3. The patient is unable to sustain treatment with antiviral drugs due to drug associated toxicities (e.g. myelosuppression [ANC< 1000μl/ml without GCSF support] or nephrotoxicity [corrected creatinine clearance ≤ 60 ml/min/1.73 m^2 or serum creatinine > 2 mg/dl]) CMV infections are life threatening, and may involve multiple organ systems such as the lungs, liver, gastrointestinal tract, hematopoietic and central nervous systems. Antiviral drugs used for treatment may also compromise renal and hematopoietic function. Therefore, dysfunctions of these organs will not affect eligibility for this protocol.