Gene Variation May Make Africans More Susceptible to HIV Infections
By GAUTAM NAIK
July 16, 2008 7:31 p.m.
An ancient genetic variation that protects people of African descent against a certain type of malaria may also make them 40% more susceptible to HIV infection, a new study has found.
The result could shed some light on why there is such a large discrepancy among world-wide populations in the prevalence of HIV, the virus the causes AIDS. Africa, for example, has 25 million people infected with HIV, a much higher infection rate than other populations that isn't entirely explained by differences in sexual behavior or social factors. The latest finding suggests that genetics also plays a significant role.
"It helps in part to explain why HIV is so prevalent in Africa. Most Africans have a slight genetic bias to being more susceptible" when exposed to the virus, said Robin Weiss, a virologist at University College London and a co-author of the paper.
But the news isn't all bad. In another twist, the researchers found that the same genetic alteration appears to prolong survival in those infected with HIV by about two years.
The study, which took more than five years to put together, was conducted by researchers in the U.S. and United Kingdom. It appears in Cell Host & Microbe, a new scientific journal.
Scientists said that while their work was part of a larger push to understand the complex underlying genetics of HIV infection, there were no immediate practical benefits. In theory, a "susceptibility test" based on the gene variant would be easy to create; however, it might persuade those who don't have the genetic trait to pursue more risky behavior and increase their chances of getting infected.
Knowing more about the genetic roots of HIV "raises the possibility that not only will we understand how disease is caused, but it also helps us in areas such as vaccine trials" in which genetic differences among individuals can yield differing results, said Sunil Ahuja, a physician who specializes in infectious disease at the University of Texas Health Science Center at San Antonio and is co-author of the paper.
In their study, the researchers focused on a gene that encodes for a protein found on the surface of red blood cells, called Duffy Antigen Receptor for Chemokines. Though the exact mechanism isn't yet well understood, here is what researchers speculate: People with the Duffy protein carry on their red cells and in their circulatory system a larger amount of immune molecules known as chemokines, which confers protection against HIV. In addition, the Duffy protein can act as a sponge and soak up infectious HIV particles, providing additional protection against the virus. People who have a variation of the gene which includes a large proportion of people of African descent don't carry the Duffy protein, and are therefore at higher risk of getting infected when exposed to HIV.
According to the study, 90% of people in Africa and 60% of African-Americans carry the variant gene. In Africa, the scientists estimate that roughly 11% of the HIV burden may be linked to this genetic variation. The study was based on data collected over 25 years by the U.S. Air Force, and included samples from both African-Americans and those of European descent.
http://online.wsj.com/article/SB121622425427558899.html?mod=googlenews_wsj
By GAUTAM NAIK
July 16, 2008 7:31 p.m.
An ancient genetic variation that protects people of African descent against a certain type of malaria may also make them 40% more susceptible to HIV infection, a new study has found.
The result could shed some light on why there is such a large discrepancy among world-wide populations in the prevalence of HIV, the virus the causes AIDS. Africa, for example, has 25 million people infected with HIV, a much higher infection rate than other populations that isn't entirely explained by differences in sexual behavior or social factors. The latest finding suggests that genetics also plays a significant role.
"It helps in part to explain why HIV is so prevalent in Africa. Most Africans have a slight genetic bias to being more susceptible" when exposed to the virus, said Robin Weiss, a virologist at University College London and a co-author of the paper.
But the news isn't all bad. In another twist, the researchers found that the same genetic alteration appears to prolong survival in those infected with HIV by about two years.
The study, which took more than five years to put together, was conducted by researchers in the U.S. and United Kingdom. It appears in Cell Host & Microbe, a new scientific journal.
Scientists said that while their work was part of a larger push to understand the complex underlying genetics of HIV infection, there were no immediate practical benefits. In theory, a "susceptibility test" based on the gene variant would be easy to create; however, it might persuade those who don't have the genetic trait to pursue more risky behavior and increase their chances of getting infected.
Knowing more about the genetic roots of HIV "raises the possibility that not only will we understand how disease is caused, but it also helps us in areas such as vaccine trials" in which genetic differences among individuals can yield differing results, said Sunil Ahuja, a physician who specializes in infectious disease at the University of Texas Health Science Center at San Antonio and is co-author of the paper.
In their study, the researchers focused on a gene that encodes for a protein found on the surface of red blood cells, called Duffy Antigen Receptor for Chemokines. Though the exact mechanism isn't yet well understood, here is what researchers speculate: People with the Duffy protein carry on their red cells and in their circulatory system a larger amount of immune molecules known as chemokines, which confers protection against HIV. In addition, the Duffy protein can act as a sponge and soak up infectious HIV particles, providing additional protection against the virus. People who have a variation of the gene which includes a large proportion of people of African descent don't carry the Duffy protein, and are therefore at higher risk of getting infected when exposed to HIV.
According to the study, 90% of people in Africa and 60% of African-Americans carry the variant gene. In Africa, the scientists estimate that roughly 11% of the HIV burden may be linked to this genetic variation. The study was based on data collected over 25 years by the U.S. Air Force, and included samples from both African-Americans and those of European descent.
http://online.wsj.com/article/SB121622425427558899.html?mod=googlenews_wsj
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