Prevalence and molecular characterization of human group C rotaviruses in Hungary

Multiple reassortment and interspecies transmission events contribute to the diversity of porcine-like human rotavirus C strains detected in South Korea

Globally, rotavirus C (RVC) causes diarrhoeal outbreaks, mainly in swine, with sporadic incidents in human, bovine, and canine populations. In this study, two human RVC strains, RVC/Human-wt/KOR/CAU13-1-77/2013 and RVC/Human-wt/KOR/CAU14-1-242/2014, were isolated in South Korea, and their complete genome sequences were compared with those of other human- and animal-origin RVC strains found worldwide. Genetic analysis revealed that these viruses have a G4-P[2]-I2-R2-C2-M3-A2-N2-T2-E2-H2 genotype constellation. Phylogenetic analysis indicated that these Korean RVC strains belong to the M3 lineage of the VP3 gene in human RVC from Japan and China and porcine RVC from Japan. These results suggest that RVC circulates in northeast Asia in both the human and porcine populations. These results also provide evidence of interspecies RVC reassortment events.

Porcine Rotaviruses: Epidemiology, Immune Responses and Control Strategies

Rotaviruses (RVs) are a major cause of acute viral gastroenteritis in young animals and children worldwide. Immunocompetent adults of different species become resistant to clinical disease due to post-infection immunity, immune system maturation and gut physiological changes. Of the 9 RV genogroups (A–I), RV A, B, and C (RVA, RVB, and RVC, respectively) are associated with diarrhea in piglets. Although discovered decades ago, porcine genogroup E RVs (RVE) are uncommon and their pathogenesis is not studied well. The presence of porcine RV H (RVH), a newly defined distinct genogroup, was recently confirmed in diarrheic pigs in Japan, Brazil, and the US. The complex epidemiology, pathogenicity and high genetic diversity of porcine RVAs are widely recognized and well-studied. More recent data show a significant genetic diversity based on the VP7 gene analysis of RVB and C strains in pigs. In this review, we will summarize previous and recent research to provide insights on historic and current prevalence and genetic diversity of porcine RVs in different geographic regions and production systems. We will also provide a brief overview of immune responses to porcine RVs, available control strategies and zoonotic potential of different RV genotypes. An improved understanding of the above parameters may lead to the development of more optimal strategies to manage RV diarrheal disease in swine and humans.

Analysis of the full genome of human group C rotaviruses reveals lineage diversification and reassortment

Group C rotaviruses (RVC) are enteric pathogens of humans and animals. Whole-genome sequences are available only for few RVCs, leaving gaps in our knowledge about their genetic diversity. We determined the full-length genome sequence of two human RVCs (PR2593/2004 and PR713/2012), detected in Italy from hospital-based surveillance for rotavirus infection in 2004 and 2012. In the 11 RNA genomic segments, the two Italian RVCs segregated within separate intra-genotypic lineages showed variation ranging from 1.9 % (VP6) to 15.9 % (VP3) at the nucleotide level. Comprehensive analysis of human RVC sequences available in the databases allowed us to reveal the existence of at least two major genome configurations, defined as type I and type II. Human RVCs of type I were all associated with the M3 VP3 genotype, including the Italian strain PR2593/2004. Conversely, human RVCs of type II were all associated with the M2 VP3 genotype, including the Italian strain PR713/2012. Reassortant RVC strains between these major genome configurations were identified. Although only a few full-genome sequences of human RVCs, mostly of Asian origin, are available, the analysis of human RVC sequences retrieved from the databases indicates that at least two intra-genotypic RVC lineages circulate in European countries. Gathering more sequence data is necessary to develop a standardized genotype and intra-genotypic lineage classification system useful for epidemiological investigations and avoiding confusion in the literature.

Zoonotic transmission of rotavirus: surveillance and control

Group A rotavirus (Rotavirus A, RVA) is the main cause of acute dehydrating diarrhea in humans and numerous animal species. RVA shows vast diversity and a variety of human strains share genetic and antigenic features with animal origin RVA strains. This finding suggests that interspecies transmission is an important mechanism of rotavirus evolution and contributes to the diversity of human RVA strains. RVA is responsible for half a million deaths and several million hospitalizations worldwide. Globally, two rotavirus vaccines are available for routine use in infants. These vaccines show a great efficacy profile and induce protective immunity against various rotavirus strains. However, little is known about the long-term evolution and epidemiology of RVA strains under selective pressure related to vaccine use. Continuous strain surveillance in the post-vaccine licensure era is needed to help better understand mechanisms that may affect vaccine effectiveness.

Canine rotavirus C strain detected in Hungary shows marked genotype diversity

Species C rotaviruses (RVC) have been identified in humans and animals, including pigs, cows and ferrets. In dogs, RVC strains have been reported anecdotally on the basis of visualization of rotavirus-like virions by electron microscopy combined with specific electrophoretic migration patterns of the genomic RNA segments. However, no further molecular characterization of these viruses was performed. Here, we report the detection of a canine RVC in the stool of a dog with enteritis. Analysis of the complete viral genome uncovered distinctive genetic features of the identified RVC strain. The genes encoding VP7, VP4 and VP6 were distantly related to those of other RVC strains and were putatively classified as G10, P8 and I8, respectively. The new strain was named RVC/Dog-wt/HUN/KE174/2012/G10P[8]. Phylogenetic analyses revealed that canine RVC was most closely related to bovine RVC strains with the exception of the NSP4 gene, which clustered together with porcine RVC strains. These findings provide further evidence for the genetic diversity of RVC strains.

Diversity of VP7, VP4, VP6, NSP2, NSP4, and NSP5 genes of porcine rotavirus C: phylogenetic analysis and description of potential new VP7, VP4, VP6, and NSP4 genotypes

Rotavirus C (RVC) is a cause of gastroenteritis in swine and has a worldwide distribution. A total of 448 intestinal or faecal samples from pigs of all ages were tested for viruses causing gastroenteritis. RVC was detected in 118 samples (26.3%). To gain information on virus diversity, the complete coding nucleotide sequences of the VP7, VP4, VP6, NSP2, NSP4, and NSP5 genes of seven RVC strains were determined. Phylogenetic analysis of VP7 nucleotide sequence divided studied Czech strains into six G genotypes (G1, G3, G5-G7, and a newly described G10 genotype) based on an 85% identity cutoff value at the nucleotide level. Analysis of the VP4 gene revealed low nucleotide sequence identities between two Czech strains and other porcine (72.2-75.3%), bovine (74.1-74.6%), and human (69.1-69.3%) RVC strains. Thus, we propose that those two Czech porcine strains comprise a new RVC VP4 genotype, P8. Analysis of the VP6 gene showed 79.9-86.8% similarity at the nucleotide level between the Czech strains and other porcine RVC strains. According to the 87% identity cutoff value, we propose the existence of three new RVC VP6 genotypes, I8-I10. Analysis of the NSP4 gene divided porcine RVC strains into two clusters (the E1 genotype and the new E4 genotype, based on an 85% nucleotide sequence identity cutoff value). Our results indicate a degree of high genetic heterogeneity, not only in the variable VP7 and VP4 genes encoding the outer capsid proteins, but also in more-conserved genes encoding the inner capsid protein VP6 and the non-structural proteins NSP2, NSP4, and NSP5. This emphasizes the need for a whole-genome-sequence-based classification system.

Prevalence of Rotaviruses Groups A and C in Egyptian Children and Aquatic Environment

The objective of this study is to compare the prevalence of rotaviruses groups A and C in Egyptian children and aquatic environment. From 110 stool specimens of children with acute diarrhea and using RT-PCR, 35 samples (31.8 %) were positive for human rotavirus group A and 15 samples (13.6 %) were positive for human rotavirus group C. From 96 samples collected from Zenin wastewater treatment plant over a 2-year period (November 2009-October 2011) and using RT-PCR, rotavirus group A was detected in (4/24) 16.7 %, (5/24) 20.8 %, (4/24) 16.7 %, and (4/24) 16.7 %, while rotavirus group C was detected in (2/24) 8.3 %, (3/24) 12.5 %, (3/24) 12.5 %, and (0/24) 0 % in raw sewage, after primary sedimentation, after secondary sedimentation, and after final chlorination, respectively. Moreover, from 96 samples collected from El-Giza water treatment plant over a 2-year period (November 2009-October 2011), rotavirus group A was detected in (7/24) 29.2 %, (6/24) 25 %, (5/24) 20.8 %, and (3/24) 12.5 %, while rotavirus group C was detected in (3/24) 12.5 %, (1/24) 4.2 %, (1/24) 4.2 %, and (0/24) 0 % in raw Nile water, after sedimentation, after sand filtration, and after final chlorination, respectively. Using SYBR Green real-time RT-PCR, the number of human rotavirus group A genome or infectious units was higher than rotavirus group C. VP6 sequence analysis of the RT-PCR positive rotavirus group C samples revealed that four clinical specimens and three environmental samples showed similar sequences clustered with Moduganari/Human Nigerian strain AF 325806 with 98 % homology, and two clinical specimens and one environmental sample showed similar sequences clustered with Dhaka CB/Human Bangladesh strain AY 754826 with 97 % homology.

Phylogenetic analysis of human group C rotavirus circulating in Brazil reveals a potential unique NSP4 genetic variant and high similarity with Asian strains

Group C rotaviruses (RVC) cause gastroenteritis in humans and animals worldwide, and the evidence for a possible zoonotic role has been recently provided. To gain information on the genetic diversity and relationships between human and animal RVC, we sequenced the VP4, VP7, and NSP4 genes of 12, 19, and 15 human strains, respectively, detected in São Paulo state during historical (1988 and 1993) and recent (2007 and 2008) Brazilian rotavirus surveillance. All RVC strains analyzed in the present study grouped into human genotype (G4-P[2]-E2), and did not show any evidence of animal ancestry. Phylogenetic analysis showed that RVC samples detected in 1988 and 1993 clustered together with strains from distinct continents, indicating that historical RVC strains circulating in São Paulo were closely related to those strains circulating worldwide. All three genes (VP7, VP4 and NSP4) of São Paulo RVC strains isolated in 2007-2008 exhibited close phylogenetic relationship with human RVC strains isolated in China and Japan, suggesting that they are genetically linked, and that a gene flow could be occurring between this Asian countries and Brazil. We identified two distinct clusters in the NSP4 phylogenetic tree. One cluster formed exclusively by human Brazilian strains detected in 1997 and 2003-2004 in Rio de Janeiro, Bahia, and Rio Grande do Sul states (Subgroup II) previously described in a different study, that displayed low sequence identities to other human strains formerly published, and to the Brazilian RVC strains (Subgroup I) characterized in the present study. These data suggests the circulation of two genetic profiles of the NSP4 gene in Brazil. High sequence diversity in NSP4 gene was previously reported in Asia, and additional diversity in NSP4 RVC strains spreading in the world should be expected. More in-depth molecular and epidemiological analysis of human RVC throughout the world will be needed to understand their diversity and clarify their evolution, as well as to develop classifications schemes.

VP6 gene diversity in 11 Brazilian strains of porcine group C rotavirus

Porcine group C rotavirus (RVC) is recognised as an enteric pathogen in piglets worldwide. The VP6 gene of RVC is divided into seven I-genotypes. Genotypes I2 and I3 are found in human and bovine strains, respectively; the porcine strains are divided into the other five genotypes (I1, I4-I7). In this study, molecular analysis of nearly the full length of the VP6 gene was performed in 11 Brazilian wild-type porcine RVC strains identified in diarrhoeic faecal samples, which were collected from eight pig farms located in five Brazilian states from piglets of 1-4 weeks of age. The nucleotide sequences of the VP6 gene showed 82.9-100 % identity between the Brazilian strains, 84.9-93.1 % with the prototype Cowden strain, and 82.4-92.2 % with other porcine RVC strains. In the 11 diarrhoeic faecal samples analysed in this study, three distinct porcine RVC genotypes (I1, I5, and I6) were identified and none were predominant. The results presented in this study revealed a high nucleotide diversity of the VP6 gene in porcine RVC field strains circulating in Brazil, which highlights the importance of further epidemiological and molecular surveys worldwide.

Prevalence study and phylogenetic analysis of group C porcine rotavirus in the Czech Republic revealed a high level of VP6 gene heterogeneity within porcine cluster I1

Group C rotavirus (RVC) has been described to be a causative agent of gastroenteritis in humans and animals. In the current study, the presence of porcine RVC was confirmed in 25.6 % of 293 porcine faecal samples collected from seven Czech farms. A significantly larger (p < 0.05) number of RVC-positive samples was detected in groups of finisher pigs and post-weaning piglets (4-12 weeks of age). Phylogenetic analysis of nine RVC-positive Czech strains and their comparison with available sequence data for the gene encoding RVC group antigen VP6 revealed two separate lineages within porcine cluster I1.

Epidemiological and genetic analysis of human group C rotaviruses isolated from outbreaks of acute gastroenteritis in Yokohama, Japan, between 2006 and 2012

Group C rotavirus (GCRV) infection has been described in several parts of the world, predominantly as sporadic cases of acute gastroenteritis. Little is known about the yearly changes in the GCRV strains from diarrheal outbreaks. Stool samples collected from outbreaks of acute gastroenteritis in Yokohama, Japan, between 2006 and 2012 that were negative for norovirus, sapovirus, and group A rotavirus, were screened for GCRV using a reverse passive hemagglutination method. The GCRV strains were characterized by nucleotide sequence and phylogenetic analysis of their VP6, VP7, VP4, and NSP4 genes. Samples from nine of 735 outbreaks in Yokohama (1 %) contained GCRV, and eight of these outbreaks occurred in primary schools. The nucleotide sequences of the strains detected in this study were more closely related to Asian strains than to those from other regions of the world. The nucleotide sequences of the VP7 gene in these nine strains differed, and yearly changes were observed in the amino acid sequences of the VP4 genes. Phylogenetic trees constructed using the nucleotide sequences of the VP6, VP7, VP4, and NSP4 genes showed that sublineage S1 has divided into S1-1 and S1-2 in the VP4 gene only. Our results confirm that the prevalent strains of GCRV change yearly in Yokohama. This is the first study to demonstrate GCRV-associated gastroenteritis outbreaks in Yokohama, Japan.

Monitoring of group C rotavirus in children with acute gastroenteritis in Brazil: an emergent epidemiological issue after rotavirus vaccine?

Group C rotavirus (GpCRV) has a worldwide distribution; however, its epidemiology and ecology are still unclear. Evidence for a possible zoonotic role has been postulated recently for Brazilian children strains. The aim of this study was to monitor GpCRV in children ≤15 years with acute gastroenteritis during the 2007-2010 national Brazilian rotavirus surveillance, and to undertake the molecular characterization of the major VP6 capsid protein. A total of 3,019 fecal samples were first screened for Group A rotavirus (GpARV). A total of 2,205 GpARV ELISA negative samples were tested further for the presence of GpCRV by SDS-PAGE, electronic microscopy, and RT-PCR for the VP6 gene. The genetic diversity of GpCRV was carried out by sequencing the VP6 gene. GpARV and GpCRV infections were detected in 24.6% (742/3,019) and 0.3% (8/3,019), respectively. The GpCRV detection rate increased from 0.2% (1/422) in 2007 to 1% (7/708) in 2008, and GpCRV cases were not detected in 2009 and 2010. The phylogenetic analysis indicated that the strains belonged to the human lineage, and showed a genetic relationship with the GpCRV strain from Japan isolated in 2009. None of the study sequences was related closely to animal GpCRV strains. This study provides further evidence that GpCRV is a minor cause of acute childhood gastroenteritis in Brazil, and does not suggest that GpCRV may assume epidemiological importance in the future, even after the introduction of a GpARV vaccine. In addition, the molecular analyses of the GpCRV samples in this study do not support the zoonotic hypothesis.

Burden of rotavirus gastroenteritis in the pediatric population in Central and Eastern Europe: serotype distribution and burden of illness

BACKGROUND

Rotaviral gastroenteritis (RVGE) is the leading cause of severe diarrhea in children under five years of age worldwide. This comprehensive review aims to estimate the burden of RVGE among children in Central and Eastern Europe.

METHODS

An extensive search of the biomedical literature (1999-2009) was conducted in major databases. Studies pertaining to the epidemiology and burden of rotavirus in Central and Eastern Europe were captured and data from each country was systematically extracted and compared.

RESULTS

This literature search captured 38 studies pertaining to RVGE infection in the region. Among children under 15 years of age, RVGE accounted for between 22.0% and 55.3% of all cases of acute gastroenteritis per year. For most countries RVGE was most common in the winter months, although it was reported year round in Bulgaria. Geographical comparison of genotyping data revealed that three genotype combinations, G1P[8], G4P[8], and G2P[4] were present in all countries for which full genotyping data was available. Genotype predominance varied on a season to season basis within each country. Only limited data was available for healthcare resource utilization, and economic burden for this region.

CONCLUSIONS

RVGE is a common disease associated with significant morbidity, and mortality. While three genotype combinations currently predominate in the region, the dominance of a certain serotype can change dramatically from year to year and from country to country. A vaccination program with broad serotype coverage may help to decrease the burden of RVGE in Central and Eastern Europe.

Zoonotic aspects of rotaviruses

Rotaviruses are important enteric pathogens of humans and animals. Group A rotaviruses (GARVs) account for up to 1 million children deaths each year, chiefly in developing countries and human vaccines are now available in many countries. Rotavirus-associated enteritis is a major problem in livestock animals, notably in young calves and piglets. Early in the epidemiological GARV studies in humans, either sporadic cases or epidemics by atypical, animal-like GARV strains were described. Complete genome sequencing of human and animal GARV strains has revealed a striking genetic heterogeneity in the 11 double stranded RNA segments across different rotavirus strains and has provided evidence for frequent intersections between the evolution of human and animal rotaviruses, as a result of multiple, repeated events of interspecies transmission and subsequent adaptation.

Detection and characterization of group C rotavirus in Buenos Aires, Argentina, 1997-2003

The role of group C rotaviruses as a cause of diarrhea was examined among children <17 years of age admitted to a Hospital in a suburban area of Buenos Aires, Argentina between 1997 and 2003. A total of 1,579 fecal samples were screened for group A (RVA) and C (RVC) rotaviruses by two in-house ELISA methods at Quilmes University (UNQ-ELISA). Samples positive, doubtful and negative by RVC specific UNQ-ELISA (n = 246) were examined further for RVC by another in-house ELISA (CDC-ELISA), electron microscopy, RT-PCR, nested PCR, and Southern hybridization. Sensitivity, specificity, and predictive values for each test were determined. While the sensitivity was comparable for the nested PCR and CDC-ELISA methods (82.5%), the molecular methods were slightly more specific. Poorly preserved particles were often seen in fecal samples, suggesting that degradation of RNA could be a factor influencing the performance of molecular methods. The incidence of RVC was estimated to be 3% without apparent differences among seasons. RVC infected patients had a significantly (P < 0.001) higher median age (6 years vs. 1 year) than those with RVA infection. Sequence of the RVC VP7 gene from six Argentinean strains and sequences reported previously in different countries showed high nucleotide (94.4-99.9%) sequence identities, indicating a high degree of conservation for human RVC VP7 genes among strains collected on five continents over a period of 17 years. These findings indicate that RVC is a significant cause of diarrhea and it is necessary to develop simple and sensitive serological methods for its detection.

Detection and molecular characterization of porcine group C rotaviruses in South Korea

Group C rotaviruses (GCRVs) cause acute diarrhea in humans and animals worldwide and the evidence for a possible zoonotic role of GCRVs has been recently provided. However, there is little evidence of porcine GCRV infections or of their genetic diversity in South Korea. We examined 137 diarrheic fecal specimens from 55 farms collected from six provinces. RT-PCR utilizing primer pairs specific for the GCRV VP6 gene detected GCRV-positive reactions in 36 (26.2%) diarrheic fecal samples. Of these, 17 samples (12.4%) tested positive for porcine GCRVs alone and 19 samples (13.8%) were also positive for other pathogens. Other enteric pathogens except for GCRV were detected in 64 feces samples (46.7%) and no enteric pathogens were evident in 37 feces samples (27.0%). Phylogenetic and sequence homology analyses of GCRV partial VP6 gene between 23 Korean and other known porcine GCRVs demonstrated that Korean strains belonged to the porcine lineage. Furthermore, one Korean porcine strain shared the highest nucleotide (89.7–89.0%) and deduced amino acid sequence (92.9–93.9%) identities with bovine GCRV strains and was placed in the bovine GCRV lineage indicative of bovine origin. In conclusion, porcine GCRV infections are widespread in piglets with diarrhea in South Korea. The infecting porcine GCRVs mostly belong to the porcine lineage with the exception of one bovine-like GCRV, which possibly originated from bovine GCRV due to interspecies transmission.

Detection and characterization of group C rotaviruses in asymptomatic piglets in Ireland

Group C rotaviruses are important human enteric pathogens that have also been detected in a variety of mammalian species, including pigs. Group C rotaviruses have been identified in piglets with diarrhea, but their ecology remains to be elucidated. By screening of 292 fecal samples collected from 4- to 5-week-old asymptomatic pigs from four herds in Ireland between 2005 and 2007, 13 (4.4%) samples tested positive by reverse transcription-PCR for group C rotavirus. Group A rotaviruses were also detected in 19 samples but not in conjunction with group C viruses. The gene encoding the major group C neutralization antigen, the outer capsid protein VP7, was sequenced. The majority of the strains were very closely related to each other (>99% amino acid [aa] identity) and were characterized as genogroup G1 since they were genetically related to the prototype porcine strain Cowden (92.6% aa identity). Conversely, two strains (1GA/05/Cork/Ire and 281/07/Dublin/Ire) were characterized as genogroup G6 since they displayed the highest identity (89.2 to 94.0% aa) to porcine G6 strains (43/06-22-like). Unexpectedly, one such G6 strain, 1GA/05/Cork/Ire, lacked the 4-aa insertion in the VP7 variable region VR8 found in all the other G6 group C rotaviruses. This study provides evidence that porcine group C rotavirus may be detected not infrequently in asymptomatic piglets. In addition, it provides evidence that, unlike the human viruses, porcine group C rotaviruses display broad genetic heterogeneity, which may pose a challenge for the development of prophylactic tools.

Detection and quantification of group C rotaviruses in communal sewage

Group C rotaviruses have been recognized as a cause of acute gastroenteritis in humans, cattle, and swine, although the true epidemiologic and clinical importance of this virus in these hosts has not yet been fully established. A real-time PCR assay based on a broadly reactive primer pair was developed and used to quantitatively determine the viral load of group C rotaviruses in environmental samples. A total of 35 raw and 35 treated sewage samples collected at the same sampling time in four Hungarian sewage treatment plants during a survey in 2005 were tested for the presence of group C rotaviruses. The overall detection rates were 91% (32 of 35) for the influent and 57% (20 of 35) for the effluent samples. Molecular characterization of the amplified partial VP6 gene revealed the cocirculation of human and animal (i.e., bovine and porcine) strains that were easily distinguishable by melting curve analysis. Human strains yielded relatively high viral loads (mean, 1.2 x 10(7); median, 6.9 x 10(5) genome equivalents per liter influent sewage) and appeared to display seasonal activity over the study period, whereas animal strains appeared to circulate throughout the year at much lower average titers (bovine strains mean, 9.9 x 10(4); median, 3.0 x 10(4); porcine strains mean, 3.9 x 10(4); median, 3.1 x 10(4) genome equivalents per liter influent sewage). Our findings suggest that monitoring of communal sewage may provide a good surrogate for investigating the epidemiology and ecology of group C rotaviruses in humans and animals.

Genetic heterogeneity in the VP7 of group C rotaviruses

Evidence for a possible zoonotic role of group C rotaviruses (GCRVs) has been recently provided. To gain information on the genetic relationships between human and animal GCRVs, we sequenced the VP7 gene of 10 porcine strains detected during a large surveillance study from different outbreaks of gastroenteritis in piglets. Four GCRV strains were genetically related to the prototype GCRV porcine Cowden strain. A completely new VP7 genotype included 4 strains (344/04-7-like) that shared 92.5% to 97.0% aa identity to each other, but <83% to human GCRVs and <79% to other porcine and bovine GCRVs. A unique 4-aa insertion (SSSV or SSTI), within a variable region at the carboxy-terminus of VP7, represented a distinctive feature for these 4 unique strains. An additional strain, 134/04-18, was clearly different from all human and animal GCRVs (<85% aa identity) and likely accounts for a distinct VP7 genotype. The VP7 of a unique strain, 42/05-21, shared similar ranges of aa sequence identities with porcine and human strains (88.0-90.7% to porcine GCRVs and 85.2-88.2% to human GCRVs). Plotting the VP7 gene of strain 42/05-21 against the VP7 of human and porcine strains revealed discontinuous evolution rates throughout the VP7 molecule, suggesting different mutational pressure or a remote intragenic recombination event. These findings provide the need for future epidemiological surveys and warrant studies to investigate the pathogenic potential of these novel GCRVs in pigs.