New Antibody "Handcuffs" Mastitis Bacteria

A high-tech molecule called a bifunctional antibody may give cows a natural way to fight mastitis, an infection of the mammary gland. The antibody "handcuffs" the mastitis bacterium to a white blood cell, which then zaps the pathogen with hydrogen peroxide.

Mastitis costs the U.S. dairy industry more than $2 billion annually. A producer with 100 cows can expect 50 to 80 cases of mastitis each year. Antibiotics are often ineffective. Producers can't sell milk from treated cows for a few days. Cows that don't respond may be sold for meat, increasing the chance of antibiotic-contaminated beef.

To find a more natural alternative, dairy scientist Max Paape has turned to bifunctional, or coupled, antibodies. These are proving effective against human cancers in early clinical trials. Paape is with the Agricultural Research Service in Beltsville, Md. To produce the first bifunctional antibody for farm animals, he enlisted help from French researchers at the National Institute for Agronomic Research, Nouzilly, France, and David Segal of the National Cancer Institute, Bethesda, Md.

One end of the bifunctional antibody hooks to a mastitis-causing bacterium,Staphylcoccus aureus. The other end snags its "terminator," a neutrophil--a specialized white blood cell from the cow's immune system. This triggers the neutrophil to release a lethal spray of hydrogen peroxide. The spray can't miss, since neutrophil and bacterium are "handcuffed" by the antibody.

It could take several years to ready the technology for farmers. Scientists must first prove bifunctional antibodies can adequately boost the killing power of the cow's neutrophils. Then they will have to refine the technology for its most effective use. Still, Paape envisions a battery of bifunctionals for a range of pathogens in a variety of farm animals.

An article about the research appears in the June issue of Agricultural Research magazine. The article also is on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/jun98/anti0698.htm.

Scientific contact: Max Paape, Immunology and Disease Resistance Laboratory, Beltsville Agricultural Research Center, Bldg. 173, Beltsville, MD 20705-2350, phone (301) 504-8302, fax (301) 504-9498, [email protected].