Biology:Tropogen

In virology, the tropogen, coined by Stanford virologist Robert David Siegel, is the glycoprotein on the outer surface of a virus that combines with the cellular receptor for the virus. The interaction between the viral tropogen and the cellular receptor is quite specific. This interaction may play a role in determining tissue tropism and host range. Tropogens are of particular interest for drug candidates, as inhibition/blocking of tropogenic receptors blocks viral adsorption.

An example of a tropogen is gp120, an envelope glycoprotein of HIV. gp120 combines in a specific fashion to its cellular receptor CD4, a protein found on various cells in the human immune system including T-helper cells, and macrophage.

Another example of a tropogen is hemagglutinin. Hemagglutinin is found on the surface of influenza virus and it binds to sialic acid found on the surface of host cells.