Gene makes Africans more susceptible to HIV
Wednesday, 16 July 2008
Cosmos Online
Higher risk: A gene which confers some protection against malaria - carried by this Anopheles mosquito - has been found to increase susceptibility to HIV.
Credit: Wikimedia
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SYDNEY: A genetic variation, which evolved to protect people of African descent against malaria has, now been shown to increase their susceptibility to HIV infection by up to 40 per cent.
Conversely, according to a new study, the same variation also appears to prolong survival of those infected with HIV by approximately two years.
The discovery marks the first genetic risk factor for HIV found only in people of African descent, and sheds light on the differences in genetic makeup that play a crucial role in susceptibility to HIV and AIDS.
25-year study
The research, published today in the journal Cell Host & Microbe, was the product of an international research project led by Sunil K. Ahuja, from the University of Texas Health Science Centre in San Antonio, USA.
Researchers there, and at University College London (UCL) in the U.K., analysed data from a 25-year study of thousands of Americans of different ethnic backgrounds.
The gene that the research focused on encodes a binding protein found on the surface of cells, called Duffy Antigen Receptor for Chemokines (DARC). The variation of this gene, which is common in people of African descent, means that they do not express DARC on red blood cells.
DARC influences the levels of inflammatory and anti-HIV blood factors called chemokines and is not the gene related to the disease sickle cell anaemia, which also confers some malaria resistance.
"In sub-Saharan Africa, the vast majority of people do not express DARC on their red blood cells and previous research has shown that this variation seems to have evolved to protect against a particular form of malaria," said co-author Robin Weiss a virologist at UCL in London. "However, this protective effect actually leaves those [people] with the variation more susceptible to HIV."
"The big message here is that something that protected against malaria in the past is now leaving the host more susceptible to HIV," said Weiss.
"Double-edged sword"
"It turns out that having this variation is a double-edged sword," added lead author Ahuja. "The finding is another valuable piece in the puzzle of HIV-AIDS genetics."
HIV affects 25 million people in sub-Saharan Africa today, an HIV burden greater than any other region of the world. Around 90 per cent of people in Africa carry the DARC genetic variation, meaning that it may be responsible for an estimated 11 per cent of the HIV burden there, said the researchers.
They noted that sexual behaviour and other social factors do not fully explain the large discrepancy in HIV prevalence in populations around the world, which is why genetic factors are a vital field of study.
With University College London.
