BACKGROUND: Human herpesvirus 6 (HHV-6) is susceptible to latency and recurrence. A less-frequent form of HHV-6 persistence is the integration of viral DNA into host chromosomes. OBJECTIVES: To investigate HHV-6 viral load after haematopoietic stem cell transplantation (HSCT) in whole blood (WB) and serum with regard to integrated HHV-6 transmission diagnosis. STUDY DESIGN: HHV-6 DNA quantitation in serum and WB was performed using quantitative polymerase chain reaction for the follow-up of a 16-year-old girl after HSCT. In whole blood, results were expressed as HHV-6 genomic equivalent copies (gec) per milliliter of WB or per million cells. RESULTS: HHV-6 viral load (undetectable before HSCT) increased up to 3.05 x 10(7)gec/10(6)cells. HHV-6 viral load in the donor sample (3.44 x 10(6)gec/10(6)cells) was in favor of viral transmission through HSCT. The correlation between viral load in WB and serum was significant (p=0.0005). Viral load results expressed as gec/10(6)cells in WB was more reliable than results expressed as gec/ml of whole blood. CONCLUSION: These findings indicate that HHV-6 may be transmitted during HSCT as integrated virus contained in the graft. This reiterates that in the setting of HSCT, HHV-6 viral load must be correctly interpreted. Using HHV-6 viral load expressed as gec/10(6) cells may be more suitable for the follow-up of patients with integrated HHV-6.
BACKGROUND:Human herpesvirus 6 (HHV-6) is susceptible to latency and recurrence. A less-frequent form of HHV-6 persistence is the integration of viral DNA into host chromosomes. OBJECTIVES: To investigate HHV-6 viral load after haematopoietic stem cell transplantation (HSCT) in whole blood (WB) and serum with regard to integrated HHV-6 transmission diagnosis. STUDY DESIGN:HHV-6 DNA quantitation in serum and WB was performed using quantitative polymerase chain reaction for the follow-up of a 16-year-old girl after HSCT. In whole blood, results were expressed as HHV-6 genomic equivalent copies (gec) per milliliter of WB or per million cells. RESULTS:HHV-6 viral load (undetectable before HSCT) increased up to 3.05 x 10(7)gec/10(6)cells. HHV-6 viral load in the donor sample (3.44 x 10(6)gec/10(6)cells) was in favor of viral transmission through HSCT. The correlation between viral load in WB and serum was significant (p=0.0005). Viral load results expressed as gec/10(6)cells in WB was more reliable than results expressed as gec/ml of whole blood. CONCLUSION: These findings indicate that HHV-6 may be transmitted during HSCT as integrated virus contained in the graft. This reiterates that in the setting of HSCT, HHV-6 viral load must be correctly interpreted. Using HHV-6 viral load expressed as gec/10(6) cells may be more suitable for the follow-up of patients with integrated HHV-6.