An Unwelcome Guest: Aspergillus Colonization in Lung Transplantation and its Association with Bronchiolitis Obliterans Syndrome

Despite the short-term success of lung transplantation, long-term outcomes remain among the worst of all routinely transplanted solid organs. The lung, perhaps because of direct environmental interactions and innate host defenses, appears uniquely vulnerable to alloimmune injury despite modern immunosuppression. Over 50 % of lung transplant recipients experience acute rejection within the first year (1). Furthermore, a majority of patients develop bronchiolitis obliterans syndrome (BOS), a condition of progressive allograft dysfunction, within five years after transplant (1). Although the precise etiology of BOS remains elusive, it was often thought a manifestation of chronic alloimmune injury. This was consistent with the observation that prior acute rejection predicted subsequent BOS. However, a more complex view is emerging, in which non-alloimmune factors like primary graft dysfunction, infection or gastroesophageal reflux also appear to contribute to the risk of BOS (2). Given the lack of reliable treatment, prevention of BOS becomes paramount to improving outcomes after lung transplantation. The identification of risk factors for the onset of BOS has therefore been the focus of intense research in the lung transplant community