Amantadine-induced reorganization of model SARS-CoV-2 lipid envelopes

Amantadine attracted renewed interest during the COVID-19 pandemic because of its known antiviral activity against influenza A. In this work, we investigated how amantadine affects a simplified model of the SARS-CoV-2 lipid envelope composed of DOPC : DMPS : PI (50 : 35 : 15), as well as monolayers of the individual lipids: DOPC, DMPS and PI. Langmuir experiments showed that the effect of the drug depends on the lipid type. In DOPC and PI monolayers, amantadine increased the area per molecule, suggesting its incorporation into more fluid layers. In contrast, in more compact DMPS monolayers, stronger electrostatic interactions led to different behaviour and promoted tighter packing at higher surface pressures. For the ternary model, excess area and compression-expansion hysteresis analyses pointed to drug-induced domain formation and changes in monolayer organization, which were confirmed by Brewster angle microscopy. To extend these results to 3D systems, liposomes and giant unilamellar vesicles were used as bilayer models. Dynamic light scattering revealed changes in hydrodynamic diameter and zeta potential, while fluorescence microscopy confirmed amantadine incorporation together with bilayer reorganization. Molecular dynamics simulations supported the experimental observations and showed that amantadine preferentially locates at the interface and partially inserts into the lipid layer. Overall, the results show that amantadine interactions with simplified SARS-CoV-2 lipid envelopes depend on both the net charge of the lipid headgroup and the membrane organization, which is influenced by the presence or absence of unsaturated alkyl chains in the hydrophobic region.