Researchers from the European Molecular Biology Laboratory in Hamburg, collaborating with Germany’s Leibniz Research Institute for Molecular Pharmacology and Charité Universitätsmedizin Berlin, have successfully mapped the intricate network of protein interactions that influenza A virus establishes inside human cells. Published in Nature Microbiology, this study represents the first large-scale, structurally resolved characterization of direct virus-host protein contacts within intact, living infected cells. The findings provide critical insights into viral hijacking mechanisms and establish a novel methodology for future antiviral drug and vaccine development. Historically, studying these interactions required lysing cells, which disrupted native compartments and introduced artificial protein contacts. To overcome this limitation, the research team employed a specialized cross-linking mass spectrometry workflow that preserves spatial and temporal dynamics inside unbroken cells. By integrating mass spectrometry data with a modified version of the AlphaFold protein structure prediction algorithm, scientists could accurately model how viral and host proteins physically interface during infection. This combined approach captured both stable complexes and transient, location-specific interactions that were previously undetectable. The analysis revealed two primary mechanisms through which influenza A commandeers host cellular machinery. First, the team traced the trajectory of hemagglutinin, the surface glycoprotein responsible for viral entry. The virus co-opts host proteins within the secretory pathway to correctly fold and modify hemagglutinin, highlighting previously uncharacterized host factors essential for viral assembly. Second, infection triggers the rapid dissolution of paraspeckles, nuclear bodies that regulate stress responses and antiviral gene expression. By dismantling these structures, the virus releases bound RNA-binding proteins for its own replication while simultaneously suppressing key cellular defense pathways. Researchers noted this effect was consistent across multiple cell lines and influenza strains, indicating a deliberate viral strategy rather than a pathological byproduct. The study underscores the value of mapping molecular interactions within their native cellular context. The collaborative effort utilized shared infrastructure across Hamburg, Berlin, and Zurich, integrating proteomics, high-resolution microscopy, and advanced computational modeling. Lead researchers Jan Kosinski and Boris Bogdanow emphasize that this in-cell cross-linking framework is highly adaptable. While the current analysis focused on a laboratory-adapted strain, the methodology is being positioned to examine emerging pandemic threats, including highly pathogenic avian influenza H5N1, and to decode interaction networks across the broader viral landscape. By delivering unprecedented structural clarity into influenza-host dynamics, this work establishes a scalable blueprint for viral interactome mapping. The identified protein interfaces and disrupted host compartments now serve as actionable targets for pharmaceutical intervention. Furthermore, the validated workflow offers a systematic pathway to preemptively analyze viral infection mechanisms, strengthening global preparedness against future influenza outbreaks and related pathogens.