Transgenic livestock as bioreactors: stable expression of human alpha-1-antitrypsin by a flock of sheep.

We have previously described the generation of transgenic sheep expressing human alpha 1-antitrypsin (h alpha 1AT) in their milk. Here, we report the fidelity of transgene transmission and expression by these animals and their progeny. Transgene transmission has been demonstrated in four of six ovine lines studied. Three of these four lines have exhibited stable transmission of the transgene, whereas the fourth has produced some offspring with reduced copy numbers. Sequential lactations of founder animals has yielded very similar levels of h alpha 1AT protein in milk. Moreover, in one line, derived from a founder male, a flock of seven G1 ewes have yielded comparable levels of h alpha 1AT protein in first and second lactation milk. Two G2 ewes of this line have also produced levels of human protein equivalent to their mother. Although the inheritance of the same transgene in mice was reminiscent of the situation in sheep, stable expression was observed in only one or four lines studied. The importance of these observations to the use of transgenic livestock as bioreactors for the production of human proteins is discussed.

Expression of human alpha 1 antitrypsin in transgenic sheep.

We have recently described the production of large amounts (< or = 65 grams per litre) of enzymatically active human alpha 1 antitrypsin in the milk of transgenic sheep (Wright et al., 1991). Here, we describe in more detail the expression of the human protein in the milk of these animals throughout the lactation period. Human alpha 1 antitrypsin is also found at much lower levels in the plasma of transgenic ewes before, during and after lactation. It is also detected in male plasma at very low levels. We have previously shown human alpha 1 antitrypsin purified from transgenic sheep milk to be indistinguishable from commercially available human plasma derived alpha 1 antitrypsin in terms of gross sugar content and in vitro activity. Here we extend this comparison to more detailed analyses of glycosylation state, amino-terminal sequence, pI value, and molecular weight determination by mass spectrometry.

High level expression of active human alpha-1-antitrypsin in the milk of transgenic sheep.

We describe the generation of five sheep transgenic for a fusion of the ovine beta-lactoglobulin gene promotor to the human alpha 1-antitrypsin (h alpha 1AT) genomic sequences. Four of these animals are female and one male. Analysis of the expression of h alpha 1AT in the milk of three of these females shows that all express the human protein at levels greater than 1 gram per liter. In one case initial levels exceeded 60 grams per liter and stabilized at approximately 35 grams per liter as lactation progressed. Human alpha 1AT purified from the milk of these animals appears to be fully N-glycosylated and has a biological activity indistinguishable from human plasma-derived material.

Tiglicaciduria in propionicacidaemia.

Tiglic acid, which has not previously been found in human body fluids, was recently detected in the urine of two patients with propionicacidaemia. These patients had a documented defect in the oxidation of propionate. A competition between acrylyl-CoA and tiglyl-CoA for crotonase could explain the accumulation of tiglic acid.