178: HHV-6 infection following Campath1H based reduced intensity conditioning (RIC) regimen in pediatric patients undergoing SCT for non-malignant disorders

Background: Human Herpes Virus 6 (HHV-6) infections have been recently recognized as complications of SCT in young patients. Limited information is available on patterns and impact of HHV-6 infection following RIC transplants using increased immunosuppression. We describe our multi-institutional experience with HHV-6 infections during SCT following a Campath IH based RIC regimen. Patients and Methods: 12 patients underwent SCT for non-malignant disorders and received Campath 1H (33mg/48mg, day -21 and day-19); Fludarabine (150mg/m2,day -8 to -4) and Melphalan (70 or 140mg/m2, day-3) prior to stem cell infusion (BM/PBSC/CB) from related or unrelated donors. Two patients had also received Thiotepa (10mg/kg on day-2). Acyclovir was used for viral prophylaxis. Patients were tested for HHV-6 pre-transplantation by a PCR based assay. Patients were monitored by HHV-6 PCR if they had fever, delayed engraftment/myelo-suppression, rash or malaise. Serial quantitative real-time PCRs (viral load) data was collected in some of these patients (Viracor Laboratories, Missouri) to gauge response to treatment. Results: All 12 patients undergoing SCT were negative for HHV-6 by PCR pre-transplant. 7 patients (58.3%) had HHV-6 detected during the course of their SCT. Infections occurred during the first month (n=4), second month (n=1), at 4 months (n=1) and at 6months (n=1) post-SCT. Common symptoms encountered were fever, rash and pancytopenia/delayed engraftment. No case of pneumonitis or encephalitis was seen. HHV-6 infection responded rapidly to Foscarnet or Gangcyclovir with decrease in viral load and was associated with no deaths. No HHV-6 infections were seen after immune-reconstitution (6 months). Conclusions: Infection with HHV-6 infection is more frequent following Campath based regimen. Most of the infections occur within the first 4 weeks and may delay engraftment; but late infections are also common due to intense immunosuppression. Therefore, close monitoring and early treatment is advocated in pediatric patients receiving Campath 1H.