Binding of the 2F5 monoclonal antibody to native and fusion-intermediate forms of human immunodeficiency virus type 1 gp41: implications for fusion-inducing conformational changes.

We investigated how the broadly neutralizing monoclonal antibody 2F5 affects the human immunodeficiency virus type 1 envelope glycoprotein as it undergoes receptor-induced conformational changes and show that 2F5 binds both native and fusion-intermediate conformations, suggesting inhibition of a late step in virus entry. We also demonstrate conformational changes in the C heptad of gp41.