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Gene May Help Prevent Mastitis in Dairy Cows

By Rosalie Marion Bliss
August 6, 2002

Agricultural Research Service scientists have filed a patent application on a cloned gene that promises to treat or prevent bacterial infections that cause mastitis in dairy cows. The gene produces a protein that is naturally present in cows' milk and blood plasma, but in amounts too small to have any therapeutic effect. The recombinant protein, named CD14, binds to and neutralizes toxins made by bacteria that cause mastitis.

Each year, about 3 million U.S. dairy cows develop acute mastitis after infection with coliform bacteria that lurk in the cleanest of barns. The microbes infiltrate dairy cows' udders, putting about one-tenth of infected cows out of commission. The problem costs dairy farmers an estimated $1.4 billion annually from incapacitated cows and milk that can't be sold.

ARS' Max Paape, a dairy scientist, and Dante Zarlenga, a molecular biologist, along with cell biologist Yan Wang, now with the National Institute of Allergy and Infectious Diseases in Rockville, Md., cloned the gene and demonstrated the effectiveness of the protein against mastitis infections. Paape and Zarlenga are in the ARS Immunology and Disease Resistance Laboratory in Beltsville, Md.

CD14 sensitizes the lining of a cow's mammary glands to the very low levels of the bacterial toxin, called endotoxin, that are produced in the early stages of an infection. Once sensitized, these mammary cells recruit white blood cells that attack and kill infiltrating bacteria before they can establish an infection.

Scientists now are conducting tests to support the new hypothesis that cows genetically engineered to produce higher-than-normal amounts of CD14 could enjoy CD14's protection from infection as well.

ARS is the U.S. Department of Agriculture's chief scientific research agency.