Viruses exploit host cell machinery to support their replication. Defining the cellular proteins and processes required for a virus during infection is crucial to understanding the mechanisms of virally induced disease and designing host-directed therapeutics. Here, we perform a genome-wide CRISPR-Cas9–based screening in lung epithelial cells infected with the PR/8/NS1-GFP virus and use GFP ^hi cell as a unique screening marker to identify host factors that inhibit influenza A virus (IAV) infection. We discovered that APOE affects influenza virus infection both in vitro and in vivo. Cell deficiency in APOE conferred substantially increased susceptibility to IAV; mice deficient in APOE manifested more severe lung pathology, increased virus load, and decreased survival rate. Mechanistically, lack of cell-produced APOE results in impaired cell cholesterol homeostasis, enhancing influenza virus attachment. Thus, we identified a previously unrecognized role of APOE in restraining IAV infection.

In order to ensure efficient multiplication, influenza virus transcribes and replicates its segmented, negative-sense viral RNA genome in highly ordered dynamics across the virus life cycle. How the virus achieves such regulation remains poorly understood.

Influenza A virus (IAV) represents a constant public health threat. The single-stranded, segmented RNA genome of IAV is replicated in host cell nuclei as a series of 8 ribonucleoprotein complexes (vRNPs) with RNA structures known to exert essential function to support viral replication. Here, we investigate RNA secondary structures and RNA interactions networks of the IAV genome and construct an in vivo structure model for each of the 8 IAV genome segments. Our analyses reveal an overall in vivo and in virio resemblance of the IAV genome conformation but also wide disparities among long-range and intersegment interactions. Moreover, we identify a long-range RNA interaction that exerts an essential role in genome packaging. Disrupting this structure displays reduced infectivity, attenuating virus pathogenicity in mice. Our findings characterize the in vivo RNA structural landscape of the IAV genome and reveal viral RNA structures that can be targeted to develop antiviral interventions.

Highly pathogenic avian influenza H5N1 poses an increasing public health risk, particularly following its spillover into dairy cows and associated human infections in the U.S. since March 2024. Here, we systematically identified critical PB2 mutations emerged during avian-to-cattle transmission and subsequent adaptation in cattle, notably PB2 M631L, which conferred pathogenicity in mice comparable to the well-characterized PB2 E627K mutation. Retrospective analysis reveals that PB2 631L also circulated in avian and human H5N1 strains during the 2013–2014 outbreaks in Cambodia and Vietnam. Additional adaptive mutations include established markers (E627K, Q591R, D701N), and novel variants (I647V, G685R, K736R). These mutations enhance polymerase activity by improving the utilization of both bovine and human ANP32A proteins, thereby increasing viral fitness and pathogenicity in mammals. The convergence of these adaptations highlights the elevated zoonotic risk of cattle-adapted H5N1 viruses and underscores the urgent need for heightened surveillance across avian and mammalian hosts.

3050Background: We performed the first phase I clinical trial (NCT02793856) to assess safety of CRISPR/Cas9-mediated knockout of PD-1 gene in autologous T lymphocytes (PD-1-/- T) therapy in patients with metastatic non-small cell lung cancer (NSCLC). Methods: We assigned patients with advanced NSCLC with positive PD-L1 expression who had progressed after 3rd line standard therapeutic regimens. Two patients were enrolled in Pre-A cohort who received PD-1-/- T therapy with 2 x 107 cells/kg for one cycle and were observed for another cycle. Then 3 cohorts (A, B, C) enrolled 3 patients in each group receiving PD-1-/- T cells therapy with 1×107/kg, 2×107/kg, 4×107/kg in each cycle, respectively. Patients received PD-1-/- T therapy until disease progression or study withdrawal. Primary outcome was safety. Secondary end points were 8 weeks disease control rate (DCR) and progression-free survival (PFS). In exploratory analyses, next-generation sequencing was performed on PD-1 editing region of T cells and CDR3 re...

Genome transcription and replication of influenza A virus (FluA), catalyzed by viral RNA polymerase (FluAPol), are delicately controlled across the virus life cycle. A switch from transcription to replication occurring at later stage of an infection is critical for progeny virion production and viral non-structural protein NS2 has been implicated in regulating the switch. However, the underlying regulatory mechanisms and the structure of NS2 remained elusive for years. Here, we determine the cryo-EM structure of the FluAPol-NS2 complex at ~3.0 Å resolution. Surprisingly, three domain-swapped NS2 dimers arrange three symmetrical FluPol dimers into a highly ordered barrel-like hexamer. Further structural and functional analyses demonstrate that NS2 binding not only hampers the interaction between FluAPol and the Pol II CTD because of steric conflicts, but also impairs FluAPol transcriptase activity by stalling it in the replicase conformation. Moreover, this is the first visualization of the full-length NS2 structure. Our findings uncover key molecular mechanisms of the FluA transcription-replication switch and have implications for the development of antivirals.