Characterization of cytomegalovirus isolates recovered during repeated infection in renal transplant recipients.

The sources of cytomegalovirus (CMV) infection in seropositive renal transplant recipients include reactivation of latent endogenous virus in the recipient, reactivation of latent virus in donated kidney, or both. If infection occurs by either source, viruses isolated from the same recipient should be the same strain, whereas if it occurs by both sources, those from the same recipient should be different. In this study, we followed prospectively 25 seropositive recipients who predominantly received a kidney from a seropositive donor to determine whether CMV isolates recovered repeatedly from them are the same or different. During an average 10 month follow-up period, six (24%) patients had excreted the virus more than twice at any site and/or at different times. Restriction enzyme analysis of viral DNA prepared by the Hirt procedure revealed that three or four isolates obtained from each of five patients were same, whereas six isolates from one patient included three different strains. Five of six patients had clinical symptoms at the times when CMV was recovered. Three patients with acute rejection and one patient with hepatitis had been infected with one single strain, and all were successfully treated. One patient with fever and acute rejection had been infected with three different strains, and he failed to recover his renal function. These results suggest that most CMV infections in seropositive recipients may be caused by one single strain. However, multiple infections with different strains can also occur. Such infections are associated with more severe clinical disease.