Prevalence of human herpes virus 6 genome in blood samples from pediatric and young adult kidney transplant recipients

Background: Human herpesvirus 6A (HHV6A) and 6B (HHV6B) are distinct species belonging to the Roseolovirus genus. HHV6 is considered an ubiquitous virus and its worldwide sero-prevalence is approaching 100%. After the primary infection, HHV6 establishes latency in the host, mainly in peripheral blood monocytes (PBMCS) and may reactivate under immunosuppression conditions, such as transplantation. The presence of HHV6A/B genomes and its replication were investigated in blood samples collected from pediatric and young adult kidney transplant recipients. Materials and Methods: Peripheral blood samples were obtained from 55 pediatric (men age: 17.0 years) and 22 young adult patients (mean age: 29.7 years). The mean time from transplant was 74.8 months (range: 1– 258 months). PBMCS and plasma were separated from blood and viral DNA was extracted. Polymerase Chain Reaction real time assay (q-PCR), targeting U67 region, was employed for the quantification of HHV6 genome in PBMCS. A nested PCR assay, able to differentiate HHV6A from HHV6B, was carried out. To discriminate the active replicating virus, both the presence of viral DNA in plasma samples and of the U100 and U67 transcripts in blood samples were analyzed by means of specific q-PCR and one step-reverse transcriptase PCR assays (RT-PCR), respectively. Results: The viral genome was detected in 16/77 patients (20.8%), with a mean viral load of 788.4 copies/ml (range: 61-1800 copies/ml). Ten out of 16 (62.5%) HHV6 positive patients were infected with the HHV6A. The viral genome was not detected in any of the tested clinical specimens, whereas the U100 and U67 transcripts were detected in one blood sample. No significant association was observed between the HHV6 infection, the patient’s age, the time passed from the transplant, the HCMV co-infection and the clinical sympto. Conclusion HHV6 infection, even if frequently detected, seems not be associated with post transplant disorders in kidney transplant recipients.