A. Statement of Hypotheses:

HIV-infected patients have an increased incidence of emphysema compared to non-HIV-infected smokers, and it has been hypothesized that this accelerated disease progression is the result of one or more latent infections that amplifies the pulmonary inflammatory response to cigarette smoke. Pneumocystis is one infectious agent that likely plays a key role in the development of HIV-associated emphysema. Colonization with Pneumocystis has been demonstrated in HIV-infected subjects, and HIV-infected smokers are particularly susceptible to Pc colonization regardless of CD4 cell count or use of prophylaxis. Pneumocystis colonization is also increased in non-HIV-infected patients with chronic obstructive pulmonary disease (COPD) and is directly related to the severity of the disease. The presence of Pneumocystis in the lungs, even at low levels as seen in colonization, produces inflammatory changes similar to those seen in COPD, with increases in the numbers of neutrophils and cytotoxic CD8+ lymphocytes. We propose that Pneumocystis accelerates emphysema in HIV-infected smokers by stimulating inflammation and tissue destruction. We will examine the role of co-infection with Pneumocystis in the pathogenesis of HIV-associated emphysema and the mechanism by which it causes emphysema progression. These studies will lead to information that will provide a rational basis for prevention and therapy of HIV-associated emphysema and provide a model for emphysema in the general population