Can you resist?
Genetic variations play a part in disease resistance
Some gene variants are good news. Take one associated with HIV/AIDS – a disease that in 2012 affected 35 million people and was responsible for 1.6 million deaths globally.
A genetic mutation called CCR5-delta 32 causes immune system cells called CD4+ T cells to lack working copies of the CCR5 receptor. This receptor is the protein that HIV latches on to when it invades CD4+ T cells. If you have two mutated copies of that gene, you lack working copies of these receptors, which provides a defence against HIV. Around 1 per cent of people of northern European descent carry two mutated copies of the CCR5 gene, and 10 per cent carry one mutated copy.
HIV/AIDS may affect the genetic make-up of populations. Because the CCR5-delta 32 mutation protects against HIV, it helps people survive. This, in turn, means the mutation is becoming more common – and more likely to spread in regions most affected by the disease.
Some scientists think that the CCR5-delta 32 variant may have offered protection from other diseases in the past. It’s been suggested that the mutation might also help to prevent smallpox and arose when that disease was an everyday hazard. Or did it protect against bubonic plague, which wiped out around a third of Europe’s population in the 14th century?Lead image:
NIAID/Flickr CC BY NC ND
- WHO Global Health Observatory: HIV
- Is anyone immune to HIV?
- CCR5: An emerging target for the control of HIV infection (2013)
- Personalized gene therapy locks out HIV, paving the way to control virus without antiretroviral drugs (2014)
- The Black Death and AIDS: CCR5-Δ32 in genetics and history (2006)
- Are you immune to HIV and smallpox?