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Paramecium bursaria chlorella virus 1 (PBCV-1) infects the unicellular eukaryotic green alga Chlorella NC64A. The virus has an ~330-kb genome and is predicted to have 365 protein-encoding genes. Yanai-Balser et al. (p. 532-542) show that 99% of these protein-encoding genes are expressed during the virus life cycle and can be divided into three highly regulated transcriptional classes (early, early/late, and late) that are dictated by viral DNA synthesis. This study provides the first comprehensive evaluation of gene expression in PBCV-1.
Cellular chaperones are implicated in the replication of numerous viruses with diverse genomes and replication strategies. Weeks et al. (p. 330-339) demonstrate that heat shock protein 70 chaperones can have either stimulatory or inhibitory effects on flock house virus RNA replication and viral polymerase synthesis. This work highlights the complexities of virus-cell interactions and demonstrates the important yet differential functions of particular cellular chaperones in positive-sense RNA virus replication.
The mechanism by which PB1-F2 contributes to the pathogenesis of influenza A virus infections is not known. McAuley et al. (p. 558-564) used several different epidemiologically important virus strains to demonstrate that enhancement of virus replication is unlikely to be the responsible mechanism. Potential contributions of PB1-F2 to immune evasion or immunopathology may be better explanations for the dichotomy in virulence between pandemic strains expressing a full-length PB1-F2 and the current swine-origin strain that encodes a truncated version.
Hepatitis C virus (HCV) belongs to the Hepacivirus genus of the family Flaviviridae. The lack of a small animal model has hampered studies of HCV. Amako et al. (p. 303-311) examined HCV infection using tree shrews (Tupaia belangeri). In this animal model, HCV infection results in alteration of liver histology consistent with hepatitis, steatosis, and cirrhosis. Moreover, HCV can establish life-long persistent infection in this species. These results suggest that tree shrews can serve as an animal model for studies of HCV pathogenesis.
Chronic wasting disease (CWD) is a contagious, uniformly fatal prion disease of North American deer and elk. CWD epidemics are occurring in free-ranging herds in 14 states and two Canadian provinces, inevitably exposing other wildlife species to potentially infectious material. Heisey et al. (p. 210-215) demonstrate that four species of native cricetid rodents exhibit high susceptibility to CWD via the intracerebral challenge route. Interestingly, one of these species has the prion amino acid sequence thought to confer CWD resistance in laboratory mice of the Mus genus. This work indicates that a minimal species barrier protects these rodents from CWD infection.