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. 2005 Oct 11;102(42):14943–14948. doi: 10.1073/pnas.0505126102

Fig. 3.

Fig. 3.

A model that illustrates accessibility of the coreceptor site region to CD4i antibody fragments after the engagement of the HIV-1 Env spike by CD4 (33). CD4 (yellow) on the target cell membrane engages the CD4bs on gp120 molecules to assemble and expose the coreceptor binding site. In the context of virus–target cell interaction, the site now appears accessible to single-chain Fv (scFv) and Fab fragments of CD4i antibodies but not to intact antibody molecules. In contrast for free monomeric gp120, soluble CD4 binding triggers the binding of intact CD4i antibodies.