Softening of vero cells induced by measles vaccine virus.

Although early biophysical changes in host cells may provide additional indicators of viral infection, the quantitative analysis of these changes is still in its early stages. In this study, we investigated the mechanical response of Vero cells following exposure to a Measles Vaccine Virus (MVV), employing atomic force microscopy (AFM) alongside confocal microscopy. We performed AFM force-distance and stress relaxation measurements in the perinuclear region to assess the elastic and viscoelastic properties of infected cells. Within 24 h post-infection (hpi), cells infected at a multiplicity of infection (MOI) of 0.5, exhibited a ∼35% reduction in median Young's modulus compared to uninfected controls, indicating significant cellular softening. Variations in the viscoelastic parameters were also observed, including decreased relaxed modulus E0 and reduced viscosities η1 and η2, comparable to those measured in cells treated with the actin depolymerisation agent cytochalasin-D. Confocal microscopy showed a dose-dependent cytoskeletal reorganization characterized by redistribution of F-actin and changes in filament morphology. Quantitative analysis revealed coordinated shifts in structural and mechanical parameters across the experimental conditions. These findings suggested that MVV infection is associated to consistent remodelling of viscoelastic behaviour and actin organization. Overall, this study provides a quantitative biomechanical characterization of MVV associated cellular changes and establishes a descriptive framework for time resolved and mechanistic investigations of virus-host interactions.