A highly divergent enteric calicivirus in a bovine calf in India.

A highly divergent bovine calicivirus was identified in an Indian calf with enteritis. The whole genome of this virus was sequenced, revealing distinct amino acid motifs in the polyprotein encoded by open reading frame 1 (ORF1) that are unique to caliciviruses. Phylogenetic analysis showed that it was related to members of the genus Nebovirus of the family Caliciviridae. Although it showed only 33.7-34.2% sequence identity in the VP1 protein to the nebovirus prototype strains, it showed 90.6% identity in VP1 to Kirklareli virus, a nebovirus detected in calves with enteritis in Turkey in 2012. An in-house-designed and optimized reverse transcription polymerase chain reaction (RT-PCR) assay was used to screen 120 archived bovine diarrhoeic fecal samples, 40 each from the Indian states of Uttar Pradesh, Haryana, and Himachal Pradesh, revealing frequent circulation of these divergent caliciviruses in the bovine population, with an overall positivity rate of 64.17% (77/120). This underscores the importance of conducting a comprehensive investigation of the prevalence of these divergent caliciviruses and assessing their associations with other pathogens responsible for enteritis in India.

Murine Norovirus: Additional Protocols for Basic and Antiviral Studies.

Murine norovirus (MNV) is a positive-sense, plus-stranded RNA virus in the Caliciviridae family. Viruses in this family replicate in the intestine and are transmitted by the fecal-oral route. MNV is related to the human noroviruses, which cause the majority of nonbacterial gastroenteritis worldwide. Given the technical challenges in studying human norovirus, MNV is often used to study mechanisms in norovirus biology since it combines the availability of a cell culture and reverse genetics system with the ability to study infection in the native host. Adding to our previous protocol collection, here we describe additional techniques that have since been developed to study MNV biology. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Indirect method for measuring cell cytotoxicity and antiviral activity Basic Protocol 2: Measuring murine norovirus genome titers by RT-qPCR Support Protocol 1: Preparation of standard Basic Protocol 3: Generation of recombinant murine norovirus with minimal passaging Basic Protocol 4: Generation of recombinant murine norovirus via circular polymerase extension reaction (CPER) Basic Protocol 5: Expression of norovirus NS1-2 in insect cell suspension cultures using a recombinant baculovirus Support Protocol 2: Isotope labelling of norovirus NS1-2 in insect cells Support Protocol 3: Purification of the norovirus NS1-2 protein Support Protocol 4: Expression of norovirus NS1-2 in mammalian cells by transduction with a recombinant baculovirus Basic Protocol 6: Infection of enteroids in transwell inserts with murine norovirus Support Protocol 5: Preparation of conditioned medium for enteroids culture Support Protocol 6: Isolation of crypts for enteroids generation Support Protocol 7: Enteroid culture passaging and maintenance Basic Protocol 7: Quantification of murine norovirus-induced diarrhea using neonatal mouse infections Alternate Protocol 1: Intragastric inoculation of neonatal mice Alternate Protocol 2: Scoring colon contents.

Isolation of a rhesus calicivirus that can replicate in human cells.

Recoviruses (rhesus enteric caliciviruses) are members of the Caliciviridae family. They are a valuable model for studying human caliciviruses such as noroviruses. It has been suggested that some recoviruses may infect humans, which necessitates detailed studies on the cell type tropism of recoviruses. For the recoviruses that have been cultured to date, successful growth has only been reported in monkey kidney cell lines, precluding their use to study virus interactions with human cells. We isolated and characterized a new recovirus, Recovirus Mo/TG30/2012, from monkey stool which grew efficiently in the monkey kidney cell line LLC-MK2. Notably, the virus can infect and replicate in several human cell lines derived from different organs. The ability to infect a human cell culture system with a recovirus expands our understanding of the potential for spillover to humans as well as increases the value of recoviruses as a model of human caliciviruses.

Characterization of a Novel RNA Virus Causing Massive Mortality in Yellow Catfish, Pelteobagrus fulvidraco, as an Emerging Genus in Caliciviridae (Picornavirales).

An emerging disease in farmed yellow catfish (Pelteobagrus fulvidraco) causing massive mortality broke out in 2020 in Hubei, China. Histopathological examination indicated significant changes in kidneys and spleens of diseased fish. Electron microscopy revealed large numbers of viral particles in the kidneys and spleens. These particles were spherical with a diameter of approximately 35 nm. By using RNA sequencing and rapid identification of cDNA ends, the full nucleotide sequence of the virus was identified. The viral genome comprises 7,432 bp and contains three open reading frames sharing no nucleotide sequence similarity with other viruses; however, the amino acid sequence partially matched that of the nonstructural (NS) proteins from viruses in the order Picornavirales. Combined with the phylogenetic analysis, the conserved amino acid motifs and the domains of the viral genome predict a genome order typical of a calicivirus. Therefore, this virus was tentatively named yellow catfish calicivirus (YcCV). Cell culture showed that YcCV could cause a cytopathic effect in the channel catfish kidney cell line (CCK) at early passages. In artificial infection, this virus could infect healthy yellow catfish and led to clinical symptoms similar to those that occurred naturally. In situ hybridization analysis detected positive signals of the virus in kidney, spleen, liver, heart, and gill tissues of diseased fish. This study represents the first report of calicivirus infection in yellow catfish and provides a solid basis for future studies on the control of this viral disease. IMPORTANCE Caliciviruses are rapidly evolving viruses that cause pandemic outbreaks associated with significant morbidity and mortality globally. A novel calicivirus identified from yellow catfish also causes substantial mortality. Using an RNA sequencing (RNA-seq) and rapid amplification of cDNA ends (RACE) method, the full nucleotide sequence was identified and characterized, and this virus was tentatively named yellow catfish calicivirus (YcCV). A nucleotide sequence similarity search found no match with other viruses, and an amino acid sequence comparison indicated approximately 23.3% amino acid homology with the viruses in the order Picornavirales. These findings may represent a new avenue to explain virus evolution and suggest a need to further study the pathogenesis of calicivirus and characterize possible interactions among interspecific viruses in the aquaculture environment.

PseudoRHDV constructed with feline calicivirus genome as vector has the characteristics of well proliferation in vitro.

Rabbit hemorrhagic disease virus (RHDV) is a major member of the Caliciviridae. which is fatal to wild and domestic European rabbit. Because RHDV does not reproduce stably in vitro, molecular studies on this pathogen have been limited. Feline calicivirus (FCV), also a member of the Caliciviridae, reproduces well in vitro and is a good viral vector. As these viruses share similar genomic structures, we hypothesized that a chimeric infectious clone could be constructed by replacing the corresponding regions of the FCV genome with the structural proteins VP60 and VP10 and the 3' non-translated region of the RHDV genome. Transfection of the infectious clone into RK13 cells made it possible to rescue the chimeric virus, named pseudoRHDV, which reproduced in an RK13 cell line with high titer. An infectious pseudoRHDV was produced, which proliferated in RK13 cells to at least 15 generations. PseudoRHDV caused significant cytopathic changes in the RK13 cells, with a viral titer was 9.74 log10 TCID50 / mL. The pseudoRHDV constructed in this study will be helpful for investigating the molecular biology of RHDV, especially its interaction with the host. The model can also be used to explore some common laws between FCV and RHDV.

High Prevalence and Diversity of Caliciviruses in a Community Setting Determined by a Metagenomic Approach.

We recently carried out a metagenomic study to determine the fecal virome of infants during their first year of life in a semirural community in Mexico. A total of 97 stool samples from nine children were collected starting 2 weeks after birth and monthly thereafter until 12 months of age. In this work, we describe the prevalence and incidence of caliciviruses in this birth cohort. We found that 54 (56%) and 24 (25%) of the samples were positive for norovirus and sapovirus sequence reads detected by next-generation sequencing, respectively. Potential infections were arbitrarily considered when at least 20% of the complete virus genome was determined. Considering only these samples, there were 3 cases per child/year for norovirus and 0.33 cases per child/year for sapovirus. All nine children had sequence reads related to norovirus in at least 2 and up to 10 samples, and 8 children excreted sapovirus sequence reads in 1 and up to 5 samples during the study. The virus in 35 samples could be genotyped. The results showed a high diversity of both norovirus (GI.3[P13], GI.5, GII.4, GII.4[P16], GII.7[P7], and GII.17[P17]) and sapovirus (GI.1, GI.7, and GII.4) in the community. Of interest, despite the frequent detection of caliciviruses in the stools, all children remained asymptomatic during the study. Our results clearly show that metagenomic studies in stools may reveal a detailed picture of the prevalence and diversity of gastrointestinal viruses in the human gut during the first year of life. IMPORTANCE Human caliciviruses are important etiological agents of acute gastroenteritis in children under 5 years of age. Several studies have characterized their association with childhood diarrhea and their presence in nondiarrheal stool samples. In this work, we used a next-generation sequencing approach to determine, in a longitudinal study, the fecal virome of infants during their first year of life. Using this method, we found that caliciviruses can be detected significantly more frequently than previously reported, providing a more detailed picture of the prevalence and genetic diversity of these viruses in the human gut during early life.

Horizontal gene transfer as a mechanism for the promiscuous acquisition of distinct classes of IRES by avian caliciviruses.

In contrast to members of Picornaviridae which have long 5'-untranslated regions (5'UTRs) containing internal ribosomal entry sites (IRESs) that form five distinct classes, members of Caliciviridae typically have short 5'UTRs and initiation of translation on them is mediated by interaction of the viral 5'-terminal genome-linked protein (VPg) with subunits of eIF4F rather than by an IRES. The recent description of calicivirus genomes with 500-900nt long 5'UTRs was therefore unexpected and prompted us to examine them in detail. Sequence analysis and structural modelling of the atypically long 5'UTRs of Caliciviridae sp. isolate yc-13 and six other caliciviruses suggested that they contain picornavirus-like type 2 IRESs, whereas ruddy turnstone calicivirus (RTCV) and Caliciviridae sp. isolate hwf182cal1 calicivirus contain type 4 and type 5 IRESs, respectively. The suggestion that initiation on RTCV mRNA occurs by the type 4 IRES mechanism was confirmed experimentally using in vitro reconstitution. The high sequence identity between identified calicivirus IRESs and specific picornavirus IRESs suggests a common evolutionary origin. These calicivirus IRESs occur in a single phylogenetic branch of Caliciviridae and were likely acquired by horizontal gene transfer.

Comparison of gut viral communities in diarrhoea and healthy dairy calves.

Calf diarrhoea has been a major cause of economic losses in the global dairy industry. Many factors, including multiple pathogen infections, can directly or indirectly cause calf diarrhoea. This study compared the faecal virome between 15 healthy calves and 15 calves with diarrhoea. Significantly lower diversity of viruses was found in samples from animals with diarrhoea than those in the healthy ones, and this feature may also be related to the age of the calves. Viruses belonging to the families Astroviridae and Caliciviridae that may cause diarrhoea in dairy calves have been characterized, which revealed that reads of caliciviruses and astroviruses in diarrhoea calves were much higher than those in healthy calves. Five complete genomic sequences closely related to Smacoviridae have been identified, which may participate in the regulation of the gut virus community ecology of healthy hosts together with bacteriophages. This research provides a theoretical basis for further understanding of known or potential enteric pathogens related to calf diarrhoea.

Generation of Nucleic Acid Aptamer Candidates against a Novel Calicivirus Protein Target.

Human norovirus is the leading cause of foodborne illness globally. One of the challenges in detecting noroviruses is the identification of a completely broadly reactive ligand; however, all detection ligands generated to date target the viral capsid, the outermost of which is the most variable region of the genome. The VPg is a protein covalently linked to the viral genome that is necessary for replication but hitherto remains underexplored as a target for detection or therapeutics. The purpose of this work was to generate nucleic acid aptamers against human norovirus (Norwalk) and cultivable surrogate (Tulane) VPgs for future use in detection and therapeutics. Eight rounds of positive-SELEX and two rounds of counter-SELEX were performed. Five and eight unique aptamer sequences were identified for Norwalk and Tulane VPg, respectively, all of which were predicted to be stable (∆G < -5.0) and one of which occurred in both pools. All candidates displayed binding to both Tulane and Norwalk VPg (positive:negative > 5.0), and all but two of the candidates displayed very strong binding (positive:negative > 10.0), significantly higher than binding to the negative control protein (p < 0.05). Overall, this work reports a number of aptamer candidates found to be broadly reactive and specific for in vitro-expressed VPgs across genus that could be used for future application in detection or therapeutics. Future work characterizing binding of the aptamer candidates against native VPgs and in therapeutic applications is needed to further evaluate their application.

Protein Nucleotidylylation in +ssRNA Viruses.

Nucleotidylylation is a post-transcriptional modification important for replication in the picornavirus supergroup of RNA viruses, including members of the Caliciviridae, Coronaviridae, Picornaviridae and Potyviridae virus families. This modification occurs when the RNA-dependent RNA polymerase (RdRp) attaches one or more nucleotides to a target protein through a nucleotidyl-transferase reaction. The most characterized nucleotidylylation target is VPg (viral protein genome-linked), a protein linked to the 5' end of the genome in Caliciviridae, Picornaviridae and Potyviridae. The nucleotidylylation of VPg by RdRp is a critical step for the VPg protein to act as a primer for genome replication and, in Caliciviridae and Potyviridae, for the initiation of translation. In contrast, Coronaviridae do not express a VPg protein, but the nucleotidylylation of proteins involved in replication initiation is critical for genome replication. Furthermore, the RdRp proteins of the viruses that perform nucleotidylylation are themselves nucleotidylylated, and in the case of coronavirus, this has been shown to be essential for viral replication. This review focuses on nucleotidylylation within the picornavirus supergroup of viruses, including the proteins that are modified, what is known about the nucleotidylylation process and the roles that these modifications have in the viral life cycle.

Pooled analysis of LAMP assay for the diagnosis of norovirus infection.

BACKGROUND: Rapid laboratory detection is essential to diagnose norovirus infection. LAMP has many advantages compared with RT-PCR for detecting norovirus, including high sensitivity, high specificity, rapidity, low cost, and intuitive results, which can be easily read with the naked eye with the help of color-based reporters. In this study, we intend to analyze the accuracy of LAMP methods for the diagnosis of norovirus infection. METHODS: Two researchers independently retrieved relevant literature up to January 2021 (PubMed, Web of Science, Cochrane Library, Embase, CNKI, Wan Fang, and VIP). The researchers screened all articles and extracted their research data for meta-analysis. QUADAS-2 tool was used to evaluate the quality of the included studies by Review Manager 5.3. Forest plots were performed by Meta-DiSc 1.4 to evaluate the accuracy of the test. Deeks' funnel plot symmetry tests were conducted by Stata 15.0 to check the potential publication bias. RESULTS: Eleven sets of data extracted from the eight included studies were included for meta-analysis. For the detection of norovirus, the pooled sensitivity, specificity, positive LR, negative LR, diagnostic OR, and their 95% CI were 0.96 (0.95-0.97), 0.99 (0.99-1.00), 91.14 (31.88-260.56), 0.06 (0.04-0.09), and 1473.68 (562.96-3857.70), respectively. Besides, AUC in the SROC curve was 0.9920. CONCLUSION: LAMP had high sensitivity and specificity in terms of the diagnosis of norovirus infection. However, further extension of this approach should be researched to ensure the accuracy and practicability of this hopeful test in the future.

Evidence of independent introductions of RHDV2 strains in Poland based on the genome analysis of viral isolates from 2016-2018.

The aim of this study was the molecular epidemiology of independently introduced RHDV2 strains in Poland. The nucleotide sequences of RHDV2 diagnosed in domestic rabbits in 2018 in the voivodeships of Swietokrzyskie (strain PIN), Malopolskie (strain LIB) and Mazowieckie (strain WAK), and RHDVa from 2015 (strain F77-3) recognized in wild rabbits in Kujawsko-Pomorskie voivodeship were compared to the genome sequences of the first native RHDV2 strains from 2016-2017. The reference sequences available in public databases, the representative for a classical RHDV (G1-G5 genogroups), RHDVa (G6), non-pathogenic caliciviruses (RCV, GI.3 and GI.4) as well as original and recombinant RHDV2 isolates were included for this analysis. Nucleotide sequence similarity among the most distanced RHDV2 strains isolated in Poland in 2018 was from 92.3% to 98.2% in the genome sequence encoding ORF1, ORF2 and 3'UTR, between 94.8-98.7% in the VP60 gene and between 91.3-98.1% in non-structural proteins (NSP) region. The diversity between three RHDV2 and RHDVa from 2015 was up to 16.3% in the VP60 region. Similarities are shown for the VP60 tree within the RHDV2 group, however, the nucleotide analysis of NSP region revealed the differences between older and new native RHDV2 strains. The Polish RHDV2 isolates from 2016-2017 clustered together with RHDV G1/RHDV2 recombinants, first identified in the Iberian Peninsula in 2012, while all strains from 2018 are close to the original RHDV2. The F77-3 strain clustered to well supported RHDVa (G6) genetic group, together with other Polish and European RHDVa isolates. Based on the results of phylogenetic characterization of RHDV2 strains detected in Poland between 2016-2018 and the chronology of their emergence it can be concluded that RHDV2 strains of 2018 and RHDV2 strains of 2016-2017 were introduced independently thus confirming their different origin and simultaneous pathway of spreading.

Rapid detection of H146-like goose calicivirus using a TaqMan-based real-time PCR assay.

H146-like goose-origin calicivirus (H146-like GCV) is a novel Caliciviridae family member in the Sanovirus genus that was recently discovered and proposed to cause runting-stunting syndrome and urate deposition in geese. At present, however, there is a lack of epidemiological information pertaining to the dynamics and distribution of H146-like GCV. The development of novel molecular diagnostic approaches capable of rapidly and accurately detecting this virus would support the strengthening, the prevention, and control of H146-like GCV infection. In the present study, we therefore used a TaqMan probe and primers specific for the viral nonstructural (NS) gene to develop a highly sensitive and specific PCR assay capable of detecting this H146-like GCV. The assay reproducibly detected 5.07 × 102 copies of a recombinant DNA plasmid containing the NS gene, with a dynamic range of 8 orders of magnitude (102-109 copies). Importantly, no cross-reactivity was observed with common viruses that affected waterfowl, and when we used this assay to evaluate clinical samples, we found it to be more sensitive and faster than traditional PCR. In summary, herein, we developed a novel TaqMan-based real-time PCR approach that could reliably detect and diagnose H146-like GCV. This tool will allow for the real-time diagnosis of H146-like GCV infections, enabling researchers to better understand the epidemiology and clinical presentation of this disease.

Genomic characterization of a nebovirus strain with a novel RdRp genotype in yaks.

Neboviruses (NeVs) are important causative agents of calf diarrhea that belong to the family Caliciviridae. In this study, we investigated the genomic characteristics of a NeV strain from yaks that has a novel RdRp genotype. The complete genome of this strain (YAK/NRG-A9/19/CH) is 7454 nt in length and shares 68.3%-79.7% nt sequence identity with those of other NeVs. The RNA-dependent RNA polymerase (RdRp) gene of this strain shares 66.5%-78.5% nt sequence identity (74.0%-89.3% aa sequence identity) with the eight available complete NeV RdRp sequences, and a phylogenetic analysis based on these sequences showed that the new strain formed an independent branch, indicating that the RdRp of strain YAK/NRG-A9/19/CH may represent a novel RdRp genotype of NeV. These results contribute to a further understanding of the molecular characteristics and genetic evolution of NeVs.

Molecular survey of parvovirus, astrovirus, coronavirus, and calicivirus in symptomatic dogs.

Gastrointestinal disorders caused by enteric viruses are frequently reported in dogs worldwide, with significant mortality rates in unvaccinated individuals. This study reports the identification and molecular characterization of Canine parvovirus (CPV-2), Canine coronavirus (CcoV), Canine astrovirus (AstV), and Canine calicivirus (CcaV) in a panel of dogs showing severe enteric clinical signs sampled in a typical Mediterranean environment (Sardinia, Italy). At least one of these viral species was detected in 92.3% samples. CPV-2 was the most frequently detected virus (87.2%), followed by AsTv (20.5%), CCoV-IIa (18%), and CCoV-I (10.3%). CCoV-IIb and CaCV were not detected in any sample. Single infection was detected in 24 samples (66.7%), mainly related to CPV-2 (91.7%). Coinfections were present in 33.3% samples with constant detection of CPV-2. Canine coronavirus was present only in coinfected animals. The VP2 sequence analysis of CPV-2 positive samples confirmed the presence of all variants, with CPV-2b most frequently detected. Phylogeny based on the CcoV-IIa spike protein (S) gene allowed to identify 2 different clades among Sardinian isolates but failed to distinguish enteric from pantropic viruses. Study on presence and prevalence of enteroviruses in dogs increase our knowledge about the circulation of these pathogens in the Mediterranean area and highlight the need for dedicated routine vaccine prophylaxis. Molecular analyses of enteric viruses are fundamental to avoid failure of vaccines caused by frequent mutations observed in these enteroviruses.

The Dynamic Life of Virus Capsids.

Protein-shelled viruses have been thought as "tin cans" that merely carry the genomic cargo from cell to cell. However, through the years, it has become clear that viruses such as rhinoviruses and caliciviruses are active and dynamic structures waiting for the right environmental cues to deliver their genomic payload to the host cell. In the case of human rhinoviruses, the capsid has empty cavities that decrease the energy required to cause conformational changes, resulting in the capsids "breathing", waiting for the moment when the receptor binds for it to release its genome. Most strikingly, the buried N-termini of VP1 and VP4 are transiently exposed during this process. A more recent example of a "living" protein capsid is mouse norovirus (MNV). This family of viruses have a large protruding (P) domain that is loosely attached to the shell via a single-polypeptide tether. Small molecules found in the gut, such as bile salts, cause the P domains to rotate and collapse onto the shell surface. Concomitantly, bile alters the conformation of the P domain itself from one that binds antibodies to one that recognizes receptors. In this way, MNV appears to use capsid flexibility to present one face to the immune system and a completely different one to attack the host tissue. Therefore, it appears that even protein-shelled viruses have developed an impressive array of tricks to dodge our immune system and efficiently attack the host.

Comparison of Illumina MiSeq and the Ion Torrent PGM and S5 platforms for whole-genome sequencing of picornaviruses and caliciviruses.

Next-generation sequencing is a powerful tool for virological surveillance. While Illumina® and Ion Torrent® sequencing platforms are used extensively for generating viral RNA genome sequences, there is limited data comparing different platforms. The Illumina MiSeq, Ion Torrent PGM and Ion Torrent S5 platforms were evaluated using a panel of sixteen specimens containing picornaviruses and human caliciviruses (noroviruses and sapoviruses). The specimens were processed, using combinations of three library preparation and five sequencing kits, to assess the quality and completeness of assembled viral genomes, and an estimation of cost per sample to generate the data was calculated. The choice of library preparation kit and sequencing platform was found to impact the breadth of genome coverage and accuracy of consensus viral genomes. The Ion Torrent S5 510 chip runs produced more reads at a lower cost per sample than the highest output Ion Torrent PGM 318 chip run, and generated the highest proportion of reads for enterovirus D68 samples. However, indels at homopolymer regions impacted the accuracy of consensus genome sequences. For lower throughput sequencing runs (i.e., Ion Torrent 510 and Illumina MiSeq Nano V2), the cost per sample was lower on the MiSeq platform, whereas with higher throughput runs (Ion Torrent 530 and Illumina MiSeq V2) there is less of a difference in the cost per sample between the two sequencing platforms ($5.47-$10.25 more per sample for an Ion Torrent 530 chip run when multiplexing 24 samples). These findings suggest that the Ion Torrent S5 and Illumina MiSeq platforms are both viable options for genomic sequencing of RNA viruses, each with specific advantages and tradeoffs.

Development of an EvaGreen based real-time RT-PCR assay for rapid detection, quantitation and diagnosis of goose calicivirus.

An unclassified calicivirus (CV) detected in geese was recently reported and proposed as a new member of the family Caliciviridae. There is limited information about the epidemiology, etiology and detection method of goose-origin CV (GCV) to date. In this study, an EvaGreen based fluorescence quantitative real-time RT-PCR assay was developed and optimized for the detection of GCVs. The assay sensitively detected GCV RNA template with a good linear standard curve. We also demonstrated the specificity and reproducibility of the detection method for GCVs. Thus, the method developed in this study will benefit the investigation of possible sporadic outbreaks of CV infections in geese, as well as epidemiological and etiological studies of GCVs.

Immune Response Modulation by Caliciviruses.

Noroviruses and Sapoviruses, classified in the Caliciviridae family, are small positive-stranded RNA viruses, considered nowadays the leading cause of acute gastroenteritis globally in both children and adults. Although most noroviruses have been associated with gastrointestinal disease in humans, almost 50 years after its discovery, there is still a lack of comprehensive evidence regarding its biology and pathogenesis mainly because they can be neither conveniently grown in cultured cells nor propagated in animal models. However, other members of this family such as Feline calicivirus (FCV), Murine norovirus (MNV), Rabbit hemorrhagic disease virus (RHDV), and Porcine sapovirus (PS), from which there are accessible propagation systems, have been useful to study the calicivirus replication strategies. Using cell cultures and animal models, many of the functions of the viral proteins in the viral replication cycles have been well-characterized. Moreover, evidence of the role of viral proteins from different members of the family in the establishment of infection has been generated and the mechanism of their immunopathogenesis begins to be understood. In this review, we discuss different aspects of how caliciviruses are implicated in membrane rearrangements, apoptosis, and evasion of the immune responses, highlighting some of the pathogenic mechanisms triggered by different members of the Caliciviridae family.

ICTV Virus Taxonomy Profile: Caliciviridae.

The family Caliciviridae includes viruses with single-stranded, positive-sense RNA genomes of 7.4-8.3 kb. The most clinically important representatives are human noroviruses, which are a leading cause of acute gastroenteritis in humans. Virions are non-enveloped with icosahedral symmetry. Members of seven genera infect mammals (Lagovirus, Norovirus, Nebovirus, Recovirus, Sapovirus, Valovirus and Vesivirus), members of two genera infect birds (Bavovirus and Nacovirus), and members of two genera infect fish (Minovirus and Salovirus). This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Caliciviridae, which is available at ictv.global/report/caliciviridae.