Production of transgenic-cloned pigs expressing large quantities of recombinant human lysozyme in milk.

Human lysozyme is a natural non-specific immune factor in human milk that plays an important role in the defense of breastfed infants against pathogen infection. Although lysozyme is abundant in human milk, there is only trace quantities in pig milk. Here, we successfully generated transgenic cloned pigs with the expression vector pBAC-hLF-hLZ-Neo and their first generation hybrids (F1). The highest concentration of recombinant human lysozyme (rhLZ) with in vitro bioactivity was 2759.6 ± 265.0 mg/L in the milk of F0 sows. Compared with wild-type milk, rhLZ milk inhibited growth of Escherichia coli K88 during the exponential growth phase. Moreover, rhLZ in milk from transgenic sows was directly absorbed by the intestine of piglets with no observable anaphylactic reaction. Our strategy may provide a powerful tool for large-scale production of this important human protein in pigs to improve resistance to pathogen infection.