The biology of human cytomegalovirus infection after bone marrow transplantation.

Human cytomegalovirus (HCMV) infection remains the most common infectious cause of morbidity after bone marrow transplantation (BMT). In a prospective study of 127 BMT recipients who received blood cultures for HCMV between days 28 to 105 after marrow grafting, HCMV viremia occurred in 68 patients (53.4%). Twenty patients (15.7%) had one or two positive cultures, and 48 (37.7%) had greater than or equal to three positive cultures. Fifty-nine patients (46.4%) had no viremia. HCMV-associated interstitial pneumonia (HCMV-IP) occurred in one-third of the viremic patients. Quantitative measurements of infectious HCMV or of HCMV DNA in lung tissue were made to determine whether HCMV replication correlated with clinical disease. Using DNA probes, viral DNA was measured by dot-blot hybridization, and this correlated with infectious HCMV. However, neither HCMV DNA nor HCMV viral titer correlated with time from the onset of pneumonia to death. The hypothesis is presented that HCMV-IP is caused by immunologic events induced after HCMV infection. In this model HCMV alterations in recipient cell surfaces induce donor alloreactivity to minor histocompatibility differences and lead to the subsequent pneumonitis which we term HCMV-IP. This model suggests that prevention of HCMV-IP will require early use of antiviral therapy or late use of immune response modification.