Comparative pathogenesis of tissue culture-adapted and wild-type Cowden porcine enteric calicivirus (PEC) in gnotobiotic pigs and induction of diarrhea by intravenous inoculation of wild-type PEC

Establishment of a Novel Caco-2-Based Cell Culture System for Human Sapovirus Propagation

Human sapovirus (HuSaV), first identified in the 1970s, is a significant cause of acute gastroenteritis, particularly in young children. Despite its clinical significance, research on HuSaV has been limited due to the absence of a reliable cell culture system. In 2020, a breakthrough study reported that HuSaV GI.1 and GII.3 strains could be cultured and serially propagated using HuTu80 cells in the presence of bile acids. However, in 2024, a subsequent study reported that effective replication in HuTu80 cells requires specialized cells that have undergone over 100 passages. In this study, we sought to identify an alternative cell culture system for HuSaV. HuSaV GI.1 can replicate and be serially propagated using Caco-2 cells under bile acid supplementation. Importantly, the Caco-2 cells were freshly sourced from the American Type Culture Collection, ensuring reproducibility for laboratories worldwide. Furthermore, Caco-2MC cells were established via single-cell cloning from in-house Caco-2/Cas9 cells with 91.5% HuSaV-susceptible. HuSaV strains GI.1, GI.2, GI.3, GII.1, GII.3, and GV.1 were successfully propagated using Caco-2MC cells, with RNA copy numbers increasing up to 4.4 log10-fold within 5 days post-infection. This efficient HuSaV cell culture system represents a significant advancement in HuSaV research.

Multiple Co-Infecting Caliciviruses in Oral Fluid and Enteric Samples of Swine Detected by a Novel RT-qPCR Assay and a 3'RACE-PCR-NGS Method

Caliciviruses including noro- and sapoviruses of family Caliciviridae are important enteric human and swine pathogens, while others, like valoviruses, are less known. In this study, we developed a detection and typing pipeline for the most prevalent swine enteric caliciviruses-sapovirus GIII (Sw-SaV), norovirus GII (Sw-NoV), and valovirus GI (Sw-VaV). The pipeline integrates triplex RT-qPCR, 3'RACE semi-nested PCR, and next-generation sequencing (NovaSeq, Illumina) techniques. A small-scale epidemiological investigation was conducted on archived enteric and, for the first time, on oral fluid/saliva samples of diarrheic and asymptomatic swine of varying ages from Hungary and Slovakia. In enteric samples, Sw-SaV was the most prevalent, detected in 26.26% of samples, primarily in diarrheic pigs with low Cq values, followed by Sw-NoV (2.53%) in nursery pigs. In oral fluid samples, Sw-NoV predominated (7.46%), followed by Sw-SaV (4.39%). Sw-VaVs were sporadically found in both sample types. A natural, asymptomatic Sw-SaV outbreak was retrospectively detected where the transient shedding of the virus was <2 weeks. Complete capsid sequences (n = 59; 43 Sw-SaV, 13 Sw-NoV, and 3 Sw-VaV) including multiple (up to five) co-infecting variants were identified. Sw-SaV sequences belong to seven genotypes, while Sw-NoV and Sw-VaV strains clustered into distinct sub-clades, highlighting the complex diversity of these enteric caliciviruses in swine.

Porcine Sapovirus in Northern Vietnam: Genetic Detection and Characterization Reveals Co-Circulation of Multiple Genotypes

Porcine sapovirus (PoSaV) has been reported in many countries over the world, which may cause gastroenteritis symptoms in pigs with all ages. There has been no report on PoSaV infection in Vietnam up to now. In this study, a total of 102 samples were collected from piglets, fattening pigs, and sows with diarrhea in several cities and provinces in northern Vietnam. The PoSaV genome was examined using polymerase chain reaction (PCR). Sequencing of the partial RNA-dependent RNA polymerase (RdRp) gene sequences (324 bp) was performed. Of the 102 tested samples, 10 (9.8%) and 7/20 (35%) were detected as positive for the PoSaV RdRp gene using the PCR method at the individual and farm levels, respectively. Genetic analysis of the partial RdRp gene region of about 324 bp indicated that the nucleotide identity of the current 10 Vietnamese viral strains ranged from 61.39% to 100%. Among the 10 strains obtained, 8 belonged to genotype III and the remaining 2 strains were clustered in genotype VIII. The Vietnamese genotype III viruses formed two sub-clusters. The Vietnamese PoSaV strains were closely related to PoSaVs reported in South Korea, Venezuela, and the Netherlands. This research was the first to describe PoSaV infection in northern Vietnam during 2022-2023.

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.

Genetic characterization of porcine sapoviruses identified from pigs during a diarrhoea outbreak in Iowa, 2019

Porcine sapovirus (SaV) was first identified by electron microscopy in the United States in 1980 and has since been reported from both asymptomatic and diarrhoeic pigs usually in mixed infection with other enteric pathogens. SaV as the sole aetiological agent of diarrhoea in naturally infected pigs has not previously been reported in the United States. Here, we used four independent lines of evidence including metagenomics analysis, real-time RT-PCR (rRT-PCR), histopathology, and in situ hybridization to confirm porcine SaV genogroup III (GIII) as the sole cause of enteritis and diarrhoea in pigs. A highly sensitive and specific rRT-PCR was established to detect porcine SaV GIII. Examination of 184 faecal samples from an outbreak of diarrhoea on a pig farm showed that pigs with clinical diarrhoea had significantly lower Ct values (15.9 ± 0.59) compared to clinically unaffected pigs (35.8 ± 0.71). Further survey of 336 faecal samples from different states in the United States demonstrated that samples from pigs with clinical diarrhoea had a comparable positive rate (45.3%) with those from asymptomatic pigs (43.1%). However, the SaV-positive pigs with clinical diarrhoea had significantly higher viral loads (Ct  = 26.0 ± 0.5) than the SAV-positive but clinically healthy pigs (Ct  = 33.2 ± 0.9). Phylogenetic analysis of 20 field SaVs revealed that all belonged to SaV GIII and recombination analysis indicated that intragenogroup recombination had occurred within the field isolates of SaV GIII. These results suggest that porcine SaV GIII plays an important aetiologic role in swine enteritis and diarrhoea and rRT-PCR is a reliable method to detect porcine SaV. Our findings provide significant insights to better understand the epidemiology and pathogenicity of porcine SaV infection.

Potential zoonotic swine enteric viruses: The risk ignored for public health

Swine could serve as a natural reservoir for a large variety of viruses, including potential zoonotic enteric viruses. The presence of viruses with high genetic similarity between porcine and human strains may result in the emergence of zoonotic or xenozoonotic infections. Furthermore, the globalization and intensification of swine industries exacerbate the transmission and evolution of zoonotic viruses among swine herds and individuals working in swine-related occupations. To effectively prevent the public health risks posed by zoonotic swine enteric viruses, designing, and implementing a comprehensive measure for early diagnosis, prevention, and mitigation, requires interdisciplinary a collaborative ''One Health" approach from veterinarians, environmental and public health professionals, and the swine industry. In this paper, we reviewed the current knowledge of selected potential zoonotic swine enteric viruses and explored swine intensive production and its associated public health risks.

The Complexity of Swine Caliciviruses. A Mini Review on Genomic Diversity, Infection Diagnostics, World Prevalence and Pathogenicity

Caliciviruses are single stranded RNA viruses, non-enveloped structurally, that are implicated in the non-bacterial gastroenteritis in various mammal species. Particularly in swine, viral gastroenteritis represents a major problem worldwide, responsible for significant economic losses for the pig industry. Among the wide range of viruses that are the proven or suspected etiological agents of gastroenteritis, the pathogenicity of the members of Caliciviridae family is among the less well understood. In this context, the present review presents and discusses the current knowledge of two genera belonging to this family, namely the Norovirus and the Sapovirus, in relation to swine. Aspects such as pathogenicity, clinical evidence, symptoms, epidemiology and worldwide prevalence, genomic diversity, identification tools as well as interchanging hosts are not only reviewed but also critically evaluated. Generally, although often asymptomatic in pigs, the prevalence of those microbes in pig farms exhibits a worldwide substantial increasing trend. It should be mentioned, however, that the factors influencing the symptomatology of these viruses are still far from well established. Interestingly, both these viruses are also characterized by high genetic diversity. These high levels of molecular diversity in Caliciviridae family are more likely a result of recombination rather than evolutionary or selective adaptation via mutational steps. Thus, molecular markers for their detection are mostly based on conserved regions such as the RdRp region. Finally, it should be emphasized that Norovirus and the Sapovirus may also infect other domestic, farm and wild animals, including humans, and therefore their surveillance and clarification role in diseases such as diarrhea is a matter of public health importance as well.

Epidemiology of Astrovirus, Norovirus and Sapovirus in Greek pig farms indicates high prevalence of Mamastrovirus suggesting the potential need for systematic surveillance

Backround

Astrovirus, Norovirus and Sapovirus exhibit a wide distribution in swine pig herds worldwide. However, the association of porcine Astrovirus (PAstV), porcine Norovirus (PoNoV) and porcine Sapovirus (PoSaV) with disease in pigs remains uncertain. In this study, we investigated the prevalence of PAstV, PoNoV and PoSaV in Greek pig farms using both conventional RT-PCR and SYBR-Green Real-time RT-PCR in an effort to compare the sensitivity of the two methods. We examined 1400 stool samples of asymptomatic pigs originating from 28 swine farms throughout Greece in pools of five.

Results

PAstV was detected in all 28 swine farms examined, with an overall prevalence of 267/280 positive pools (95.4%). Porcine Caliciviruses prevalence was found at 36 and 57 out of the 280 examined samples, by the conventional and SYBR-Green Real time RT-PCR, respectively. Sequencing and phylogenetic analysis of the positive samples revealed that the detected PAstV sequences are clustered within PAstV1, 3 and 4 lineages, with PAstV3 being the predominant haplotype (91.2%). Interestingly, sequencing of the Calicivirus positive samples demonstrated the presence of non-target viruses, i.e. Sapovirus, Kobuvirus and Sapelovirus sequences and one sequence highly similar to bat Astrovirus, while no Norovirus sequence was detected.

Conclusions

The high prevalence of PAstV in Greek pig farms poses a necessity for further investigation of the pathogenicity of this virus and its inclusion in surveillance programs in case that it proves to be important. To our knowledge, this is the first epidemiological study of these viruses in pig farms in Greece.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40813-021-00245-8.

Dynamics of the Enteric Virome in a Swine Herd Affected by Non-PCV2/PRRSV Postweaning Wasting Syndrome

A commercial pig farm with no history of porcine circovirus 2 (PCV2) or porcine reproductive and respiratory syndrome virus (PRRSV) repeatedly reported a significant reduction in body weight gain and wasting symptoms in approximately 20–30% of the pigs in the period between three and six weeks after weaning. As standard clinical interventions failed to tackle symptomatology, viral metagenomics were used to describe and monitor the enteric virome at birth, 3 weeks, 4 weeks, 6 weeks, and 9 weeks of age. The latter four sampling points were 7 days, 3 weeks, and 6 weeks post weaning, respectively. Fourteen distinct enteric viruses were identified within the herd, which all have previously been linked to enteric diseases. Here we show that wasting is associated with alterations in the enteric virome of the pigs, characterized by: (1) the presence of enterovirus G at 3 weeks of age, followed by a higher prevalence of the virus in wasting pigs at 6 weeks after weaning; (2) rotaviruses at 3 weeks of age; and (3) porcine sapovirus one week after weaning. However, the data do not provide a causal link between specific viral infections and the postweaning clinical problems on the farm. Together, our results offer evidence that disturbances in the enteric virome at the preweaning stage and early after weaning have a determining role in the development of intestinal barrier dysfunctions and nutrient uptake in the postweaning growth phase. Moreover, we show that the enteric viral load sharply increases in the week after weaning in both healthy and wasting pigs. This study is also the first to report the dynamics and co-infection of porcine rotavirus species and porcine astrovirus genetic lineages during the first 9 weeks of the life of domestic pigs.

Visualization of intestinal infections with astro- and sapovirus in mink (Neovison vison) kits by in situ hybridization

Clarification of the infection microbiology remains a challenge in the pre-weaning diarrhea (PWD) syndrome in farmed mink (Neovison vison). Duodenal, jejunal and colon sections from 36 mink kits with PWD were systematically examined by chromogen in situ hybridization targeting two incriminated viruses: mink astrovirus and mink sapovirus. Using the RNAscope® 2.5 HD Duplex Assay, astrovirus and sapovirus were visualized and simultaneously demonstrated in the gut tissue. Both viruses infect enterocytes in the small intestine with a specific localization pattern; astrovirus affects the two apical thirds of the villi, whereas sapovirus generally affects the basal parts of the villi. Furthermore, we demonstrated that astrovirus in mink does not target the goblet cells. This is the first time astro- and calicivirus have been visualized in mink kit gut tissue, and these findings might be important in clarification of the impact of these viruses in the PWD syndrome.

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.

Porcine sapoviruses: Pathogenesis, epidemiology, genetic diversity, and diagnosis

The first porcine Sapovirus (SaV) Cowden strain was discovered in 1980. To date, eight genogroups (GIII, V-IX) and three genogroups (GIII, GV, and GVI) of porcine SaVs have been detected from domestic pigs worldwide and wild boars in Japan, respectively based on the capsid sequences. Although GIII Cowden strain replicated in the villous epithelial cells and caused intestinal lesions in the proximal small intestines (mainly in duodenal and less in jejunum), leading to mild to severe diarrhea, in the orally inoculated neonatal gnotobiotic pigs, the significance of porcine SaVs in different ages of pigs with diarrhea in the field is still undetermined. This is due to two reasons: 1) similar prevalence of porcine SaVs was detected in diarrheic and non-diarrheic pigs; and 2) co-infection of porcine SaVs with other enteric pathogens is common in pigs. Diagnosis of porcine SaV infection is mainly based on the detection of viral nucleic acids using reverse transcription (RT)-PCR and sequencing. Much is unknown about these genetically diverse viruses to understand their role in pig health and to evaluate whether vaccines are needed to prevent SaV infection.

One-step triplex reverse-transcription PCR detection of porcine epidemic diarrhea virus, porcine sapelovirus, and porcine sapovirus

Swine diarrhea can be caused by multiple agents, including porcine epidemic diarrhea virus (PEDV), porcine sapelovirus (PSV), and porcine sapovirus (SaV). We designed a one-step triplex reverse-transcription PCR (RT-PCR) detection method including 3 pairs of primers that focused on the S1 gene of PEDV, a conserved gene of PSV, and the VP1 gene of SaV. The optimal concentrations of upstream and downstream primers in the triplex RT-PCR were 0.24 μM for PEDV, 0.15 μM for PSV, and 0.2 μM for SaV, and the optimal annealing temperature was 55.5°C. Triplex RT-PCR assessment of 402 piglet diarrhea samples was compared with conventional individual RT-PCR. Concordance rates in both tests for individual viruses were 100%, 97.6%, and 94.4% for PEDV, PSV, and SaV, respectively. PEDV, PSV, and SaV were detected in 57.2%, 10.4%, and 9.0% of the samples, respectively. The high sensitivity and specificity of this triplex RT-PCR-based detection method for PEDV, PSV, and SaV could allow rapid detection and analysis of mixed infections by these 3 viruses.

Molecular detection of enteric viruses and the genetic characterization of porcine astroviruses and sapoviruses in domestic pigs from Slovakian farms

Background

Surveillance and characterization of pig enteric viruses such as transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), rotavirus, astrovirus (PAstV), sapovirus (PSaV), kobuvirus and other agents is essential to evaluate the risks to animal health and determination of economic impacts on pig farming. This study reports the detection and genetic characterization of PAstV, PSaV in healthy and diarrheic domestic pigs and PEDV and TGEV in diarrheic pigs of different age groups.

Results

The presence of PAstV and PSaV was studied in 411 rectal swabs collected from healthy (n = 251) and diarrheic (n = 160) pigs of different age categories: suckling (n = 143), weaned (n = 147) and fattening (n = 121) animals on farms in Slovakia. The presence of TGEV and PEDV was investigated in the diarrheic pigs (n = 160). A high presence of PAstV infections was detected in both healthy (94.4%) and diarrheic (91.3%) pigs. PSaV was detected less often, but also equally in clinically healthy (8.4%) and diarrheic (10%) pigs. Neither TGEV nor PEDV was detected in any diarrheic sample. The phylogenetic analysis of a part of the RdRp region revealed the presence of all five lineages of PAstV in Slovakia (PAstV-1 – PAstV-5), with the most frequent lineages being PAstV-2 and PAstV-4. Analysis of partial capsid genome sequences of the PSaVs indicated that virus strains belonged to genogroup GIII. Most of the PSaV sequences from Slovakia clustered with sequences originating from neighbouring countries.

Conclusions

Due to no significant difference between healthy and diarrheic pigs testing of the presence of PAstV and PSaV provides no diagnostic value. Genetic diversity of PAstV was very high as all five lineages were identified in pig farms in Slovakia. PSaV strains were genetically related to the strains circulating in Central European region.

Diarrhea caused by rotavirus A, B, and C in suckling piglets from southern Brazil: molecular detection and histologic and immunohistochemical characterization

Rotavirus (RV) is an important viral pathogen causing diarrhea in piglets and other mammals worldwide. We describe 34 cases from 4 diarrheal outbreaks caused by RV in unvaccinated farrowing units in southern Brazil from 2011 to 2013. We performed autopsy, histologic examinations, bacterial culture, RV immunohistochemistry (IHC), and enteric virus detection through molecular assays for rotavirus A, B, and C, transmissible gastroenteritis virus, porcine epidemic diarrhea virus, sapovirus, norovirus, and kobuvirus. Histologically, villus atrophy (29 of 34) and epithelial vacuolation (27 of 34) occurred in all 4 outbreaks. Cell debris in the lamina propria occurred in 20 cases, mostly from outbreaks A (8 of 11), C (4 of 6), and D (7 of 11). IHC was positive for RV in 21 of 34 samples. RT-PCR was positive for RV in 20 of 30 samples; RV-C was the most frequently detected RV ( n = 17). Kobuvirus was detected in 11 samples, and, in 3 of them, there was single detection of this enteric virus.

Short communication: Immune responses in sows induced by porcine sapovirus virus-like particles reduce viral shedding in suckled piglets

Porcine sapovirus (PoSaV) is a potential threat to public health owing to its capacity for reassortment with human sapovirus strains. However, there is still no vaccine available for the prevention and control of this infectious disease. In this study, we developed PoSaV virus-like particles (VLPs) using a baculovirus expression system. Immunization with PoSaV VLPs induced high titers of serum antibody specific for VP1 in sows. The results of our challenge study demonstrated that maternally-derived antibodies (MDA) induced by VLP immunization dramatically reduced viral shedding of PoSaV in the feces of next generation piglets. Therefore, the results of this study indicate that the immune responses of sows elicited by PoSaV VLPs can inhibit in vivo viral replication in their offspring and represent a promising strategy for developing vaccines against PoSaV.

No evidence of enteric viral involvement in the new neonatal porcine diarrhoea syndrome in Danish pigs

BACKGROUND

The aim of this study was to investigate whether the syndrome New Neonatal Porcine Diarrhoea Syndrome (NNPDS) is associated with a viral aetiology. Four well-managed herds experiencing neonatal diarrhoea and suspected to be affected by NNPDS were included in a case-control set up. A total of 989 piglets were clinically examined on a daily basis. Samples from diarrhoeic and non-diarrhoeic piglets at the age of three to seven days were selected for extensive virological examination using specific real time polymerase chain reactions (qPCRs) and general virus detection methods.

RESULTS

A total of 91.7% of the animals tested positive by reverse transcription qPCR (RT-qPCR) for porcine kobuvirus 1 (PKV-1) while 9% and 3% were found to be positive for rotavirus A and porcine teschovirus (PTV), respectively. The overall prevalence of porcine astrovirus (PAstV) was 75% with 69.8% of the PAstV positive pigs infected with PAstV type 3. No animals tested positive for rotavirus C, coronavirus (TGEV, PEDV and PRCV), sapovirus, enterovirus, parechovirus, saffoldvirus, cosavirus, klassevirus or porcine circovirus type 2 (PCV2). Microarray analyses performed on a total of 18 animals were all negative, as were eight animals examined by Transmission Electron Microscopy (TEM). Using Next Generation de novo sequencing (de novo NGS) on pools of samples from case animals within all herds, PKV-1 was detected in four herds and rotavirus A, rotavirus C and PTV were detected in one herd each.

CONCLUSIONS

Our detailed analyses of piglets from NNPDS-affected herds demonstrated that viruses did not pose a significant contribution to NNPDS. However, further investigations are needed to investigate if a systemic virus infection plays a role in the pathogenesis of NNPDS.

High-resolution phylogeny providing insights towards the epidemiology, zoonotic aspects and taxonomy of sapoviruses

The evolution, epidemiology and zoonotic aspects of Sapoviruses (SaV) are still not well explored. In this study, we applied high-resolution phylogeny to investigate the epidemiological and zoonotic origins as well as taxonomic classification of animal and human SaV. Bayesian framework analyses showed an increase in porcine SaV (PoSaV) population dynamics and genetic diversity between 1975 and 1982, resulting in a SaV gene flow and generation of new strains among porcine and human populations. Our results also show the contribution of different animal populations involved in SaV epidemiology and highlight zoonotic aspects, as exemplified by the crucial role that swine, dogs, mink and humans play in SaV spread. Additionally, phylogenetic analysis suggests that bats may play key role in SaV epidemiology. According to our hypothesis, these animals may act as reservoirs or intermediate host species, contributing to viral spread in zoonotic and other epidemiological scenarios and facilitating the generation of new SaV genogroups and genotypes through recombination events. Data from large-scale phylogeny partition based on patristic distance, did not show a correlation between transmission clusters on generation of SaV genogroups, nevertheless we present both important findings about SaV taxonomy and important considerations useful for further taxonomical studies.

Genetic diversity and intergenogroup recombination events of sapoviruses detected from feces of pigs in Japan

Sapoviruses (SaV) are enteric viruses infecting humans and animals. SaVs are highly diverse and are divided into multiple genogroups based on structural protein (VP1) sequences. SaVs detected from pigs belong to eight genogroups (GIII, GV, GVI, GVII, GVIII, GIX, GX, and GXI), but little is known about the SaV genogroup distribution in the Japanese pig population. In the present study, 26 nearly complete genome (>6000 nucleotide: nt) and three partial sequences (2429nt, 4364nt, and 4419nt in length, including the entire VP1 coding region) of SaV were obtained from one diarrheic and 15 non-diarrheic porcine feces in Japan via a metagenomics approach. Phylogenetic analysis of the complete VP1 amino acid sequence (aa) revealed that 29 porcine SaVs were classified into seven genogroups; GIII (11 strains), GV (1 strain), GVI (3 strains), GVII (6 strains), GVIII (1 strain), GX (3 strains), and GXI (4 strains). This manuscript presents the first nearly complete genome sequences of GX and GXI, and demonstrates novel intergenogroup recombination events.

Divergent Sapovirus Strains and Infection Prevalence in Wild Carnivores in the Serengeti Ecosystem: A Long-Term Study

The genus Sapovirus, in the family Caliciviridae, includes enteric viruses of humans and domestic animals. Information on sapovirus infection of wildlife is limited and is currently lacking for any free-ranging wildlife species in Africa. By screening a large number of predominantly fecal samples (n = 631) obtained from five carnivore species in the Serengeti ecosystem, East Africa, sapovirus RNA was detected in the spotted hyena (Crocuta crocuta, family Hyaenidae), African lion (Panthera leo, family Felidae), and bat-eared fox (Otocyon megalotis, family Canidae), but not in golden or silver-backed jackals (Canis aureus and C. mesomelas, respectively, family Canidae). A phylogenetic analysis based on partial RNA-dependent RNA polymerase (RdRp) gene sequences placed the sapovirus strains from African carnivores in a monophyletic group. Within this monophyletic group, sapovirus strains from spotted hyenas formed one independent sub-group, and those from bat-eared fox and African lion a second sub-group. The percentage nucleotide similarity between sapoviruses from African carnivores and those from other species was low (< 70.4%). Long-term monitoring of sapovirus in a population of individually known spotted hyenas from 2001 to 2012 revealed: i) a relatively high overall infection prevalence (34.8%); ii) the circulation of several genetically diverse variants; iii) large fluctuations in infection prevalence across years, indicative of outbreaks; iv) no significant difference in the likelihood of infection between animals in different age categories. The likelihood of sapovirus infection decreased with increasing hyena group size, suggesting an encounter reduction effect, but was independent of socially mediated ano-genital contact, or the extent of the area over which an individual roamed.

First detection and molecular characterization of sapoviruses and noroviruses with zoonotic potential in swine in Ethiopia

Noroviruses (NoVs) and sapoviruses (SaVs), which belong to the family Caliciviridae, are important human and animal enteric pathogens with zoonotic potential. In Ethiopia, no study has been done on the epidemiology of animal NoVs and SaVs. The aim of this study was to detect and characterize NoVs and SaVs from swine of various ages. Swine fecal samples (n = 117) were collected from commercial farms in Ethiopia. The samples were screened for caliciviruses by reverse transcription polymerase chain reaction (RT-PCR) using universal and genogroup-specific primer pairs. Phylogenetic analysis was conducted using a portion of the RNA-dependent RNA polymerase (RdRp) region and the VP1 region of genome sequences of caliciviruses. Among 117 samples, potential caliciviruses were detected by RT-PCR in 17 samples (14.5 %). Of the RT-PCR-positive fecal samples, four were sequenced, of which two were identified as human NoV GII.1 and the other two as porcine SaV GIII. The porcine SaV strains that were detected were genetically related to the porcine enteric calicivirus Cowden strain genogroup III (GIII), which is the prototype porcine SaV strain. No porcine NoVs were detected. Our results showed the presence of NoVs in swine that are most similar to human strains. These findings have important implications for NoV epidemiology and food safety. Therefore, continued surveillance of NoVs in swine is needed to define their zoonotic potential, epidemiology and public and animal health impact. This is the first study to investigate enteric caliciviruses (noroviruses and sapoviruses) in swine in Ethiopia.

Prevalence and molecular characterization of human noroviruses and sapoviruses in Ethiopia

Viral gastroenteritis is a major public health problem worldwide. In Ethiopia, very limited studies have been done on the epidemiology of enteropathogenic viruses. The aim of this study was to detect and characterize noroviruses (NoVs) and sapoviruses (SaVs) from acute gastroenteritis patients of all ages. Fecal samples were collected from diarrheic patients (n = 213) in five different health centers in Addis Ababa during June-September 2013. The samples were screened for caliciviruses by reverse transcription polymerase chain reaction (RT-PCR) using universal and genogroup-specific primer pairs. Phylogenetic analyses were conducted using the sequences of the PCR products. Of the clinical samples, 25.3 % and 4.2 % were positive for NoV and SaV RNA, respectively. Among the norovirus positives, 22 were sequenced further, and diverse norovirus strains were identified: GI (n = 4), GII (n = 17) and GIV (n = 1). Most strains were GII (n = 17/22: 77.2 %), which were further divided into three different genotypes (GII.4, GII.12/GII.g recombinant-like and GII.17), with GII.17 being the dominant (7/17) strain detected. GI noroviruses, in particular GI.4 (n = 1), GI.5 (n = 2) and GI.8 (n = 1), were also detected and characterized. The GIV strain detected is the first from East Africa. The sapoviruses sequenced were also the first reported from Ethiopia. Collectively, this study showed the high burden and diversity of noroviruses and circulation of sapoviruses in diarrheic patients in Ethiopia. Continued surveillance to assess their association with diarrhea is needed to define their epidemiology, disease burden, and impact on public health.

Mechanism of Cell Culture Adaptation of an Enteric Calicivirus, the Porcine Sapovirus Cowden Strain

The porcine sapovirus (SaV) (PoSaV) Cowden strain is one of only a few culturable enteric caliciviruses. Compared to the wild-type (WT) PoSaV Cowden strain, tissue culture-adapted (TC) PoSaV has two conserved amino acid substitutions in the RNA-dependent RNA polymerase (RdRp) and six in the capsid protein (VP1). By using the reverse-genetics system, we identified that 4 amino acid substitutions in VP1 (residues 178, 289, 324, and 328), but not the substitutions in the RdRp region, were critical for the cell culture adaptation of the PoSaV Cowden strain. The other two substitutions in VP1 (residues 291 and 295) reduced virus replication in vitro. Three-dimensional (3D) structural analysis of VP1 showed that residue 178 was located near the dimer-dimer interface, which may affect VP1 assembly and oligomerization; residues 289, 291, 324, and 328 were located at protruding subdomain 2 (P2) of VP1, which may influence virus binding to cellular receptors; and residue 295 was located at the interface of two monomeric VP1 proteins, which may influence VP1 dimerization. Although reversion of the mutation at residue 291 or 295 from that of the TC strain to that of the WT reduced virus replication in vitro, it enhanced virus replication in vivo, and the revertants induced higher-level serum and mucosal antibody responses than those induced by the TC PoSaV Cowden strain. Our findings reveal the molecular basis for PoSaV adaptation to cell culture. These findings may provide new, critical information for the cell culture adaptation of other PoSaV strains and human SaVs or noroviruses.

IMPORTANCE

The tissue culture-adapted porcine sapovirus Cowden strain is one of only a few culturable enteric caliciviruses. We discovered that 4 amino acid substitutions in VP1 (residues 178, 289, 324, and 328) were critical for its adaptation to LLC-PK cells. Two substitutions in VP1 (residues 291 and 295) reduced virus replication in vitro but enhanced virus replication and induced higher-level serum and mucosal antibody responses in gnotobiotic pigs than those induced by the tissue culture-adapted strain. Structural modeling analysis of VP1 suggested that residue 178 may affect VP1 assembly and oligomerization; residues 289, 291, 324, and 328 may influence virus binding to cellular receptors; and residue 295 may influence VP1 dimerization. Our findings will provide new information for the cell culture adaptation of other sapoviruses and possibly noroviruses.

Repeated examination of natural sapovirus infections in pig litters raised under experimental conditions

Background

Porcine sapovirus, belonging to the family Caliciviridae, is an enteric virus that is widespread in the swine industry worldwide. A total of 14 sapovirus genogroups have been suggested and the most commonly found genogroup in swine is genogroup III (GIII). The goal of the present experiment was to examine the presence of sapovirus in 51 naturally infected pigs at two different time points. The pigs were kept under experimental conditions after weaning. Previous studies on sapovirus have primarily been of a cross sectional nature, typically prevalence studies performed on farms and abattoirs. In the present study, faecal samples, collected from each pig at 5½ weeks and 15–18 weeks of age, were analysed for sapovirus by reverse transciptase polymerase chain reaction and positive findings were genotyped by sequencing.

Results

At 5½ weeks of age, sapovirus was detected in the majority of the pigs. Sequencing revealed four different strains in the 5½ week olds—belonging to genogroups GIII and GVII. Ten to 13 weeks later, the virus was no longer detectable from stools of infected pigs. However, at this time point 13 pigs were infected with another GIII sapovirus strain not previously detected in the pigs studied. This GIII strain was only found in pigs that, in the initial samples, were virus-negative or positive for GVII.

Conclusions

At 5 weeks of age 74 % of the pigs were infected with sapovirus. At 15–18 weeks of age all pigs had cleared their initial infection, but a new sapovirus GIII strain was detected in 25 % of the pigs. None of the pigs initially infected with the first GIII strain were reinfected with this new GIII strain, which may indicate the presence of a genogroup-specific immunity.

Comprehensive review of human sapoviruses

Sapoviruses cause acute gastroenteritis in humans and animals. They belong to the genus Sapovirus within the family Caliciviridae. They infect and cause disease in humans of all ages, in both sporadic cases and outbreaks. The clinical symptoms of sapovirus gastroenteritis are indistinguishable from those caused by noroviruses, so laboratory diagnosis is essential to identify the pathogen. Sapoviruses are highly diverse genetically and antigenically. Currently, reverse transcription-PCR (RT-PCR) assays are widely used for sapovirus detection from clinical specimens due to their high sensitivity and broad reactivity as well as the lack of sensitive assays for antigen detection or cell culture systems for the detection of infectious viruses. Sapoviruses were first discovered in 1976 by electron microscopy in diarrheic samples of humans. To date, sapoviruses have also been detected from several animals: pigs, mink, dogs, sea lions, and bats. In this review, we focus on genomic and antigenic features, molecular typing/classification, detection methods, and clinical and epidemiological profiles of human sapoviruses.

Both α2,3- and α2,6-linked sialic acids on O-linked glycoproteins act as functional receptors for porcine Sapovirus

Sapovirus, a member of the Caliciviridae family, is an important cause of acute gastroenteritis in humans and pigs. Currently, the porcine sapovirus (PSaV) Cowden strain remains the only cultivable member of the Sapovirus genus. While some caliciviruses are known to utilize carbohydrate receptors for entry and infection, a functional receptor for sapovirus is unknown. To characterize the functional receptor of the Cowden strain of PSaV, we undertook a comprehensive series of protein-ligand biochemical assays in mock and PSaV-infected cell culture and/or piglet intestinal tissue sections. PSaV revealed neither hemagglutination activity with red blood cells from any species nor binding activity to synthetic histo-blood group antigens, indicating that PSaV does not use histo-blood group antigens as receptors. Attachment and infection of PSaV were markedly blocked by sialic acid and Vibrio cholerae neuraminidase (NA), suggesting a role for α2,3-linked, α2,6-linked or α2,8-linked sialic acid in virus attachment. However, viral attachment and infection were only partially inhibited by treatment of cells with sialidase S (SS) or Maackia amurensis lectin (MAL), both specific for α2,3-linked sialic acid, or Sambucus nigra lectin (SNL), specific for α2,6-linked sialic acid. These results indicated that PSaV recognizes both α2,3- and α2,6-linked sialic acids for viral attachment and infection. Treatment of cells with proteases or with benzyl 4-O-β-D-galactopyranosyl-β-D-glucopyranoside (benzylGalNAc), which inhibits O-linked glycosylation, also reduced virus binding and infection, whereas inhibition of glycolipd synthesis or N-linked glycosylation had no such effect on virus binding or infection. These data suggest PSaV binds to cellular receptors that consist of α2,3- and α2,6-linked sialic acids on glycoproteins attached via O-linked glycosylation.

Norovirus: targets and tools in antiviral drug discovery

The development of antiviral strategies to treat or prevent norovirus infections is a pressing matter. Noroviruses are the number 1 cause of acute gastroenteritis, of foodborne illness, of sporadic gastroenteritis in all age groups and of severe acute gastroenteritis in children less than 5 years old seeking medical assistance [USA/CDC]. In developing countries, noroviruses are linked to significant mortality (~200,000 children <5 years old). Noroviruses are a major culprit for the closure of hospital wards, and associated with increased hospitalization and mortality among the elderly. Transplant patients have significant risk of acquiring persistent norovirus gastroenteritis. Control and prevention strategies are limited to the use of disinfectants and hand sanitizers, whose efficacy is frequently insufficient. Hence, there is an ample need for antiviral treatment and prophylaxis of norovirus infections. The fact that only a handful of inhibitors of norovirus replication have been reported can largely be attributable to the hampering inability to cultivate human noroviruses in cell culture. The Norwalk replicon-bearing cells and the murine norovirus-infected cell lines are the available models to assess in vitro antiviral activity of compounds. Human noroviruses have been shown to replicate (to some extent) in mice, calves, gnotobiotic pigs, and chimpanzees. Infection of interferon-deficient mice with the murine norovirus results in virus-induced diarrhea. Here we review recent developments in understanding which norovirus proteins or host cell factors may serve as targets for inhibition of viral replication. Given the recent advances, significant progress in the search for antiviral strategies against norovirus infections is expected in the upcoming years.

Expression of porcine sapovirus VP1 gene and VP1 specific monoclonal antibody production

Sapovirus (SaV) is an agent of human and porcine gastroenteritis and a member of the family Caliciviridae. SaV has been classified based on VP1 full gene nucleotide sequences into five genogroups (GI-GV), among which GIII is known to infect pigs. The VP1 folds into two major domains designated S and P for the shell and protruding domain, respectively. The P domain is divided into two subdomains, P1 and P2. In this study, the VP1 full gene and the S, P, and P2 regions of the VP1 gene of porcine SaV were expressed using a baculovirus expression system. Expressed proteins in the recombinant virus were confirmed by polymerase chain reaction, indirect fluorescence antibody (IFA) testing, and Western blot analysis. Four hybridomas secreting VP1-specific monoclonal antibodies (MAbs) against porcine sapovirus were generated. Four MAbs were characterized according to their IFA and Western blot analysis results. All of the hybridomas produced in this study secreted MAbs binding to S domain of VP1 protein specifically. The MAbs produced in this study can be used as specific diagnostic reagents for detecting porcine SaV.

Internalization of sapovirus, a surrogate for norovirus, in romaine lettuce and the effect of lettuce latex on virus infectivity

Noroviruses are the leading cause of food-borne outbreaks, including those that involve lettuce. The culturable porcine sapovirus (SaV) was used as a norovirus surrogate to study the persistence and the potential transfer of the virus from roots to leaves and from outer to inner leaves of lettuce plants. Treatment of lettuce with SaV was done through the roots of young plants, the soil, or the outer leaves of mature plants. Sampling of roots, xylem sap, and inner and outer leaves followed by RNA extraction and SaV-specific real-time reverse transcription (RT)-PCR was performed at 2 h and on postinoculation days (PID) 2, 5, 7, 14, and/or 28. When SaV was inoculated through the roots, viral RNA persisted on the roots and in the leaves until PID 28. When the virus was inoculated through the soil, viral RNA was detected on the roots and in the xylem sap until PID 14; viral RNA was detected in the leaves only until PID 2. No infectious virus was detected inside the leaves for either treatment. When SaV was inoculated through the outer leaves, viral RNA persisted on the leaves until PID 14; however, the virus did not transfer to inner leaves. Infectious viral particles on leaves were detected only at 2 h postinoculation. The milky sap (latex) of leaves, but not the roots' xylem sap, significantly decreased virus infectivity when tested in vitro. Collectively, our results showed the transfer of SaV from roots to leaves through the xylem system and the capacity of the sap of lettuce leaves to decrease virus infectivity in leaves.

Emerging and re-emerging swine viruses

In the past two decades or so, a number of viruses have emerged in the global swine population. Some, such as porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2), cause economically important diseases in pigs, whereas others such as porcine torque teno virus (TTV), now known as Torque teno sus virus (TTSuV), porcine bocavirus (PBoV) and related novel parvoviruses, porcine kobuvirus, porcine toroviruses (PToV) and porcine lymphotropic herpesviruses (PLHV), are mostly subclinical in swine herds. Although some emerging swine viruses such as swine hepatitis E virus (swine HEV), porcine endogenous retrovirus (PERV) and porcine sapovirus (porcine SaV) may have a limited clinical implication in swine health, they do pose a potential public health concern in humans due to zoonotic (swine HEV) or potential zoonotic (porcine SaV) and xenozoonotic (PERV, PLHV) risks. Other emerging viruses such as Nipah virus, Bungowannah virus and Menangle virus not only cause diseases in pigs but some also pose important zoonotic threat to humans. This article focuses on emerging and re-emerging swine viruses that have a limited or uncertain clinical and economic impact on pig health. The transmission, epidemiology and pathogenic potential of these viruses are discussed. In addition, the two economically important emerging viruses, PRRSV and PCV2, are also briefly discussed to identify important knowledge gaps.

Seroprevalence of porcine cytomegalovirus and sapovirus infection in pigs in Hunan province, China

The seroprevalence of porcine cytomegalovirus (PCMV) and sapovirus (SaV) infections in pigs was investigated in Hunan province, China, between May 2005 and October 2010. A total of 500 pig serum samples collected from 10 representative administrative regions in Hunan province were evaluated for antibodies against PCMV and SaV using enzyme-linked immunosorbent assay (ELISA). The overall seroprevalence of porcine cytomegalovirus and sapovirus in pigs was 96.40% (482/500) and 63.40% (317/500), and the seropositivity of 10 herds we surveyed varied, ranging from 94.74% to 98.48% and 56.36% to 72.50%, respectively. The highest prevalence was found in breeding sows (96.67% for PCMV and 83.33% for SaVs). The results of the present survey indicated that infections with porcine cytomegalovirus and sapovirus are highly prevalent in pigs in Hunan province, China.

Diagnostic investigation of porcine periweaning failure-to-thrive syndrome: lack of compelling evidence linking to common porcine pathogens

Porcine periweaning failure-to-thrive syndrome (PFTS), an increasingly recognized syndrome in the swine industry of North America, is characterized by the anorexia of nursery pigs noticeable within 1 week of weaning, and progressive loss of body condition and lethargy during the next 1-2 weeks. Morbidity caused by PFTS is moderate, but case fatality is high. The etiology of PFTS is presently unknown and may include infectious agent(s), noninfectious factors, or both. PFTS was identified in a high health status farm with good management in early 2007. A diagnostic investigation was undertaken to identify the pathological lesions of, and infectious agents associated with, pigs demonstrating typical clinical signs. Affected (PFTS-SICK) and unaffected (PFTS-HLTHY) pigs from an affected farm, and unaffected pigs from 2 unaffected farms, were examined. The most prevalent lesions in PFTS-SICK pigs were superficial lymphocytic fundic gastritis, atrophic enteritis, superficial colitis, lymphocytic and neutrophilic rhinitis, mild nonsuppurative meningoencephalitis, and thymic atrophy. Rotavirus A and Betacoronavirus 1 (Porcine hemagglutinating encephalomyelitis virus) were identified only in PFTS-SICK pigs, but the significance of the viruses is uncertain because PFTS is not consistent with the typical presentation following infection by these pathogens. Porcine reproductive and respiratory syndrome virus, Porcine circovirus-2, Influenza A virus, Alphacoronavirus 1 (Transmissible gastroenteritis virus), Torque teno virus 1, Brachyspira hyodysenteriae, and Brachyspira pilosicoli were not identified in PFTS-SICK pigs. Suid herpesvirus 2 (Porcine cytomegalovirus), Porcine enteric calicivirus, Torque teno virus 2, pathogenic Escherichia coli, and coccidia were detected in both PFTS-SICK and PFTS-HLTHY pigs. It was concluded that there is a lack of compelling evidence that PFTS is caused by any of these pathogens.

Identification of genetic diversity of porcine Norovirus and Sapovirus in Korea

It is well known that Norovirus (NoV) and Sapovirus (SaV) identified in humans and pigs have heterogeneous genome sequences. In this study, a total of three strains of NoV and 37 strains of SaV were detected in 567 porcine fecal samples by RT-PCR, corresponding detection rates of 0.5 and 6.5%, respectively. Phylogenetic analyses were conducted using amino acid sequences of the partial RNA-dependent RNA polymerase (RdRp) and complete capsid proteins of both viruses to determine their genogroups. Analysis with the RdRp sequences indicated that all three NoV strains HW41, DG32, and DO35 detected in this study were classified into genogroup II (GII). A further analysis with the complete capsid sequence demonstrated that the DO35 strain belonged to subgenotype b in GII-21 (GII-21b) along with the SW918 strain. A total of 26 strains out of 27 strains that were selected from the 37 porcine SaVs were classified into genogroup III when they were analyzed with the RdRp sequences. The remaining strain (DO19) was not clustered with any of the previously classified SaV strains, thereby suggesting the advent of a new genogroup virus. Additional analyses with the amino acid sequence of the capsid and the nucleotide sequence of the RdRp and capsid junction region supported the notion that the DO19 strain belonged to a novel genogroup of SaV. To the best of our knowledge, this is the first report to describe a novel porcine SaV belonging to an unknown genogroup in Korea.

Chimpanzees as an animal model for human norovirus infection and vaccine development

Noroviruses are global agents of acute gastroenteritis, but the development of control strategies has been hampered by the absence of a robust animal model. Studies in chimpanzees have played a key role in the characterization of several fastidious hepatitis viruses, and we investigated the feasibility of such studies for the noroviruses. Seronegative chimpanzees inoculated i.v. with the human norovirus strain Norwalk virus (NV) did not show clinical signs of gastroenteritis, but the onset and duration of virus shedding in stool and serum antibody responses were similar to that observed in humans. NV RNA was detected in intestinal and liver biopsies concurrent with the detection of viral shedding in stool, and NV antigen expression was observed in cells of the small intestinal lamina propria. Two infected chimpanzees rechallenged 4, 10, or 24 mo later with NV were resistant to reinfection, and the presence of NV-specific serum antibodies correlated with protection. We evaluated the immunogenicity and efficacy of virus-like particles (VLPs) derived from NV (genogroup I, GI) and MD145 (genogroup II, GII) noroviruses as vaccines. Chimpanzees vaccinated intramuscularly with GI VLPs were protected from NV infection when challenged 2 and 18 mo after vaccination, whereas chimpanzees that received GII VLPs vaccine or a placebo were not. This study establishes the chimpanzee as a viable animal model for the study of norovirus replication and immunity, and shows that NV VLP vaccines could induce protective homologous immunity even after extended periods of time.

Clinical characteristics of viral intestinal infection in preterm and term neonates

The clinical presentation of the viral enteric pathogens in newborn infants has not been adequately examined. The aim of this study was to evaluate the clinical characteristics of viral intestinal infections in newborn infants. Clinical data of all term and preterm infants admitted to our tertiary neonatal intensive care unit from 1998 to 2007 with clinical signs of gastroenteritis (GE) or necrotizing enterocolitis (NEC) were retrospectively reviewed and compared between infants with different viral enteric pathogens in stool specimens. In 34 infants with signs of GE or NEC, enteropathogenic viruses were found in stool specimens. Rotavirus was detected in 12 cases, of which two infants had NEC. Compared with infants with rotavirus or norovirus, infants with astrovirus more frequently suffered from NEC (p<0.05). In addition, an acute systemic inflammatory response was significantly more common in patients with astrovirus infection (astrovirus vs. rotavirus and astrovirus vs. norovirus, p < 0.01 and p < 0.05, respectively). Of eight children infected with norovirus, one infant had a systemic acute inflammatory response and NEC. This study demonstrates that in newborn infants, intestinal rotavirus, norovirus, and astrovirus infections may be associated with severe illness such as hemorrhagic enteritis resulting in bloody diarrhea or even NEC.

Seroepidemiology of porcine enteric sapovirus in pig farms in Venezuela

Porcine enteric sapovirus (PES) has been shown to cause diarrhea under experimental conditions in gnotobiotic piglets. However, the role of PES as enteric pathogens in porcine farms remains unclear. To further understand the PES-host interactions under field conditions, a serological survey was carried out. To this end the capsid gene of a PES isolate was cloned in the baculovirus expression system and an ELISA was developed based on virus-like particles from the baculovirus-expressed PES capsid protein. A total of 85 serum samples collected from pigs ranging from 8 weeks to over 54 weeks of age were analyzed. An overall seroprevalence to PESs of 62% was found, with significant differences (p<0.05) found between ages. Pigs younger than 10 weeks old and older than 12 weeks old showed high seroprevalences (70-100%), while pigs aged 10-12 weeks showed no detectable serum antibodies levels. Our results suggest that PES infections are common in pigs and that passively acquired maternal antibodies are soon replaced by actively acquired antibodies, whose titers increase gradually with age and that probably are maintained during lifetime.

Incidence, diversity, and molecular epidemiology of sapoviruses in swine across Europe

Porcine sapovirus is an enteric calicivirus in domestic pigs that belongs to the family Caliciviridae. Some porcine sapoviruses are genetically related to human caliciviruses, which has raised public health concerns over animal reservoirs and the potential cross-species transmission of sapoviruses. We report on the incidence, genetic diversity, and molecular epidemiology of sapoviruses detected in domestic pigs in a comprehensive study conducted in six European countries (Denmark, Finland, Hungary, Italy, Slovenia, and Spain) between 2004 and 2007. A total of 1,050 swine fecal samples from 88 pig farms were collected and tested by reverse transcription-PCR for sapoviruses, and positive findings were confirmed by sequencing. Sapoviruses were detected in 80 (7.6%) samples collected on 39 (44.3%) farms and in every country. The highest prevalence was seen among piglets aged 2 to 8 weeks, and there was no significant difference in the proportion of sapovirus-positive findings for healthy animals and animals with diarrhea in Spain and Denmark (the only countries where both healthy animals and animals with diarrhea were tested). On the basis of the sequence of the RNA polymerase region, highly heterogeneous populations of viruses representing six different genogroups (genogroups III, VI, VII, and VIII, including potential new genogroups IX and X) were identified, with a predominance of genogroup GIII (50.6%). Genogroup VIII, found in five of the six countries, had the highest degree of homology (up to 66% at the amino acid level) to human sapovirus strains. Sapoviruses are commonly circulating and endemic agents in swine herds throughout Europe. Highly heterogeneous and potential new genogroups of sapoviruses were found in pigs; however, no "human-like" sapoviruses were detected.

Model systems for the study of human norovirus Biology

The relative contribution of norovirus to disease burden on society has only recently been established and they are now established as a major cause of gastroenteritis in the developed world. However, despite the medical relevance of these viruses, an efficient in vitro cell culture system for human noroviruses has yet to be developed. As a result, much of our knowledge on the basic mechanisms of norovirus biology has come from studies using other members of the Caliciviridae family of small positive stranded RNA viruses. Here we aim to summarise the recent advances in the field, highlighting how model systems have played a key role in increasing our knowledge of this prevalent pathogen.