Production of human lactoferrin and lysozyme in the milk of transgenic dairy animals: past, present, and future

Abstract

Genetic engineering, which was first developed in the 1980s, allows for specific additions to animals' genomes that are not possible through conventional breeding. Using genetic engineering to improve agricultural animals was first suggested when the technology was in the early stages of development by Palmiter et al. (Nature 300:611-615, 1982). One of the first agricultural applications identified was generating transgenic dairy animals that could produce altered or novel proteins in their milk. Human milk contains high levels of antimicrobial proteins that are found in low concentrations in the milk of ruminants, including the antimicrobial proteins lactoferrin and lysozyme. Lactoferrin and lysozyme are both part of the innate immune system and are secreted in tears, mucus, and throughout the gastrointestinal (GI) tract. Due to their antimicrobial properties and abundance in human milk, multiple lines of transgenic dairy animals that produce either human lactoferrin or human lysozyme have been developed. The focus of this review is to catalogue the different lines of genetically engineered dairy animals that produce either recombinant lactoferrin or lysozyme that have been generated over the years as well as compare the wealth of research that has been done on the in vitro and in vivo effects of the milk they produce. While recent advances including the development of CRISPRs and TALENs have removed many of the technical barriers to predictable and efficient genetic engineering in agricultural species, there are still many political and regulatory hurdles before genetic engineering can be used in agriculture. It is important to consider the substantial amount of work that has been done thus far on well established lines of genetically engineered animals evaluating both the animals themselves and the products they yield to identify the most effective path forward for future research and acceptance of this technology.

A new paradigm for regulating genetically engineered animals that are used as food

“…Lysozyme is a naturally occurring antimicrobial found at 1,500-times greater amounts in human milk than in goat milk. Substantial data demonstrate both that the GE animals producing hLZ at levels approaching human milk are healthy and that consumption of pasteurized hLZ-containing goats' milk by young pigs results in positive benefits and can aid in recovery from an Escherichia coli-caused diarrheal infection (13). There is no production of the transgene product in muscle; so, when consuming meat from these animals, only the DNA is being eaten.…”

Lactoferrin from Milk: Nutraceutical and Pharmacological Properties

“…On the other hand [89] they demonstrated also that Lactoferrin administration decreases MCP-1 and TNF-α expression levels and markers for oxidative damage while increases the volume of tear secretion. Moreover, a combined dietary supplement containing fish oil, lactoferrin, zinc, vitamin C, lutein, vitamin E, γ-aminobutanoic acid, and Enterococcus faecium WB2000 improves the symptoms of dry eye syndrome with no side effects [90]. …”

Nutritive and Bioactive Proteins in Breastmilk

“…Higher amounts of lysozyme have been observed in colostrum at approximately 0.36 g/L that is reduced slightly in mature milk to 0.30 g/L [55] . Attempts have also been made to produce recombinant human lysozyme and lactoferrin in dairy animals [56] . The mechanism is yet unclear, but lysozyme of BM origin also contains activity against HIV type 1 [57] .…”