Artwork of the retrovirus HIV-1 (green spheres) responsible for AIDS, Acquired Immune Deficiency Syndrome, and a target T-helper lymphocyte cell (bottom left). The outer envelope of the virus is crossed by green spikes of glycoprotein gp120 which will link the virus to the CD4 receptor molecules (pink) on the surface of the lymphocyte. The lymphocyte becomes infected and may die or the virus may remain dormant with the possibility of later reactivation. A possible way of deactivating the virus is to produce synthetic CD4 molecules (yellow) which, by becoming attached to the gp120 spikes, avoid the link with the receptor sites on the T-helper membrane.