Inside a dairy cow's mammary gland, immune cells that seek out and destroy invading bacteria have a tough time finding their targets. Staphylococcus aureus and other mastitis pathogens have a capsule that makes recognition by immune cells difficult. As a result, a dairy producer with 100 cows can expect 50 to 80 obvious cases of mastitis in the herd each year. The drugs are often ineffective because of resistant pathogens or, in older cows, repeated treatments.
Producers have to wait a few days to sell milk from antibiotic-treated cows.
Coupled, or bifunctional, antibodies are proving effective against human cancers in clinical trials of patients who don't respond to traditional therapy, says Paape. He is with the Immunology and Disease Resistance Laboratory in Beltsville, Maryland. This contact triggers the neutrophil to release a lethal spray of hydrogen peroxide. Yan Wang, a doctoral candidate working in Paape's lab, made monoclonal antibodies that bind to a few of these trigger proteins on the surface of bovine neutrophils. Paape enlisted French researchers Pascal Rainard and Bernard Poutrel to construct a monoclonal antibody that zeros in on a specific molecule on the capsule of S. aureus.