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This article is part of the supplement: AIDS Vaccine 2009

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P12-13. Structure-guided design and immunological characterization of immunogen constructs presenting the HIV-1 gp120 V3 loop on a CTB scaffold

M Totrov1*, X Jiang2, X Kong2, S Cohen2, C Krachmarov3, C Williams2, T Cardozo2, M Gorny2, S Wang4, S Lu4, A Pinter3 and S Zolla-Pazner2

  • * Corresponding author: M Totrov

Author Affiliations

1 M olsoft, La Jolla, CA, USA

2 NYU Langone School of Medicine, New York, USA

3 PHRI Center, University of Medicine and Dentistry of New Jersey, Newark, NJ, USA

4 University of Massachusetts Medical School, Worcester, MA, USA

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Retrovirology 2009, 6(Suppl 3):P179  doi:10.1186/1742-4690-6-S3-P179

The electronic version of this article is the complete one and can be found online at:

Published:22 October 2009

© 2009 Totrov et al; licensee BioMed Central Ltd.


The V3 loop is a major neutralizing determinant of the HIV-1 virus. Cholera toxin subunit B (CTB) is a highly immunogenic protein and it has been used in fusion constructs to enhance immunogenicity of target proteins. We hypothesized that a rationally designed immunogen, based on V3 and CTB, could induce high titers of Abs with binding mode and epitope specificity similar to known broadly neutralizing anti-V3 mAbs.


We used molecular modeling and available crystallographic structures of the V3 loop in the HIV-1 gp120 context, the V3 loop fragment bound to broadly neutralizing mAbs, as well as the structure of the CTB to design two novel V3-scaffold immunogen constructs: a full-length V3-CTB presenting the complete 35 amino-acid residue V3 loop in a structural context mimicking the V3 in gp120, and a short V3-CTB presenting a smaller segment of V3 in the conformation recognized by mAb 447-52D.


Antigenic properties were evaluated on a panel of 24 anti-V3 human mAbs. The full V3 construct was recognized with high affinity by the large majority of mAbs, with some preference by mAbs derived from clade B-infected individuals. Short V3 construct exhibited high affinity binding to mAb 447-52D and only a few additional mAbs. Immunogenicity of the constructs was evaluated in rabbits using a DNA prime/protein boost protocol. Boosting with the full-length V3-CTB resulted in serum anti-V3 titers that neutralized multiple HIV virus strains from various HIV-1 clades. Short V3-CTB construct was ineffective in boosting the Ab


The results suggest that while (1) a scaffold immunogen that presents a single epitope (designed to fit a single mAb) may result in a poor Ab response, (2) focusing the immune response on a specific immunogenic region, such as the V3 loop, can elicit a robust Ab response, and (3) the CTB scaffold can efficiently present V3