Study On The Infection Of Human Herpesvirus 6 After Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation(HSCT) is the only method to cure Hematologic malignancy disease,virus infection after HSCT are one of the main reason which influence transplantation achievement ratio and life quality of patient.Human herpesvirus 6(HHV-6) was a new herpesviruses first isolated in 1986 from patients with lymphoprolifetative disorders, a member of the β herpesvirinae subfamily, is a double-stranded DNA virus,have two distinct variants (HHV-6A and HHV-6B). HHV-6 is a ubiquitous pathogen with high infection rate in the humanpopulation, primary infection with HHV-6 causes exanthem subitum.HHV-6 is thought to remain latent in peripheral blood mononuclear cells(PBMCs) and salivary gland after primary infection, reactivating under conditions of immunosuppression. Recently the study on HHV-6 infection after HSCT become hot spot, some study find HHV-6 reactivating early after HSCT, and the infection rate was about 45%～75%. HHV-6 reactivation also associated with bone marrow suppression, graft-versus-host disease(GVHD), central nervous system dusfunction. But reports about HHV-6 infection internal are rare.In this study we decided to investigate the HHV-6 infection rate after HSCT in our's transplantation center, and establish a quickly, convenient way to detect HHV-6.We used nest-PCR for HHV-6 to assay PBMC samples prospectively collected form 19 HSCT recipients and plasma samples form 40 HSCT recipients, the amplified products of HHV-6 were respectively digested by restriction enzyme Hind III to identify its specificity. Samples form health people and hematologic disease patients are as normal control and disease control. The results find HHV-6 detected in 33(66%) of the 50 normal control in this region, mainly in PBMCs and all was HHV-6 B.The positive rate of HHV-6 infection in plasma of normal control was 6%,much lower than PBMCs. The positive rate of HHV-6 infection detected in 15 disease control was 60%, and noplasma samples detected HHV-6.The positive rate of HHV-6 infection in 19 patient PBMCs before HSCT was 58% and after HSCT the positive rate was 68%. The positive rate of HHV-6 infection in 40 patient plasma before HSCT was 3%;then after HSCT the positive rate was 42.5%,much more higher than before HSCT and the difference was significant (P<0.01).The difference of positive rate of HHV-6 in plasma are significant among after HSCT, normal control and disease control. Further more,we used real-time PCR to quantitate assay HHV-6 in plasma of normal control, disease control and HSCT patients. The positive rate of HHV-6 in plasma of normal control used Real-time PCR was 6%, and the median maximum level of HHV-6 viral load was 828 ± 317.5copes/ml. No plasma samples detected HHV-6 of disease control. The positive rate of HHV-6 in plasma of HSCT patient s used Real-time PCR was 45%. The median maximum level of HHV-6 viral load was 4884.4±374.4 copes/ml ,much more higher than normal control.The median time to onset of positive HHV-6 DNA results was 14.5 days(range,0-23days) after transplantation. aGVHD was observed in 14(35%) of the 40 HSCT recipients,the median time to onset of aGVHD was 20 days(range,8～40 days).The median time to onset of HHV-6 is obviously earlier than aGVHD (P<0.05) .Positive results for HHV-6 were observed in 11(78%) of the 14 HSCT recipients who experienced aGVHD.The positive rate of HHV-6 of HSCT recipients who experienced aGVHD was much morehigher than who not experienced aGVHD (P<0.05).Conclusion:1. The detection rate of HHV-6 in normal contral is 68%,and the type is HHV-6B.2. The detection rate of HHV-6 in PBMCs after HSCT is 68%, the detection rate of HHV-6 in plasma is 45%, and the type is HHV-6B.The HHV-6 viral load after HSCT are much more higher than before HSCT and normal control by quantitate assay.3. The time of HHV-6 reactivate after HSCT is early,almost in 2-4 weeks after HSCT,the major type is HHV-6B.4. HHV-6 infection after HSCT is possible relate to aGVHD.5. The real-time PCR method for HHV-6 was established showed good sensitivity, good specificity, good reproducibility, and can be used for clinical assay.