The specific inhibition of influenza A virus maturation by amantadine: an electron microscopic examination.

Amantadine specifically inhibits the release of virus particles from cells infected with the Rostock (H7N1) strain of influenza A virus, apparently as a consequence of a membrane protein M2-mediated conversion of haemagglutinin (HA) to its low pH conformation. Electron microscopic observations, together with immunogold labelling, showed that amantadine action does not alter the distribution of HA on the cell surface nor does it prevent the formation of budding virus particles. It was not possible, however, to discern whether low pH HA inhibited the final stage in virus maturation, i.e. pinching off, or simply prevented release of fully formed particles.