Plant BioFactory Ramps Up Relief for Dairy Cows

US - Agricultural Research Service (ARS) scientists are testing a plant-produced, therapeutic protein, which thwarts bacteria that cause inflammatory udder disease in dairy cows. They turned a laboratory-produced plant virus into a delivery vehicle that carries a specific gene. The target gene expresses large quantities of a protein called CD14. When the virus reproduces itself inside plant cells, it generates CD14.
calendar icon 1 October 2007
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Plant pathologist Rosemarie Hammond and molecular biologist Lev Nemchinov (right) point out to molecular biologist Dante Zarlenga the virus symptoms on a plant containing the CD14 gene.

The researchers designed the virus to use the plant as a patent-pending "biofactory" that rapidly accumulates usable quantities of the therapeutic CD14 protein. A tagging system—which the researchers built into the technology—allows high levels of the CD14 protein to be harvested from mashed leaves. Potentially, fifty plants could provide enough purified protein to treat a herd of 500 cows.

The CD14 protein is naturally present in cows' milk and blood plasma. Increased amounts of the protein in body fluids may help improve protection against bacterial attack. CD14 binds to and neutralizes a toxin which is present in the outer membrane of the bacterium Escherichia coli that causes mastitis. This binding enhances the cow's immune response, which contributes to a rapid clearance of bacteria before infection gains a foothold.

ARS molecular biologist Lev Nemchinov and plant pathologist Rosemarie Hammond produced the unique plant virus at the agency's Molecular Plant Pathology Laboratory in Beltsville, Md. After a small drop of the virus' transmittable RNA has been rubbed onto plant leaves, the CD14 gene begins to make the protein.

ARS colleagues infused the protein into one of a test cow's four teats, or quarters. All four quarters were then exposed to E. coli. Fewer viable bacteria were recovered from the quarter that received the CD14 treatment than from those that did not receive the plant-derived protein.

Mastitis costs dairy farmers billions annually from incapacitated cows and milk that can't be sold, according to experts.

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