HIV Antigen Production in Transgenic Plants

Development and production of a suitable vaccine is the ultimate goal in the attempts to stop the spread of acquired immunodeficiency syndrome (AIDS). Despite more than 20 years of intense research efforts, however, there is still no effective vaccine in sight. The ideal vaccine against human immunodeficiency virus (HIV), scientists say, should efficiently prevent virus transmission and at the same time be provided at very low cost to allow widespread use in developing countries.

Researchers from the Max Planck Institute for Molecular Plant Physiology in Germany and Cambridge University in the United Kingdom explored the potential of transplastomic plants to produce HIV antigens as potential components of an AIDS vaccine. The scientists specifically expressed the HIV antigens p24, which is the major target of T-cell-mediated immune responses in HIV-positive individuals, and Nef in tobacco and tomato plastids.

Optimized p24-Nef fusion gene cassettes trigger antigen protein accumulation to up to approximately 40 percent of the leaf protein. This is a yield 100-fold higher than that obtained in previous attempts to produce p24 by conventional nuclear transformation and demonstrates the enormous potential of plastid transformation for large scale production of pharmaceutical proteins in plants. The scientists hypothesize that the mild phenotype seen in transgenic plants result from the exhaustion of the gene expression capacity of the chloroplast by overuse of its ribosomes for the production of the recombinant protein.

Subscribers can download the paper published by the Plant Biotechnology Journal at http://dx.doi.org/10.1111/j.1467-7652.2008.00356.x Nonsubscribers can read the abstract at http://www3.interscience.wiley.com/journal/121393720/abstract?CRETRY=1&SRETRY=0