Isolation of caliciviruses from skunks that are antigenically and genotypically related to San Miguel sea lion virus

Genetic characterization of a novel calicivirus from a chicken

We describe the identification and genetic characterization of a novel enteric calicivirus, detected by transmission electron microscopy and RT-PCR in two clinically normal chickens and in a chicken with runting and stunting syndrome from different flocks in southern Germany. Positive findings were confirmed by sequencing. The complete nucleotide sequence and genome organization of one strain (Bavaria/04V0021) was determined. The genome of the Bavaria virus is 7,908 nt long and contains two coding open reading frames. Phylogenetic analysis of the deduced partial 2C helicase/NTPase, 3C cysteine protease, RNA-dependent RNA polymerase and complete VP1 capsid protein amino acid sequences showed that the virus is genetically related to but distinct from sapoviruses and lagoviruses. Morphologically, the Bavaria virus particles are 37-42 nm in diameter and exhibit characteristic cup-shaped surface depressions.

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.

Genomic characterization of novel marine vesiviruses from Steller sea lions (Eumetopias jubatus) from Alaska

Marine vesiviruses were isolated in cell culture from oral and rectal swabs and vesicular fluid from Alaskan Steller sea lions (SSL; Eumetopias jubatus). Further characterization by RT-PCR, complete genomic sequencing, and phylogenetic analyses indicated that these viruses are most closely related to the marine vesiviruses, but are distinct viruses and represent two novel genotypes. The complete genome of these two SSL isolates was sequenced after cloning their viral cDNA. The genomes were found to be 8302 and 8305 nucleotides in length, organized in three open reading frames and contained 5' and 3' untranslated regions (UTR) of 19 and 180 nucleotides, respectively. The complete genomes of both SSL viruses were most closely related to each other and shared 83.0% nucleotide identity. Using the very limited number of complete genomic vesivirus sequences available in the NCBI database, these novel SSL vesiviruses seem most closely related to vesicular exanthema of swine virus-A48 and least related to rabbit vesivirus and walrus calicivirus. Specific antiserum against some evolutionary closer marine vesiviruses did not neutralize these isolates supporting the novel nature of these SSL viruses.

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.

Development of a real-time reverse transcription polymerase chain reaction assay for detection of marine caliciviruses (genus Vesivirus)

Marine caliciviruses form a distinct lineage within the genus Vesivirus (family Caliciviridae). This group includes vesicular exanthema of swine virus (VESV) and San Miguel sea lion virus (SMSV) and other related viruses which have been proposed to be marine in origin isolated from a variety of terrestrial and marine animals. Rapid and reliable detection of marine caliciviruses is important as these viruses appear to be widespread and can cause vesicular disease in a wide variety of susceptible hosts including pigs and experimentally infected cattle where clinical signs cannot be easily distinguished from foot-and-mouth disease (FMD), swine vesicular disease (SVD) and vesicular stomatitis (VS). A real-time RT-PCR assay targeting conserved nucleotide sequences in the RNA-dependent RNA polymerase (3D) region of the genome successfully detected cell culture-grown virus preparations of more than thirty marine calicivirus serotypes. Only the atypical SMSV serotypes 8 and 12 failed to be detected, which provided further indication of genetic divergence between these and the other calicivirus serotypes said to be marine in origin. The real-time RT-PCR assay also specifically amplified RNA from samples collected following experimental inoculation of pigs with VESV. No cross-reactivity was demonstrated when the assay was tested with RNA prepared from representative viruses of FMD, SVD and VS. The real-time RT-PCR assay described is a sensitive and specific tool for detection and differential diagnosis of these viruses from other vesicular-disease causing viruses.

Vesivirus viremia and seroprevalence in humans

Pathogenic caliciviruses of the genus Vesivirus circulate in oceanic ecosystems and spread to and among terrestrial mammals. Isolation of Vesivirus from natural and laboratory infections in humans led to this investigation of Vesivirus seroprevalence and viremia. Sera from four groups were tested for antibodies to Vesivirus as follows: blood donors whose units were cleared for donation, blood donors whose units were not accepted for donation solely because of elevated blood liver alanine aminotransferase (ALT) concentrations, patients with clinical hepatitis of unknown but suspected infectious cause, and patients with clinical hepatitis of unknown cause but associated with blood transfusion or dialysis. Additionally, sera were tested for Vesivirus genome by three methods: dot‐blot and two reverse transcription‐polymerase chain reaction (RT‐PCR) methods. The calculated seroprevalence against Vesivirus virions within these groups (N = 765) was 12%, 21%, 29%, and 47%, respectively (P < 0.001 for group differences). Additionally, 11 (9.8%) of 112 sera tested yielded RT‐PCR amplicons that by nucleotide sequence were distinct from each other and related to known Vesivirus. These data indicate that some blood donors in the population tested have serologic evidence of previous Vesivirus infection and some also have Vesivirus viremia. These results justify further investigation of an association between Vesivirus infection and illness in humans. J. Med. Virol. 78:693–701, 2006. © 2006 Wiley‐Liss, Inc.

Development of a reverse transcription polymerase chain reaction procedure for the detection of marine caliciviruses with potential application for nucleotide sequencing

A reverse transcription polymerase chain reaction (RT-PCR) procedure is described for the detection of marine caliciviruses including vesicular exanthema of swine virus (VESV), San Miguel sea lion virus (SMSV), bovine Tillamook virus (BCV Bos-1) and caliciviruses (CV) isolated from dolphin (Cetacean CV), gorilla (Primate CV) and rattlesnake (Reptile CV) using primers (1F and 1R) designed from the capsid-coding region of the viral genome. These primers were compared with those described by Neill, J.D. and Seal, B.S., 1995: Development of PCR primers for specific amplification of two distinct regions of the genomes of San Miguel sea lion and vesicular exanthema of swine viruses, Mol. Cell. Probes 9, 33-38 (Hel1/Hel2), which had been designed from the 2C-like region of the calicivirus genome. Both sets proved to be extremely useful diagnostic tools for all of the known marine calicivirus serotypes with the exception of three: SMSV-8 and -12 and mink CV suggesting that these three caliciviruses may belong to a different group. Neither of the two primer sets reacted with strains of the vesicular disease viruses of foot-and-mouth disease (FMD), swine vesicular disease (SVD) or vesicular stomatitis (VS) nor with two feline caliciviruses (FCV). The 1F/1R primer set has the advantage over the Hel1/Hel2 set in that it generates a larger PCR product for nucleotide sequence investigations and so provides greater opportunity for identifying molecular differences between the viruses.

Physical and genetic maps of the human herpesvirus 7 strain SB genome

Human herpesvirus 7 (HHV-7) is a close relative of human herpesvirus 6A (HHV-6A) and human herpesvirus 6B (HHV-6B) based on limited biologic and genetic data. In this work we describe physical and genetic maps for HHV-7 strain SB [HHV-7(SB)], which was obtained from the saliva of a healthy adult. The HHV-7(SB) genome length is approximately 144 kb by clamped homogeneous electric field gel electrophoresis and approximately 135 kb by summation of restriction endonuclease fragments. We constructed plasmid clones and PCR amplimers that span the HHV-7 genome, except for the genomic termini, and determined the maps of the restriction endonuclease cleavage sites for BamHI, PstI, and SacI. The HHV-7(SB) genome is composed of a single unique region of approximately 122 kb bounded at each end by a 6 kb direct repeat. Homologs to thirty-five herpesvirus genes were identified. The highest similarity was with the HHV-6 genes, with an average amino acid identity of 50%, followed by the human cytomegalovirus counterpart. The genomic and genetic maps indicated that the HHV-7 and HHV-6 genomes are colinear. There was no sequence variation in a segment of the gene encoding the DNA polymerase-associated factor homolog among six HHV-7 isolates, while the corresponding segment of the HHV-6A and HHV-6B counterparts differed by 4.6%. These data support previous observations that the closest genetic relatives of HHV-7 are betaherpesviruses.