Antiretroviral therapy significantly reduces HIV levels in the lungs and may potentially reduce the high risk of chronic obstructive pulmonary disease (COPD) and other respiratory illnesses documented in people living with HIV, say researchers of a study published in the January 1 issue of the Journal of Infectious Diseases.
Because rates of lung diseases are high in people with HIV, Homer Twigg III, MD, from the division of pulmonary and critical care medicine at Indiana University Medical Center in Indianapolis, and his colleagues set out to determine whether HAART could reduce HIV levels in the lungs and potentially improve respiratory immune function. The team, from the AIDS Clinical Trials Group (ACTG) protocol 723, initially screened 40 HIV-positive patients, 30 men and 10 women, who were ready to initiate HAART, and who had CD4 counts of 500 or less and a viral load of 5,000 or more. They performed viral load tests on blood and lung fluid at baseline—before starting HAART—and then at 4 and 24 weeks after starting HAART. Ultimately, Twigg’s team had complete data involving 37 participants.
Not surprisingly, HAART significantly lowered HIV levels in blood. After nearly six months, 50 percent of the participants had undetectable viral loads —a virus level of less than 50 copies—and 82 percent had either a one-log drop in virus or an undetectable viral load. HIV levels in the lungs fell even more. Whereas 28 people had detectable HIV levels in the lungs at baseline, only four people had detectable HIV in the lungs by week 24. Though at first glance it may appear that HAART is even more effective in lungs than in the blood, the authors state that this may be partly due to the fact that viral load tests in lung fluid were less sensitive than in blood; “undetectable” in lung fluid was anything less than 1,500 copies.
Measures of immune activity improvement in the lungs confirmed the viral load results. In HIV-negative people, 85 to 90 percent of immune cells in the lungs are macrophages, and 10 to 12 percent are lymphocytes. In people with HIV who are not on HAART, the percentage of lymphocytes is typically much higher than in healthy HIV-negative people. This higher level of immune activation in the lungs, the authors point out, may increase the risk of COPD, especially among HIV-positive smokers.
Among the ACTG study participants, lymphocytes accounted for 20 percent of the immune cell samples collected before the start of HIV treatment. This ratio moved back toward normal after 24 weeks of HAART, at least among nonsmokers and a subgroup of smokers with the highest levels of lymphocytes at baseline.
Though the results of the study are hopeful, it is still unclear whether lowering viral load in the lungs will result in lower rates of lung disorders in people with HIV. The authors state that the impact of antiretroviral therapy on respiratory illnesses is currently being researched.
