Innate and Adaptive Immunity in Individuals Experiencing Chronic Obstructive Pulmonary Disease Exacerbations

BACKGROUND: COPD is one of the most pressing healthcare problems facing our nation. AE-COPD is responsible for the bulk of healthcare costs and much of the morbidity and decline in health status among individuals with this common disease. The lack of accepted animal models of AE-COPD necessitates novel approaches using human samples. Advances in the understanding of the pathogenesis have been slowed, in part, due to controversy as to how exacerbations should be defined. The prevailing paradigm has defined AE-COPD as event-based. Such definitions clearly identify groups of patients with accelerated loss of pulmonary function and increased mortality. However, limited data show that symptom-based definitions of AE-COPD also capture episodes inducing significant morbidity and functional decline, and hence of concern to patients. Fundamental mechanisms are lacking to explain AE-COPD defined by either means. Controversy also surrounds triggers of AE-COPD. Bacteria and viruses are involved in some episodes, but the relative importance of each is intertwined with disputes over the definition of AE-COPD. Progress at linking specific pathogens to molecular pathogenesis has been slow, both due to their diversity, and to the high rates of bacterial colonization of patients with COPD, even in the stable state. Moreover, in many AE-COPD cases, no pathogen can be identified. Without negating the value of analyzing infections with specific species of pathogens, it appears that progress in molecular pathogenesis could be accelerated by focusing on unifying features of the pulmonary immune response during AE-COPD. DESIGN NARRATIVE: A prospective patient cohort will be studied extensively physiologically, functionally, and immunologically upon enrollment while in the stable state. As part of the study, participants will be trained in the use of peak flow meters, so that they can record daily first morning peak expiratory flow rates (PEFR). To confirm the range of fluctuations in their basal state, participants will be then be followed at three-month intervals for face-to-face interviews and more limited physiological and functional testing described below. Participants will also be reminded at each scheduled visit to contact the study coordinator when they feel that an AE-COPD may be present. If they do contact the study coordinator, they will be evaluated at one of the study sites within 48 hours. A diagnosis of AE-COPD will incorporate a modification of the definition used by the COPD Clinical Research Network (CCRN). The diagnosis will be made in one of two ways: severe AE-COPD will be defined as a change in respiratory symptoms above the participant's baseline measurements plus evaluation in the emergency room (ER) or requiring hospitalization; or mild-to-moderate AE-COPD will be defined as a change in respiratory symptoms above the participant's baseline measurements and requiring a change in therapy (addition of either antibiotics, oral steroids, or both), but without evaluation in the ER or hospitalization. In the latter case, therapy could be changed either at the advice of the patient's own caregivers or a study physician based on clinical judgment, or could be self-initiated in the case of participants authorized to do so by their caregiver. A concerted effort will be made to capture these milder AE-COPD during both winter and non-winter seasons. Upon enrolling participants, the following will be performed: review of medical history; review of demographic and smoking history; physical examination, blood and sputum collection; six-minute walk test; and questionnaires to assess shortness of breath (MMRC and University of California San Diego SOBQ), sputum production (modified Chronic Bronchitis Symptom Questionnaire), health status (SF-36 and St. George's Respiratory Questionnaire), and psychological traits (Hospital Anxiety/Depression Score, Illness Perception Questionnaire, Coping Index, and an individualized 30-minute clinical interview via telephone). Participants will attend study visits every 3 months to review symptoms. During an AE-COPD (episode of acute bronchitis), sputum and blood will be collected, and a five-symptom questionnaire will be filled out. Subjects are reimbursed $25 per scheduled visit and $50 per unscheduled visit (at the time of perceived exacerbation) to help defray travel expenses.