Stability of human cytomegalovirus genotypes in persistently infected renal transplant recipients.

Although most genes are highly conserved among strains of human cytomegalovirus (HCMV), several are unusually variable. By analyzing the sequence of two variable genes (UL146 and UL74) amplified directly from whole blood DNA extracts, multiple HCMV strains were detected in blood samples from 5/11 virus-infected renal transplant patients. These five patients were seronegative prior to transplantation and their likely acquisition of the virus was via the donated organ; HCMV-positive immunocompetent donors may thus be capable of harboring and transmitting multiple virus genotypes. In sequential samples taken up to 140 days post transplant no mutations in either gene were detected from 9/10 patients, and in the remaining patient a single nucleotide change was detected in UL146, and none in UL74. All sequences grouped into previously defined genotypes, with the detection of multiple members of the UL74 group 5 genotype establishing this previously tentative genotype. Additionally, identical sequences were identified in viruses from different patients, including examples from geographically distinct regions. Thus, although UL146 and UL74 exhibit impressive variation among strains, their sequences are maintained stably within and between infected individuals, suggesting that sequence differences between genotypes may be driven by differing gene function.