Plastids vaccines

Since plastids have a limited set of protein degradation pathways, foreign proteins that exhibit harmful effects to the plant in the cytoplasm may be more stable when they accumulate within the chloroplast (Heifetz, 2000). For example, the vaccine protein cholera toxin B subunit was shown to be toxic even when it accumulated to very low levels within the plant cytoplasm, but was nontoxic when it accumulated to large quantities within the chloroplast. Plastids also possess the ability to form disulfide bonds, a requirement for many correctly folded mammalian proteins (Daniell et al., 2005a). These properties have made them attractive for the production of biopharmaceuticals in plants. 

Chlorogen Plastid accumulation of vaccines, proinsulin, antibodies, human serum albumin 111-114... 

In conclusion, plastid-based expression systems provide for potentially higher expression levels than the majority of nuclear expression systems, and with a higher level of transgene containment, but the platform provides limited post-translational processing choices. Also, despite reports of successful plastid transformation of new species beyond Nicotiana, the choice of production host is stiU predominantly restricted to the Nicotiana family. However, this hmita-tion does not present a serious drawback for production of pharmaceutical proteins (except perhaps for edible vaccines ) since tobacco is a non-feed/non-food crop with a weU-estabhshed agriculture. 

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