β-Defensins: Antimicrobial peptides contribute to the immune defense against bovine mastitis

Bovine mastitis, caused by bacterial, viral or fungal pathogens and resulting in an elevated level of somatic cells in milk, is one of the most costly dairy-based disease worldwide. Phagocyte cells constitute a major part of the defense mechanism of the bovine mammary gland against mastitis. Defensins contribute to the innate immune response and are effective against a variety of microorganism. Expression of β-Defensins varies in the epithelial cell, with the highest level being in those tissue that are constantly exposed to, and colonized by microorganisms. The presence of β-Defensin genes were reported to be up-regulated in response to mastitis within the bovine mammary gland. Defensin proteins function in first-line host defense by antagonizing a wide range of microbes including bacteria, fungi and enveloped viruses. The antibiotic activity is thought to be based on their cationic, amphiphathic nature, which enables the peptides to impair vital membrane functions. Molecular details for such activities have been elaborated with several models, however there is increasing evidence that these models may not reflect the complex processes involved in killing of microbes. The peptidal structure and the nucleotide sequence of several-defensin genes in human and animals have been well determined. Our goal is to enhance mastitis resistance of dairy animals by enabling the cell of the mammary gland to express and secrete more β-defensins, antimicrobial proteins. In contrast the immune system of transgenic animal will not consider the transgenic protein as being foreign. As the transgenic approach to insertion of new genetic material into agriculturally important animals is feasible but requires extensive prior evaluation of the trangene and trangene product in model system.