Localization of a bacterial protein in starch granules of transgenic maize kernels

Abstract

The B subunit of Escherichia coli heat labile enterotoxin (LT-B) is a potent oral immunogen with potential for use as a vaccine, a carrier molecule to deliver antigens to gut-associated lymphoid tissues, and possibly an adjuvant to make coadministered vaccines more effective. LT-B produced in plants was shown to be functional and immunogenic in animals and humans. In this work, we show that maize-derived LT-B is strongly associated with starch granules in endosperm. Using immunogold labeling͞electron microscopy, cell fractionation, and protein analysis techniques, we observed that LT-B protein could be detected both internally and externally in starch granules. This strong association confers an effective copurification of the antigen with the starch fraction of maize kernels, thermostability desirable in maize processing, and resistance to peptic degradation in simulated gastric fluid digests, an important attribute for an orally delivered antigen.LT-B ͉ starch localization

Unexpected Deposition Patterns of Recombinant Proteins in Post-Endoplasmic Reticulum Compartments of Wheat Endosperm

“…Among these three proteins, only phaseolin is glycosylated, and no precise tracking was performed. In maize, recombinant Escherichia coli toxin B was found in starch granules, contrary to the predicted extracellular secretion (Chikwamba et al, 2003). In wheat, only three recombinant proteins have been localized: HSA-KDEL, phytase (this study), and pea legumin .…”

Rice-based mucosal vaccine as a global strategy for cold-chain- and needle-free vaccination

“…2B). In contrast, LTB expressed in maize kernel seems to be less resistant to peptic degradation when compared to CTB in the rice seed because LTB protein was accumulated mainly in the starch granules of transgenic maize kernels (40). These finding indicated that accumulation of vaccine antigen in PB-I would provide physicochemical stability against digestive enzymatic effects.…”

Seed-based oral vaccines as allergen-specific immunotherapies

“…It was reported that E. coli LTB were unexpectedly targeted to amyloplasts as starch granules of maize endosperm by using a common signal peptide sequence as the targeting signal. 50 However, accumulation levels were extremely low, although targeting recombinant proteins to starch granules could still potentially be very useful for the oral or mucosal delivery of vaccines. Similar alterations of intracellular localization have often been observed irrespective of the presence considered.…”