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This article is part of the supplement: AIDS Vaccine 2009

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P12-16. Biochemical and immunological characterization of the plant-derived candidate HIV-1 mucosal vaccine CTB-MPR

N Matoba1, I Cherni3, S Kessans3, J Frater3, K Preston3, M Bomsel2 and TS Mor3*

  • * Corresponding author: TS Mor

Author Affiliations

1 James Graham Brown Cancer Center and University of Louisville School of Medicine, Owensboro, USA

2 Institute Cochin, Paris, France

3 Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, AZ, USA

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Retrovirology 2009, 6(Suppl 3):P182  doi:10.1186/1742-4690-6-S3-P182

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

Published:22 October 2009

© 2009 Matoba et al; licensee BioMed Central Ltd.


One of the targets of a future multi-component vaccine against HIV-1 should be one of the virus' chief mucosal penetration processes, namely epithelial transcytosis. We further reported that fusion proteins based on the membrane proximal region (MPR) of gp41, playing a key role in the transcytotic process, and the mucosal targeting subunit B of cholera toxin (CTB) are successful immunogens eliciting such transcytosis blocking immune responses and that such proteins can be produced in plants


Here, we report on the molecular characterization of CTB-MPR expressed in bacteria and transgenic plants and its immunological properties.


We show that bacterially and plant-produced CTB-MPR can be purified to homogeneity. The MPR domain could specifically and reversibly self-associate. The affinities of the mAbs 4E10 and 2F5 to CTB-MPR from either source were equivalent to their affinities toward an MPR peptide. The fusion protein's affinity to GM1-ganglioside was comparable to that of native CTB. Mice and rabbits immunized with CTB-MPR shwoed modest anti-MPR antibody response, but a prime-boost immunization with CTB-MPR and a second MPR-based immunogen elicited a stronger response. These Abs strongly blocked the epithelial transcytosis of primary clade B and D isolates in a human tight epithelial model. The Abs recognized epitopes at the N-terminal portion of the MPR peptide, away from the neutralizing epitopes and were not effective in neutralizing infection of CD4+ cells. These results indicate distinct vulnerabilities of two separate interactions of HIV-1 with human cells – Abs against the C-terminal portion of the MPR can neutralize CD4+-dependent infection, while Abs targeting the MPR's N-terminal portion can effectively block GalCer-dependent transcytosis


We conclude that Abs induced by MPR-based immunogens may provide broad protective value independent of infection neutralization and that plant-based expression can be a viable alternative for the production of subunit HIV-1 vaccine candidates.