract infections with unidentified pathogens could have been caused by sapovirus. To better understand the characteristics of a sapovirus infection in a high-risk group we initiated this study. METHODS: Over a period of 6 months, all transplant recipients with diarrhea and later identified viral/unknown pathogens were included. Kidney function, levels of immunosuppressants and  c-reactive protein, acid-base balance, onset of symptoms and time of hospitalization were analyzed. RESULTS: Among 13 hospitalized kidney transplant recipients sapovirus was detected in four patients, while in the remaining nine, three were diagnosed with norovirus, one with cytomegalovirus, one with inflammatory bowel disease and in four patients no pathogen was identified. Even though statistically not significant, creatinine levels at admission tended to be higher in sapovirus patients (median: sapovirus: 3.3 mg/dl (1.3; 5.0), non-sapovirus: 2.5 mg/dl (1.1; 4.9), p = 0.710). Also, Tacrolimus levels showed the same trend (sapovirus: 13.6 ng/ml (12.9; 13.6), non-sapovirus: 7.1 ng/ml (2.6; 22.6), p = 0.279). On discharge creatinine levels improved equally in both groups (sapovirus: 1.7 mg/dl (1.4; 3.2), non-sapovirus: 2 mg/dl (1.0; 3.6), p = 0.825). CONCLUSION: In high-risk patients, early symptomatic treatment remains crucial to protect the transplant`s function. In our cohort all patients recovered well. Larger cohorts and longer follow-up times are needed to detect the long-term consequences and a potential need for further research regarding specific treatment. TRIAL REGISTRATION: The study has been registered on DRKS (trialsearch.who.int), Reg. Nr. DRKS00033311 (December 28th 2023).

Activated sludge and UV-C254 for Sapovirus, Aichivirus, Astrovirus, and Adenovirus processing.

In this study, the detection rates of four enteric viruses, Human Astrovirus (HAstVs), Aichivirus (AiVs), Human Adenovirus (HAdVs), and Sapovirus (SaVs) are carried out to assess the virological quality of the treated wastewater. A total of 140 samples was collected from wastewater treatment plant WWTP of Tunis-City. Real-time RT-PCR and conventional RT-PCR results showed high frequencies of detection of the four enteric viruses investigated at the entry and exit of the biological activated sludge procedure and a significant reduction in viral titers after tertiary treatment with UV-C254 irradiation. These results revealed the ineffectiveness of the biological activated sludge treatment in removing viruses and the poor quality of the treated wastewater intended for recycling, agricultural reuse, and safe discharge into the natural environment. The UV-C254 irradiation, selected while considering the non-release of known disinfection by-products because of eventual reactions with the large organic and mineral load commonly present in the wastewater.

Sapovirus Infections in an Australian Community-Based Healthy Birth Cohort During the First 2 Years of Life.

BACKGROUND: Sapovirus is an important cause of acute gastroenteritis (AGE) in young children. However, knowledge gaps remain in community settings. We investigated the epidemiology, disease characteristics, and healthcare use associated with sapovirus infections in Australian children during their first 2 years of life. METHODS: Children in the Brisbane-based Observational Research in Childhood Infectious Diseases birth cohort provided daily gastrointestinal symptoms (vomiting/loose stools), weekly stool swabs, and healthcare data until age 2 years. Swabs were batch-tested for sapovirus using real-time polymerase chain reaction assays. Incidence rates and estimates of associations were calculated. RESULTS: Overall, 158 children returned 11 124 swabs. There were 192 sapovirus infection episodes. The incidence rate in the first 2 years of life was 0.89 infections per child-year (95% confidence interval [CI], .76-1.05), and the symptomatic incidence rate was 0.26 episodes per child-year (95% CI, .17-.37). Age ≥6 months, the fall season, and childcare attendance increased disease incidence significantly. Fifty-four of the 180 (30%) infections with linked symptom diaries were symptomatic, with 72% recording vomiting and 48% diarrhea. Prior infection reduced risk of further infections (adjusted hazard ratio, 0.70 [95% CI, .54-.81]) in the study period. Viral loads were higher and viral shedding duration was longer in symptomatic than asymptomatic children. Twenty-three (43%) symptomatic episodes required healthcare, including 6 emergency department presentations and 2 hospitalizations. CONCLUSIONS: Sapovirus infections are common in Australian children aged 6-23 months. Efforts to reduce childhood AGE after the global rollout of rotavirus vaccines should include sapovirus where estimates of its incidence in communities will be crucial.

Prevalence, Clinical Severity, and Seasonality of Adenovirus 40/41, Astrovirus, Sapovirus, and Rotavirus Among Young Children With Moderate-to-Severe Diarrhea: Results From the Vaccine Impact on Diarrhea in Africa (VIDA) Study.

BACKGROUND: While rotavirus causes severe diarrheal disease in children aged <5 years, data on other viral causes in sub-Saharan Africa are limited. METHODS: In the Vaccine Impact on Diarrhea in Africa study (2015-2018), we analyzed stool from children aged 0-59 months with moderate-to-severe diarrhea (MSD) and without diarrhea (controls) in Kenya, Mali, and The Gambia using quantitative polymerase chain reaction. We derived the attributable fraction (AFe) based on the association between MSD and the pathogen, accounting for other pathogens, site, and age. A pathogen was attributable if the AFe was ≥0.5.The severity of attributable MSD was defined by a modified Vesikari score (mVS). Monthly cases were plotted against temperature and rainfall to assess seasonality. RESULTS: Among 4840 MSD cases, proportions attributed to rotavirus, adenovirus 40/41, astrovirus, and sapovirus were 12.6%, 2.7%, 2.9%, and 1.9%, respectively. Attributable rotavirus, adenovirus 40/41, and astrovirus MSD cases occurred at all sites, with mVS of 11, 10, and 7, respectively. MSD cases attributable to sapovirus occurred in Kenya, with mVS of 9. Astrovirus and adenovirus 40/41 peaked during the rainy season in The Gambia, while rotavirus peaked during the dry season in Mali and The Gambia. CONCLUSIONS: In sub-Saharan Africa, rotavirus was the most common cause of MSD; adenovirus 40/41, astrovirus, and sapovirus contributed to a lesser extent among children aged <5 years. Rotavirus- and adenovirus 40/41-attributable MSD were most severe. Seasonality varied by pathogen and location. Efforts to increase the coverage of rotavirus vaccines and to improve prevention and treatment for childhood diarrhea should continue.

Atomic Structure of the Human Sapovirus Capsid Reveals a Unique Capsid Protein Conformation in Caliciviruses.

Sapovirus (SaV) is a member of the Caliciviridae family, which causes acute gastroenteritis in humans and animals. Human sapoviruses (HuSaVs) are genetically and antigenically diverse, but the lack of a viral replication system and structural information has hampered the development of vaccines and therapeutics. Here, we successfully produced a self-assembled virus-like particle (VLP) from the HuSaV GI.6 VP1 protein, and the first atomic structure was determined using single-particle cryo-electron microscopy (cryo-EM) at a 2.9-Å resolution. The atomic model of the VP1 protein revealed a unique capsid protein conformation in caliciviruses. All N-terminal arms in the A, B, and C subunits interacted with adjacent shell domains after extending through their subunits. The roof of the arched VP1 dimer was formed between the P2 subdomains by the interconnected ß strands and loops, and its buried surface was minimized compared to those of other caliciviruses. Four hypervariable regions that are potentially involved in the antigenic diversity of SaV formed extensive clusters on top of the P domain. Potential receptor binding regions implied by tissue culture mutants of porcine SaV were also located near these hypervariable clusters. Conserved sequence motifs of the VP1 protein, "PPG" and "GWS," may stabilize the inner capsid shell and the outer protruding domain, respectively. These findings will provide the structural basis for the medical treatment of HuSaV infections and facilitate the development of vaccines, antivirals, and diagnostic systems. IMPORTANCE SaV and norovirus, belonging to the Caliciviridae family, are common causes of acute gastroenteritis in humans and animals. SaV and norovirus infections are public health problems in all age groups, which occur explosively and sporadically worldwide. HuSaV is genetically and antigenically diverse and is currently classified into 4 genogroups consisting of 18 genotypes based on the sequence similarity of the VP1 proteins. Despite these detailed genetic analyses, the lack of structural information on viral capsids has become a problem for the development of vaccines or antiviral drugs. The 2.9-Å atomic model of the HuSaV GI.6 VLP presented here not only revealed the location of the amino acid residues involved in immune responses and potential receptor binding sites but also provided essential information for the design of stable constructs needed for the development of vaccines and antivirals.

The emergence of recombinant norovirus GII.12[P16] and predominance of GII.3[P12] strains in pediatric patients with acute gastroenteritis in Thailand, 2019-2020.

Norovirus (NoV) and sapovirus (SaV) are important pathogens that cause acute gastroenteritis (AGE) in all age groups, commonly in children worldwide. Recently, a number of studies have reported a wide variety of NoV recombinant strains. This study aimed to investigate the distribution of NoV and SaV recombinant strains circulating in Chiang Mai, Thailand, during 2019-2020. One hundred and twenty-four NoV and seven SaV strains detected in children admitted to the hospital with AGE were included in this study. The partial RNA-dependent RNA-polymerase (RdRp)/VP1 regions of these NoV and SaV strains were analyzed by phylogenetic analysis, Simplot, and RDP software. Overall, eight recombination patterns of NoV were detected. NoV GII.4[P16] was the most common strain detected (39.1%), followed by GII.3[P12] (25.0%), GII.4[P31] (17.2%), and other recombinant strains were detected at a lower rate. NoV GII.12[P16] strains were detected for the first time in Thailand. For SaV, none of the recombinant strains was detected. All SaV strains, GI.1/GI.1, GI.2/GI.2, and GII.5/GII.5, exhibited VP1 genotype corresponded to RdRp genotype. In conclusion, this study demonstrates the distribution and diversity of NoV and SaV recombinant strains circulating in pediatric patients with AGE in Chiang Mai, during 2019-2020 with the emergence of NoV GII.3[P12] and GII.12[P16].

Sapovirus infections in Japan before and after the emergence of the COVID-19 pandemic: An alarming update.

An increasing trend of sapovirus (SaV) infections in Japanese children during 2009-2019, particularly after the introduction of the voluntary rotavirus (RV)-vaccination program has been observed. Herein, we investigated the epidemiological situation of SaV infections from 2019 to 2022 when people adopted a precautionary lifestyle due to the emergence of the COVID-19 pandemic, and RV vaccines had been implemented as routine vaccines. Stool samples were collected from children who attended outpatient clinics with acute gastroenteritis and analyzed by reverse transcriptase-polymerase chain reaction to determine viral etiology. Among 961 stool samples, 80 (8.3%) were positive for SaV: 2019-2020 (6.5%), 2020-2021 (0%), and 2021-2022 (12.8%). The trend of SaV infection in Japanese children yet remained upward with statistical significance (p = 0.000). The major genotype was GI.1 (75%) which caused a large outbreak in Kyoto between December 2021 and February 2022. Phylogenetic, gene sequence and deduced amino acid sequence analyses suggested that these GI.1 strains detected in the outbreak and other places during 2021-2022 or 2019-2020 remained genetically identical and widely spread. This study reveals that SaV infection is increasing among Japanese children which is a grave concern and demands immediate attention to be paid before SaV attains a serious public health problem.

The analysis of the genotype of Sapovirus outbreaks in Zhejiang Province.

BACKGROUND: Sapovirus (SaV) infection is increasing globally. Concurrently, several SaV-outbreaks were observed in children of Zhejiang province, China, in recent years, In this study, the genotypes of Sapovirus from seven outbreaks in the Zhejiang province were analysed. METHODS: A total of 105 faecal samples were collected from children aged between 4 and 17 years from the Zhejiang Provincial Center for Disease Control and Prevention between October 2021 and February 2023. Genotypes were processed using reverse transcription polymerase chain reaction and Sanger sequencing, while next-generation sequencing was used to generate a complete viral genome. Deduced amino acid sequences were analysed to detect VP1 gene mutations. RESULTS: In total, 60 SaV-positive patients were detected at a 57.14% (60/105) positivity rate. Positive rates in the seven outbreaks were: 22.22% (2/9), 15.00% (3/20), 93.10% (27/29), 84.21% (16/19), 28.57% (2/7), 53.33% (8/15) and 33.33% (2/6), respectively. Four genotypes were identified in the seven outbreaks, of which, GI.1 accounted for 14.29% (1/7), GI.2 accounted for 14.29% (1/7), GI.6 and GII.5 accounted for 14.29% (1/7), and GI.6 accounted for 57.14% (4/7). All patients were children and outbreaks predominantly occurred in primary schools and during cold seasons. Additionally, the complete sequence from the GI.6 outbreak strain showed high homology (identity: 99.99%) with few common substitutions (Y300S, N302S and L8M) in VP1 protein. CONCLUSIONS: SaV genotype diversity was observed in the seven outbreaks, with GI.6 being the main SaV genotype in Zhejiang province. It demonstrated high homology and may provide a platform for SaV prevention and control measures.

Global molecular prevalence and genotype distribution of Sapovirus in children with gastrointestinal complications: A systematic review and meta-analysis.

Sapovirus (SaV) is an emerging cause of children gastrointestinal complications such as acute gastroenteritis (AGE). The aim of the present systematic review and meta-analysis was to estimate the global prevalence of the SaV in children and association of infection with SaVs and AGE in children based on case-control studies. Four international databases (PubMed, Scopus, Web of Sciences and Google Scholar) were used to retrieve English-language studies published between January 2000 and December 2020. Comprehensive Meta-Analysis software was applied to estimate the overall prevalence, publication bias and heterogeneity index. The pooled prevalence of SaV infection among children with gastroenteritis was 3.4% [95% confidence interval (CI): 2.9%-3.9%] based on a random-effects meta-analysis. Genogroup I was the dominant genogroup of SaV in children with gastroenteritis [2.2% (95% CI: 1.6%-3.0%)], association analysis showed that SaV was associated with gastroenteritis [OR: 1.843 (95% CI: 1.27-2.66)]. Given the significant prevalence of the virus in children, it is necessary to pay more attention to this situation. Therefore, preventive health measures in children should be a priority.

Influence of herd immunity on norovirus: a long-term field study of repeated viral gastroenteritis outbreaks at the same facilities.

BACKGROUND: Viral acute gastroenteritis (AG) is detected worldwide annually. Outbreaks caused by viruses associated with gastroenteritis have been reported repeatedly at the same facilities in Yokohama, Japan over several years. We investigated the statuses of these repeated outbreaks to consider herd immunity at the facility level. METHODS: Between September 2007 and August 2017, 1459 AG outbreaks were reported at 1099 facilities. Stool samples were collected for virological testing, and the norovirus gene was amplified and sequenced to determine the genotype using the N-terminal region of the capsid. RESULTS: The outbreaks were caused by norovirus, sapovirus, rotavirus A, and rotavirus C. Norovirus was consistently predominant over the 10-year period. Of 1099 facilities, 227 reported multiple outbreaks, of which norovirus-only combinations accounted for 76.2%. More outbreaks were due to different genotype combinations than the same genotype combinations. For facilities that experienced two norovirus outbreaks, the average interval between outbreaks was longer for groups with the same combinations than for groups with different genogroup or genotype combinations, although no statistically significant differences were observed. At 44 facilities, outbreaks occurred repeatedly during the same AG season, and most exhibited combinations of different norovirus genotypes or viruses. Among 49 combinations with the same norovirus genotype at the same facilities over 10 years, the most prevalent genotypes were combinations of genogroup II genotype 4 (GII.4), followed by GII.2, GII.6, GII.3, GII.14, and GI.3. The mean interval between outbreaks was 31.2 ± 26.8 months for all combinations, and the mean intervals were longer for non-GII.4 genotype cases than for GII.4 cases, and statistically significant differences were observed (t-test, P < 0.05). Additionally, these average intervals were longer for kindergarten/nursery schools and primary schools than for nursing homes for older adults (t-test, P < 0.05). CONCLUSIONS: Repeated AG outbreaks at the same facilities in Yokohama during the 10-year study period included mainly norovirus combinations. Herd immunity at the facility level was maintained for at least the same AG season. Norovirus genotype-specific herd immunity was maintained for an average of 31.2 months during the study period, and these intervals differed depending on genotype.

Human sapovirus propagation in human cell lines supplemented with bile acids.

Human sapoviruses (HuSaVs) cause acute gastroenteritis similar to human noroviruses. Although HuSaVs were discovered four decades ago, no HuSaV has been grown in vitro, which has significantly impeded the understanding of viral biology and the development of antiviral strategies. In this study, we identified two susceptible human cell lines, that originated from testis and duodenum, that support HuSaV replication and found that replication requires bile acids. HuSaVs replicated more efficiently in the duodenum cell line, and viral RNA levels increased up to ∼6 log10-fold. We also detected double-stranded RNA, viral nonstructural and structural proteins in the cell cultures, and intact HuSaV particles. We confirmed the infectivity of progeny viruses released into the cell culture supernatants by passaging. These results indicate the successful growth of HuSaVs in vitro. Additionally, we determined the minimum infectious dose and tested the sensitivities of HuSaV GI.1 and GII.3 to heat and ultraviolet treatments. This system is inexpensive, scalable, and reproducible in different laboratories, and can be used to investigate mechanisms of HuSaV replication and to evaluate antivirals and/or disinfection methods for HuSaVs.

Clinical Profiles of Childhood Astrovirus-, Sapovirus-, and Norovirus-Associated Acute Gastroenteritis in Pediatric Emergency Departments in Alberta, 2014-2018.

BACKGROUND: Infections by previously underdiagnosed viruses astrovirus and sapovirus are poorly characterized compared with norovirus, the most common cause of acute gastroenteritis. METHODS: Children <18 years old with acute gastroenteritis were recruited from pediatric emergency departments in Alberta, Canada between 2014 and 2018. We described and compared the clinical course of acute gastroenteritis in children with astrovirus, sapovirus, and norovirus. RESULTS: Astrovirus was detected in 56 of 2688 (2.1%) children, sapovirus was detected in 146 of 2688 (5.4%) children, and norovirus was detected in 486 of 2688 (18.1%) children. At illness onset, ~60% of astrovirus cases experienced both diarrhea and vomiting. Among sapovirus and norovirus cases, 35% experienced diarrhea at onset and 80% of 91% (sapovirus/norovirus) vomited; however, diarrhea became more prevalent than vomiting at approximately day 4 of illness. Over the full course of illness, diarrhea was 18% (95% confidence interval [CI], 8%- 29%) more prevalent among children with astrovirus than norovirus infections and had longer duration with greater maximal events; there were a median of 4.0 fewer maximal vomiting events (95% CI, 2.0-5.0). Vomiting continued for a median of 24.8 hours longer (95% CI, 9.6-31.7) among children with sapovirus versus norovirus. Differences between these viruses were otherwise minimal. CONCLUSIONS: Sapovirus infections attended in the emergency department are more similar to norovirus than previously reported, whereas astrovirus infections have several distinguishable characteristics.

The Epidemiology of Sapovirus in the Etiology, Risk Factors, and Interactions of Enteric Infection and Malnutrition and the Consequences for Child Health and Development Study: Evidence of Protection Following Natural Infection.

BACKGROUND: Sapovirus is one of the principal agents of acute viral enteritis in children. Because it has not been routinely included in diagnostic evaluations, the epidemiology and natural history remain poorly described. METHODS: A birth cohort of 1715 children from 8 countries contributed surveillance samples (n = 35 620) and diarrheal specimens (n = 6868) from 0 to 24 months of age. Sapovirus was detected by quantitative polymerase chain reaction concurrently to other enteropathogens using multiarray cards. Logistic regression was used to identify risk factors, and longitudinal models were employed to estimate incidence rates and evaluate evidence of protective immunity. RESULTS: Sapovirus was detected in 24.7% (n = 1665) of diarrheal stools and 12.8% (n = 4429) of monthly surveillance samples. More than 90% of children were infected and 60% experienced sapovirus diarrhea in the first 2 years of life. Breastfeeding and higher socioeconomic status were associated with reduced incidence of infection and illness. Specimens with sapovirus detected had an increased odds of coinfection with rotavirus (odds ratio [OR], 1.6 [95% confidence interval {CI}, 1.3-2.0]), astrovirus (OR, 1.5 [95% CI, 1.3-1.7]), adenovirus (OR, 1.3 [95% CI, 1.1-1.5]), and Shigella (OR, 1.4 [95% CI, 1.3-1.6]). Prior infection with sapovirus conferred a risk reduction of 22% for subsequent infection (hazard ratio [HR], 0.78 [95% CI, .74-.85]) and 24% for subsequent diarrhea (95% CI, 11.0%-35.0%; HR, 0.76). CONCLUSIONS: Sapovirus is a common cause of early childhood diarrhea. Further research on coinfections is warranted. Evidence of acquired immunity was observed even in the absence of genotype-specific analysis for this pathogen of known genetic diversity.