Expression Of Human Lactoferrin And CD14 In Plants

Human lactoferrin has some important physiological functions such as antimicrobial activities, antioxidant activity and immunomodulatory activity. To date, it has become evident that lactoferrin exerts various beneficial effects against diseases and is safe for health. This enlarges the application potential of lactoferrin. Human CD14 is involved in the innate immunity system and the inflammation reaction. As the receptor for the LPS of gram-negative bacteria or the peptidoglycan of gram-positive bacteria, CD14 elicits a series of physiological and pathological responses. Human CD14 exists either as a membrane-bound protein (mCD14) or as a soluble protein (sCD14). During the past twenty years, the ability of sCD14 to protect against infection and the potential of therapeutic had been described in numerous in vitro and in vivo studies. The research on lactoferrin and CD14 has been arousing more and more interest from the public. However, producing human lactoferrin on a factory scale has a high cost and a dissatisfactory yield. Low concentration of CD14 in milk and the presence of numerous other proteins make it a difficult task to purify a relatively large quantity of CD14. Therefore, to make best use of lactoferrin and CD14, more attention has been focused on using gene-engineering technology to produce low cost proteins.Plants are now considered as viable and competitive expression systems for the production of recombinant proteins. Some proteins have been successfully produced in plants. Compared to other organisms, plants offer several advantages for producing foreign proteins. They have eukaryotic post-translational modification machinery and the correct folding and assembling of protein in plants are very similar to the situation in mammalian cells. Furthermore, plant expression systems present no risk of product contamination by mammalian viruses, pathogens and oncogens, and present a potential for lower cost of production when using field crops. However, plant expression systems are developing, and there are some problems to solve such as low expression. The study was on a mission to lay a foundation for using maize to produce human lactoferrin and CD14. To increase the expression of recombinant proteins, the signal peptide from maize zein was used. We had engineered two constructs containing either the native signal peptide from human lactoferrin/CD14 or signal peptide from maize zein fused to human lactoferrin/CD14 encoding cDNA. The plant expression vectors contained human lactoferrin and CD14 gene were introduced into tobacco and maize by Agrobacterium-mediated. Western blot analysis showed human lactoferrin and CD14 had expressed in transgenic tobacco under the control of the CaMV-35S promoter. The concentration of recombinant protein in tobacco was assessed by ELISA. The result suggested that the use of signal peptide from maize zein increased the expression level of recombinant protein. The recombinant human lactoferrin expressed in tobacco had antibacterial ability for both constructs.The study in transgenic tobacco provided some important data for the expression study of human lactoferrin and CD14 in maize. Transgenic maize plants with expressing the two proteins under the maize seed endosperm specific promoter for increasing the expression level of recombinant proteins in endosperm of seed were just obtained, and the analyses of these maize plants are carring out.