Monday, July 11, 2005

Good News: Virology

Scientific American has a nice, short article about a major discovery.  The SARS virus produces a protein known as Spike, that interacts with a well-known protein, ACE2 [angiotensin I converting enzyme (peptidyl-dipeptidase A) 2].  Apparently Spike reduces the expression of ACE2.  The article isn't clear about the nature of the interaction; whether Spike acts on the gene itself:

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or whether it binds to the protein itself.  In any case, there is a reduction in activity of ACE2.  This apparently causes or contributes to the respiratory distress that is characteristic of SARS:
SARS infection, and specifically the SARS protein known as Spike, reduces ACE2 expression. As a result, blood vessels in the lungs become damaged and the lung becomes flooded as a result.
Treating mice with a related condition, ARDS (1 2), with ACE2 protects the animals from pulmonary failure.  ARDS has a number of causes, and is common in humans.  

The significance of this is twofold.  First, and most obviously, it could point to a treatment to help patients with SARS, should there be another outbreak.  Second, and more importantly, it could point to a treatment for ARDS.  If so, this could have widespread applications:
"We of course need to extend these findings in mice now to humans," Penninger says. "Yet in essence, SARS pointed us to a protein that may help millions of people affected with a previously untreatable disease." Indeed, John Nicholls and Malik Peiris of the University of Hong Kong note in an accompanying commentary in Nature Medicine that the results could be applied to acute lung injuries arising from viruses and other causes, including a potential avian flu pandemic.
One of my professors in medical school remarked, upon hearing of the retroviral nature of HIV, "we are going to learn a lot from this disease."  Indeed, we have.  Now it appears that we may learn something important from SARS as well.  Cripes, if we can figure out how to ameliorate lung injury in ARDS, we could help a lot of people.  ARDS is reported to have a mortality of 20-30%, in one of the references; 40-70% in another.  (Most patients with ARDS have some other, very serious, condition, at the same time.  Thus, it is difficult to estimate the risk posed by ARDS alone.)  The incidence is estimated at 150,000-200,000 cases per year in the USA.  Thus, the importance of this discovery extends far beyond the treatment of SARS alone.  This is really cool.  
Chest radiograph of a patient with adult respiratory distress syndrome (ARDS) Histologic section of the lung showing diffuse alveolar damage in adult respiratory distress syndrome (ARDS).

Categories: science, medicine
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