Johns Hopkins researchers, in the largest study to date, will map the genetic code for asthma in people of African descent in hopes of better understanding why the disease and other allergy-related ailments disproportionately afflict that population.
Until now, the link between genetics and asthma has been studied using mostly men and women of white European descent. The Hopkins researchers announced Thursday that they will leverage data from other genome projects to take the first wide-scale look at how hereditary factors affect African-Americans who have the disease, which causes wheezing and difficulty breathing, and which can lead to death if not treated.
The National Heart, Lung and Blood Institute has given the Hopkins team of experts in genetics, immunology, epidemiology and allergic disease $9.5 million to fund the four-year study.
"It would be the largest and most comprehensive study to identify genes and rare genetic variants of interest for asthma in African-Americans," said James Kiley, the director of lung disease for the institute.
Those who work in asthma prevention said such a study could help in their effort to better treat the disease by leading to new medicines and helping to identify it at the earliest stages or even before symptoms develop. If not treated early enough, asthma can lead to irreversible lung damage.
Nationwide, about 20 percent of African-Americans have asthma, including more than 120,000 in Maryland. Baltimore leads the state in asthma-related deaths — the disease is exacerbated by environmental factors such as old, dusty buildings, rodent feces and poor air quality. The city also has the highest rate of children hospitalized because of the disease. In general, African-Americans are more likely than whites to die from asthma or end up in the emergency room.
The Hopkins researchers will map the genetic code of 1,000 people of African descent — 500 with asthma and 500 without — from research centers in Baltimore and in other states, the Caribbean, South America and West Africa. They believe the research could also be used to study other allergies and diseases that disproportionately affect African-Americans.
They also plan to work with a San Diego company to develop a customized gene chip, which they will call the "African power chip," that will detect mutations in the genes of African-Americans that may be linked to an increased risk for asthma. The gene mutations on the chip will be compared to an individual's genetic makeup to see if there is a susceptibility to asthma.
Some of these mutations have been identified in other studies, said lead investigator and Hopkins immunogeneticist Kathleen Barnes. The University of Chicago Medical Center recently led a consortium that discovered a new asthma gene associated with African-Americans and confirmed four other genes found in previous studies, according to the NHLBI.
But Barnes said the large number of participants in the Hopkins study will allow identification of new mutations and determination whether those already identified are more common in African-Americans. Barnes said current chips on the market don't represent for variants in minority groups.
The genetic link to asthma has long been known, but only recently, with the advancement in genome research, has the issue been studied more closely. If one parent has asthma, there is a 1 in 3 chance that person's children will have it, according to the Asthma and Allergy Foundation of America in Landover. If both parents have asthma, the chances increase to 7 in 10.
"This research will help us to be able to tease out how much the causes of asthma come from nature and genetics and how much are from the environment," said Mike Tringale, vice president of external affairs for the asthma and allergy foundation.
Still, most in the field said that asthma treatment would still need to be addressed from an approach that looks at genetics, environmental factors and social factors such as poverty and access to medical care. Many African-Americans' asthma problems are worsened by their environments.
"It is a combination of the mutations and other exposure that lead to asthma," Barnes said.
Because the African population is the oldest in the world, Barnes thinks that the hereditary makeup would naturally have more genetic diversity and allow researchers to identify more mutations and genetic causes of asthma. This could ultimately lead to better treatments, Barnes said.
"We can develop better medicines for people with asthma because we will be able to target the protein associated with the disease," Barnes said.
Barnes said that over the long run, the genetic research could also lead to gene therapy that could be used to reduce people's susceptibility to the disease.
Rachel Hess-Mutinda, asthma control program coordinator for the state of Maryland, said the state's prevention efforts focus mostly on educating people about the environmental and social links to asthma, such as air quality and old houses. She said knowing more about the genetic link could help the state's prevention efforts.
"Asthma isn't something you can cure, but it is something you can maintain," said Hess-Mutinda. "Getting the tools to help us better understand who may develop asthma would help us target our efforts."
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