Role of Src family kinases Fyn and Lyn in arenavirus infection

Arenaviruses encompass a diverse group of infectious agents, some of which, like Lassa virus (LASV), pose significant threats to global public health due to their acute virulence, while others, such as lymphocytic choriomeningitis virus (LCMV), are less pathogenic but still clinically relevant. Both Old World arenaviruses LASV and LCMV exploit host tyrosine kinase signaling to establish infection, though the molecular mechanisms remain incompletely understood. In this study, phosphorylated receptor tyrosine kinase antibody array screening revealed that recombinant LASV (rLCMV-LASV GP) infection specifically activates Src family kinases (SFKs), Fyn and Lyn, with their phosphorylation levels markedly elevated during early infection. Subsequent co-immunoprecipitation assays confirmed rLCMV-LASV GP-induced tyrosine phosphorylation of Fyn and Lyn activation. RNAi experiments demonstrated that knockdown of Fyn/Lyn significantly suppressed rLCMV-LASV GP and LCMV nucleocapsid protein expression, viral RNA synthesis, and viral production, highlighting the critical role of SFKs in viral infection. Further investigations showed that saracatinib, an Src inhibitor, exhibited broad-spectrum antiviral activity against LCMV strains, as well as the authentic LASV strain Lassa_HX strain. <i>In vivo</i> studies revealed that saracatinib substantially reduced viral loads in splenic and hepatic tissues and alleviated infection-associated histopathological damage. These findings identify Src family kinase Fyn/Lyn as novel host targets for arenavirus and provide new targets of prevention and treatment for arenaviral infection.IMPORTANCEArenaviruses, including the highly pathogenic Lassa virus (LASV) and clinically relevant lymphocytic choriomeningitis virus (LCMV), pose severe global health threats due to limited therapeutic options. This study unveils a critical host-pathogen interaction mechanism by which Src family kinases (SFKs) Fyn and Lyn facilitate LASV and LCMV infection. Through phosphorylation profiling and functional validation, we establish that viral activation of these kinases drives arenavirus infection. Moreover, the FDA-approved Src inhibitor saracatinib exhibits broad-spectrum efficacy, suppressing LCMV strains as well as the authentic LASV <i>in vitro</i>, while reducing LCMV viral loads and histopathology <i>in vivo</i>. These findings redefine tyrosine kinases as host targets, offering a novel host-directed antiviral strategy by repurposing existing clinical compounds.