Although the fact that Mad Cow disease causes variant CJD had already been strongly established, researchers at the University College of London nevertheless created transgenic mice complete with “humanized†brains genetically engineered with human genes to try to prove the link once and for all. When the researchers injected one strain of the “humanized†mice with infected cow brains, they came down with the same brain damage seen in human variant CJD, as expected. But when they tried this in a different strain of transgenic “humanized†mice, those mice got sick too, but most got sick from what looked exactly like sporadic CJD!