Chronic infiltative lung disease and viruses

A role for viruses in the development or course of the main idiopathic chro nic infiltrative lung disease has been suggested for a long rime. Viruses t hat have usually been incriminated in cryptogenic fibrosing alveolitis are hepatitis C virus, whose role has not been accurately proven, and latent vi ruses including Epstein-Barr virus and adenovirus. These latent viruses mig ht be re-activated in the lung of patients immunocompromised by treatments and might be accountable for disease progression. However, published studie s have been very conflicting and the only clinical trial testing ribavirin has failed to demonstrate a beneficial effect. In sarcoidosis, the responsi bility of human herpesvirus 6 and 8 and retroviruses has nor been proven. F inally, data in the literature do not support a link between Langerhans cel l histiocytosis and human herpesvirus 6 and 8. These viruses may act by sev eral mechanisms: viral proteins may be antigens driving an appropriate immu ne response: they may also behave as transactivating factors to control the expression of various genes involved in immune response, cell growth or sy nthesis of matrix proteins.