Woodchuck hepatitis virus (WHV) is often used as surrogate to study mechanism of HBV infection. Currently, most infections are conducted using strains WHV7 or WHV8 that have very high sequence identity. This study focused on natural strain WHVNY that is more genetically distant from WHV7. Three naive adult woodchucks inoculated with WHVNY developed productive acute infection with long lasting viremia. However, only one of two woodchucks infected with WHV7 at the same multiplicity demonstrated productive liver infection. Quantification of intracellular WHV RNA and DNA replication intermediates; percentages of core antigen-positive hepatocytes; and serum relaxed circular DNA, showed that strains WHVNY and WHV7 displayed comparable replication levels and capacities to induce acute infection in naive adult woodchucks. Strain WHVNY was therefore validated as valuable reagent to analyze the mechanism of hepadnavirus infection, especially in co- and super-infection settings, which required discrimination between two related virus genomes replicating in the same liver.

Aminoacyl-tRNA synthetases (AARSs) are an important family of enzymes that catalyze tRNA aminoacylation reaction (Ibba and Soll in Annu Rev Biochem 2000, 69:617-650) [1]. AARSs are grouped into two broad classes (class I and II) based on sequence/structural homology and mode of their interactions with the tRNA molecule (Ibba and Soll in Annu Rev Biochem 2000, 69:617-650) [1]. As protein dynamics play an important role in enzyme function, we explored the intrinsic dynamics of these enzymes using normal mode analysis and investigated if the two classes and six subclasses (Ia-c and IIa-c) of AARSs exhibit any distinct patterns of motion. The present study found that the intrinsic dynamics-based classification of these enzymes is similar to that obtained based on sequence/structural homology for most enzymes. However, the classification of seryl-tRNA synthetase was not straightforward; the internal mobility patterns of this enzyme are comparable to both IIa and IIb AARSs. This study revealed only a few general mobility patterns in these enzymes--(1) the insertion domain is generally engaged in anticorrelated motion with respect to the catalytic domain for both classes of AARSs and (2) anticodon binding domain dynamics are partly correlated and partly anticorrelated with respect to other domains for class I enzymes. In most of the class II AARSs, the anticodon binding domain is predominately engaged in anticorrelated motion with respect to the catalytic domain and correlated to the insertion domain. This study supports the notion that dynamic-based classification could be useful for functional classification of proteins.

Which anti-nausea medications are more likely to increase QTc interval? EVIDENCE-BASED ANSWEROndansetron, haloperidol, and aprepitant have little effect on the QTc interval, whereas droperidol prolongs QTc compared with placebo (SOR: B, metaanalysis of low-quality studies). Dolasetron combined with dexamethasone significantly increases risk of QTc prolongation compared to ondansetron combined with dexamethasone (SOR: B, systemic review). A single dose of ondansetron 8 mg is associated with transient QTc prolongation when compared to 4 mg (SOR: B, single randomized controlled trial).