Detection of norovirus-, sapovirus- and rhesus enteric calicivirus-specific antibodies in captive juvenile macaques

Detection of viruses from feces of wild endangered Macaca maura: a potential threat to moor macaque survival and for zoonotic infection

BACKGROUND

To date, there is a scarcity of information and literature on Macaca maura health status relative to viral diseases. The objectives of the present study were to investigate on the potential spread of enteric and non-enteric viruses shed in the environment through a wild macaque feces and to understand the possible interrelation in the spread of zoonotic viruses in a poorly studied geographical area, the Sulawesi Island. This study will also contribute providing useful information on potential threats to the health of this endangered species.

METHODS

The sampling was conducted between 2014 and 2016 in the Bantimurung Bulusaraung National Park, in the south of the Sulawesi Island and non-invasive sampling methods were used to collect fresh stools of the M. maura, one of the seven macaque species endemic to the island of Sulawesi, Indonesia. The population under study consisted in two wild, neighboring social macaque groups with partially overlapping home ranges; twenty-four samples were collected and examined using negative staining electron microscopy and a panel of PCR protocols for the detection of ten RNA and two DNA viruses.

RESULTS

Viral particles resembling parvovirus (5 samples), picornavirus (13 samples) and calicivirus (13 samples) were detected by electron microscopy whereas the PCR panel was negative for the 12 viruses investigated, except for one sample positive for a mosquito flavivirus. The results did not correlate with animal sex; furthermore, because all of the animals were clinically healthy, it was not possible to correlate feces consistency with viral presence.

CONCLUSIONS

As information on viral infections in wild moor macaques remains limited, further studies are yet required to identify the fecal-oral and blood transmitted potentially zoonotic viruses, which may infect the moor macaque and other macaque species endemic to the South Sulawesi Island.

The Coxsackievirus and Adenovirus Receptor, a Required Host Factor for Recovirus Infection, Is a Putative Enteric Calicivirus Receptor

Human norovirus (HuNoV) is a leading cause of acute gastroenteritis in both developed and developing countries. Studies of HuNoV host cell interactions are limited by the lack of a simple, robust cell culture system. Due to their diverse HuNoV-like biological features, including histo-blood group antigen (HBGA) binding, rhesus enteric caliciviruses (ReCVs) are viable surrogate models for HuNoVs. In addition, several ReCV strains can be propagated to high titers in standard nonhuman primate cell lines while causing lytic infection and cell death. To identify the ReCV entry receptor, we performed CRISPR/Cas9 library screening in Vero cells, which identified the coxsackievirus and adenovirus receptor (CAR) as a candidate ReCV entry receptor. We showed that short interfering RNA, anti-human CAR (hCAR) monoclonal antibody RmcB treatment, and recombinant hCAR ectodomain blocked ReCV replication in LLC-MK2 cells. CRISPR/Cas9-targeted knockout of CAR in LLC-MK2 and Vero cells made these cell lines resistant to ReCV infection, and susceptibility to infection could be restored by transient expression of CAR. CHO cells do not express CAR or HBGAs and are resistant to ReCV infection. Recombinant CHO cells stably expressing hCAR or the type B HBGA alone did not support ReCV infection. However, CHO cells expressing both hCAR and the type B HBGA were susceptible to ReCV infection. In summary, we have demonstrated that CAR is required for ReCV infection and most likely is a functional ReCV receptor, but HBGAs are also necessary for infection.IMPORTANCE Because of the lack of a simple and robust human norovirus (HuNoV) cell culture system surrogate, caliciviruses still represent valuable research tools for norovirus research. Due to their remarkable biological similarities to HuNoVs, including the utilization of HBGAs as putative attachment receptors, we used rhesus enteric caliciviruses (ReCVs) to study enteric calicivirus host cell interactions. Using CRISPR/Cas9 library screening and functional assays, we identified and validated the coxsackievirus and adenovirus receptor (CAR) as a functional proteinaceous receptor for ReCVs. Our work demonstrated that CAR and HBGAs both are necessary to convert a nonsusceptible cell line to being susceptible to ReCV infection. Follow-up studies to evaluate the involvement of CAR in HuNoV infections are ongoing.

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.

Leptospira spp., rotavirus, norovirus, and hepatitis E virus surveillance in a wild invasive golden-headed lion tamarin (Leontopithecus chrysomelas; Kuhl, 1820) population from an urban park in Niterói, Rio de Janeiro, Brazil

The world currently faces severe biodiversity losses caused by anthropogenic activities such as deforestation, pollution, the introduction of exotic species, habitat fragmentation, and climate changes. Disease ecology in altered environments is still poorly understood. The golden-headed lion tamarin (GHLT, Leontopithecus chrysomelas) is an endangered species that became invasive in an urban park in Niterói, Rio de Janeiro, Brazil. The initially few invasive GHLT individuals became hundreds, adapted to living in proximity to humans and domestic animals. These GHLTs were captured as part of a conservation project; some animals were translocated to Bahia and some were kept in captivity. This study tested 593 GHLT for Leptospira serology; 100 and 95 GHLT for polymerase chain reaction (PCR) toLeptospira and hepatitis E virus genotype 3 (HEV-3), respectively, and 101 familiar groups for PCR to viruses (rotavirus A, norovirus GI and GII, and HEV-3). One animal had antibodies for Leptospira serovar Shermani and another for serovar Hebdomadis. One saprophyticLeptospira was found by the 16S PCR and sequencing. Viruses were not detected in samples tested. Findings suggest that the epidemiological importance of such pathogens in this GHLT population is either low or nonexistent. These data are important to understand the local disease ecology, as well as monitoring a translocation project, and to contribute data for species conservation.

Seroprevalence for norovirus genogroups GII and GIV in captive non-human primates

Noroviruses (NoVs) are a major cause of epidemic gastroenteritis in children and adults. Several pieces of evidence suggest that viruses genetically and antigenically closely related to human NoVs might infect animals, raising public health concerns about potential cross-species transmission. The natural susceptibility of non-human primates (NPHs) to human NoV infections has already been reported, but a limited amount of data is currently available. In order to start filling this gap, we screened a total of 86 serum samples of seven different species of NPHs housed at the Zoological Garden (Bioparco) of Rome (Italy), collected between 2001 and 2017, using an enzyme-linked immunosorbent assay (ELISA) based on virus-like particles (VLPs) of human GII.4 and GIV.1 NoVs. Antibodies specific for both genotypes were detected with an overall prevalence of 32.6%. In detail, IgG antibodies against GII.4 NoVs were found in 18 Japanese macaques (29.0%, 18/62), a mandrill (10.0%, 1/10), a white-crowned mangabey (16.6%, 1/6) and in an orangutan (33.3%, 1/3). Twelve macaques (19.3%, 12/62), five mandrills (50.0%, 5/10), two chimpanzees (100%, 2/2) and a white-crowned mangabey (16.6%, 1/6) showed antibodies for GIV.1 NoVs. The findings of this study confirm the natural susceptibility of captive NHPs to GII NoV infections. In addition, IgG antibodies against GIV.1 were detected, suggesting that NHPs are exposed to GIV NoVs or to antigenically related NoV strains.

Non-Human Primate Models of Enteric Viral Infections

There is an important role non-human primates (NHP) play in biomedical research. Phylogenetic proximity of any of the NHP species to Homo sapiens assures that much better translatability of research outcomes from model studies involving human diseases can be achieved than from those generated with other pre-clinical systems. Our group and others used during past two decades NHPs in research directed towards viral and autoimmune disorders of the gastrointestinal tract. This review summarizes progress made in the area of enteric viral infections including its applicability to human disease.

The fecal virome of red-crowned cranes

The red-crowned crane is one of the rarest crane species, and its population is decreasing due to loss of habitat, poisoning, and infections. Using a viral metagenomics approach, we analyzed the virome of feces from wild and captive red-crowned cranes, which were pooled separately. Vertebrate viruses belonging to the families Picornaviridae, Parvoviridae, Circoviridae, and Caliciviridae were detected. Among the members of the family Picornaviridae, we found three that appear to represent new genera. Six nearly complete genomes from members of the family Parvoviridae were also obtained, including four new members of the proposed genus “Chapparvovirus”, and two members of the genus Aveparvovirus. Six small circular DNA genomes were also characterized. One nearly complete genome showing a low level of sequence identity to caliciviruses was also characterized. Numerous viruses believed to infect insects, plants, and crustaceans were also identified, which were probably derived from the diet of red-crowned cranes. This study increases our understanding of the enteric virome of red-crowned cranes and provides a baseline for comparison to those of other birds or following disease outbreaks.

Norovirus vaccines: Correlates of protection, challenges and limitations

Norovirus (NoV) is responsible for at least 50% of all gastroenteritis outbreaks worldwide. NoVs are classified into 6 different genogroups (GGI- GGVI) based on the viral capsid protein with NoV genogroup II genotype 4 (GII.4) being the predominant strain causing human diseases. Supportive therapy involving reversal of dehydration and electrolyte deficiency is the main treatment of NoV gastroenteritis. However, the worldwide increased recognition of NoV as an important agent of diarrheal gastroenteritis prompted researchers to focus on establishing preventive strategies conferring long-lasting immunity. This review describes the current status of animal and human vaccine models/studies targeting NoV and addresses the factors hampering the development of a broadly effective vaccine.

Abiotic Stress and Phyllosphere Bacteria Influence the Survival of Human Norovirus and Its Surrogates on Preharvest Leafy Greens

Foodborne outbreaks of human noroviruses (HuNoVs) are frequently associated with leafy greens. Because there is no effective method to eliminate HuNoV from postharvest leafy greens, understanding virus survival under preharvest conditions is crucial. The objective of this study was to evaluate the survival of HuNoV and its surrogate viruses, murine norovirus (MNV), porcine sapovirus (SaV), and Tulane virus (TV), on preharvest lettuce and spinach that were subjected to abiotic stress (physical damage, heat, or flood). We also examined the bacteria culturable from the phyllosphere in response to abiotic stress and in relation to viral persistence. Mature plants were subjected to stressors 2 days prior to inoculation of the viruses on leaves. We quantified the viral RNA, determined the infectivity of the surrogates, and performed bacterial counts on postinoculation days (PIDs) 0, 1, 7, and 14. For both plant types, time exerted significant effects on HuNoV, MNV, SaV, and TV RNA titers, with greater effects being seen for the surrogates. Infectious surrogate viruses were undetectable on PID 14. Only physical damage on PID 14 significantly enhanced HuNoV RNA persistence on lettuce, while the three stressors differentially enhanced the persistence of MNV and TV RNA. Bacterial counts were significantly affected by time and plant type but not by the stressors. However, bacterial counts correlated significantly with HuNoV RNA titers on spinach and with the presence of surrogate viruses on both plant types under various conditions. In conclusion, abiotic stressors and phyllosphere bacterial density may differentially influence the survival of HuNoV and its surrogates on lettuce and spinach, emphasizing the need for the use of preventive measures at the preharvest stage.

The molecular pathology of noroviruses

Norovirus infection in humans typically results in acute gastroenteritis but may also occur in many animal species. Noroviruses are recognized as one of the most common causes of acute gastroenteritis in the world, being responsible for almost 20% of all cases. Despite their prevalence and impact, our knowledge of the norovirus life cycle and the pathological processes associated with norovirus-induced disease is limited. Whilst infection of the intestine is the norm, extraintestinal spread and associated pathologies have also been described. In addition, long-term chronic infections are now recognized as a significant cause of morbidity and mortality in the immunocompromised. This review aims to summarize the current state of knowledge with respect to norovirus pathology and the underlying mechanisms that have been characterized to date.

Rhesus enteric calicivirus surrogate model for human norovirus gastroenteritis

Human noroviruses are one of the major causes of acute gastroenteritis worldwide. Due to the lack of an efficient human norovirus cell culture system coupled with an animal model, human norovirus research mainly relies on human volunteer studies and surrogate models. Current models either utilize human norovirus-infected animals including the gnotobiotic pig or calf and the chimpanzee models, or employ other members of the family Caliciviridae including cell culture propagable surrogate caliciviruses such as the feline calicivirus, murine norovirus and most recently the Tulane virus. One of the major features of human noroviruses is their extreme biological diversity, including genetic, antigenic and histo-blood group antigen binding diversity, and possible differences of virulence and environmental stability. This extreme biological diversity and its effect on intervention/prevention strategies cannot be modelled by uniform groups of surrogates, much less by single isolates. Tulane virus, the prototype recovirus strain, was discovered in 2008. Since then, several other novel recoviruses have been described and cell culture adapted. Recent studies indicate that the epidemiology, the biological features and diversity of recoviruses and the course of infection and clinical disease in recovirus-infected macaques more closely reflect those properties of human noroviruses than any of the current surrogates. This review aims to summarize what is currently known about recoviruses, highlight their biological similarities to human noroviruses and discuss applications of the model in addressing questions relevant for human norovirus research.

Characterization of a novel calicivirus causing systemic infection in atlantic salmon (Salmo salar L.): proposal for a new genus of caliciviridae

The Caliciviridae is a family of viruses infecting humans, a wide range of animals, birds and marine fish and mammals, resulting in a wide spectrum of diseases. We describe the identification and genetic characterization of a novel calicivirus replicating in Atlantic salmon. The virus has a high prevalence in farmed salmon and is found in fish suffering from several diseases and conditions and also in presumable healthy fish. A challenge and vaccination trial shows that the calicivirus replicates in Atlantic salmon and establishes a systemic infection, which can be reduced by vaccination with formalin-inactivated virus preparation. The virus, named Atlantic salmon calicivirus (ASCV), is found in two genetically distinct variants, a cell culture isolated and a variant sequenced directly from field material. The genomes are 7,4 kb and contain two open reading frames where typical conserved amino acid motifs and domains predict a gene order reminiscent of calicivirus genomes. Phylogenetic analysis performed on extracted capsid amino acid sequences segregated the two ASCV variants in a unique cluster sharing root with the branch of noroviruses infecting humans and the unassigned Tulane virus and St-Valérien like viruses, infecting rhesus monkey and pig, respectively, with relatively large distance to the marine calicivirus subgroup of vesiviruses. Based on the analyses presented, the ASCV is predicted to represent a new genus of Caliciviridae for which we propose the name Salovirus.

Relationship between genotypes and serotypes of genogroup 1 recoviruses: a model for human norovirus antigenic diversity

Human norovirus (NoV) research greatly relies on cell culture-propagable surrogate caliciviruses, including murine NoVs and the prototype 'recovirus' (ReCV), Tulane virus. However, the extreme biological diversity of human NoVs cannot be modelled by a uniform group of viruses or single isolate. Based on a diverse group of recently described ReCVs, a more advanced model reflecting human NoV biological diversity is currently under development. Here, we have reported the genotypic and serotypic relationships among 10 G1 ReCV isolates, including Tulane virus and nine other recent cell culture-adapted strains. Based on the amino acid sequences of virus capsid protein, VP1, and classification constraints established for NoVs, G1 ReCVs were separated into three genotypes, with variable organization of the three open reading frames. Interestingly, cross-neutralization plaque assays revealed the existence of four distinct serotypes, two of which were detected among the G1.2 strains. The amino acid (aa) difference between the two G1.2 ReCV serotypes (12%) was less than the minimum 13% difference established between NoV genotypes. Interestingly, one of the G1.3 ReCVs was equally neutralized by antisera raised against the G1.3 (6% aa difference) and G1.1 (25% aa difference) representative strains. These results imply the existence of a large number of human NoV serotypes, but also shared cross-neutralization epitopes between some strains of different genotypes. In conclusion, the newly developed ReCV surrogate model can be applied to address biologically relevant questions pertaining to enteric CV diversity.

Chemical derivatives of a small molecule deubiquitinase inhibitor have antiviral activity against several RNA viruses

Most antiviral treatment options target the invading pathogen and unavoidably encounter loss of efficacy as the pathogen mutates to overcome replication restrictions. A good strategy for circumventing drug resistance, or for pathogens without treatment options, is to target host cell proteins that are utilized by viruses during infection. The small molecule WP1130 is a selective deubiquitinase inhibitor shown previously to successfully reduce replication of noroviruses and some other RNA viruses. In this study, we screened a library of 31 small molecule derivatives of WP1130 to identify compounds that retained the broad-spectrum antiviral activity of the parent compound in vitro but exhibited improved drug-like properties, particularly increased aqueous solubility. Seventeen compounds significantly reduced murine norovirus infection in murine macrophage RAW 264.7 cells, with four causing decreases in viral titers that were similar or slightly better than WP1130 (1.9 to 2.6 log scale). Antiviral activity was observed following pre-treatment and up to 1 hour postinfection in RAW 264.7 cells as well as in primary bone marrow-derived macrophages. Treatment of the human norovirus replicon system cell line with the same four compounds also decreased levels of Norwalk virus RNA. No significant cytotoxicity was observed at the working concentration of 5 µM for all compounds tested. In addition, the WP1130 derivatives maintained their broad-spectrum antiviral activity against other RNA viruses, Sindbis virus, LaCrosse virus, encephalomyocarditis virus, and Tulane virus. Thus, altering structural characteristics of WP1130 can maintain effective broad-spectrum antiviral activity while increasing aqueous solubility.

Familial aggregation of chronic diarrhea disease (CDD) in rhesus macaques (Macaca mulatta)

Chronic diarrheal disease (CDD) is a critical problem for breeders of captive rhesus macaque (Macaca mulatta), as it results in significant levels of morbidity and death annually. As with other inflammatory disorders, CDD is thought to be caused by environmental and/or genetic factors. Although correspondence between the characters defined as Mendelian by pedigree or segregation analysis and functional genes is difficult to establish, such analyses provide essential entry points into understanding CDD in captive bred rhesus macaques. To investigate the familial aggregation of CDD in captive rhesus macaque, we performed pedigree, segregation and heritability analyses on genealogical data from 55 severely affected individuals (probands) through whom relatives with a history of CDD were ascertained from routine computerized colony records comprising vital and demographic statistics of 10,814 rhesus macaques. We identified 175 rhesus macaques with CDD and estimated its incidence as approximately 2% in the colony. The disease strongly clustered in eight multi-generation pedigrees. Inspection of the pedigrees, segregation analysis and heritability estimate of CDD suggest that susceptibility to the disease is under strong genetic control. Identification of the locations of susceptibility genes in the rhesus macaque genome could facilitate the reduction of their frequency in captive breeding facilities.

Presence of antibodies against genogroup VI norovirus in humans

Background

Noroviruses are important enteric pathogens in humans and animals. Recently, we reported a novel canine norovirus (CaNoV) in dogs with diarrhea belonging to a new genogroup (GVI). No data are available on exposure of humans to this virus.

Methods

Sera from 373 small animal veterinarians and 120 age-matched population controls were tested for IgG antibodies to CaNoV by a recombinant virus like particle based enzyme-linked immunosorbent assay.

Results

Antibodies to CaNoV were found in 22.3% of the veterinarians and 5.8% of the control group (p < 0.001). Mean corrected OD₄₅₀ values for CaNoV antibodies were significantly higher in small animal veterinarians compared to the control group.

Conclusions

These findings suggest that CaNoV may infect humans and small animal veterinarians are at an increased risk for exposure to this virus. Additional studies are needed to assess if this virus is able to cause disease in humans.

High incidence of rhesus enteric calicivirus infections and diarrhea in captive juvenile macaques: a likely association

BACKGROUND

The rhesus enteric caliciviruses (ReCVs) were recently described.

METHODS

Prevalence of ReCV antibodies was tested in six species of captive non-human primates.

RESULTS

High ReCV seroprevalence was revealed in rhesus and cynomolgus macaques.

CONCLUSIONS

High rates of ReCV seroprevalence and diarrhea in juvenile macaques suggest that ReCVs may play a role in morbidity.

Experimental inoculation of juvenile rhesus macaques with primate enteric caliciviruses

BACKGROUND

Tissue culture-adapted Tulane virus (TV), a GI.1 rhesus enteric calicivirus (ReCV), and a mixture of GII.2 and GII.4 human norovirus (NoV)-containing stool sample were used to intrastomacheally inoculate juvenile rhesus macaques (Macaca mulatta) in order to evaluate infection caused by these viruses. METHODOLOGY & FINDINGS: Two of the three TV-inoculated macaques developed diarrhea, fever, virus-shedding in stools, inflammation of duodenum and 16-fold increase of TV-neutralizing (VN) serum antibodies but no vomiting or viremia. No VN-antibody responses could be detected against a GI.2 ReCV strain FT285, suggesting that TV and FT285 represent different ReCV serotypes. Both NoV-inoculated macaques remained asymptomatic but with demonstrable virus shedding in one animal. Examination of duodenum biopsies of the TV-inoculated macaques showed lymphocytic infiltration of the lamina propria and villous blunting. TV antigen-positive (TV+) cells were detected in the lamina propria. In most of the TV+ cells TV co-localized perinuclearly with calnexin--an endoplasmic reticulum protein. A few CD20+TV+ double-positive B cells were also identified in duodenum. To corroborate the authenticity of CD20+TV+ B cells, in vitro cultures of peripheral blood mononuclear cells (PBMCs) from healthy macaques were inoculated with TV. Multicolor flow cytometry confirmed the presence of TV antigen-containing B cells of predominantly CD20+HLA-DR+ phenotype. A 2-log increase of viral RNA by 6 days post inoculation (p<0.05) suggested active TV replication in cultured lymphocytes.

CONCLUSIONS/SIGNIFICANCE

Taken together, our results show that ReCVs represent an alternative cell culture and animal model to study enteric calicivirus replication, pathogenesis and immunity.

Discovery and genomic characterization of a novel bat sapovirus with unusual genomic features and phylogenetic position

Sapovirus is a genus of caliciviruses that are known to cause enteric disease in humans and animals. There is considerable genetic diversity among the sapoviruses, which are classified into different genogroups based on phylogenetic analysis of the full-length capsid protein sequence. While several mammalian species, including humans, pigs, minks, and dogs, have been identified as animal hosts for sapoviruses, there were no reports of sapoviruses in bats in spite of their biological diversity. In this report, we present the results of a targeted surveillance study in different bat species in Hong Kong. Five of the 321 specimens from the bat species, Hipposideros pomona, were found to be positive for sapoviruses by RT-PCR. Complete or nearly full-length genome sequences of approximately 7.7 kb in length were obtained for three strains, which showed similar organization of the genome compared to other sapoviruses. Interestingly, they possess many genomic features atypical of most sapoviruses, like high G+C content and minimal CpG suppression. Phylogenetic analysis of the viral proteins suggested that the bat sapovirus descended from an ancestral sapovirus lineage and is most closely related to the porcine sapoviruses. Codon usage analysis showed that the bat sapovirus genome has greater codon usage bias relative to other sapovirus genomes. In summary, we report the discovery and genomic characterization of the first bat calicivirus, which appears to have evolved under different conditions after early divergence from other sapovirus lineages.

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.

Genetic diversity and histo-blood group antigen interactions of rhesus enteric caliciviruses

Recently, we reported the discovery and characterization of Tulane virus (TV), a novel rhesus calicivirus (CV) (T. Farkas, K. Sestak, C. Wei, and X. Jiang, J. Virol. 82:5408-5416, 2008). TV grows well in tissue culture, and it represents a new genus within Caliciviridae, with the proposed name of Recovirus. We also reported a high prevalence of CV antibodies in macaques of the Tulane National Primate Research Center (TNPRC) colony, including anti-norovirus (NoV), anti-sapovirus (SaV), and anti-TV (T. Farkas, J. Dufour, X. Jiang, and K. Sestak, J. Gen. Virol. 91:734-738, 2010). To broaden our knowledge about CV infections in captive nonhuman primates (NHP), 500 rhesus macaque stool samples collected from breeding colony TNPRC macaques were tested for CVs. Fifty-seven (11%) samples contained recovirus isolates. In addition, one NoV was detected. Phylogenetic analysis classified the recovirus isolates into two genogroups and at least four genetic types. The rhesus NoV isolate was closely related to GII human NoVs. TV-neutralizing antibodies were detected in 88% of serum samples obtained from primate caretakers. Binding and plaque reduction assays revealed the involvement of type A and B histo-blood group antigens (HBGA) in TV infection. Taken together, these findings indicate the zoonotic potential of primate CVs. The discovery of a genetically diverse and prevalent group of primate CVs and remarkable similarities between rhesus enteric CVs and human NoVs opens new possibilities for research involving in vitro and in vivo models of human NoV gastroenteritis.

Antiviral strategies to control calicivirus infections

Caliciviridae are human or non-human pathogenic viruses with a high diversity. Some members of the Caliciviridae, i.e. human pathogenic norovirus or rabbit hemorrhagic disease virus (RHDV), are worldwide emerging pathogens. The norovirus is the major cause of viral gastroenteritis worldwide, accounting for about 85% of the outbreaks in Europe between 1995 and 2000. In the United States, 25 million cases of infection are reported each year. Since its emergence in 1984 as an agent of fatal hemorrhagic diseases in rabbits, RHDV has killed millions of rabbits and has been dispersed to all of the inhabitable continents.

In view of their successful and apparently increasing emergence, the development of antiviral strategies to control infections due to these viral pathogens has now become an important issue in medicine and veterinary medicine. Antiviral strategies have to be based on an understanding of the epidemiology, transmission, clinical symptoms, viral replication and immunity to infection resulting from infection by these viruses. Here, we provide an overview of the mechanisms underlying calicivirus infection, focusing on the molecular aspects of replication in the host cell. Recent experimental data generated through an international collaboration on structural biology, virology and drug design within the European consortium VIZIER is also presented. Based on this analysis, we propose antiviral strategies that may significantly impact on the epidemiological characteristics of these highly successful viral pathogens.