The relationship between beta-herpesviruses reactivation and the development of complications after autologous peripheral blood stem cell transplantation was investigated. Viral genomic sequences were detected by the polymerase chain reaction, virus-specific antibodies by ELISA, and human herpesvirus (HHV)-6 variants by restriction endonuclease analysis. Virus reactivation, serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, soluble IL-2 receptor (sIL-2R), IL-2, and IL-4 were compared with clinical features in 44 patients before and after transplantation. Anti-CMV and anti-HHV-6 antibodies were found in 70.5% and 81.8% of patients, respectively. The frequency of plasma viremia was significantly higher in patients after transplantation (41% vs. 11.4%). Reactivation of more than one virus was identified in 55.6% of patients and reactivation of HHV-7 alone in 44.4%. In cases of concurrent infection, HHV-7 was reactivated before HHV-6, and both HHV-6 and HHV-7 were reactivated before CMV. There was a significant increase in HHV-6 load in peripheral blood leukocytes DNA during viremia. In all cases HHV-6B variant was detected. Complications after transplantation occurred in 27.3% of patients and virus reactivation was detected in all patients with complications. The significant increases in the rate of HHV-6 and HHV-7 reactivation and in serum levels of TNF-α, IL-1β, and sIL-2R, as well as aggravated immunosuppression, suggest that both viruses were involved in the complications after autologous peripheral blood stem cell transplantation, via their immunomodulatory activity. The kinetics of reactivation suggests a potential role of HHV-7 as a co-factor of HHV-6 reactivation, and of both HHV-6 and HHV-7 as co-factors of CMV reactivation.

Communicated by Ludmila VîksnaThe relationship between HHV-6 and HHV-7 reactivation and development of post-autologous peripheral stem cell transplantation complications was examined. The presence of viral genomic sequences in whole peripheral blood and cell free plasma was determined by nested PCR, load by real-time PCR, virus specific antibodies and cytokines in serum by ELISA, and HHV-6 variants by restriction endonuclease analysis. Clinical features, reactivation of viruses and serum TNF-a, and IL-6 concentrations were determined in seventy-six patients with Roseolovirus infection before and after transplantation. Anti-HHV-6 antibodies were found in 62 of 76 (81.6%) patients before transplantation. A significantly higher rate of single HHV-7 infection was found in patients with viral infection in comparison with single HHV-6 infection (p = 0.0003) and concurrent (HHV-6 and HHV-7) infection (p = 0.0017). Complications after transplantation developed in 30.3% of patients and reactivation of viruses was detected in all of these patients. Significant increase of HHV-6 and HHV-7 reactivation with simultaneous increase of pro-inflammatory cytokines serum levels suggests that both viruses may be involved in the development of complications after autologous peripheral blood stem cell transplantation via their immunomodulatory ability. The kinetics of the Roseolovirus reactivation may reflect the potential role of HHV-7 as a co-factor for

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