Multiplex real-time PCR to identify a possible reinfection with different strains of human cytomegalovirus in allogeneic hematopoietic stem cell transplant recipients.

Human cytomegalovirus (HCMV) infection remains the leading cause of serious contagious complications after allogeneic hematopoietic stem cell transplantation. These infections in HCMV-seropositive recipients can be due to reactivation or reinfection. Different HCMV strains were identified by determining the genotypes isolated from repeatedly tested patients. The UL55 sequences encoding viral glycoprotein B (gB) have been chosen as the target gene. The region, in which the gB precursor protein is cleaved into two fragments by a cellular endoprotease, is characterized by genetic variability, and based on that HCMV is classified into four major genotypes: gB1, gB2, gB3 and gB4. Multiplex real-time PCR assay enabled both, HCMV gB genotyping, as well as simultaneous quantitative assessment of the detected genotypes. This study was carried out in 30 transplant recipients, from whom 105 isolates of HCMV DNA were genotyped. In 40% of recipients, a mixed infection with two or three genotypes was detected. Genotype gB1 dominated in general, and characteristically for mixed infections, the genotype gB3 or gB4 was always present. Although there were no significant differences in the load for each genotype, in case of multiple infections, the number of copies of gB1 genotype was significantly higher when compared to a single gB1 infection. In patients with mixed genotypes, chronic HCMV infections and graft versus host disease were observed more often, as well as antiviral treatment was less effective. It was assumed that these adverse effects can be related to the presence of gB3 and gB4 genotypes.