Relenza

How does Relenza work? It blocks the action of the enzyme neuraminidase (also called sialidase) on the surface of types A and B influenza viruses, preventing them from spreading to other cells. Influenza viruses bind to sialic acids on the surface of host cells through the viral haemagglutinin glycoprotein. The haemagglutinin causes the virus envelope to fuse with the membrane of the endosome, allowing the virus ribonucleprotein (RNP) into the cytoplasm. The RNP complex then moves to the nucleus for transcription and amplification. Newly formed virus RNPs leave the nucleus and then virus particles bud from the cell at the plasma membrane. Normally, neuraminidase ‘untethers’ newly assembled virus particles bound to sialic acid on the surface of the cell and on the glycoproteins of other virus particles, but neuraminidase inhibitors can block virus spread at this stage. In cultured cells, virus aggregates can be seen at the cell surface when Relenza is present (see Figure).