Sunday, November 30, 2008
An ounce of prevention....or a dose of evolutionary biology
I hope that everybody reading this has made it through the Thanksgiving holidays healthy and whole. Wherever I have been these past few days though, I have been hearing more of the seasonal coughs and sneezes, which turns me to thinking about colds, and hoping that I don't sound too much like a hypochondriac, a couple of stories about viruses on the "Science Today" website caught my attention today.
The first article (http://www.sciencedaily.com/releases/2008/11/081120073115.htm)
was about the evolution of a virus that causes colds in young children, and which a new study shows originated in birds and "crossed the species barrier" about 200 years ago. This virus, human metapneumovirus (HMPV), is not the same as the rhinovirus that causes up to half of the common colds, yet the symptoms triggered by this virus are much like those typically associated with common colds (runny nose, sore throat, cough, etc.). Researchers in the Netherlands have determined that this virus is very similar to avian metapneumovirus (AMPV-C). What caught my attention in this article was the role that evolution played in the development and transmission of this virus, and how these scientists were able to establish when it migrated from birds to humans. The HMPV and AMPV are both "highly evolutionary," and in addition to determining when AMPV migrated from birds to humans, the researchers studied mutation rates and selection pressures on these viruses. As one of the principal researchers in the study, Dr. Ron Fouchier, summarized it, "An understanding of how viruses evolve and how they adapt to new hosts and their immune systems is important, especially if we are to prepare for new, potentially pandemic diseases."
The second article about colds that had an evolutionary twist was one that showed how viruses manipulate genes to create conditions favorable for the spread of the virus (http://www.sciencedaily.com/releases/2008/10/081024084206.htm). In a recent study conducted by researchers at the University of Calgary and the University of Virginia (with, interestingly, sponsorship from Proctor and Gamble), scientists identified two groups of genes that when "hijacked" by human rhinovirus (HRV), are either "up-regulated" or "down-regulated" by the virus, leading to an increase in production of pro-inflammatory cytokines and a change in the production of antiviral proteins (I was unclear from the article whether the virus lead to a decrease in the production of such proteins, as one would expect, or an increase, as the article at one point seemed to suggest).
In both articles, I was reminded of Gary Ewald's assertion in his book "The Evolution of Infectious Diseases," to the effect that it is important to understand the evolution of such viruses rather than merely trying to develop medicines that in the end simply treat symptoms or to which viruses eventually adapt. Both of these articles seem to be examples of the type of approach that he recommended.