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Structural Basis of Immune Evasion at the Site of CD4 Attachment on HIV-1 gp120

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Science  20 Nov 2009:
Vol. 326, Issue 5956, pp. 1123-1127
DOI: 10.1126/science.1175868

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Abstract

The site on HIV-1 gp120 that binds to the CD4 receptor is vulnerable to antibodies. However, most antibodies that interact with this site cannot neutralize HIV-1. To understand the basis of this resistance, we determined co-crystal structures for two poorly neutralizing, CD4–binding site (CD4BS) antibodies, F105 and b13, in complexes with gp120. Both antibodies exhibited approach angles to gp120 similar to those of CD4 and a rare, broadly neutralizing CD4BS antibody, b12. Slight differences in recognition, however, resulted in substantial differences in F105- and b13-bound conformations relative to b12-bound gp120. Modeling and binding experiments revealed these conformations to be poorly compatible with the viral spike. This incompatibility, the consequence of slight differences in CD4BS recognition, renders HIV-1 resistant to all but the most accurately targeted antibodies.

  • * These authors contributed equally to this work.

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