So I was originally going to talk about Cystic Fibrosis, but time got 
tight, and I wanted to say something briefly about it here.  CF results 
from a single missing protein that causes mucus throughout your body to be 
thicker than it should.  It's the most common lethal recessive genetic 
disease in America, occurring something like 1 in 3300 live births amongst 
caucasians.  While the mucus can cause assorted problems by clogging 
various portions of your body, the most severe problem occurs in the 
lungs.  In the lungs, the mucus blocks airways, causing severe strain as 
the lungs struggle to clear it out, and provides a habitat for nasty 
bacteria. <p>

CF was also a very early target for gene therapy, using a virus especially 
suited for infecting the lungs: adenovirus, source of the common cold (and 
the virus depiced in my cartoons).  Unfortunately, gene therapy hit a 
serious stall due to the make-up of the lungs.  Most of the cells in your 
lungs don't actually divide at all - they are created by adult lung stem 
cells, they live for a while, and they die.  As a result, the treatment 
(which appeared it might work in one very small scale clinical experiment) 
results in only a very short term improvement, which goes away when the 
treated cells die. Unfortunately, the immune system makes it nearly 
impossible to keep re-treating every generation of a patient's lung cells, 
as the adenovirus is just too bad at keeping a low profile.  <p>

So, scientist are trying to find better viruses that don't attract 
attention, and aren't likely to cause damage (the patient at UPenn I 
mentioned earlier died from a reaction to an adenovirus).  Obviously, what 
we really want is the ability to treat the lung STEM CELLS of CF patients, 
as that could produce a permanent cure.  This isn't an easy task, though.  
Even the most common adult stem cells are only at a frequency of one stem 
cell amongst 10,000 regular cells in a tissue, and the only way to really 
get at those within a tissue is to hack a chunk of the organ out of your 
body and see what parts of it can grow.  It's not known whether viruses 
can even get AT these cells in the body, and at any rate serious damage 
will probably occur if you're infecting enough cells to have affected a 
substantial number of stem cells (one million regular cells gets you only 
100 stem cells AT BEST).  <p>

What possibilities does that leave?  Well, as I said at the beginning, 
there is work being done on finding out exactly how serious adult stem 
cells are about only producing certain kinds of cells.  If it's possible 
to convince stem cells we CAN get at easily from the blood or bone marrow 
to become lung stem cells, there is a very attractive treatment option.  
Maybe someone will find a way to engineer a virus that specifically goes 
looking for stem cells (not totally impossible - many viruses infect 
certain types of cells by looking for protein markers on the outside of 
the cell, and if stem cells turn out to have unique markers....).  Or 
maybe people will succeed in finding a virus that both can't make people 
sick and CAN evade the immune system, producing a safe vector for repeated 
treatments.  At any rate, it is my belief that, with the number of people 
afflicted with this disease and the number of smart scientists out there, 
a cure for it WILL be found, and not a day too soon.<p>

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