Washington Post: Scientists announce mad cow breakthrough

A research company has succeeded, apparently, in producing a dozen calves in which the gene that codes for the production of prions has been "knocked out," leaving the animals with no normal prions.

Mad cow disease is caused when malformed prions introduced into an animal pass their deformation to existing normal prions present in the animal. Prions cannot reproduce themselves, but can transmit their deformity to "good prions" that happen to be present.

The implication of these "genetically engineered" cattle is that they should be completely immune to mad cow disease, as they have no natural prions.

These experimental stock were produced to permit production of sera for other medical uses that would not be susceptible to inclusion of the mad cow prions. They were not intended, at this time, for use as food. The FDA has approved use of cloned animals for food, but has not yet approved "genetically engineered" animals for such use; and it is likely that gaining approval will be much more difficult than for clones.

It is estimated that it will take at least 6 months to be reasonably assured that the calves produced will survive without problems, although at present they appear "normal" in all respects. Some researchers have believed that normal prions are required in some biological processes, particularly in brain development; but for now the absence of prions in these dozen critters doesn't seem to have harmed them.

Stay tuned for more - maybe in about a year...

John