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Light At The End Of The Tunnel? 16 October 1998 Why, I wonder, of all the myriad variety of cellular structures in the human body, does the substantia nigra of the midbrain become so vulnerable in PD that its component cells essentially curl up and die, leading to Parkinson's disease? And why, if over 99% of all people don't get PD, do the remaining 1% harbor this vulnerability? Certainly, a seductive answer is that SN cells of that unlucky 1% differ genetically from those of everybody else. Now, to cure PD (or any other disease) there are 3 requirements: (1) Stop the progression of the disease that impairs function. (2) Restore the lost function of the diseased organ. (3) Prevent future impairment or recurrence. If the disease is caused by loss or death of vulnerable cells, it follows that they must be replaced by less vulnerable ones. One way to do that is gene therapy, where the surviving cells in question are made to produce offspring that lack the disease- prone defect. In gene therapy, the DNA (or reproductive formula) of the defective cells is altered, usually by infecting them with a relatively benign virus that has been "engineered" in the laboratory to carry DNA having the desired properties. But, getting that altered DNA into the cells where it is wanted is complicated, difficult, and risky. Gene therapy is usually reserved for severe and medically refractory disorders because of the toxicity, potential long-term risks, and invasiveness of most gene transfer protocols. Now, that obstacle may be breached. An article in the current Nature Medicine (*) describes a successful experiment with animals, where the virus vector was simply given by mouth, much like the multiple pills that we all take every day. The disease selected for the trial was lactase deficiency, an autosomal-recessive disorder that afflicts over 50% of the world's population with intolerance for milk or milk products. The experimental rats were truly cured, as defined above, and a future step is to try the scheme on people. And later on, who knows? Perhaps Parkinson's? * During M et al; Nature Medicine, October 1998, 1131-35, and Alton E et al; ibid, 112l (editorial) Cheers, Joe -- J. R. Bruman (818) 789-3694 3527 Cody Road Sherman Oaks, CA 91403-5013