Viral Variability

Conceptual illustration of how an immune system response against one mutant of the AIDS virus is not necessarily effective against other HIV mutants. An antibody (top) binds to the surface glycoprotein (gp120) of an HIV mutant (middle), much as a socket wrench fits a bolt head. However, because of slight differences in molecular shape (conformation), this same antibody will fail to bind to the gp120 structure of a different viral mutant (bottom). Both arms of an antibody are identical in conformation, but in this illustration, one arm has been cut away to facilitate viewing of the antibody's binding with gp120.

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