22 February 2011,
A mutated immune system gene increases the risk of developing tuberculosis in African Americans who carry the TB bacteria, said researchers led by those from Baylor College of Medicine and the Methodist Hospital Research Institute in a report in the open-access journal PLoS One.
Only one in 10 people infected with the bacteria that cause tuberculosis actually go on to develop the disease, said Dr. Katherine Y. King, an instructor in the department of pediatrics – infectious diseases at BCM.
"We spend a lot of energy screening for tuberculosis and treating the people who test positive," she said. "It would be better to know who among those who test positive are most at risk of developing the disease. Then we could focus more attention on that group."
Tuberculosis caused by Mycobacterium tuberculosis is the second deadliest single infectious disease worldwide, causing 1.8 million deaths each year.
Mutation in IRGM1 gene
King and her colleagues determined the genotype (the genetic sequence) for the IRGMI1 gene and the nearby area of the genome for 370 African-Americans and 177 Caucasians with tuberculosis and compared them to the genotypes of 180 African Americans and 110 Caucasians who did not have the disease.
They found that the African Americans with tuberculosis were more likely to carry a specific mutation in the IRGM1 gene. The gene had single nucleotide polymorphisms or single letter changes in the genetic code in two places along with a deletion of genetic material in an area near the gene.
That mean the mutations in the gene increased the risk of developing tuberculosis for the African Americans who carry.
"We still do not know how the protein associated with this gene works in humans," said King. "Some studies indicate it might be important in the engulfment of bacteria by macrophages." Macrophages are immune system cells that engulf and degrade or digest bacteria and other foreign invaders.
Focusing on those who need care the most
Treatment for people who carry the TB bacteria but do not have the disease can last as long as nine months. Finding out who is at greatest risk can reduce such treatment and enable health care workers to focus their attention on people who most need such care.
Studies such as the one done by King and her colleagues can also improve understanding about immunity to TB and may lead to new approaches to treatment, she said.
In addition, this mutation in the IRGM1 is also associated with the development of Crohn's disease and this new study strengthens the possibility that that gastrointestinal disorder could have an infectious beginning that includes a misdirected immune response. (Crohn's disease is an inflammatory bowel disorder characterized by pain and severe diarrhea.)
Others who took part in this work include Dr. Margaret A. Goodell of BCM, Justin D. Lew, Ngan P. Ha, Xin Ma and Edward A. Graviss of Methodist Hospital Research Institute in Houston and Jeffery S. Lin of the University of California, Berkeley.
Funding for this work came from the Simmons Foundation Collaborative Research Fund.
http://www.redorbit.com/news/health/2000560/mutated_immune_gene_increases_tb_risk_for_african_americans/
A mutated immune system gene increases the risk of developing tuberculosis in African Americans who carry the TB bacteria, said researchers led by those from Baylor College of Medicine and the Methodist Hospital Research Institute in a report in the open-access journal PLoS One.
Only one in 10 people infected with the bacteria that cause tuberculosis actually go on to develop the disease, said Dr. Katherine Y. King, an instructor in the department of pediatrics – infectious diseases at BCM.
"We spend a lot of energy screening for tuberculosis and treating the people who test positive," she said. "It would be better to know who among those who test positive are most at risk of developing the disease. Then we could focus more attention on that group."
Tuberculosis caused by Mycobacterium tuberculosis is the second deadliest single infectious disease worldwide, causing 1.8 million deaths each year.
Mutation in IRGM1 gene
King and her colleagues determined the genotype (the genetic sequence) for the IRGMI1 gene and the nearby area of the genome for 370 African-Americans and 177 Caucasians with tuberculosis and compared them to the genotypes of 180 African Americans and 110 Caucasians who did not have the disease.
They found that the African Americans with tuberculosis were more likely to carry a specific mutation in the IRGM1 gene. The gene had single nucleotide polymorphisms or single letter changes in the genetic code in two places along with a deletion of genetic material in an area near the gene.
That mean the mutations in the gene increased the risk of developing tuberculosis for the African Americans who carry.
"We still do not know how the protein associated with this gene works in humans," said King. "Some studies indicate it might be important in the engulfment of bacteria by macrophages." Macrophages are immune system cells that engulf and degrade or digest bacteria and other foreign invaders.
Focusing on those who need care the most
Treatment for people who carry the TB bacteria but do not have the disease can last as long as nine months. Finding out who is at greatest risk can reduce such treatment and enable health care workers to focus their attention on people who most need such care.
Studies such as the one done by King and her colleagues can also improve understanding about immunity to TB and may lead to new approaches to treatment, she said.
In addition, this mutation in the IRGM1 is also associated with the development of Crohn's disease and this new study strengthens the possibility that that gastrointestinal disorder could have an infectious beginning that includes a misdirected immune response. (Crohn's disease is an inflammatory bowel disorder characterized by pain and severe diarrhea.)
Others who took part in this work include Dr. Margaret A. Goodell of BCM, Justin D. Lew, Ngan P. Ha, Xin Ma and Edward A. Graviss of Methodist Hospital Research Institute in Houston and Jeffery S. Lin of the University of California, Berkeley.
Funding for this work came from the Simmons Foundation Collaborative Research Fund.
http://www.redorbit.com/news/health/2000560/mutated_immune_gene_increases_tb_risk_for_african_americans/
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