|
Links |
How are humans adapting to selection pressures produced by HIV? What will the future bring?
|
|
|
What is MHC and what does it do? What is the molecular basis of chimpanzee resistance to SIVcpz? Are there allelic variants in human population that are protective against HIV? How are humans adapting to selection pressures produced by HIV? What will the future bring?
|
It is important to remember that several evolutionary forces other than natural section are continuously acting on a population, thus the fate of beneficial alleles is not always fixation. The influence of genetic drift in the evolution of alleles that provide protection against HIV must be considered as the frequency of these alleles in the human population is very low. Consequently, the selection coefficient would have to be particularly high for the protective alleles to become fixed in the human population. Nevertheless, regardless of the intensity of selection many beneficial alleles will inevitably be lost due to drift. It is possible however, that in the absence of medical intervention, similar to chimpanzees, the human population will evolve and ultimately adapt to HIV infection (6). Conversely in the face of increasing medical intervention, the intense selection pressure necessary to generate a selective sweep is absent. As the efficacy of HIV drug treatments increases, having alleles that do not afford protection against the HIV virus becomes less deleterious for the individual as mortality and morbidity will significantly decrease. Moreover, as the fitness deficit associated with these non-protective alleles decreases, the type of selection pressure on loci that confer protection against HIV may change. However, medical intervention may also pose a problem for the future as HIV evolves and adapts to treatments regimes. This is an especially large problem in places where patients are not religiously taking their antiretroviral medications (1). As the HIV virus modifies its mechanisms of action to evade medical treatments, natural resistance may differentiate between individuals who succumb to HIV and individuals who survive the epidemic. Perhaps many generations from now our descendants will be able to see evidence of a selective sweep caused by HIV in our genomes, analogous to that of the chimpanzees.
|