Transgenic livestock for biopharmaceuticals: Which therapeutic protein has been produced in the milk of transgenic sheep for replacement therapy in individuals at risk of emphysema?

Introduction / Context:
Transgenic livestock can serve as bioreactors to produce complex human proteins in milk, blood, or eggs. A landmark example is the production of alpha-1 antitrypsin (AAT) in sheep milk for patients with AAT deficiency who are at risk of early-onset emphysema due to unopposed neutrophil elastase activity in the lungs.

Given Data / Assumptions:

• AAT deficiency predisposes to lung tissue destruction.
• Transgenic expression uses mammary gland–specific promoters to secrete protein into milk.
• Purified recombinant AAT can be used for augmentation therapy.

Concept / Approach:
Identify which listed protein is clinically relevant to emphysema risk. AAT is the canonical replacement therapy target; its deficiency underlies emphysema in susceptible individuals. The transgenic sheep platform demonstrated scalable production of functional human AAT in milk, later purified for therapeutic use.

Step-by-Step Solution:

Verification / Alternative check:
Scientific and regulatory literature cite transgenic sheep and goats producing human AAT as classic case studies in pharming.

Why Other Options Are Wrong:

• tPA targets thrombosis, not AAT deficiency.
• Casein is a milk protein scaffold, not a therapy for emphysema.
• APP relates to neurobiology, not lung protease balance.
• Insulin treats diabetes, unrelated to AAT deficiency.

Common Pitfalls:
Confusing biopharming examples (e.g., antithrombin in goat milk versus AAT in sheep); mixing therapeutic indications.

Final Answer:
Alpha-1 antitrypsin (AAT)