Hyperactivated ZBP1-Mediated Necroptosis Exacerbates Pneumonia in Mice Co-Infected with Low-Lethality H1N1 and HCoV-229E

Influenza virus causes millions of infections annually, with severe viral pneumonia accounting for a substantial proportion of associated mortality. Co-infections with other respiratory pathogens further worsen clinical outcomes, yet the underlying mechanisms remain poorly defined. Clinical observations have documented influenza–coronavirus co-infections, but their pathological interplay has not been elucidated.To address this gap, we established a murine model of sequential H1N1 (FM1 or PR8 strains) and human coronavirus 229E (HCoV-229E) infection, which recapitulated the fatal pneumonia observed in patients. Strikingly, co-infected mice exhibited accelerated mortality and exacerbated lung pathology despite reduced viral loads, revealing a paradoxical “low-virus, high-inflammation” state.Targeted transcriptional and functional analyses identified ZBP1-dependent necroptosis as the central driver of pathology. Lung tissues showed robust activation of the ZBP1–RIPK3–MLKL axis, which correlated with cytokine overproduction and histopathological damage. Notably, inhibition of RIPK3—rather than direct antiviral treatment—restored lung function and improved survival, highlighting the causal role of necroptosis independent of viral replication. Furthermore, this ZBP1-driven mechanism was conserved across diverse influenza strains, emphasizing its broad biological relevance.Collectively, our findings reveal a previously unrecognized immunopathological axis in which influenza-primed lungs undergo coronavirus-triggered necroptotic storm, directly linking viral co-infection to fatal pneumonia. These results identify ZBP1 and RIPK3 as promising therapeutic targets for decoupling inflammation from viral clearance in severe respiratory co-infections.