Pneumocystis colonization, airway inflammation, and pulmonary function decline in acquired immunodeficiency syndrome

As a result of improved diagnosis, treatment, and supportive care for HIV-infected patients, AIDS in developed countries has now become a chronic infection with prolonged survival time, but longterm complications are increasing contributors to morbidity and mortality. HIV-infected patients are at increased risk for the development of pulmonary complications, including chronic obstructive pulmonary disease (COPD); however, the mechanisms associated with this increased susceptibility have not been defined. Infectious agents may contribute to the development of COPD by upregulating inflammatory mediators in the lung that act in concert with cigarette smoke to promote lung pathology. Studies in human subjects and non-human primate models of AIDS suggest that the inflammatory response to asymptomatic carriage or colonization by the opportunistic pathogen, Pneumocystis sp. (Pc), is similar to that of COPD, which is characterized by influx of CD8+ T cells, neutrophils, and macrophages into the lungs. We have shown a high frequency of Pc colonization among asymptomatic HIV-infected subjects and in non-HIV infected subjects with COPD. To investigate the role of Pc in the progression of obstructive lung disease in HIV infections, we developed a non-human primate model of Pc colonizatoin and infection in simian immunodeficiency virus (SIV)-infected macaques. These animals develop a prolonged colonization state characterized by a persistent influx of CD8+ T cells and neutrophils, and local increases in IL-8, IFN-gamma, and TNF-alpha. SIV-infected Pc-colonized monkeys show progressive decline in pulmonary function compared to SIV-infected monkeys. We hypothesize that in the context of AIDS-immune dysfunction, Pc colonization induces inflammatory responses leading to changes in pulmonary function and architecture similar to that seen in emphysema. Information gained from these studies will lead to the development of interventions to prevent lung injury associated with Pc colonization and the development of HIV-associated COPD.