You may have heard last month’s news about an aggressive form of HIV that had public health officials in New York scared out of their professional gourds. They isolated the virus from a single man, and reported that it was resistant to anti-HIV drugs and drove its victim into full-blown AIDS in a manner of months, rather than the normal period of a few years. Skeptics wondered whether all the hoopla was necessary or useful. The virus might not turn out to be all that unusual, some said; perhaps the man’s immune system had some peculiar twist that gave the course of his disease such a devastating arc. But everyone did agree that the final judgment would have to wait until the scientists started publishing their research.
Today the first data came out in the Lancet. One of the figures jumped out at me, and I’ve reproduced it here. The scientists drew the evolutionary tree of this new strain. Its branch is marked here as “index case.” The researchers compared the sequence of one its genes to sequences from other HIV strains, looking to see how closely related it was to them. The length of the branches shows how different the genetic sequences are from one another. The tree shows that this is not a case of contamination from some other well-known strain. Instead, this new strain sticks way out on its own. The researchers say that they’re now working their way through a major database of HIV strains maintained at Los Alamos to find a closer relative.
This tree is a road map for future research on this new strain. It will allow scientists to pinpoint the evolutionary changes caused by natural selection or other factors that made this strain so resistant to anti-HIV drugs. Scientists will also be able to rely on evolutionary studies of other viruses. Often drug-resistant pathogens have to pay a reproductive cost for their ability to withstand attack from our medicines. Under normal conditions, they reproduce more slowly than resistant strains. But scientists have also found that pathogens can then undergo new mutations that compensate for this handicap and make them as nasty as their resistant counterparts. It’s possible that the new strain has undergone compensatory mutations, which might make it such a threat.
So here we have evolutionary trees and natural selection at the very core of a vitally important area of medical research. Yet we are told again and again by op-ed columnists and certain members of boards of education that evolution is nothing but an evil religion and that creationism of one flavor or another is the future of science. You’d expect then that Intelligent Design or some other form of creationism would help reveal something new about this HIV. But it has not. That should count for something.
Originally published March 18, 2005. Copyright 2005 Carl Zimmer.