Characterization of Human Immunodeficiency Virus Type 1 Monomeric and Trimeric gp120 Glycoproteins Stabilized in the CD4-Bound State: Antigenicity, Biophysics, and Immunogenicity

Authors

Barna Dey, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
Marie Pancera, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
Krisha Svehla, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
Yuuei Shu, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
Shi-Hua Xiang, University of Nebraska-LincolnFollow
Jeffrey Vainshtein, Dana-Farber Cancer Institute, Boston, Massachusetts
Yuxing Li, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
Joseph Sodroski, Harvard Medical SchoolFollow
Peter D. Kwong, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
John R. Mascola, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
Richard Wyatt, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MarylandFollow

Date of this Version

2007

Citation

Journal of Virology, June 2007, p. 5579–5593 Vol. 81, No. 11

Comments

Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Abstract

The human immunodeficiency virus type 1 exterior gp120 envelope glycoprotein is highly flexible, and this flexibility may contribute to the inability of monomeric gp120 immunogens to elicit broadly neutralizing antibodies. We previously showed that an S375W modification of a critical interfacial cavity central to the primary receptor binding site, the Phe43 cavity, stabilizes gp120 into the CD4-bound state. However, the immunological effects of this cavity-altering replacement were never tested. Subsequently, we screened other mutations that, along with the S375W alteration, might further stabilize the CD4-bound state. Here, we define a selected second cavity-altering replacement, T257S, and analyze the double mutations in several gp120 envelope glycoprotein contexts. The gp120 glycoproteins with the T257S-plus-S375W double mutation (T257S+S375W) have a superior antigenic profile compared to the originally identified single S375W replacement in terms of enhanced recognition by the broadly neutralizing CD4 binding-site antibody b12. Isothermal titration calorimetry measuring the entropy of the gp120 interaction with CD4 indicated that the double mutant was also stabilized into the CD4-bound state, with increasing relative fixation between core, full-length monomeric, and full-length trimeric versions of gp120. A significant increase in gp120 affinity for CD4 was also observed for the cavity-filling mutants relative to wild-type gp120. The most conformationally constrained T257S+S375W trimeric gp120 proteins were selected for immunogenicity analysis in rabbits and displayed a trend of improvement relative to their wild-type counterparts in terms of eliciting neutralizing antibodies. Together, the results suggest that conformational stabilization may improve the ability of gp120 to elicit neutralizing antibodies.