1. Rational Drug Design Solving the influenza problem

2. Introduction Influenza viruses are continually changing into new strains. This prevents us from being able to build up an immunity to influenza Scientists have tried to solve this problem using a technique called rational drug design. The process essentially involves finding out how the infective agent works against a cell and using that information to design a drug that prevents the infective agent from being able to do what it does.

3. How it works? When a virus enters a cell it rapidly multiplies using the cells organelles and then all the new particles then effect more cells and so on. Scientists discovered that the influenza virus used an enzyme called ‘neuraminidase’ to release new virus buds from the cell. So scientists designed a drug that interacts with the active site of this enzyme, stopping it from being able to release the new virus particles, meaning the virus cannot be spread to other cells. This drug was designed using computer modelling so that the active sites exact shape could be used to model the drug (lock and key).

4. Virus becomes attached to receptive sites on the cell surface.

5. Influenza virus enters the cell.

6. Viral components are rapidly produced.

7. Viral components move the cell surface and new viruses bud prior to exit.

8. New virus remains at cell surface until neuraminidase cuts the attachment to the cell.

9. Unless stopped, the process of infecting cells continues and the symptoms of influenza develop.

10. If anti-influenza drug is present, it binds to the active sites of the neurominidase.

11. Virus is trapped at cell surface, unable to infect other cells.

12. The immune system then acts on the relatively few virus particles that do exist.

13. Overview The first thing scientists have to do in rational drug design is figure out the mode of infection and what enzymes are aiding the particle. Scientist then have to design a substance that interferes with the active site of this substance so that the cycle of replication can’t be completed. It is possible that the scientists could have designed a drug that stopped the enzyme that were responsible for the entry of the virus into the cell.