Studies of epidemiology and seroprevalence of bovine noroviruses in Germany

Metagenomic analysis reveals high diversity of gut viromes in yaks (Bos grunniens) from the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau (QTP), renowned for its exceptional biological diversity, is home to numerous endemic species. However, research on the virology of vulnerable vertebrates like yaks remains limited. In this study, our objective was to use metagenomics to provide a comprehensive understanding of the diversity and evolution of the gut virome in yak populations across different regions of the QTP. Our findings revealed a remarkably diverse array of viruses in the gut of yaks, including those associated with vertebrates and bacteriophages. Notably, some vertebrate-associated viruses, such as astrovirus and picornavirus, showed significant sequence identity across diverse yak populations. Additionally, we observed differences in the functional profiles of genes carried by the yak gut virome across different regions. Moreover, the virus-bacterium symbiotic network that we discovered holds potential significance in maintaining the health of yaks. Overall, this research expands our understanding of the viral communities in the gut of yaks and highlights the importance of further investigating the interactions between viruses and their hosts. These data will be beneficial for revealing the crucial role that viruses play in the yak gut ecology in future studies.

First Detection and Genomic Characterization of Bovine Norovirus from Yak

Yak are a unique free-grazing bovine species in high-altitude areas. The objective of this study was to investigate the presence and molecular characteristics of BNoV in yak. A total of 205 diarrheal samples of yak (aged ≤ 3 months) were collected from 10 farms in Sichuan Province, China, from May 2018 to October 2020, and four samples were detected as BNoV-positive with RT-PCR. Moreover, a nearly full-length genome of SMU-YAK-J1 containing three complete ORFs was successfully sequenced. Sequence analysis with only nine genome sequences of the GIII genogroup showed that SMU-YAK-J1 was most closely related with GIII.P2 GIII.4, sharing 90.9% gnomic nucleotide identity, but only shared 71.6–85.9% with other genotypes, which confirmed that SMU-YAK-J1 belongs to genotype GIII.P2 GIII.4. However, compared with the sole genome of GIII.4 in GenBank, the BNoV in this study also exhibited many unique amino acid changes among all the three ORFs, which may represent the unique genetic evolution of BNoV in yak. This study first determined the presence of BNoV in yak, contributing to a better understanding of the prevalence and genetic evolution of BNoV.

Viral Enteritis in Cattle: To Well Known Viruses and Beyond

Livestock products supply about 13 percent of energy and 28 percent of protein in diets consumed worldwide. Diarrhea is a leading cause of sickness and death of beef and dairy calves in their first month of life and also affecting adult cattle, resulting in large economic losses and a negative impact on animal welfare. Despite the usual multifactorial origin, viruses are generally involved, being among the most important causes of diarrhea. There are several viruses that have been confirmed as etiological agents (i.e., rotavirus and coronavirus), and some viruses that are not yet confirmed as etiological agents. This review summarizes the viruses that have been detected in the enteric tract of cattle and tries to deepen and gather knowledge about them.

Evolutionary history and spatiotemporal dynamic of GIII norovirus: From emergence to classification in four genotypes

Noroviruses belong to a genetically diverse group of viruses infecting a wide range of mammalian host species, and those detected in cattle and sheep are classified within genogroup III (GIII). The current classification of norovirus in genogroups and genotypes is based on phylogenetic clustering and average distances within and between these phylogenetic clusters; however, the classification studies have been focused mainly on human norovirus, being GIII norovirus relegated. Due to the increasing number of studies on GIII norovirus, the need of an updated and extensive classification is evident. The aim of this study was to update the classification of norovirus within GIII, to describe the emergence of a circulating recombinant strain, and to reconstruct the evolutionary history of this genogroup. Two P-types (GIII.P1-2) and four genotypes (GIII.1-4) were described. For the genogroup GIII, the evolutionary rate estimated was 2.78E-3 s/s/y (95%HPD, 1.79E-3 s/s/y-3.78E-3 s/s/y), and the tMRCA was estimated around 1500 (95%HPD, 1247-1688). Despite the long history of this genogroup, the genotypes detected at present emerged in the last 100 years. Interestingly, most of the recombinant GIII.2P[1] strains detected worldwide were originated from a single recombination event and this recombinant strain was later dispersed through the world. Finally, our results indicate that a scenario of genotypes replacement through the time is highly probable.

Detection, risk factors and molecular diversity of norovirus GIII in cattle in Uruguay

Uruguay is a leading exporter of bovine meat and dairy products, and cattle production is one of the principal economic backbones in this country. A main clinical problem faced by livestock farmers is neonatal calf diarrhea (NCD); however, causes of NCD have not been extensively studied in Uruguay. Bovine norovirus (BoNoV) has been proposed as one of the possible etiologies of NCD as experimentally infected calves developed diarrhea and enteropathy, although limited information is available from field surveys. The aims of this study were to determine the frequency of infection, to investigate possible risk factors, and to determine the molecular diversity of BoNoV in Uruguay. A total of 761 samples of feces or intestinal contents from dairy and beef calves were analyzed through RT-qPCR. The overall frequency of detection of BoNoV was 66.1% with higher frequency in dairy (70.5%) than beef (15.9%) calves (p < 0.01). BoNoV was detected similarly in diarrheic (78.8%) and non-diarrheic (76.2%) dairy calves (p = 0.50). Calves ≤2 weeks of age (84%) were infected more often than older (62.7%) calves (p < 0.01). Phylogenetic analysis confirmed the presence of GIII.1 and GIII.2 genotypes. In addition, we reported the circulation of recombinant strains and the detection of a strain with the recently described novel VP1 genotype. This study represents the first report describing the circulation, the associated risk factors, and the molecular diversity of BoNoV in Uruguay.

Animals as Reservoir for Human Norovirus

Norovirus is the most common cause of non-bacterial gastroenteritis and is a burden worldwide. The increasing norovirus diversity is currently categorized into at least 10 genogroups which are further classified into more than 40 genotypes. In addition to humans, norovirus can infect a broad range of hosts including livestock, pets, and wild animals, e.g., marine mammals and bats. Little is known about norovirus infections in most non-human hosts, but the close genetic relatedness between some animal and human noroviruses coupled with lack of understanding where newly appearing human norovirus genotypes and variants are emerging from has led to the hypothesis that norovirus may not be host restricted and might be able to jump the species barrier. We have systematically reviewed the literature to describe the diversity, prevalence, and geographic distribution of noroviruses found in animals, and the pathology associated with infection. We further discuss the evidence that exists for or against interspecies transmission including surveillance data and data from in vitro and in vivo experiments.

Molecular prevalence of bovine noroviruses and neboviruses in newborn calves in Iran

In this study, bovine enteric caliciviruses (BECs) were detected in 49.4% of a total of 253 stool specimens for diarrheic calves collected from 42 industrial dairy farms from March 2010 to February 2012. Genogroup III norovirus (NoVsGIII) were more prevalent (39.5%) than neboviruses (NBs) (15%), and coinfections were observed in 5.1% of the samples tested. Sequence analysis of the partial polymerase gene from 13 NoVsGIII samples indicated the circulation of both genotype 1 and genotype 2 strains. Among the six NB strains sequenced, five were related to the Bo/Nebraska/80/US strain, while one was related to the Bo/Newbury1/76/UK strain.

First detection of Nebovirus and Norovirus from cattle in China

Neboviruses and genogroup III noroviruses (NoVsGIII) are causative agents of calf diarrhea. The purpose of this study was to investigate the presence of neboviruses and noroviruses in cattle in China. Twenty-eight diarrhea fecal samples collected from 5 different farms were analyzed by RT-PCR. The results showed that 3 nebovirus positive samples were detected on 2 farms, with two strains being related to Bo/DijonA216/06/FR strain and the other one clustering with NB-like strains. Meanwhile, 3 norovirus positive samples were detected on 3 farms, all of which belonged to genotype 1. Our results confirmed the presence of neboviruses and NoVsGIII in China for the first time, and supported the presence of a novel “DijonA216-like” nebovirus genotype.

Bovine noroviruses: A missing component of calf diarrhoea diagnosis

Noroviruses are RNA viruses that belong to the Genus Norovirus, Family Caliciviridae, and infect human beings and several animal species, including cattle. Bovine norovirus infections have been detected in cattle of a range of different ages throughout the world. Currently there is no suitable cell culture system for these viruses and information on their pathogenesis is limited. Molecular and serological tests have been developed, but are complicated by the high genetic and antigenic diversity of bovine noroviruses. Bovine noroviruses can be detected frequently in faecal samples of diarrhoeic calves, either alone or in association with other common enteric pathogens, suggesting a role for these viruses in the aetiology of calf enteritis.

Retrospective serosurveillance of bovine norovirus (GIII.2) and nebovirus in cattle from selected feedlots and a veal calf farm in 1999 to 2001 in the United States

There is a dearth of information on the seroprevalence of bovine norovirus (BoNoV) and nebovirus in cattle of the US. In this retrospective study, serum IgG antibodies to two bovine enteric caliciviruses, GIII.2 BoNoV (Bo/CV186-OH/00/US) and genetically and antigenically distinct nebovirus (Bo/NB/80/US), were evaluated in feedlot and veal calves from different regions of the US during 1999-2001. Three groups of 6- to 7-month-old feedlot calves from New Mexico (NM) (n=103), Arkansas (AR) (n=100) and Ohio (OH) (n=140) and a group of 7- to 10-day-old Ohio veal calves (n=47) were studied. Serum samples were collected pre-arrival or at arrival to the farms for the NM, AR and OH calves and 35 days after arrival for all groups for monitoring seroconversion rates during the period. Virus-like particles of Bo/CV186-OH/00/US and Bo/NB/80/US were expressed using the baculovirus expression system and were used in ELISA to measure antibodies. A high seroprevalence of 94-100 % and 78-100 % was observed for antibodies to GIII.2 BoNoV and nebovirus, respectively, in the feedlot calves tested. In the Ohio veal farm, an antibody seroprevalence of 94-100 % and 40-66 % was found for GIII.2 BoNoV and nebovirus, respectively. Increased seropositive rates of 38-85 % for GIII.2 BoNoV and 26-83 % for nebovirus were observed at 35 days after arrival and commingling on farms for all groups. Infection of calves with either GIII.2 BoNoV or nebovirus, or both viruses, appeared to be common in the regions studied in the US during 1999-2001. These two viruses likely remain endemic because no commercial vaccines are available.

Genetic and evolutionary perspectives on genogroup III, genotype 2 bovine noroviruses

Bovine noroviruses are enteric pathogens that are detected in stool samples from cattle. Five genogroups are currently described in the genus Norovirus (family Caliciviridae), and within the genogroups, sequences are further divided into genotypes according to genetic homology and phylogenetic relationships. In this study, stool specimens from Belgian cattle were screened by RT-PCR. All of the sequences that were detected were phylogenetically related to genogroup III genotype 2 bovine noroviruses, confirming their higher prevalence in comparison with strains from genotype 1. When other sequences from around the world were introduced, phylogenetic inferences allowed neither the determination of phylogenetic lineages over time nor the deduction of topotypes for genotype 2 bovine noroviruses. Three complete genotype 2 bovine norovirus sequences were also compared genetically (Newbury2/1976 /UK, Dumfries/1994/UK and B309/2003/BE). Interestingly, the genetic divergence of the complete genomes of these three strains was relatively low, but a region of the N-terminal protein encoded by ORF1, the hypervariable region of the capsid gene encoded by ORF2, and a region of the minor structural protein encoded by ORF3 seem to be the most exposed to genetic evolution. Bayesian inference also showed that genetic evolution of genogroup III, genotype 2 bovine noroviruses over a 30-year period seemed to be lower than that already reported for noroviruses from the genotypes 3 and 4 in genogroup II.

A review of known and hypothetical transmission routes for noroviruses

Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding during asymptomatic infections, and a high environmental persistence, NoVs are easily transmitted pathogens. Norovirus (NoV) outbreaks have often been reported and tend to affect a lot of people. NoV is spread via feces and vomit, but this NoV spread can occur through several transmission routes. While person-to-person transmission is without a doubt the dominant transmission route, human infective NoV outbreaks are often initiated by contaminated food or water. Zoonotic transmission of NoV has been investigated, but has thus far not been demonstrated. The presented review aims to give an overview of these NoV transmission routes. Regarding NoV person-to-person transmission, the NoV GII.4 genotype is discussed in the current review as it has been very successful for several decades but reasons for its success have only recently been suggested. Both pre-harvest and post-harvest contamination of food products can lead to NoV food borne illness. Pre-harvest contamination of food products mainly occurs via contact with polluted irrigation water in case of fresh produce or with contaminated harvesting water in case of bivalve molluscan shellfish. On the other hand, an infected food handler is considered as a major cause of post-harvest contamination of food products. Both transmission routes are reviewed by a summary of described NoV food borne outbreaks between 2000 and 2010. A third NoV transmission route occurs via water and the spread of NoV via river water, ground water, and surface water is reviewed. Finally, although zoonotic transmission remains hypothetical, a summary on the bovine and porcine NoV presence observed in animals is given and the presence of human infective NoV in animals is discussed.

Development of an optimized method for the recovery of infectious F-RNA coliphage MS2 from meat

F-RNA coliphages, part of the gut flora and likely to be deposited on meat along with other enteric organisms during carcass dressing and processing, may be regarded as an indicator and/or surrogate for potential zoonotic enteric viruses. There is no recommended sampling method for viruses on meats and there is a lack of information on the attachment of enteric viruses or F-RNA coliphages to gauze swabs, cellulose sponges and muscle and fat tissue. The objective of this work was to optimize the recovery of MS2 from muscle and fat tissue of meat by comparing phosphate buffered saline (PBS), 10% beef extract pH 7.2, and tryptose phosphate (2.9%) glycine (6%) broth pH 9.5 as eluants. The sampling techniques of excision, swabbing with gauze or cellulose sponges were compared with homogenizing the inoculated entire muscle or fat surface area. The recovery of MS2 from cellulose sponges using beef extract was significantly higher (P=0.001) than tryptose phosphate glycine broth which was significantly higher (P=0.0001) than PBS. There was no significant difference in the recovery between tryptose phosphate glycine broth and beef extract (P=0.92) and there was no significant difference between PBS and beef extract (P=0.10) when MS2 was recovered from gauze. No significant differences were observed between the different eluants with muscle tissue (P=0.91). When MS2 was recovered from muscle tissue with beef extract significant differences were observed (P=0.002); the sampling techniques of homogenizing the entire sample (56%) was equal to excision (43%) (P=0.23) and swabbing with a cellulose sponge (38%) (P=0.06) which were significantly higher than swabbing with gauze (28%), a second grouping of means indicated that homogenizing the entire sample was significantly higher than the other three sampling techniques. When MS2 was recovered from fat, significant differences were observed (P=0.000); homogenizing the entire sample (78%) was equal to excision (74%), which were significantly higher than swabbing with gauze (49%) or cellulose sponge (29%). The recovery of MS2 from meat is affected by the sampling technique. When choosing a nondestructive sampling method such as a cellulose sponge, a higher recovery can be obtained with beef extract as an eluant.

Seroprevalence of St-Valerien-like caliciviruses in Italian swine

St-Valérien-like viruses are newly recognized porcine caliciviruses recently detected in North America and Europe. In this study, baculovirus-expressed virus-like particles of the St-Valérien strain 25A/ITA were generated and used for the development of an antibody-detection ELISA kit to assess the seroprevalence of these novel caliciviruses in swine. Antibodies specific for St-Valérien-like virus were detected in 63 (10.3 %) of 614 serum samples tested with titres ranging from 1 : 50 (28.6 %) to 1 : 800 (40.7 %). These results indicate that St-Valérien-like infections are common among domestic pigs, italy.

Infection of calves with bovine norovirus GIII.1 strain Jena virus: an experimental model to study the pathogenesis of norovirus infection

The experimental infection of newborn calves with bovine norovirus was used as a homologous large animal model to study the pathogenesis of norovirus infection and to determine target cells for viral replication. Six newborn calves were inoculated orally with Jena virus (JV), a bovine norovirus GIII.1 strain, and six calves served as mock-inoculated controls. Following infection, calves were euthanized before the onset of diarrhea (12 h postinoculation [hpi]), shortly after the onset of diarrhea (18 to 21 hpi), and postconvalescence (4 days pi [dpi]). Calves inoculated with JV developed severe watery diarrhea at 14 to 16 hpi, and this symptom lasted for 53.5 to 67.0 h. Intestinal lesions were characterized by severe villus atrophy together with loss and attenuation of villus epithelium. Viral capsid antigen (JV antigen) was detected by immunohistochemistry in the cytoplasm of epithelial cells on villi. In addition, granular material positive for JV antigen was detected in the lamina propria of villi. Lesions first appeared at 12 hpi and were most extensive at 18 to 19 hpi, extending from midjejunum to ileum. The intestinal mucosa had completely recovered at 4 dpi. There was no indication of systemic infection as described for norovirus infection in mice. JV was found in intestinal contents by reverse transcription-PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) as early as 12 hpi. Fecal shedding of the virus started at 13 hpi and stopped at 23 hpi or at necropsy (4 dpi), respectively. Throughout the trial, none of the control calves tested positive for JV by ELISA or RT-PCR.

First report on the phylogeny of bovine norovirus in Turkey

Bovine norovirus (BoNoV) is an important cause of diarrhea in calves and has been reported in several countries. The aims of this study were to investigate for the first time the presence of norovirus in Turkish calves by real-time reverse transcription-polymerase chain reaction (qRT-PCR) and to determine the phylogeny of any circulating strains. Fecal samples from 70 diarrheic calves were collected and analysed by SYBR Green qRT-PCR. BoNoV was detected in fecal samples from six calves. The capsid gene was partially sequenced, and phylogenetic analysis was performed. This showed that the six Turkish BoNoVs clustered with the GIII-2 prototype.

Molecular detection of kobuviruses and recombinant noroviruses in cattle in continental Europe

Two genotypes (Jena and Newbury2) and two intergenotype recombinant strains have been recognized in bovine noroviruses. Several studies have shown an apparent predominance of bovine infection with Newbury2-related (genotype 2) strains. Bovine stool samples were screened with two primer pairs targeting both the polymerase and the capsid genes. Among the predominant genotype 2 sequences, two were genetically related to the recombinant strain Thirsk10. The detection of sequences genetically related to Thirsk10, together with the very low rate of detection of Jena-related sequences, characterized the bovine norovirus population in Belgium, a representative region of continental Europe. Unexpectedly, bovine kobuvirus-related sequences were also amplified, extending their distribution area in Europe.

Molecular characterization of a new PToV strain. Evolutionary implications

Toroviruses are emergent viruses, belonging to the Nidovirales order, that remain mostly ignored, despite they are able to infect different species of domestic animals and humans, causing enteric diseases and diarrhea. Thus far, only five variants of porcine torovirus (PToV) have been identified. In this report we describe the identification and partial characterization of a new strain of porcine torovirus (PToV-BRES) that was detected by RT-PCR in a swine faecal specimen from a farm in Brescia (Italy). The complete genes coding for the nucleocapsid (N), hemagglutinin-esterase (HE) and membrane (M) proteins were amplified, and sequence analysis showed that PToV-BRES is a new PToV strain that, based on the HE gene sequence, is phylogenetically related to P4 strain, that was up to now the only member of a distinct PToV lineage. The nucleocapsid protein from PToV-BRES was expressed in insect cells as a his-tagged protein, purified by affinity chromatography and used to develop an ELISA method to detect antibodies against PToV. This assay was evaluated using a serum collection including 45 samples from three commercial farms from Spain. High antibody prevalence against PToV was observed in the three farms, both in adult animals and in piglets, which could suggest that PToV might be endemic in Spanish porcine population. The ELISA method developed in this work could be useful in future epidemiological surveys about toroviruses.

Epidemiological study of bovine norovirus infection by RT-PCR and a VLP-based antibody ELISA

Noroviruses, belonging to the family Caliciviridae, have been identified in human beings and in several animal species including cattle. The distribution of bovine norovirus infections was investigated by both RT-PCR to detect norovirus genomes and a virus-like particles-based ELISA to detect genotype 2 bovine norovirus antibodies. During a 1-year systematic study, a virus prevalence of 7.5% (CI 95%: [3.7; 13.4%]) (10 out of 133 samples) was found in stool samples from diarrhoeic calves screened by RT-PCR. Nucleotide sequencing performed on the polymerase region classified all the norovirus amplicons in the bovine norovirus genotype 2. Rather surprisingly, some rotavirus sequences were also detected. On the basis of the polymerase region, genotype 1 bovine norovirus was not identified. Other enteropathogens were found in all samples. By ELISA, a genotype 2 seroprevalence of 93.2% (CI 95%: [90.4; 95.3%]) was found from calves and adult cattle. Antibody levels against genotype 2 bovine noroviruses rose in the first 6 months of life and were maintained in adults. Together the results of virus prevalence and seroprevalence studies suggest that bovine norovirus infection occurs early in life and that re-infection with serologically related bovine noroviruses strains could occur in adult cattle as reported for rotaviruses. The antibody rise against genotype 2 bovine noroviruses in the adult cattle also suggests a short lived and/or strain specific immunity as already shown in human noroviruses. Genotype 2 bovine noroviruses are endemic in the region investigated.

Self-assembly of the recombinant capsid protein of a swine norovirus into virus-like particles and evaluation of monoclonal antibodies cross-reactive with a human strain from genogroup II

Noroviruses (NoVs) are responsible for the majority of gastroenteritis outbreaks in humans. Recently, NoV strains which are genetically closely related to human genogroup II (GII) NoVs have been detected in fecal specimens from swine. These findings have raised concern about the possible role of pigs as reservoirs for NoVs that could infect humans. To better understand the epidemiology of swine NoVs in both the swine and the human populations, rapid immunoassays are needed. In this study, baculovirus recombinants were generated to express the capsid gene of a swine NoV GII genotype 11 (GII.11) strain which self-assembled into virus-like particles (VLPs). Subsequently, the purified VLPs were used to evoke monoclonal antibodies (MAbs) in mice. A panel of eight promising MAbs was obtained and evaluated for their ability to bind to heterologous VLPs, denaturated antigens, and truncated capsid proteins. The MAbs could be classified into two groups: two MAbs that recognized linear epitopes located at the amino-terminal half (shell domain) of the swine NoV GII.11 VLPs and that cross-reacted with human GII.4 NoV VLPs. The other six MAbs bound to conformational epitopes and did not cross-react with the human GII.4 VLPs. To our knowledge, this is the first report on the characterization of MAbs against swine NoVs. The swine NoV VLPs and the MAbs described here may be further used for the design of diagnostic reagents that could help increase our knowledge of the prevalence of NoV infections in pigs and the possible role of pigs as reservoirs for NoVs.

Norovirus–host interaction: implications for disease control and prevention

Noroviruses (NVs) are a major cause of acute gastroenteritis epidemics in both developing and developed countries and affect people of all ages. Three main human histo-blood group antigens (HBGAs) – the ABO, Lewis and secretor families – are involved in NV recognition and eight strain-specific receptor-binding patterns in two major binding groups have been described. The receptor-binding interface is located at the outermost surface of the P domain of the viral capsid. Each interface contains two major binding sites and each site interacts with a carbohydrate side-chain of the HBGAs via multiple hydrogen bonds. Soluble HBGAs in human milk are able to block binding of NV to HBGA receptors, suggesting a potential decoy receptor for the protection of infants from NV infection. Phylogenetic analysis has revealed limited genetic relatedness among NVs with similar receptor-binding patterns. This review summarises and discusses recent advances and highlights implications for future studies in the control and prevention of NV gastroenteritis.

Sensitive multiplex real-time reverse transcription-PCR assay for the detection of human and animal noroviruses in clinical and environmental samples

In this study, we developed a triplex real-time reverse transcription-PCR (RT-PCR)-based method that detects and distinguishes between noroviruses belonging to genogroups I, II, and III and that targets the junction between the regions of open reading frame 1 (ORF1) and ORF2. This is the first assay to include all three genogroups and the first real-time RT-PCR-based method developed for the detection of bovine noroviruses. The assay was shown to be broadly reactive against a wide spectrum of norovirus genotypes, including GI/1 through GI/7, GII/1 through GII/8, GII/10, GII/12, and GII/17, in different matrices (including fecal specimens, treated and raw sewage, source water, and treated drinking water). The assay is highly sensitive, detecting low copy numbers of plasmids that carry the target sequence. A new bovine norovirus, Bo/NLV/Norsewood/2006/NZL, was identified by this assay and was further genetically characterized. The results implicate a broad range of possible applications, including clinical diagnostics, tracing of fecal contaminants, and due to its sensitivity and broad reactivity, environmental studies.

Serotype 1 and 2 bovine noroviruses are endemic in cattle in the United kingdom and Germany

The genomically and antigenically distinct bovine noroviruses Bo/Jena/1980/DE and Bo/Newbury2/1976/UK have been associated with calf diarrhea. In the present seroprevalence study, both were found to be endemic in cattle from Germany and the United Kingdom, a finding in contrast to previous virus prevalence studies. They were less common than group A rotaviruses, particularly in calves, suggesting a different epidemiology.

Porcine enteric caliciviruses: genetic and antigenic relatedness to human caliciviruses, diagnosis and epidemiology

Porcine enteric caliciviruses include sapoviruses and noroviruses. Porcine sapoviruses infect pigs of all ages and cause diarrhea in young pigs, whereas porcine noroviruses were detected exclusively from adult pigs without clinical signs. Importantly, certain porcine norovirus strains were genetically and antigenically related to human noroviruses. This raises public health concerns that pigs may be reservoirs for emergence of epidemic human norovirus strains. This article reviews the discovery of porcine noroviruses and sapoviruses, their classification, diagnosis, epidemiology and genetic and antigenic relatedness to human caliciviruses.

Development of an enzyme immunoassay for detection of sapovirus-specific antibodies and its application in a study of seroprevalence in children

Sapoviruses (SVs) are an important cause of acute pediatric gastroenteritis. Due to the lack of appropriate diagnostic methods, the epidemiology of SV-associated illness remains poorly understood. Baculovirus and Escherichia coli expression systems were evaluated for the development of antibody detection enzyme immunoassays (EIA). Age-related antibody prevalence in children was studied using the new EIA. Because of the low yield of the baculovirus system, the E. coli-expressed SV capsid proteins were used to develop the EIA. The antigenic specificities of the E. coli-expressed SV capsid proteins were demonstrated using hyperimmune antisera raised in animals and sera collected from patients. A high prevalence (>90%) of antibodies to both SV (strain Mex340) and norovirus (strain VA387) was observed in children involved in a birth cohort at 20 to 24 months of age; however, at 1 to 3 months of age, <25% of the children possessed anti-SV antibodies versus >90% with anti-NV antibodies. The E. coli-derived SV proteins are an excellent source of antigens for the EIA. SV infection is common in the first 2 years of life. The low prevalence of maternal antibodies detected in Mexican children against SVs in this study is unique and needs to be addressed in future studies.

Complete genomic characterization and antigenic relatedness of genogroup III, genotype 2 bovine noroviruses

Bovine enteric noroviruses form a genogroup, III, distinct from the 2 human norovirus genogroups, I and II. Two genogroup III genotypes were suggested by partial genomic analyses. In the present study, analysis of the full-length genome sequence of Bo/Newbury2/76/UK and the more contemporary Newbury2-like virus, Bo/Dumfries/1994/UK, showed that both were 7311 nucleotides in length and had three open reading frames (ORFs), amino acids motifs typical of noroviruses, and 95% or greater amino acid identities to each other in all regions of their genome. Apart from the ORF1 NTPase region, their ORF1 regions had less than 90% identity to the genogroup III genotype 1 Bo/Jena/80/DE virus, confirming two genogroup III genotypes. A close antigenic relationship was demonstrated by ELISA between the genotype 2 viruses, which will allow their serological diagnosis.

Characterization of a cross-reactive linear epitope in human genogroup I and bovine genogroup III norovirus capsid proteins

The Southampton norovirus (SV) capsid protein was expressed as VLPs by recombinant baculoviruses in insect cells and was used to immunize mice for the production of monoclonal antibodies (mAbs). One mAb, CM54, showed broad cross-reactivity to genogroup I (GI) noroviruses, but was not reactive to GII capsid proteins. Interestingly mAb CM54 reacted to a bovine norovirus capsid protein. Immunoblot analysis indicated the binding site for CM54 was located in the shell domain between amino acid residues 102-225 of the SV capsid protein. The epitope was mapped to high resolution using a peptide array and was located to the sequence LEDVRN at amino acid residues 162-167. Alignment of norovirus capsid protein sequences confirmed the epitope sequence was common to particular groups of human and bovine noroviruses. Modeling of the epitope onto the recombinant NV capsid protein revealed it was located to the inner surface of the shell domain.

Genotype 1 and genotype 2 bovine noroviruses are antigenically distinct but share a cross-reactive epitope with human noroviruses

The bovine enteric caliciviruses Bo/Jena/1980/DE and Bo/Newbury2/1976/UK represent two distinct genotypes within a new genogroup, genogroup III, in the genus Norovirus of the family Caliciviridae. In the present study, the antigenic relatedness of these two genotypes was determined for the first time to enable the development of tests to detect and differentiate between both genotypes. Two approaches were used. First, cross-reactivity was examined by enzyme-linked immunosorbent assay (ELISA) using recombinant virus-like particles (VLPs) and convalescent-phase sera from calves infected with either Jena (genotype 1) or Newbury2 (genotype 2). Second, cross-reactivity was examined between the two genotypes with a monoclonal antibody, CM39, derived using Jena VLPs. The two genotypes, Jena and Newbury2, were antigenically distinct with little or no cross-reactivity by ELISA to the heterologous VLPs using convalescent calf sera that had homologous immunoglobulin G titers of log10 3.1 to 3.3. CM39 reacted with both Jena and heterologous Newbury2 VLPs. The CM39 epitope was mapped to nine amino acids (31PTAGAQIAA39) in the Jena capsid protein, which was not fully conserved for Newbury2 (31PTAGAPVAA39). Molecular modeling showed that the CM39 epitope was located within the NH2-terminal arm inside the virus capsid. Surprisingly, CM39 also reacted with VLPs from two genogroup II/3 human noroviruses by ELISA and Western blotting. Thus, although the bovine noroviruses Jena and Newbury2 corresponded to two distinct antigenic types or serotypes, they shared at least one cross-reactive epitope. These findings have relevance for epidemiological studies to determine the prevalence of bovine norovirus serotypes and to develop vaccines to bovine noroviruses.

Genetic analysis of calicivirus genomes detected in intestinal contents of piglets in Japan

Enteric caliciviruses, noroviruses, and sapoviruses are emerging pathogens responsible for diarrhea or gastroenteritis in their respective hosts. In this study, swine enteric caliciviruses were detected in ten samples of intestinal contents from 24 piglets in Japan by reverse transcription-polymerase chain reaction using a broadly reactive primer pair (P290/289) that targeted the highly conserved RNA polymerase regions of the enteric caliciviruses. From the positive samples, the entire viral genome of strain K7/JP and 3'-end parts of the genomes of strains K5/JP and K10/JP were cloned and sequenced. K7/JP had an RNA genome of 7144 bases, excluding its 3' poly (A) tail. The K7/JP genome possessed two open reading frames and characteristics common to sapoviruses. In phylogenetic analysis using amino acid sequences of VP1, K5/JP was demonstrated to be close to the noroviruses previously detected in pigs, and K7/JP and K10/JP were considered to be classified as a new genogroup of sapoviruses.

Detection of serum antibodies to bovine norovirus in veterinarians and the general population in the Netherlands

The close genetic relationship of human and animal strains of norovirus has raised the possibility of transmission of noroviruses from animals to humans and may explain the emergence of certain norovirus strains. To assess if exposure to bovine noroviruses (NoV) might result in infection in humans, an enzyme immunoassay (EIA) was designed and validated in order to detect antibodies against bovine norovirus. This and two other EIAs were used to test sera from 210 veterinarians and 630 matched population controls for IgG and IgA antibodies to recombinant capsid protein of bovine NoV (rBoV), Norwalk virus (rNV), and Lordsdale virus (rLDV). Of 840 participants, IgG reactivity to rBoV was found in 185 (22%), to rNV in 638 (76%) and to rLDV in 760 (90%). IgG reactivity to rBoV was more common in veterinarians (58/210: 28%) than in controls (127/630: 20% [P = 0.03]). IgA reactivity to rBoV was similar in both veterinarians and controls. Cross-reactivity of IgA and IgG antibodies to rBoV and rNV was seen, but 26% of all specimens positive rBoV antibodies showed high IgG reactivity to rBoV but low reactivity to rNV, suggesting a specific response to bovine antigen. No evidence of overall cross-reactivity of antibodies to rBoV and rLDV was seen. Among veterinarians, youth spent on farm (Odds Ratio [OR] = 1.8) and membership of the bovine practitioners' society (OR = 2.7) were significantly associated with IgG seroreactivity to rBoV. These data indicate that bovine strains of NoV may infect humans though less frequently than human strains.

Immune responses to bovine norovirus-like particles with various adjuvants and analysis of protection in gnotobiotic calves

We evaluated serum and fecal antibody responses to bovine norovirus (BoNoV) virus-like particles (VLP) and protection against virulent BoNoV in gnotobiotic calves. Calves were vaccinated with two or three doses of VLPs (250 microg/dose) coadministered with oil, mutant E. coli heat-labile toxin (R192G) (mLT) or immunostimulating complexes (ISCOM). Fecal IgA antibody was detected only in calves vaccinated intranasally with VLP+mLT and after challenge, partial protection with delayed, shortened diarrhea (1-2 days) was observed only in these calves. Diarrhea presented from 2 to 6 days in calves vaccinated with VLP with oil or ISCOM and 8 to 9 days in controls. Virus shedding was detected post-challenge by ELISA in all vaccinated calves. All calves recovered from BoNoV infection had high titers of fecal IgA antibodies and were completed protection against challenge. We conclude that only BoNoV VLP+mLT given intranasally stimulated both serum and fecal IgA antibodies and partial protection.

Self-assembly of the recombinant capsid protein of a bovine norovirus (BoNV) into virus-like particles and evaluation of cross-reactivity of BoNV with human noroviruses

None of the enteric caliciviruses except Po/Sapo/GIII/Cowden/80/US replicates in cell culture, which complicates efforts to develop control strategies or to study viral replication. To develop serological assays for bovine noroviruses (BoNVs) and to determine the cross-reactivity of BoNV with human noroviruses, we generated two recombinant baculoviruses, rCV186-OH and rJNCV, to express the capsid genes of Bo/CV186-OH/00/US (Norovirus genogroup III [GIII], genotype 2 [GIII/2]). rCV186-OH expressed the expected 57-kDa capsid protein, but rJNCV expressed a truncated capsid protein of 35 kDa. Sequence analysis of rJNCV identified a single nucleotide deletion in the P domain of the capsid gene, which introduced a stop codon at amino acid 323. The recombinant capsid protein produced by rCV186-OH but not that produced by rJNCV self-assembled into virus-like particles (VLPs) similar to native BoNV. An antibody-capture enzyme-linked immunosorbent assay (ELISA) and antigen-capture ELISA (Ag-ELISA) detected serum antibody and antigen, respectively, from calves infected with Bo/CV186-OH/00/US but not antibodies or antigens to other enteric viruses. In other tests of the GIII/2 BoNV Ag-ELISA, no cross-reactivity was observed with VLPs from one GI and four GII human noroviruses and porcine sapovirus Cowden strain. Because, like human noroviruses, BoNVs do not grow in cell culture, the BoNV VLPs will be useful in the serological assays described for the detection of BoNV antibody and antigen. Consistent with the phylogenetic analysis of the capsid genes of bovine and human noroviruses (M. G. Han, J. R. Smiley, C. Thomas, and L. J. Saif, J. Clin. Microbiol. 42:5214-5224, 2004), the results suggest that GIII/2 BoNV does not share significant antigenic relationships with the five characterized human noroviruses tested.

Seroprevalence of noroviruses in swine

Noroviruses (NVs) are important human pathogens that cause acute gastroenteritis. Genetically related animal enteric NVs have also been described, but there is no evidence of interspecies transmission of NVs. In this study we characterized antibody prevalence among domestic pigs by using recombinant capsid antigens of two human NVs (Norwalk and Hawaii) and one swine NV (SW918) that is genetically related to GII human NVs. Recombinant SW918 capsid protein expressed in baculovirus self-assembled into virus-like particles (VLPs) that were detected by antibodies against GII (Hawaii and Mexico), but not GI (Norwalk and VA115), human NVs. NVs recognize human histo-blood group antigens as receptors, but SW918 VLPs did not bind to human saliva samples with major histo-blood group types. Seventy-eight of 110 (71%) pig serum samples from the United States and 95 of 266 (36%) pig serum samples from Japan possessed antibodies against SW918. Serum samples from pigs in the United States were also tested for antibodies against human NVs; 63% were positive for Norwalk virus (GI) and 52% for Hawaii virus (GII). These results indicate that NV infections are common among domestic pigs; the finding of antigenic relationships between SW918 and human NVs and the detection of antibodies against both GI and GII human NVs in domestic animals highlights the importance of further studies on NV gastroenteritis as a possible zoonotic disease.

Norovirus and its histo-blood group antigen receptors: an answer to a historical puzzle

Recent findings demonstrate that human histo-blood group antigens (HBGAs) serve as receptors for norovirus infection. The recognition of human HBGAs by noroviruses is a typical protein-carbohydrate interaction, in which the protruding domain of the viral capsid protein forms an interface with the oligosaccharide side-chains of the antigens, with a wide diversity among different strains. The human HBGA system is also highly polymorphic and is controlled by multiple gene families with silent alleles. The presence of such diversified molecules on the cell surfaces indicates a possible host defense mechanism against the changing external environment. As mild pathogens that replicate possibly only in the intestinal tract, noroviruses have developed unique strategies to overcome the host defense system. This has been shown by their genetic and structural variations, which explains why norovirus-associated diseases are so common and widespread in every population worldwide.

Norovirus disease: changing epidemiology and host susceptibility factors

Noroviruses cause the majority of acute viral gastroenteritis cases that occur worldwide. The increased recognition of noroviruses as the cause of outbreaks and sporadic disease is due to the recent availability of improved norovirus-specific diagnostics. Transmission of these viruses is facilitated by their high prevalence in the community, shedding of infectious virus particles from asymptomatic individuals and the high stability of the virus in the environment. Currently, the spectrum of clinical disease and the understanding of host susceptibility factors are changing. Cases of chronic norovirus gastroenteritis have been observed in transplant recipients and unusual clinical presentations have been recognized in otherwise healthy adults that are under physical stress. Recently, noroviruses were found to bind to gut-expressed carbohydrates, leading to a correlation between a person's genetically determined carbohydrate expression and their susceptibility to Norwalk virus infection. Greater community surveillance and further investigation of carbohydrate receptor-binding properties could provide further insights into norovirus transmission, susceptibility and pathogenesis, and should aid in developing vaccines and antiviral therapies for this common viral disease.