Plant BioFactory Ramps Up Relief for Dairy
Cows By Rosalie
Marion Bliss September 28, 2007
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.
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 systemwhich the researchers built
into the technologyallows 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
Nemchinov and plant pathologist
Hammond produced the unique plant virus at the agency's
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.
more about this research in the September 2007 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.