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Why Do Certain HIV-Positive Individuals Develop Emphysema?

Although huge advances made in the treatment of HIV have enabled infected individuals to live longer, healthier lives than ever before, HIV is not a benign illness. Even when receiving antiretroviral therapy, HIV-positive individuals are at higher risk of other serious conditions including diseases of the cardiovascular system, brain, renal system, and lungs. In addition, the antiretroviral therapy used to treat HIV can cause serious side effects such as liver damage.
Now, a study coming out of Weill Cornell Medicine in New York, published in the journal Cell Reports, sheds light on the mechanisms behind the development of chronic obstructive pulmonary disease (COPD), presenting as the lung ailment emphysema, in 30% of HIV-positive individuals—smokers and nonsmokers alike.
The study team extracted basal stem cells from the airways of healthy individuals and exposed them to HIV. Rather than replicate inside the basal cells, as might be expected, the HIV proceeded to bind to the stem cells, which then transformed into different cells that released enzymes known as proteases. Over a period of days, the proteases caused holes in the stem cells and damaged previously healthy connective tissue—which is the kind of damage seen in the lungs of patients with emphysema. The researchers believe the study results support the idea that HIV changes the airway stem cells into a destructive force that destroys healthy tissue and results in emphysema.
The exact mechanisms by which emphysema develops in HIV sufferers are not fully understood. Some in the medical community have hypothesized that, along with HIV, antiretroviral therapy itself may bear some of the responsibility. The Weill Cornell study’s lead author discounts that. “It most likely is the HIV itself,” said Ronald Crystal, MD, chairman of the Department of Genetic Medicine at Weill Cornell Medicine and a pulmonologist at New York-Presbyterian Hospital to Contagion®. “Whether or not the medications may be involved has been studied, with no definitive data implicating the drugs used to treat HIV.”
Although anyone with HIV can develop emphysema, smokers put themselves at particular risk. “It occurs in nonsmokers, but is accelerated by smoking,” said Dr. Crystal. “Until we work on therapies that directly prevent the HIV from inducing the emphysema, the best advice to an HIV-positive patient is to not smoke and stay away from secondary smoke and heavy pollution.”
Adults with HIV smoke at a rate two to three times that of the rest of the population. In addition to the risk of emphysema, HIV-positive smokers are at risk of acquiring an oral infection known as thrush, mouth sores, bacterial pneumonia, and pneumocystis pneumonia, a potentially fatal lung infection.
According to the US Department of Veterans Affairs, a study conducted at VA medical centers found that veterans with HIV were 50% to 60% more likely to have COPD than veterans without HIV. Other factors were considered, including age, race, smoking history, and drug and alcohol history, and researchers concluded that HIV is an independent risk factor for the lung disease.
More than 100,000 people in the United States each year die from complications of COPD, the fourth leading cause of death in this country.

Laurie Saloman, MS, is a health writer with more than 20 years of experience working for both consumer and physician-focused publications. She is a graduate of Brandeis University and the Medill School of Journalism at Northwestern University. She lives in New Jersey with her family. 
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