Expression of human lactoferrin in transgenic rice grains for the application in infant formula

Breast-fed infants are healthier than formula-fed infants, which may in part be due to the lack of components like human lactoferrin (HLF) in infant formula. Thus, fortification of infant formula with bioactive proteins such as recombinant HLF (rHLF) may provide health benefits. A synthetic HLF gene linked to a rice glutelin 1 promoter and signal sequence was transformed to rice cells to produce rHLF. The expression level was up to 0.5% of dehusked rice grain weight. The rHLF was specifically expressed in the rice grain but not in other tissues. Rice grains expressing rHLF were advanced for four generations and expression levels were stable. Biochemical and physical characterization showed that rHLF is identical to HLF in N-terminal sequence, pI, iron-binding capacity, antimicrobial activity against a human pathogen and resistance to protease digestion. Receptor binding activity assessed by Caco-2 cells, a human small intestinal cell line, was also retained for rHLF. Since rice may be used in infant formula, it is feasible that rice grains expressing rHLF can be directly incorporated into infant formula without purification of the rHLF, providing a convenient advantage over other expression systems.