Infectious etiology of bronchiolitis obliterans: The respiratory viruses connection - Myth or reality?

A variety of viruses, such as the influenza viruses A and B, the human respiratory syncytial virus, the parainfluenza viruses, and the adenoviruses, cause seasonal respiratory tract infections in young children and adults. Also, studies indicate that these viruses are an important group of pathogens in pediatric and adult lung transplant recipients. More importantly, accumulating data on these infections among lung transplant patients suggest that these illnesses may have immediate and long-term implications for the function of the transplanted lung, including the development of bronchiolitis obliterans. This is important because patient survival and allograft function in lung transplantation remain limited by the development of bronchiolitis obliterans. Models of lung transplantation indicate that respiratory viral infections cause acute and chronic airway damage after transplantation. The mechanism leading to allograft damage by respiratory viruses may be related to the production of alloreactive cytokines such as interleukin (IL)-1, tumor necrosis factor, IL-6 and IL-8 during viral replication. Current clinical data are suggestive of a possible role for respiratory viruses in the development of bronchiolitis obliterans, but further control studies are required to evaluate the significance of respiratory virus infections as a causal factor in the development of bronchiolitis obliterans in lung transplantation.