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Journal of Virology, July 2008, p. 6359-6368, Vol. 82, No. 13
0022-538X/08/$08.00+0     doi:10.1128/JVI.00293-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

A Glycoconjugate Antigen Based on the Recognition Motif of a Broadly Neutralizing Human Immunodeficiency Virus Antibody, 2G12, Is Immunogenic but Elicits Antibodies Unable To Bind to the Self Glycans of gp120

Rena D. Astronomo,¹ Hing-Ken Lee,^3,4, Christopher N. Scanlan,^1,6 Ralph Pantophlet,¹ Cheng-Yuan Huang,^3,4, Ian A. Wilson,^2,3 Ola Blixt,^2,5, Raymond A. Dwek,⁶ Chi-Huey Wong,^3,4 and Dennis R. Burton^1,2*

Department of Immunology and Microbial Science,¹ Department of Molecular Biology,² The Skaggs Institute for Chemical Biology,³ Department of Chemistry,⁴ the Glycan Array Synthesis Core D, Consortium for Functional Glycomics, The Scripps Research Institute, La Jolla, California 92037,⁵ The Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom⁶

Received 8 February 2008/ Accepted 14 April 2008

The glycan shield of human immunodeficiency virus type 1 (HIV-1) gp120 contributes to viral evasion from humoral immune responses. However, the shield is recognized by the HIV-1 broadly neutralizing antibody (Ab), 2G12, at a relatively conserved cluster of oligomannose glycans. The discovery of 2G12 raises the possibility that a carbohydrate immunogen may be developed that could elicit 2G12-like neutralizing Abs and contribute to an AIDS vaccine. We have previously dissected the fine specificity of 2G12 and reported that the synthetic tetramannoside (Man₄) that corresponds to the D1 arm of Man₉GlcNAc₂ inhibits 2G12 binding to gp120 as efficiently as Man₉GlcNAc₂ itself, indicating the potential use of Man₄ as a building block for creating immunogens. Here, we describe the development of neoglycoconjugates displaying variable copy numbers of Man₄ on bovine serum albumin (BSA) molecules by conjugation to Lys residues. The increased valency enhances the apparent affinity of 2G12 for Man₄ up to a limit which is achieved at 10 copies per BSA molecule, beyond which no further enhancement is observed. Immunization of rabbits with BSA-(Man₄)₁₄ elicits significant serum Ab titers to Man₄. However, these Abs are unable to bind gp120. Further analysis reveals that the elicited Abs bind a variety of unbranched and, to a lesser extent, branched Man₉ derivatives but not natural N-linked oligomannose containing the chitobiose core. These results suggest that Abs can be readily elicited against the D1 arm; however, potential differences in the presentation of Man₄ on neoglycoconjugates, compared to glycoproteins, poses challenges for eliciting anti-mannose Abs capable of cross-reacting with gp120 and HIV-1.

Published ahead of print on 23 April 2008.

Present address: Intertek Testing Services Shenzhen Ltd., 7/F Shekou Technology Main Building, Industrial 7th Road, Shekou, Nanshan District, Shenzhen, China 518067.

Present address: Research Center for Materials Science, Nagoya University, Nagoya 464-8602, Japan.

Present address: Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Blegdamsvej 3B, Copenhagen N 2200, Denmark.