Cytomegalovirus is the most important opportunistic infection after kidney transplant, with increased in mortality, morbidity and higher costs of transplantation. Despite the favorable efficacy (lower acute rejection) results of the most worldwide used regime, tacrolimus, mycophenolate and prednisone, or the investigators local common regimen, tacrolimus, azathioprine and prednisone, this combinations are associated with higher incidence of cytomegalovirus infection, disease and recurrence.

Namely, sirolimus use is associated with decreased risk of cytomegalovirus infection/disease, and there is not a prospective cohort to evaluate the conversion to sirolimus efficacy to decrease the cytomegalovirus infection recurrence.

Given this, the investigators propose a study of their own initiative that attends local needs: evaluate the conversion to sirolimus efficacy in decrease the cytomegalovirus recurrence after kidney transplant.

This protocol is a prospective, randomized, single center, designed to evaluate incidence of cytomegalovirus recurrence infection/disease in two immunosuppressive regimens, after the first episode of cytomegalovirus: (1) conversion of azathioprine or mycophenolate to sirolimus, in a regimen wih low doses tacrolimus and prednisone; ( 2) Maintenance of the current regimen during the first episode of cytomegalovirus infection ( azathioprine or mycophenolate, in combination to tacrolimus or prednisone). Our hypothesis is that conversion from azathioprine or sodium mycophenolate to sirolimus, with low doses of tacrolimus, and prednisone results in lower recurrence of cytomegalovirus infection/disease in kidney transplant recipients.

Inclusion Criteria:

• Adult kidney transplant recipients > 18 y.o.
• Kidney Transplant recipients, after the first episode of cytomegalovirus infection, using the current immunosuppressive regimen: azathioprine or mycophenolate, tacrolimus and prednisone.

Exclusion Criteria:

• Re-transplant;
• Patients with any panel reactive antibody (PRA) equal to or above 50%, class I or class II;
• Acute rejection episode in the last 30 days, or episode > 2A in the Banff criteria;
• GFR (MDRD) < 40 ml/min;
• Proteinuria > 0,5 g/l;
• Hemoglobin < 10 g/l and/or leucocytes < 4000 cels/mm3 and/or platelets < 150.000 cels/mm3;
• Triglycerides > 500 mg/dl with or without use of fibrate;
• Cholesterol total > 300 mg/dl with or without use of statin;
• Hepatic abnormalities;
• Significant periphery edema;
• Pulmonary abnormalities or breast x-ray abnormalities;
• Hyper sensibility to sirolimus formula;