Figure 7. Analysis of lysostaphin protein expression in milk of knock-in cows.

(a) Western blot analysis of milk probed with antibody against recombinant lysostaphin: 1 μl milk from gene-targeted cows GT12120, GT12128 and nontransgenic cow AU1119. Bacterially derived recombinant lysostaphin in saline (10 ng). (b) Western blot analysis for the expression of β-casein: 1 μl milk from gene-targeted cows GT12120, GT12128 and nontransgenic cow AU1119 were used. (c) Bacterial plate assay for staphylolytic activity. Lytic zones developed on a lawn of S. aureus 12 h after sample application: 10 μl milk from nontransgenic cow (1) and 10 μl (500 ng ml⁻¹) recombinant lysostaphin (2) and 10 μl milk from gene-targeted cows (3, 4). (d) Eight gene-targeted calves lived for more than one month.