The USDA is promoting a potentially disastrous strategy for controlling mastitis in cows that could enhance a host of other diseases and create new disease agents. Prof. Joe Cummins
Mastitis is a bacterial disease of the mammary, bovine mastitis is an increasing problem in the dairy industry. The gram negative bacterium, Escherichia coli is responsible for most cases of bovine mastitis in North America . Increase in mastitis is, in part, caused by the treatment of the cattle with recombinant (genetically modified) bovine somatotropin . The United States Department of Agriculture Research Service (USDA ARS) has found that treatment of cattle with recombinant receptor protein CD14 can reduce the severity of mastitis. The CD14 receptor protein binds to the bacterial surface lipopolysaccharides (LPS), a proinflammatory molecule that activates mammalian cells to produce and secrete cytokines that induce fever, dysregulated coagulation, and vascular collapse. The CD14-related innate immune responses facilitate clearance and neutralization of LPS, thereby reducing the severity of mastitis. The recombinant bovine CD14 gene is produced by USDA/ARS first in insect cell transformed by a baculovirus vector system [2,3], and by the transformation of tobacco plants using the potato virus X as vector for the gene for CD14. The recombinant bovine protein was recovered from the recombinant virus infected plants . The incorporation of recombinant CD14 in tobacco host plant offers the advantage that a large quantity of the recombinant protein can be produced in a short time and at very little cost . However, the recombinant potato virus X in tobacco plants raises serious safety concerns. Recombination between the viral vector and wild virus will lead to widespread dispersal of the rec ombinant CD14 gene with untoward consequences.
While CD14 is important in controlling infection by gram-negative bacteria such as E. coli, it facilitates invasion by gram-positive bacteria such as Streptococcus pneumoniae . Early intestinal colonization of the human infant with Staphylococcus aureus gram-positive bacteria are associated with increased levels of soluble circulating levels of CD14 . USDA/ARS, in promoting the use of recombinant CD14 to treat mastitis in cattle, seems to have given little thought to the incidence of pneumonia and toxic shock syndrome caused by the elevated levels of soluble CD14 in milk. Furthermore, Staphylococcus mastitis may simply take over from E. coli mastitis.
USDA is not only promoting CD14 to control mastitis in cattle, but it is also regulating the production of the protein in GM tobacco plants. So far, USDA has not discussed the potential of CD14 to enhance diseases caused by gr am-positive bacteria nor has it discussed the problems associated with the release of the recombinant viral CD14 in the environment- the potential for recombination with wild viruses or the transfer of the CD14 gene to food crops such as the potato. This is a good time to call on the USDA to consider such problems.
Article first published 02/10/07
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