The main target of HIV is a group of human immune system cells marked with the CD4 glycoprotein. By altering these cells and using them as a host to help manufacture more of the HIV virus, the human immune system and therefore the infected person is vulnerable to infection from other harmful viruses. Without an effective immune system, even the common cold can become life-threatening.
However, individuals with a CCR5-delta 32 mutation of the CD4 gene are immune to the HIV virus. Their cells prevent HIV from entering their cells. Biologists from the the University of Liverpool discovered in 2005 why Europeans in Scandanavia had substantially higher levels of this gene than Europeans near the Mediterranean Sea. It was due to the Black Death, a series of viral haemorrhagic fevers that swept across Europe killing millions. These viruses were found to have been using CCR5 as the access into the cells. The viruses lasted much longer in Northern Europe than in the South, meaning that there was greater amount of time for there to be selective pressure on the gene.
Basically, people who were immune to the haemorrhagic viruses due to a genetic mutation were more prevalent in the Northern European populations. This immunity also applied to HIV because HIV uses a similar method of infection to that of the Black Death viruses. This is an example of natural selection within the human population. If scientists could somehow learn from this mutation to confer immunity to HIV for those who don’t naturally have the gene, it could be a great boon for the advancement of medical science.
University Of Liverpool. “Biologists Discover Why 10 Percent Of Europeans Are Safe From HIV Infection.” ScienceDaily. ScienceDaily, 3 April 2005. <www.sciencedaily.com/releases/2005/03/050325234239.htm>.
Paoli, Julia. “HIV Resistant Mutation.” Scitable. Nature Education, 6 October 2013. Web. Accessed 21 Oct. 2014.