Cytomegalovirus (CMV) is often present in bronchoalveolar lavage (BAL) fluid of immunosuppressed patients without CMV pneumonitis. The amount of viral DNA within BAL cells of patients with definite CMV pneumonitis and of viral shedders was quantitated by polymerase chain reaction (PCR) and the extent of CMV gene expression within BAL cells was defined by reverse transcription - PCR. No viral DNA was detected in 6 viral shedders, and 12 had low copy numbers (mean, 72 copies/10(5) BAL cells; median, 20) compared with numbers in pneumonitis patients (267,580 and 57,000, respectively). When CMV intranuclear inclusions were absent within BAL cells of patients with pneumonitis, copy numbers (mean, 9362; median, 7110) were still significantly higher than among shedders. Expression of viral glycoprotein H mRNA was detected in BAL cells of all 11 pneumonitis patients tested but in 0 of 18 viral shedders. Thus, high-grade infection and viral replication within BAL cells are integral features of CMV pneumonitis but not viral shedding.

The cytomegalovirus (CMV) DNA load in leukocytes was measured in 26 immunocompromised patients with CMV disease before and after 10 days of intravenous ganciclovir therapy. Before therapy, the circulating DNA burden of bone marrow transplant recipients was significantly lower than that of other transplant or AIDS patients. Ganciclovir induction therapy significantly decreased the viral DNA load in the leukocyte populations of most patients.

Murine cytomegalovirus (MCMV) can only be propagated effectively in mouse embryo fibroblast (MEF) cells. We demonstrate that MCMV replicates significantly better in M2-10B4 cells, a continuous line of murine bone marrow stromal cells. M2-10B4 cells were also comparable to MEF cells for detection of small amounts of MCMV reactivating from latently infected spleen explants. M2-10B4 cells will be very useful for studies of MCMV pathogenesis.

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