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This article is part of the supplement: AIDS Vaccine 2009

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P04-09. Induction of cross-clade neutralizing antibodies with a prime/boost vaccine strategy focused on a neutralizing epitope

S Zolla-Pazner1*, X Kong2, T Cardozo2, C Hioe2, S Cohen2, X Jiang2, MK Gorny2, M Totrov3, A Pinter4, C Krachmarov4, MS Seaman5, S Wang6 and S Lu6

  • * Corresponding author: S Zolla-Pazner

Author Affiliations

1 Pathology, NYU School of Medicine, New York, USA

2 New York University School of Medicine, New York, USA

3 Molsoft, LLC, La Jolla, CA, USA

4 Public Health Research Institute, Newark, USA

5 Beth Israel Deaconess Medical Center, Boston, MA, USA

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

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Retrovirology 2009, 6(Suppl 3):P37  doi:10.1186/1742-4690-6-S3-P37

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

Published:22 October 2009

© 2009 Zolla-Pazner et al; licensee BioMed Central Ltd.


Experiments were designed based on the hypothesis that recombinant vaccine constructs can focus the immune response on shared HIV-1 neutralizing epitopes, and that if not diverted by other biologically irrelevant epitopes, high titers of cross-clade neutralizing antibodies (ccNAbs) will be induced. Indeed, previous experiments showed that when the immune response was focused on V3, ccNAbs were induced (Zolla-Pazner et al, Virology, 2008).


A prime/boost regimen was used in which rabbits were primed (3×) with clade C gp120 DNA and boosted (2×) with: 1) a fusion protein in which the consensus clade C V3 sequence was fused to the C-terminus of MuLV gp70 (V3-gp70), or 2) the same V3 sequence was inserted into a structurally compatible site on cholera toxin B (V3-CTB). Sera were tested for neutralizing activity in TZM-bl cells against a panel of primary isolates and a selection of Tier 1, Tier 2 clade B, and Tier 2 clade C pseudoviruses (psVs) from the standard panel.


Sera from rabbits boosted with V3-CTB neutralized four primary isolates from clades A, AG and B with higher 50% neutralizing titers (NT50) than sera from V3-gp70-boosted rabbits. For example, sera from all five V3-CTB rabbits neutralized Bx08 (with a geometric mean titer [GMT50] = 1:153) whereas only one of five V3-gp70 rabbit responded (1:11). Similarly, serum titers in response to V3-CTB were greater than those to V3-gp70 against 4/4 Tier 1 clade B and C psVs (GMT50 = 1:188 vs. 1:60 for V3-gp70-immunized rabbits). Tier 2 clade C psVZM109F was also neutralized by sera from V3-CTB rabbits (GMT50 = ~1:20).


A prime/boost vaccine regimen using gp120 DNA and V3-scaffold protein immunogens induced ccNAbs. A newly designed V3-CTB protein boost induced the strongest ccNAb response.