Vesivirus viremia and seroprevalence in humans

A systematic review on global zoonotic virus-associated mortality events in marine mammals

Marine mammals play a critical role as sentinels for tracking the spread of zoonotic diseases, with viruses being the primary causative factor behind infectious disease induced mortality events. A systematic review was conducted to document marine mammal mortality events attributed to zoonotic viral infections in published literature across the globe. This rigorous search strategy yielded 2883 studies with 88 meeting inclusion criteria. The studies spanned from 1989 to 2023, with a peak in publications observed in 2020. Most of the included studies were retrospective, providing valuable insights into historical trends. The United States (U.S.) reported the highest number of mortality events followed by Spain, Italy, Brazil and the United Kingdom. Harbor seals were the most impacted species, particularly in regions like Anholt, Denmark and the New England Coast, U.S. Analysis revealed six main viruses responsible for mortality events, with Morbillivirus causing the highest proportion of deaths. Notably, the occurrence of these viral events varied geographically, with distinct patterns observed in different regions. Immunohistochemistry emerged as the most employed detection method. This study underscores the importance of global surveillance efforts in understanding and mitigating the impact of viral infections on marine mammal populations, thereby emphasizing the necessity of collaborative One Health approaches to address emerging threats at the human-animal-environment interface. Additionally, the potential transfer of zoonotic viruses to aquatic organisms used in food production, such as fish and shellfish, highlights the broader implications for food safety, food security and public health.

Multiple novel caliciviruses identified from stoats (Mustela erminea) in the United Kingdom

The Caliciviridae family, comprising positive-sense RNA viruses, is characterised by its non-enveloped, small virions, broad host range, and notable tendency for host switching. These viruses are primarily associated with gastroenteric disease, though they can lead to haemorrhagic or respiratory infections. Our study employed a metagenomics analysis of faecal samples from stoats (Mustela erminea), identifying two novel calicivirus species, named stoat vesivirus and stoat valovirus. Stoat vesivirus was identified in three samples (ST008, ST006, ST004), exhibiting a genome wide nucleotide identity of approximately 92 %. The complete coding sequences of these samples were 8471 (ST004) and 8322 (ST006) nucleotides in length, respectively. Each comprised three open reading frames (ORF), closely resembling the Vesivirus mink calicivirus (China/2/2016), with 70-72 % similarity in ORF1, 61-62 % in ORF2 and 71 % in ORF3. Phylogenetic analysis robustly supported stoat vesivirus as belonging within the Vesivirus genus. The second calivicirus (stoat valovirus), detected solely in sample ST008, was 6527 nucleotides in length and with complete coding sequences present. It shared highest similarity with St-Valérien swine virus and marmot norovirus HT16, showing 39.5 and 38.8 % protein identity with ORF1 and 43.3 and 42.9 % for VP1. Stoat valovirus is borderline for meeting the ICTV criteria for a new genus, demonstrating 60 % divergence in ORF1 compared to the other valovirus', however it clusters basally within the Valovirus genus, supporting leaving it included in this genus.

Comprehensive Genomics Investigation of Neboviruses Reveals Distinct Codon Usage Patterns and Host Specificity

Neboviruses (NeVs) from the Caliciviridae family have been linked to enteric diseases in bovines and have been detected worldwide. As viruses rely entirely on the cellular machinery of the host for replication, their ability to thrive in a specific host is greatly impacted by the specific codon usage preferences. Here, we systematically analyzed the codon usage bias in NeVs to explore the genetic and evolutionary patterns. Relative Synonymous Codon Usage and Effective Number of Codon analyses indicated a marginally lower codon usage bias in NeVs, predominantly influenced by the nucleotide compositional constraints. Nonetheless, NeVs showed a higher codon usage bias for codons containing G/C at the third codon position. The neutrality plot analysis revealed natural selection as the primary factor that shaped the codon usage bias in both the VP1 (82%) and VP2 (57%) genes of NeVs. Furthermore, the NeVs showed a highly comparable codon usage pattern to bovines, as reflected through Codon Adaptation Index and Relative Codon Deoptimization Index analyses. Notably, yak NeVs showed considerably different nucleotide compositional constraints and mutational pressure compared to bovine NeVs, which appear to be predominantly host-driven. This study sheds light on the genetic mechanism driving NeVs' adaptability, evolution, and fitness to their host species.

Molecular Identification of Enteric Viruses in Domestic Animals in Northeastern Gabon, Central Africa

Astroviruses (AstVs), enteroviruses (EVs), and caliciviruses (CaVs) infect several vertebrate taxa. Transmitted through the fecal-oral route, these enteric viruses are highly resistant and can survive in the environment, thereby increasing their zoonotic potential. Here, we screened for AstVs, EVs, and CaVs to investigate the role of domestic animals in the emergence of zoonoses, because they are situated at the human/wildlife interface, particularly in rural forested areas in Central Africa. Rectal swabs were obtained from 123 goats, 41 sheep, and 76 dogs in 10 villages located in northeastern Gabon. Extracted RNA reverse-transcribed into cDNA was used to detect AstVs, EVs, and CaVs by amplification of the RNA-dependent RNA polymerase (RdRp), or capsid protein (VP1) gene using PCR. A total of 23 samples tested positive, including 17 goats for AstVs, 2 goats, 2 sheep, 1 dog for EVs, and 1 dog for CaVs. Phylogenetic analyses revealed that AstV RdRp sequences clustered with sheep-, goat-, or bovine-related AstVs. In addition, one goat and two sheep VP1 sequences clustered with caprine/ovine-related Evs within the Enterovirus G species, and the CaV was a canine vesivirus. However, human-pathogenic Evs, EV-B80 and EV-C99, were detected in goats and dogs, raising questions on the maintenance of viruses able to infect humans.

A novel vesivirus (family Caliciviridae) in European badgers (Meles meles) in Hungary, 2020/2021

In this study, a novel vesivirus (family Caliciviridae) was detected and characterized in faecal and tissue (blood and spleen) specimens collected from three (23.1%) out of 13 European badgers (Meles meles) in Hungary that were tested using RT-PCR and sequencing methods. The complete genome of the vesivirus strain European badger/B40/2021/HUN (OQ161773) is 8,375 nucleotides in length. The ORF1, ORF2, and ORF3 proteins have 81.1%, 70.5%, and 64.2% amino acid sequence identity, respectively, to the corresponding proteins of Asian badger vesivirus, which was first reported in badgers in China in 2022. These results indicate that more than one lineage/species of vesiviruses circulates in mustelid badgers in geographically different regions.

Caliciviridae Other Than Noroviruses

Besides noroviruses, the Caliciviridae family comprises four other accepted genera: Sapovirus, Lagovirus, Vesivirus, and Nebovirus. There are six new genera proposed: Recovirus, Valovirus, Bavovirus, Nacovirus, Minovirus, and Salovirus. All Caliciviridae have closely related genome structures, but are genetically and antigenically highly diverse and infect a wide range of mammalian host species including humans. Recombination in nature is not infrequent for most of the Caliciviridae, contributing to their diversity. Sapovirus infections cause diarrhoea in pigs, humans and other mammalian hosts. Lagovirus infections cause systemic haemorrhagic disease in rabbits and hares, and vesivirus infections lead to lung disease in cats, vesicular disease in swine, and exanthema and diseases of the reproductive system in large sea mammals. Neboviruses are an enteric pathogen of cattle, differing from bovine norovirus. At present, only a few selected caliciviruses can be propagated in cell culture (permanent cell lines or enteroids), and for most of the cultivatable caliciviruses helper virus-free, plasmid only-based reverse genetics systems have been established. The replication cycles of the caliciviruses are similar as far as they have been explored: viruses interact with a multitude of cell surface attachment factors (glycans) and co-receptors (proteins) for adsorption and penetration, use cellular membranes for the formation of replication complexes and have developed mechanisms to circumvent innate immune responses. Vaccines have been developed against lagoviruses and vesiviruses, and are under development against human noroviruses.

The Threat from Viruses

Infectious disease represent the most significant threat to human health. Significant geologic cataclysmic events have caused the extinction of countless species, but these “Wrath of God” events predate the emergence of Homo sapiens. Pandemic infections have accompanied the rise of human civilization frequently re-occurring leaving a lasting imprint on human history punctuated by profound loss of life. Emerging infections become endemic and are here to stay marking their presence with an annual death toll. Each decade brings a new onslaught of emerging infectious agents. We are surprised again and again but are never prepared. The long-term consequences often remain unrecognized and are always inconvenient including cancer, cardiovascular disease and immune associated diseases that threaten our health. Reliance on clusters of clinical symptoms in the face of diverse and non-descriptive viral infection symptoms is a foolhardy form of crisis management. Viral success is based on rapid replication resulting in large numbers. Single-stranded RNA viruses with their high replication error rate represent a paradigm for resilience.

Molecular Detection of Circovirus and Adenovirus in Feces of Fur Seals (Arctocephalus spp.)

In some regions, little is known about exposure to viruses in coastal marine mammals. The present study aimed to detect viral RNA or DNA in 23 free-ranging fur seals on the northern coastline of Rio Grande do Sul State, Brazil. Polymerase chain reaction was used to detect nucleic acids of circoviruses, adenoviruses, morbilliviruses, vesiviruses, and coronaviruses in the feces from twenty-one South American fur seals (Arctocephalus australis) and two Subantarctic fur seals (A. tropicalis). Adenovirus DNA fragments were detected in two South American fur seals; nucleotide sequences of these fragments revealed a high degree of similarity to human adenovirus type C. Circovirus DNA fragments were detected in six animals of the same species. Two were phylogenetically similar to the Circovirus genus, whereas the other four nucleotide fragments showed no similarity to any of the known genera within the family Circoviridae. RNA fragments indicating the presence of coronavirus, vesivirus, and morbillivirus were not detected. These findings suggest that adenoviruses and circoviruses are circulating in fur seal populations found along the coast of Rio Grande do Sul State, Brazil.

Identification of Human Junctional Adhesion Molecule 1 as a Functional Receptor for the Hom-1 Calicivirus on Human Cells

The Hom-1 vesivirus was reported in 1998 following the inadvertent transmission of the animal calicivirus San Miguel sea lion virus to a human host in a laboratory. We characterized the Hom-1 strain and investigated the mechanism by which human cells could be infected. An expression library of 3,559 human plasma membrane proteins was screened for reactivity with Hom-1 virus-like particles, and a single interacting protein, human junctional adhesion molecule 1 (hJAM1), was identified. Transient expression of hJAM1 conferred susceptibility to Hom-1 infection on nonpermissive Chinese hamster ovary (CHO) cells. Virus infection was markedly inhibited when CHO cells stably expressing hJAM were pretreated with anti-hJAM1 monoclonal antibodies. Cell lines of human origin were tested for growth of Hom-1, and efficient replication was observed in HepG2, HuH7, and SK-CO15 cells. The three cell lines (of hepatic or intestinal origin) were confirmed to express hJAM1 on their surface, and clustered regularly interspaced short palindromic repeats/Cas9-mediated knockout of the hJAM1 gene in each line abolished Hom-1 propagation. Taken together, our data indicate that entry of the Hom-1 vesivirus into these permissive human cell lines is mediated by the plasma membrane protein hJAM1 as a functional receptor.IMPORTANCE Vesiviruses, such as San Miguel sea lion virus and feline calicivirus, are typically associated with infection in animal hosts. Following the accidental infection of a laboratory worker with San Miguel sea lion virus, a related virus was isolated in cell culture and named Hom-1. In this study, we found that Hom-1 could be propagated in a number of human cell lines, making it the first calicivirus to replicate efficiently in cultured human cells. Screening of a library of human cell surface membrane proteins showed that the virus could utilize human junctional adhesion molecule 1 as a receptor to enter cells and initiate replication. The Hom-1 virus presents a new system for the study of calicivirus biology and species specificity.

Elevated post-transfusion serum transaminase values associated with a highly significant trend for increasing prevalence of anti-Vesivirus antibody in Korean patients

A highly significant increase in anti-Vesivirus (family Caliciviridae) antibody prevalence, along the axis from healthy blood donors; donors with elevated transaminase; patients with clinical hepatitis; and patients with post-transfusion/dialysis hepatitis, has been reported in human sera from the USA and Europe. Asian samples have now been tested retrospectively using serology and enzyme immunoassay (EIA) with a Vesivirus partial-capsid antigen expressed as a fusion protein. Anti-vesiviral antibodies were measured by optical densities (OD(650)) and compared in patients separated by age, gender and Groups A-F as follows: Control Group A, an Experimental Group B, which was divided further into Group C, patients with elevated enzymes (alanine transaminase (ALT), aspartate transaminase (AST), and γ-glutamyl transpeptidase (γ-GT); Group D, patients receiving transfused blood; Group E, patients with high enzyme levels after transfusion; and Group F, hepatitis B and C positive patients. Using multivariate logistic regression analyses, a significantly greater proportion of patients receiving transfusion(s), were positive for anti-Vesivirus antibody compared with non-transfused patients (P = 0.008; OR: 3.86, 95% CI: 1.43-10.43). Also, anti-Vesivirus antibody was significantly associated with elevated biochemical liver function tests: ALT ≥ 20 IU or AST ≥ 120 IU (P = 0.017; OR: 4.23, 95% CI: 1.30-13.80). In the blood transfusion group, anti-Vesivirus antibody was significantly correlated with high enzyme levels (ALT, P = 0.018; AST, P = 0.010; γ-GT, P = 0.020). These data provide serologic evidence of vesiviral transfusion-transmission-associated disease, which could include infection of any organ system where cytopathology resulted in high levels of either ALT or AST.

Marine mammal zoonoses: a review of disease manifestations

Marine mammals evoke strong public affection as well as considerable scientific interest. However, the resultant close contact with marine wildlife poses human health risks, including traumatic injury and zoonotic disease transmission. The majority of zoonotic marine mammal diseases result in localized skin infections in man that resolve spontaneously or with appropriate medical therapy. However, other marine mammal zoonoses, if left untreated, induce life‐threatening systemic diseases that could pose public health risks. As the number of zoonotic diseases rises, the diagnosis of and treatment for these emerging pathogens pose special challenges requiring the expertise of physicians, veterinarians and wildlife biologists. Here, we provide a comprehensive review of the bacterial, viral and fungal marine mammal zoonotic diseases that we hope will be utilized by public health professionals, physicians, veterinarians and wildlife biologists to better understand, diagnose and prevent marine mammal zoonotic diseases.

The fecal viral flora of California sea lions

California sea lions are one of the major marine mammal species along the Pacific coast of North America. Sea lions are susceptible to a wide variety of viruses, some of which can be transmitted to or from terrestrial mammals. Using an unbiased viral metagenomic approach, we surveyed the fecal virome in California sea lions of different ages and health statuses. Averages of 1.6 and 2.5 distinct mammalian viral species were shed by pups and juvenile sea lions, respectively. Previously undescribed mammalian viruses from four RNA virus families (Astroviridae, Picornaviridae, Caliciviridae, and Reoviridae) and one DNA virus family (Parvoviridae) were characterized. The first complete or partial genomes of sapeloviruses, sapoviruses, noroviruses, and bocavirus in marine mammals are reported. Astroviruses and bocaviruses showed the highest prevalence and abundance in California sea lion feces. The diversity of bacteriophages was higher in unweaned sea lion pups than in juveniles and animals in rehabilitation, where the phage community consisted largely of phages related to the family Microviridae. This study increases our understanding of the viral diversity in marine mammals, highlights the high rate of enteric viral infections in these highly social carnivores, and may be used as a baseline viral survey for comparison with samples from California sea lions during unexplained disease outbreaks.

Metagenomics for the discovery of novel human viruses

Modern laboratory techniques for the detection of novel human viruses are greatly needed as physicians and epidemiologists increasingly deal with infectious diseases caused by new or previously unrecognized pathogens. There are many clinical syndromes in which viruses are suspected to play a role, but for which traditional microbiology techniques routinely fail in uncovering the etiologic agent. In addition, new viruses continue to challenge the human population owing to the encroachment of human settlements into animal and livestock habitats, globalization, climate change, growing numbers of immunocompromised people and bioterrorism. Metagenomics-based tools, such as microarrays and high-throughput sequencing are ideal for responding to these challenges. Pan-viral microarrays, containing representative sequences from all known viruses, have been used to detect novel and distantly-related variants of known viruses. Sequencing-based methods have also been successfully employed to detect novel viruses and have the potential to detect the full spectrum of viruses, including those present in low numbers.

Molecular characterization and phylogenetic analysis of the complete genome of a porcine sapovirus from Chinese swine

Background

Porcine sapovirus was first identified in the United States in 1980, hitherto, several Asian countries have detected this virus. In 2008, the first outbreak of gastroenteritis in piglets caused by porcine sapovirus in China was reported. The complete genome of the identified SaV strain Ch-sw-sav1 was sequenced and analyzed to provide gene profile for this outbreak.

Methods

The whole genome of Ch-sw-sav1 was amplified by RT-PCR and was sequenced. Sequence alignment of the complete genome or RNA dependent RNA polymerase (RdRp) gene was done. 3' end of ORF2 with 21-nt nucleotide insertion was further analyzed using software.

Results

Sequence analysis indicated that the genome of Ch-sw-sav1 was 7541 nucleotide long with two ORFs, excluding the 17 nucleotides ploy (A) at the 3' end. Phylogenetic analysis based on part of RdRp gene of this strain showed that it was classified into subgroup GIII. Sequence alignment indicated that there was an inserted 21-nt long nucleotide sequence at the 3' end of ORF2. The insertion showed high antigenicity index comparing to other regions in ORF2.

Conclusion

Ch-sw-sav1 shared similar genetic profile with an American PEC strain except the 21-nt nucleotide at the 3' end of ORF2. The insert sequence shared high identity with part gene of Sus scrofa clone RP44-484M10.

Characterization of San Miguel sea lion virus populations using pyrosequencing-based methods

San Miguel Sea Lion Virus (SMSV) is a small RNA virus in the genus Vesivirus with an unusually broad host range. Three populations of SMSV were examined by PCR amplification of the capsid precursor and putative helicase genes, followed by pyrosequencing. The populations were nasal swabs from two SMSV infected California sea lions (Zalophus californianus) from two different years, and a virus isolate from the earlier swab that was passaged in cell culture five times. In the capsid precursor, extensive deletions were prevalent in the passaged virus but uncommon in the clinical samples. A greater prevalence of point mutations was seen in the capsid precursor gene than in the putative helicase gene. In culture, the minority sequence in the capsid precursor at nucleotide position 5826 rapidly shifted after five passages to become the majority sequence. Levels of diversity at individual sites showed much more similarity between the two clinical samples than between the earlier clinical sample and the passaged culture from the same sample. SMSV appears to behave as a quasispecies. Assessment of original patient samples is preferable for understanding clinical SMSV populations.

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

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

Expression and self-assembly of virus-like particles from two genotypes of marine vesiviruses and development of an ELISA for the detection of antibodies

Sequences encoding the major and minor capsid proteins (VP1 and VP2) from two marine vesivirus isolates (Steller sea lion viruses V810 and V1415) were engineered for expression of virus-like particles (VLPs) in the baculovirus system. The resulting VLPs were morphologically similar to native vesivirus virions. Purified VLPs were probed in immunoblots with pooled antisera specific for nine San Miguel sea lion virus (SMSV) types, and a predominant protein of approximately 60kDa was detected. An enzyme linked immunosorbent assay (ELISA) for the detection of antibodies was developed in which the VLPs served as antigen. The VLPs were adsorbed to the wells of a microplate, and the specificity of the ELISA was established with hyperimmune sera raised against 24 serotypes of the genus Vesivirus. The ELISA was used to screen for the presence of vesivirus specific antibodies in the sera of free-ranging Steller sea lions. The ELISA results demonstrated that Steller sea lions that inhabit the Pacific Ocean waters of southeast Alaska are widely exposed to antigenically related marine vesiviruses, while no previous exposure could be demonstrated using VLP antigens in 17 Steller sea lions from the Aleutian Islands. The broad reactivity of these VLPs and their non-infectious nature will facilitate global sero-epidemiological studies aimed at determining the incidence and prevalence of marine vesiviruses in mammals that inhabit the Pacific and Atlantic oceans as well as susceptible terrestrial animals.

A capsid gene-based real-time reverse transcription polymerase chain reaction assay for the detection of marine vesiviruses in the Caliciviridae

A real-time reverse transcription polymerase chain reaction (rtRT-PCR) assay was developed for the identification of marine vesiviruses. The primers were designed to target a 176-nucleotide fragment within a highly conserved region of the San Miguel sea lion viruses (SMSVs) capsid gene. The assay detected viral RNA from nine marine vesivirus serotypes described previously, including two serotypes (SMSV-8 and -12) not identified with presently available molecular assays, a highly related bovine vesivirus strain (Bos-1), a mink vesivirus strain (MCV), and two novel genotypes isolated recently from Steller sea lions (SSL V810 and V1415). The real-time assay did not amplify sequences from the corresponding genomic regions of feline calicivirus (also in the genus Vesivirus) and representative members of the genus Norovirus. The rtRT-PCR assay described below may prove useful as a diagnostic tool for the detection of currently circulating, emerging and previously described marine vesiviruses in clinical samples, especially when large numbers are screened in surveillance studies of these restricted viruses.

RNA viruses in the sea

Viruses are ubiquitous in the sea and appear to outnumber all other forms of marine life by at least an order of magnitude. Through selective infection, viruses influence nutrient cycling, community structure, and evolution in the ocean. Over the past 20 years we have learned a great deal about the diversity and ecology of the viruses that constitute the marine virioplankton, but until recently the emphasis has been on DNA viruses. Along with expanding knowledge about RNA viruses that infect important marine animals, recent isolations of RNA viruses that infect single-celled eukaryotes and molecular analyses of the RNA virioplankton have revealed that marine RNA viruses are novel, widespread, and genetically diverse. Discoveries in marine RNA virology are broadening our understanding of the biology, ecology, and evolution of viruses, and the epidemiology of viral diseases, but there is still much that we need to learn about the ecology and diversity of RNA viruses before we can fully appreciate their contributions to the dynamics of marine ecosystems. As a step toward making sense of how RNA viruses contribute to the extraordinary viral diversity in the sea, we summarize in this review what is currently known about RNA viruses that infect marine organisms.

A new generic real-time reverse transcription polymerase chain reaction assay for vesiviruses; vesiviruses were not detected in human samples

Different viruses belonging to the genus Vesivirus infect a broad range of animals, and cause gastroenteritis, vesicular skin lesions, hemorrhagic disease, respiratory diseases and other conditions. A recent report on Vesivirus viremia, as detected by PCR, in samples from patients with hepatitis of unknown etiology in the USA suggested a zoonotic potential for vesiviruses. These results have not been confirmed by another laboratory. In order to do so, a generic PCR assay on the RNA polymerase region was developed, and validated with RNA from 69 different Vesivirus species. Except SMSV serotype-8, all species tested were detected, including the ones that were suggested to be involved in zoonotic transmission in the USA (SMSV serotype-5).

The generic Vesivirus assay was used on RNA extracted from serum samples from patients with hepatitis, stool samples from patients with gastroenteritis, throat-swab specimens of patients with rash illnesses, throat-swab and nose-swabs of patients with acute respiratory diseases, and cell cultures with cytopathologic effect from enterovirus surveillance in which no pathogen was found. None were found positive. In this study a generic Vesivirus assay was developed and it was concluded that vesiviruses are an unlikely cause of common illnesses in humans in the Netherlands.

Molecular virology of feline calicivirus

Caliciviridae are small, nonenveloped, positive-stranded RNA viruses. Much of our understanding of the molecular biology of the caliciviruses has come from the study of the naturally occurring animal caliciviruses. In particular, many studies have focused on the molecular virology of feline calicivirus (FCV), which reflects its importance as a natural pathogen of cats. FCVs demonstrate a remarkable capacity for high genetic, antigenic, and clinical diversity; "outbreak" vaccine resistant strains occur frequently. This article updates the reader on the current status of clinical behavior and pathogenesis of FCV.

Virus-specific antiviral treatment for controlling severe and fatal outbreaks of feline calicivirus infection

OBJECTIVE

To test the life-sparing and therapeutic effect of a parenterally administered virus-specific antiviral phosphorodiamidate morpholino oligomer (PMO) for treating kittens during outbreaks of severe viral disease.

ANIMALS

112 kittens of various sex and age in 4 trials involving 3 outbreaks of naturally developing caliciviral disease.

PROCEDURES

Each trial provided an opportunity to investigate the disease. A calicivirus isolated from the liver of a cat that died with hemorrhage and hepatitis was sequenced, and a PMO that had sequence specificity complementary to a 5' region was synthesized. In vitro efficacy of the PMO was tested against the isolate, followed by 3 trials in outbreaks of severe caliciviral disease. The PMO was administered starting on day 1 of disease onset (0.7 to 5.0 mg/kg, SC, q 24 h) and continuing for up to 7 days. Survival time, clinical recovery, and caliciviral shedding were compared by use of various antiviral dosages. In a fourth trial involving nonfatal disease, a control treatment was administered for comparison.

RESULTS

In vitro blockage of caliciviral replication by the PMO was dose dependent. In trials 1 to 3 in which survival was the endpoint, 47 of 59 cats receiving PMO survived but only 3 of 31 survived without PMO treatment. Antiviral treatment reduced viral shedding and hastened clinical recovery, as measured by weight gains and clinical condition.

CONCLUSIONS AND CLINICAL RELEVANCE

These data provided evidence that virus-specific PMOs were effective in treating kittens with severe Vesivirus disease and suggested a broader application for other viruses and species, including humans.

Marine viruses--major players in the global ecosystem

Viruses are by far the most abundant 'lifeforms' in the oceans and are the reservoir of most of the genetic diversity in the sea. The estimated 10(30) viruses in the ocean, if stretched end to end, would span farther than the nearest 60 galaxies. Every second, approximately 10(23) viral infections occur in the ocean. These infections are a major source of mortality, and cause disease in a range of organisms, from shrimp to whales. As a result, viruses influence the composition of marine communities and are a major force behind biogeochemical cycles. Each infection has the potential to introduce new genetic information into an organism or progeny virus, thereby driving the evolution of both host and viral assemblages. Probing this vast reservoir of genetic and biological diversity continues to yield exciting discoveries.

Verses, viruses, and the vulnerability of the blood supply in industrialized countries

In the last 30 years, tremendous progress in identifying transfusion-transmitted viruses such as HBV, HCV, and HIV in industrialized countries has been achieved. Currently, the residual risk of transmitting these viruses through transfusion is very low especially after the introduction of "minipool" nucleic acid-amplification tests. Despite these major technical advances, there remains a legitimate concern as to the transmission of other blood-borne infectious agents through blood transfusion. Among these agents are HBV mutants, occult HBV, and HCV infections, malaria, Chagas, West Nile, dengue, and vesiviruses, bacterial infections such as Yersinia enterocolitica, and tick borne diseases such as human monocytic ehrlichiosis, human granulocytic ehrlichiosis, Rocky Mountain spotted fever, and Lyme and prion diseases such as Creutzfeldt and variant Creutzfeldt. Most of these agents are very rarely transmitted by transfusion in industrialized countries. However, an awareness of their possible transmission is essential for the control of spread of these diseases among the public by human-to-human transmission via blood transfusion. This review summarizes the current status of prevalence and diagnosis of these emerging diseases and also updates our knowledge on recently discovered non-pathogenic blood-borne viruses such as GB virus C and Torque Tenoviruses.

Enteric caliciviruses in domestic pigs in Hungary

Caliciviruses closely related to human norovirus and sapovirus were recently detected in domestic pigs, causing discussions about the animal reservoir and the potential for zoonotic transmission to humans. To detect porcine caliciviruses, 17 fecal samples collected on two swine farms in southwestern Hungary were tested by reverse transcription-polymerase chain reaction. Three (17.6%) samples were positive for caliciviruses. This study confirms the presence of caliciviruses, both porcine sapovirus (genus Sapovirus) and porcine norovirus (genus Norovirus), in domestic pigs in Hungary and provides additional information on the viral genetic diversity and relationship to viruses referred to as human caliciviruses.

X-ray structure of a native calicivirus: structural insights into antigenic diversity and host specificity

Caliciviruses, grouped into four genera, are important human and veterinary pathogens with a potential for zoonosis. In these viruses, capsid-related functions such as assembly, antigenicity, and receptor interactions are predominantly encoded in a single protein that forms an icosahedral capsid. Understanding of the immunologic functions and pathogenesis of human caliciviruses in the Norovirus and Sapovirus genera is hampered by the lack of a cell culture system or animal models. Much of our understanding of these viruses, including the structure, has depended on recombinant capsids. Here we report the atomic structure of a native calicivirus from the Vesivirus genus that exhibits a broad host range possibly including humans and map immunological function onto a calicivirus structure. The vesivirus structure, despite a similar architectural design as seen in the recombinant norovirus capsid, exhibits novel features and indicates how the unique modular organization of the capsid protein with interdomain flexibility, similar to an antibody structure with a hinge and an elbow, integrates capsid-related functions and facilitates strain diversity in caliciviruses. The internally located N-terminal arm participates in a novel network of interactions through domain swapping to assist the assembly of the shell domain into an icosahedral scaffold, from which the protruding domain emanates. Neutralization epitopes localize to three hypervariable loops in the distal portion of the protruding domain surrounding a region that exhibits host-specific conservation. These observations suggest a mechanism for antigenic diversity and host specificity in caliciviruses and provide a structural framework for vaccine development.