Lactation performance of transgenic goats expressing recombinant human butyryl-cholinesterase in the milk

Abstract

The production of recombinant proteins in the milk of transgenic animals has attracted significant interest in the last decade, as a valuable alternative for the production of recombinant proteins that cannot be or are inefficiently produced using conventional systems based on microorganisms or animal cells. Several recombinant proteins of pharmaceutical and biomedical interest have been successfully expressed in high quantities (g/l) in the milk of transgenic animals. However, this productivity may be associated with a compromised mammary physiology resulting, among other things, from the extraordinary demand placed on the mammary secretory cells. In this study we evaluated the lactation performance of a herd of 50 transgenic goats expressing recombinant human butyryl-cholinesterase (rBChE) in the milk. Our findings indicate that high expression levels of rBChE (range 1-5 g/l) are produced in these animals at the expense of an impaired lactation performance. The key features characterizing these transgenic performances were the decreased milk production, the reduced milk fat content which was associated with an apparent disruption in the lipid secretory mechanism at the mammary epithelium level, and a highly increased presence of leukocytes in milk which is not associated with mammary infection. Despite of having a compromised lactation performance, the amount of rBChE produced per transgenic goat represents several orders of magnitude more than the amount of rBChE present in the blood of hundreds of human donors, the only other available source of rBChE for pharmaceutical and biodefense applications. As a result, this development constitutes another successful example in the application of transgenic animal technology.

Milk composition studies in transgenic goats expressing recombinant human butyrylcholinesterase in the mammary gland

“…They were randomly selected from a herd of 50 transgenic goats produced by artificial insemination of purebred Saanen and Toggenburg goats imported from New Zealand (a scrapie-free country), with semen from a single transgenic Saanen male derived from a selected female founder, as previously described (Baldassarre et al 2008). All transgenic animals in this study have been determined to carry 10-12 copies of the human BChE encoding gene, under the regulation of the goat beta-casein promoter.…”

“…In a previous study (Baldassarre et al 2008), we described the lactation parameters of 50 transgenic goats expressing recombinant human butyrylcholinesterase (rBChE). This enzyme is considered to be the most suitable bioscavenger for the protection of humans against organophosphate toxicity (Doctor and Saxena 2005).…”

Recent advances in the development of new transgenic animal technology

“…The presence of recombinant human butyrylcholinesterase in goat milk can reach 1-5 g/l [60]. Since there is a low insertion efficiency of extrinsic DNA into specific gene sites mediated by homologous DNA sequence or gene targeting in mammalian somatic cells, Bertolini et al (2009) studied the reductive effect of gene targeting on the non-homologous end junction (NHEJ) protein level.…”

Recent Advances in Reproductive Biotechnologies in Sheep and Goat

“…During the last decade, research has focused on producing transgenic animals which secrete recombinant proteins in their milk. These animals produce relatively high quantities of recombinant proteins compared to other conventional methods due to the physiological nature of the mammary gland for its unique ability to synthesize proteins [84,78,85,86,87,88]. A few examples of transgenic small ruminants producing recombinant proteins in milk for pharmaceutical and biomedical interest are sheep producing human clotting factor VIII [89] and factor IX [82] and goats synthesizing human antithrombin III [90], human alpha-fetoprotein [91], human monoclonal antibodies [92,93], malaria antigens [94] spider silks [95], human granulocyte colony stimulating factor (96) and human butyryl-cholinesterase [97,98].…”

“…A few examples of transgenic small ruminants producing recombinant proteins in milk for pharmaceutical and biomedical interest are sheep producing human clotting factor VIII [89] and factor IX [82] and goats synthesizing human antithrombin III [90], human alpha-fetoprotein [91], human monoclonal antibodies [92,93], malaria antigens [94] spider silks [95], human granulocyte colony stimulating factor (96) and human butyryl-cholinesterase [97,98]. Although these animals have shown high expression of the transgene product in the milk, a recent report suggests that the transgene may have some negative effects on the physiology of mammary gland function, leading to a compromised situation [87]. However, the first protein produced by transgenic animals, ATryn, a recombinant human anti-thrombinproduced in transgenic goats' milk, received approval for use in humans in 2009.…”