Birgitta Versluijs

43 Association between respiratory virus and alloimmune lung syndromes Introduction Pulmonary complications are common after allogeneic hematopoietic stem cell trans- plantation (HSCT). Between 30% and 60% of adult HSCT recipients reportedly expe- rience pulmonary complications, representing a major cause of mortality. 1-4 In children undergoing HSCT, the incidence of pulmonary complications varies from 10% to 25%, and onset is a poor prognostic event carrying a significantly increased risk of mortality. 5,6 At one time, most pulmonary complications were directly related to infection; today, however, noninfectious pulmonary complications, such as idiopathic pneumonia syn- drome (IPS) and bronchiolitis obliterans syndrome (BOS), are seen more frequently. 2,5,6 Respiratory virus (RV) infections occur in 1%-56% of HSCT recipients. Most previous studies have examined the progression from upper respiratory tract infection (URTI) to lower respiratory tract infection (LRTI) and described the risk factors for this progressi- on. 7-16 Some have reported an association of early RV infection with late, obstructive lung injury. 17 An association between RV infection and alloimmunity in lung transplant reci- pients was recently reported. 18 Lung transplant recipients develop more acute and chro- nic graft rejection after common RV infection early (<100 days) after transplantation. 18 Isolated alloimmune lung disease (ie, BOS or IPS) after HSCT suggests a specific trig- ger making the lung a target organ for alloreactivity. This is in line with the 3-step pro- cess reflecting the current view of the development of alloreactivity: (1) tissue damage, resulting in (2) release of inflammatory cytokines, resulting in (3) activation and influx of T lymphocytes. 19 We speculated that the presence of a common RV might trigger allo- immune lung syndrome (allo-LS) in HSCT. We prospectively studied the influence of these RVs on the development of allo-LS and overall survival (OS) in a cohort of pediatric HSCT recipients. Patients and methods Study desgin and population All patients who underwent allogeneic HSCT between January 2004 and May 2008 at the pediatric Hematology and Immunology Department of the Wilhelmina Children’s Hospital, University Medical Center Utrecht were included in this prospective study. Patients were enrolled in the HSCT protocol after providing written informed consent for the HSCT and the research protocol. 3