A genetic variant peculiar to Africans substantially raises their risk of infection with HIV, according to research that suggests evolved susceptibility may be helping to drive the continent’s Aids epidemic.

The 90 per cent of Africans who carry the DNA variation are 40 per cent more likely to contract HIV than those without it, after similar exposure to the virus, scientists from Britain and America have found.

As the genetic change is common among people of African ancestry but virtually unknown among other ethnic groups, it could explain in part why HIV-Aids is more prevalent in sub-Saharan Africa. The United Nations estimates that 22.5 million people there are HIV-positive, more than two thirds of the global total of approximately 33.2 million.

The variant, known as “Duffy-negative”, is so common in Africa that it could be responsible for about 11 per cent of the continent’s HIV burden, or 2.5 million cases, scientists said.

“It is an Africa-specific variant, which is why it’s so interesting in the context of Aids research,” said Robin Weiss, Professor of Infection and Immunity at University College London, a member of the study team.

“It could certainly be a contributing factor to the scale of the epidemic in sub-Saharan Africa. It’s the first time, so far as we understand, that a genetic factor that increases susceptibility to infection has come into play.”

Sexual behaviour is also involved in the epidemic in Africa, the only part of the world in which it predominantly affects heterosexuals.

The Duffy-negative gene has probably spread so widely through the African population because it provides resistance to a form of malaria called Plasmodium vivax. Professor Weiss believes it may also once have increased resistance against a precursor of the most deadly malaria parasite, Plasmodium falciparum.

These traits would have been highly advantageous in evolutionary Africa. As HIV is a new human pathogen, thought to have jumped from chimpanzees to people between 1910 and 1950, the gene’s effect on the virus would have had no negative consequences until recently. “Something that protected against malaria in the past is now leaving the host more susceptible to HIV,” Professor Weiss said.

Matthew Dolan, of the San Antonio Military Medical Centre in Texas, said: “After thousands of years of adaptation, this Duffy variant rose to high frequency because it helped protect against malaria. Now, with another global pandemic on the scene, this same variant renders people more susceptible to HIV. It shows the complex interplay between historically important diseases and susceptibility in contemporary times.”

For the study, published in the journal Cell Host & Microbe, scientists examined a group of US Air Force personnel, of whom more than 1,200 are HIV-positive, and who have been followed for nearly 22 years. The Duffy-negative genotype was seen almost exclusively in African-Americans.

A continent cursed

— Sub-Saharan Africa is the globe’s most Aids-affected region. In 2005, 24.5 million of its people were living with HIV and of all Aids sufferers, 64 per cent live there

— In 2005, about 2.7 million people became infected with HIV and more than two million died

— More than two million children under 15 are HIV-positive and more than 90 per cent live in Africa

— About 12 million African children under 17 have lost one or both parents to Aids

— About 72 per cent of all people needing anti-retroviral treatment live in Africa, and only one in six receives the necessary medicine

— Swaziland has the highest HIV rate, at 33.4 per cent of population. Botswana has 24.1 per cent and Zimbabwe 20.1 per cent

Source: UNAids

Have your say

Good news in furthering our understanding of this disease hence a possible approach to a cure. The link between sickle cell disease among African-Americans and Afro-Caribbeans is established. Genes suitable for one environment and not so in another and so the consequences. Ignore conspiracy theories

Cheryl , Kingston, Jamaica

What Whites largely do not know is that they all have black blood. We were the first created, and from our "MIX" all the rest were created. Therefore not only Blacks are susceptible to AIDS to that degree. If it targets the Black Gene it will find it in the white man hidden away. Same goes for all .

HELEN K MAYERS, Maxwell, B'dos, W.I.

the saying that a continent that is cursed is in my terms of opinion very absurd to say ,who are you to claim that the continent of africa is cursed,this cursed continent shall one day raise from the ashes and shall claim her place in the world but i ask who you are to call the people of god cursed

source: http://www.timesonline.co.uk/tol/life_and_style/health/article4345263.ece