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Volume 6 Supplement 3

AIDS Vaccine 2009

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


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.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Matoba, N., Cherni, I., Kessans, S. et al. P12-16. Biochemical and immunological characterization of the plant-derived candidate HIV-1 mucosal vaccine CTB-MPR. Retrovirology 6 (Suppl 3), P182 (2009).

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