TRIM25 and ZAP target the Ebola virus ribonucleoprotein complex to mediate interferon-induced restriction.

Ebola virus (EBOV) causes highly pathogenic disease in primates. Through screening a library of human interferon-stimulated genes (ISGs), we identified TRIM25 as a potent inhibitor of EBOV transcription-and-replication-competent virus-like particle (trVLP) propagation. TRIM25 overexpression inhibited the accumulation of viral genomic and messenger RNAs independently of the RNA sensor RIG-I or secondary proinflammatory gene expression.

Mammalian antiviral RNAi is on the move.

Recent work reported the existence of a mammalian cell-autonomous antiviral defence based on RNA interference (RNAi), which relies on the accumulation of virus-derived small interfering RNAs (vsiRNAs) to guide the degradation of complementary viral RNAs. In a new study, Zhang et al (2022) find that, in infected mice, vsiRNAs can enter the bloodstream via their incorporation into extracellular vesicles (EVs) and confer sequence-specific antiviral activity to recipient cells, thus indicating that mammalian antiviral RNAi participates in both cell-autonomous and non-cell-autonomous host defence.

Influenza A Virus Virulence Depends on Two Amino Acids in the N-Terminal Domain of Its NS1 Protein To Facilitate Inhibition of the RNA-Dependent Protein Kinase PKR.

The RNA-dependent protein kinase (PKR) has broad antiviral activity inducing translational shutdown of viral and cellular genes and is therefore targeted by various viral proteins to facilitate pathogen propagation. The pleiotropic NS1 protein of influenza A virus acts as silencer of PKR activation and ensures high-level viral replication and virulence. However, the exact manner of this inhibition remains controversial.

Influenza virus-induced caspase-dependent enlargement of nuclear pores promotes nuclear export of viral ribonucleoprotein complexes.

Unlabelled: Influenza A viruses (IAV) replicate their segmented RNA genome in the nucleus of infected cells and utilize caspase-dependent nucleocytoplasmic export mechanisms to transport newly formed ribonucleoprotein complexes (RNPs) to the site of infectious virion release at the plasma membrane. In this study, we obtained evidence that apoptotic caspase activation in IAV-infected cells is associated with the degradation of the nucleoporin Nup153, an integral subunit of the nuclear pore complex. Transmission electron microscopy studies revealed a distinct enlargement of nuclear pores in IAV-infected cells.

The novel human influenza A(H7N9) virus is naturally adapted to efficient growth in human lung tissue.

Unlabelled: A novel influenza A virus (IAV) of the H7N9 subtype has been isolated from severely diseased patients with pneumonia and acute respiratory distress syndrome and, apparently, from healthy poultry in March 2013 in Eastern China. We evaluated replication, tropism, and cytokine induction of the A/Anhui/1/2013 (H7N9) virus isolated from a fatal human infection and two low-pathogenic avian H7 subtype viruses in a human lung organ culture system mimicking infection of the lower respiratory tract. The A(H7N9) patient isolate replicated similarly well as a seasonal IAV in explanted human lung tissue, whereas avian H7 subtype viruses propagated poorly.