Volume 6 Supplement 3

AIDS Vaccine 2009

Open Access

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
Retrovirology20096(Suppl 3):P179


Published: 22 October 2009


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

Authors’ Affiliations

M olsoft
NYU Langone School of Medicine
PHRI Center, University of Medicine and Dentistry of New Jersey
University of Massachusetts Medical School


© Totrov et al; licensee BioMed Central Ltd. 2009

This article is published under license to BioMed Central Ltd.