HIV: An invasive species
From a biological perspective, there's not much difference between an invasive species running wild in a hospitable, island ecosystem and an HIV infecting a new host, other than the sizes and timescales involved. In the case of sexual transmission, an HIV infection begins with a single virus or a few closely related virus particles, which then multiply exponentially, without competition or ecological checks. As it multiplies, it accumulates mutations and evolves, just as invasive species do. Within days or weeks, the host's blood is packed with virus copies, and the virus will have invaded different "niches" in the body from the spleen to the central nervous system. Once the body's immune response kicks in, levels of virus in the blood will drop again but at that point the virus has already incorporated its genome into cells all over the body.
Satish was intrigued by the possibility that, as the virus invades different organs and tissues, it evolves in predictable ways and that its predictability might allow us to overcome one of the biggest barriers to vaccine development: HIV's extremely high levels of genetic variation.
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Photo provided by Satish Pillai
Understanding Evolution © 2015 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California