A Novel PA-X Protein Translated from Influenza A Virus Segment 3

The pathogenicity of influenza A viruses is a multigenic trait, which is orchestrated by the global networks between eight viral genomic constituents and their cellular interacting partners. A recent report provided information on the finding of a new PA ribosomal frameshifting product, the PA-X protein, in the influenza A virus segment 3, and an endonuclease property was suggested for a possible role of the PA-X protein. In cultured cells, viral growth was not affected by the PA-X protein expression. However, the reduced pathogenicity of mice appeared to be closely associated with the PA-X protein expression. It was also revealed that the PA-X protein was able to modulate host gene expression. Considered together, the PA-X protein can be a cellular signaling modulator and subsequently control viral pathogenicity. By reviewing recent publications, we present new insights in the contribution of the PA-X protein to the cellular signaling network and the resultant viral pathogenicity.

Double-stranded RNA virus in Korean Isolate IH-2 of Trichomonas vaginalis

In this study, we describe Korean isolates of Trichomonas vaginalis infected with double-stranded (ds) RNA virus (TVV). One T. vaginalis isolate infected with TVV IH-2 evidenced weak pathogenicity in the mouse assay coupled with the persistent presence of a dsRNA, thereby indicating a hypovirulence effect of dsRNA in T. vaginalis. Cloning and sequence analysis results revealed that the genomic dsRNA of TVV IH-2 was 4,647 bp in length and evidenced a sequence identity of 80% with the previously-described TVV 1-1 and 1-5, but only a 42% identity with TVV 2-1 and 3 isolates. It harbored 2 overlapping open reading frames of the putative capsid protein and dsRNA-dependent RNA polymerase (RdRp). As previously observed in the TVV isolates 1-1 and 1-5, a conserved ribosomal slippage heptamer (CCUUUUU) and its surrounding sequence context within the consensus 14-nt overlap implied the gene expression of a capsid protein-RdRp fusion protein, occurring as the result of a potential ribosomal frameshift event. The phylogenetic analysis of RdRp showed that the Korean TVV IH-2 isolate formed a compact group with TVV 1-1 and 1-5 isolates, which was divergent from TVV 2-1, 3 and other viral isolates classified as members of the Giardiavirus genus.