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Haemorrhagic disease of lagomorphs: evidence for a calicivirus.

Studies on the aetiological agents of rabbit haemorrhagic disease (RHD) and European brown hare syndrome show that the viruses responsible for these infections can be placed in the family Caliciviridae. Established members of this group are vesicular exanthema virus (prototype), San Miguel sea lion virus and feline calcivirus. The human hepatitis E virus and the Norwalk agent may soon be included. The RHD virus genome consists of a positive stranded RNA molecule composed of 7437 nucleotides. A major subgenomic RNA of 2.2 kb, colinear with the 3' end of the genomic RNA, can also be recovered from infected liver tissue, and both RNAs are enclosed within viral capsids formed by a single major protein of approximately 60 kDa. Electron microscopic examination of organ suspensions from diseased animals shows two types of particle; 35-40 nm complete virions have the regularly arranged cup-shaped depressions typical of calcivirus morphology, and 23-25 nm smooth particles resulting from degradation of the outer surface structures of the complete virions.

Animals

Novel avian calicivirus genome with type IV internal ribosomal entry site (IRES) in black-headed gull (Chroicocephalus ridibundus) in Hungary.

In this study, a taxonomically novel avian calicivirus detected and characterized by next generation sequencing, RT-PCR and Sanger sequencing methods in faecal specimen collected from black-headed gull (Chroicocephalus ridibundus) in Hungary. The complete genome length of the calicivirus strain gull/HA15097/HUN/2018 (PZ810127) is remarkably long, 8,845 nucleotides, which had type IV internal ribosomal entry site (IRES) at the 5', and a stem-loop-II-like (s2m) sequence motif at the 3' untranslated regions. The VP1 capsid protein had less than 26% aa identity to the members of the known calicivirus genera. Caliciviruses appear to be widespread not only in mammals including humans but also in various bird species.

Animals

An outbreak of gastroenteritis associated with calicivirus in an infant home.

In October 1977 an outbreak of acute infectious diarrhea occurred in an infant home in the city of Sapporo, Japan. Of 34 residents aged two to 20 months, 26 (77%) suffered from diarrhea. In ten of these patients the diarrhea was accompanied by vomiting. Electron microscopic examinations revealed typical calicivirus particles in eight faecal specimens, seven of which were from the group of 26 affected patients (28%) and one of which was from the group of eight infants without symptoms (13%). Immune electron microscopy tests for antibody responses against one of the isolated strains of calicivirus were carried out on 27 paired pre- and post-outbreak sera. Seroconversions were demonstrated in 18 of 19 (95%) affected infants and in six of eight (75%) unaffected infants. One patient with lack of antibody response was the youngest child--two months old. Periodic surveys on enteric viruses circulating in the home revealed that calicivirus was specifically associated with the outbreak of gastroenteritis. These observations provide further evidence for the causative role of calicivirus in acute gastroenteritis in children.

Antibodies, Viral

The occurrence of calicivirus in infants with acute gastroenteritis.

Calicivirus was detected in 8 (1.2%) of 647 hospitalized patients during a survey of acute gastroenteritis in infants and young children, conducted between December 1974 and September 1977. Morphologically calicivirus was approximately 30 nm in diameter with an easily recognizable staining "star of David" configuration. Its buoyant density in cesium chloride was 1.38-1.40 gm/ml. The serologic response to calicivirus by immune electron microscopy (IEM) was demonstrated only in paired sera from patients who shed the virus in their stools. The results suggest that calicivirus might be a cause of acute gastroenteritis in infants and young children.

Acute Disease

Integrating Enzyme-DNA Complex and CRISPR/Cas12a for Robust Norovirus Detection.

Human norovirus (NoV) is a primary cause of acute gastroenteritis in children, making accurate and rapid detection essential for effective disease prevention and control. In this study, we developed a sensitive and efficient platform for pathogen nucleic acid detection by integrating asymmetric nucleic acid sequence-based amplification (asymmetric NASBA), enzyme-DNA molecular complex, and the clustered regularly interspaced short palindromic repeats (CRISPR) system, namely an A-enDMC platform. The target recognition capability of the enzyme-DNA complex operates independently from the signal amplification function of the CRISPR system. By decoupling the CRISPR reaction from the dependence on specific target sequences, the platform's universality and modularity are enhanced. The assay is fast (<&#x2009;1.5 h), highly sensitive (<&#x2009;5&#x2009;copies/&#xb5;L), and demonstrates no cross-reactivity with other common viruses. Compared to the widely used RT-qPCR method, the platform demonstrates high consistency in detection results, with the detection coincidence rate of 96.77% and a kappa value of 0.87. This platform provides a versatile technological tool for highly sensitive and specific RNA detection, demonstrating its extensive potential in real sample analysis.

Norovirus

Genotypic Analysis and Clinical Findings of Sapovirus-Associated Acute Gastroenteritis in Mie Prefecture, Japan, 2010-2022.

Sapovirus (SaV) is one of the major viruses causing acute gastroenteritis. Of the 1981 fecal specimens collected through sentinel pediatric acute gastroenteritis pathogen surveillance in Mie Prefecture, Japan (2010-2022), 236 were positive for SaV, according to PCR screening. Whole or near-whole genome sequences were determined for 158 strains by next-generation sequencing. Genotype GI.1 was the most common of the nine SaV genotypes detected, followed by GII.3 and GII.1. Phylogenetic analysis showed that SaVs of these three genotypes separated into three different clusters depending on the year of detection, suggesting continuous genetic changes in the same genotype. Coinfections involving different SaV genotypes, as well as reinfections with SaV in the same individual, were observed in this study. The main clinical manifestations were diarrhea (68.4%) and vomiting (61.6%), with an increased rate of emesis, particularly in patients over 3 years of age. In addition, 18.1% of the children had fever. This study clarified the prevalence of viral genotypes as well as clinical findings of SaV-positive gastroenteritis in children, and revealed trends by age.

Humans

Variation in Severity of Symptoms Associated With Two Snow Mountain Virus Inocula.

Snow Mountain Virus (SMV), the prototype of genogroup II and genotype II Norovirus (NoV), was used in human challenge studies to examine the infectivity, pathogenicity, and immune response to NoV. Clinical and laboratory data from two previously completed SMV human challenge trials using two different inocula (primary and secondary) were analyzed to compare the infectivity, illness, viral shedding, and serum IgG conversion. The primary and secondary SMV inocula were sequenced for detecting single nucleotide mutations. Of 15 subjects challenged with the primary inoculum between 2000 and 2002, nine were infected, and seven presented with acute gastroenteritis. Of 33 subjects challenged with the secondary inoculum between 2016 and 2018, 25 were infected, and nine presented with acute gastroenteritis. There were no statistically significant differences in overall infection and illness rates between subjects challenged with the primary inoculum versus the secondary inoculum. However, subjects infected with the primary inoculum experienced more severe clinical symptoms of acute gastroenteritis, showing higher severity scores (6.00 vs. 2.94, p&#x2009;=&#x2009;0.003) compared with those infected with the secondary inoculum. We also observed that infection with the secondary inoculum resulted in longer viral shedding compared with the primary inoculum. Partial sequencing of the SMV genome identified three mutations in both inocula. Understanding the differences between these two SMV inocula is critical for NoV vaccine evaluation and using a less pathogenic inoculum for a vaccine trial will require more participants to meet the target reduction in illness when evaluating the efficacy of candidate vaccines.

Humans

Construction of Reverse Genetics System for Feline Calicivirus FCV-BJ616 and Proteomic Analysis.

Feline calicivirus (FCV) is a primary cause of upper respiratory tract infections and oral ulcerative disease in cats and exhibits substantial genetic diversity that complicates prevention and control. In this study, we isolated the FCV-BJ616 strain, established a reverse-genetics system, and investigated its pathogenic mechanisms, thereby providing a foundation for antibody-based therapies and broad-spectrum vaccine development. The virus was purified by three rounds of plaque cloning, and its morphology was examined by electron microscopy. VP1 expression was confirmed by immunofluorescence and Western blotting. Using integrated systems-biology and reverse-genetics approaches, an infectious clone of rFCV-BJ616 was successfully assembled and rescued, exhibiting genetic stability comparable to that of the parental strain. In vivo infection experiments showed that rFCV-BJ616 retained wild-type virulence, causing persistent high fever, weight loss, and multiorgan pathology in infected cats. Proteomic analysis indicated that infection with FCV-BJ616 or rFCV-BJ616 markedly activated cytokine-mediated inflammatory signaling pathways. Both FCV-BJ616 and rFCV-BJ616 significantly upregulated the expression of IL-8, S100A8/A9, and TLR3, which are associated with acute inflammation and tissue damage. Furthermore, elevated IFN-&#x3b2; levels concomitant with STAT1 downregulation suggested a transient attenuation of antiviral signaling during early immune activation. These findings were corroborated by ELISA-based validation of serum cytokine profiles. Collectively, this study provides new insights into the molecular pathogenesis and evolution of FCV-BJ616 and establishes a robust reverse-genetics platform for precise genome manipulation and future vaccine development.

Animals

Ultrastructural studies of the development of feline calicivirus in a feline embryo cell line.

The ultrastructural changes in a feline embryo continuous cell line infected with feline calicivirus at a multiplicity of infection of approximately 1 were studied. Virus was found only in the cytoplasm and was observed as single particles, as extensive, non-regular accumulations, as paracrystalline arrays, and as single or multiple linear arrays associated with microfbrils. Mature virus particles were readily distinguished from ribosomes in that they were larger (35nm diameter) and consisted of a central, electron-dense core 20 nm diameter surrounded by a less electron-dense coat. Other changes ovserved in infected cells included rounding of the cell and nucleus and loss of pseudopodia. There was extensive production of smooth-membrane bound vesicles in the cytoplasm. Virus accumulations of each type, but especially paracrystalline arrays, were frequently closely associated with collections of these vesicles. The cisternae of the endoplasmic reticulum and the space between the two layers of the nuclear membrane was distended. By Feulgen staining and light microscopy, as well as electron microscopy, it was established that nuclear chromatin undergoes profound changes consisting of condensation usually into a single, rounded, central mass.

Animals

Electron microscopic observation of feline kidney cells infected with a feline calicivirus.

An electron microscopic study of kitten kidney cells infected with a feline calicivirus (a member of the family Picornaviridae) has been carried out. Although cells appeared to be synchronised by the light microscope, electron microscopic changes were extremely variable. The first observable and consistent changes occurred in the nucleus followed by the formation of membrane bound vesicles in the cytoplasm. A variety of arrangements of virus particle accumulation were observed in infected cells. These included crystalline arrays, membranous cisternae and accumulation of particles in fine fibrillar material. The finding of accumulations of virus particles in association with smooth membranes is of importance in respect of the recent biochemical evidence of poliovirus assembly in relation to smooth membranes.

Animals

A new calicivirus isolated from a marine mammal.

A new serotype of calicivirus, designated as San Miguel sea lion virus type 6 (SMSV-6), was isolated from vesicular lesions on the flipper of a California sea lion pup. Serologic studies show that SMSV-6 neutralizing antibodies (SN) occur frequently among California sea lions and occasionally among northern fur seals. Feral swine, 1- to 6-week elephant seal pups and grey whales tested negative for SMSV-6 antibody.

Animals

Feline calicivirus carrier state. A study of the host/virus relationship.

The inter-epidemic phase of feline calicivirus was studied in a number of cats. During this period animals asymptomatically shed infective virus which was monitored at a number of sites and during different environmental conditions. Analysis of the amounts of virus shed by different cats showed that excretion occurred almost exclusively from the oropharynx, fluctuated with time, but was not influenced by periods of natural or artificial stress. Viral excretion from one individual cat was fairly constant although it appears that cats might be divided into high, medium or low level excretors. This variation in levels of excretion appears to have epidemiological importance in that high-level excretors more easily infect susceptible individuals.

Animals