The development of transgenic mice for the expression of large amounts of human lysozyme in milk.

Human lysozyme (hLYZ) has important potential applications as antimicrobial medicine and food additive. To develop a robust expression vector that ensures expression of large amounts of hLYZ in milk, here a 26,267 bp chimeric mouse whey acidic protein (mWAP)::hLYZ cassette was constructed and used as a mammary gland-specific expression vector, in which a 3,010 bp genomic sequence in the 24,466 bp mWAP gene locus was substituted by a 4,811 bp genomic sequence of hLYZ, exactly from the start codon to the stop codon. Corresponding transgenic mice were generated, and enzymatically-active hLYZ was expressed at 18.4-35 g l(-1) in the milk of most transgenic mouse lines. Our transgenic mice carrying chimeric mWAP::hLYZ represent a model system for cost-effective production of hLYZ.