SHORT REPORT Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) DNA sequences are absent in leukapheresis products and ex vivo expanded CD34  cells from multiple myeloma patients C ATHERINE D E G REEF ,WENDY VAN D E VOORDE ,MARLEEN B AKKUS ,J URGEN C ORTHALS ,* C ARLO H EIRMAN,* R IK S CHOTS ,PATRICK L ACOR ,B EN VAN C AMP AND I VA N VAN R IET Department of Haematology-Immunology, and *Department of Physiology, Free University of Brussels (VUB), Belgium Received 23 December 1998; accepted for publication 17 June 1999 Summary. Recently it was reported that Kaposi's sarcoma- associated herpesvirus (KSHV/HHV-8) infects bone marrow (BM) dendritic cells (DC) in multiple myeloma (MM) patients and therefore might play a role in MM development. Because of the use of myeloid growth factors like GM-CSF and G-CSF for the mobilization of peripheral blood progenitor cells (PBPC), the subsequent increase of DC precursors might imply a risk for KSHV contamination in PBPC grafts. Therefore, in this study leukapheresis products and ex vivo cultured CD34  cell suspensions were analysed. KSHV DNA could not be ampli®ed in any of them. Keywords: Kaposi's sarcoma-associated herpesvirus, leukapheresis products, mobilization, myeloma. In a recent study Kaposi's sarcoma-associated herpesvirus (KSHV, HHV-8) sequences have been found in dendritic-like cells (DC) in the bone marrow (BM) of multiple myeloma (MM) patients (Rettig et al, 1997a). Although several reports have shown evidence for the presence of virus DNA (Said et al, 1997; Chauhan et al, 1999), a considerable number of studies reported contradictory ®ndings (Tarte et al, 1998; Cull et al, 1998; Tisdale et al, 1998). The continuing debate and the discordant results men- tioned above cast doubt on the safety of using mobilized peripheral blood progenitor cells (PBPCs) for autografting in myeloma. The in vivo use of myeloid growth factors like GM-CSF and G-CSF does not only allow mobilization of PBPC with early and late potential, but also increases the number of circulating dendritic cell precursors and their progeny. As long as the role of KSHV in MM pathogenesis remains uncertain, it might be safer to avoid the reintroduction of virally infected cells. We determined whether KSHV could be detected in 23 different leukapheresis products from 22 MM patients. For four patients, CD34  enriched cells were also tested before and after ex vivo expansion with a combination of cytokines that have the potential to generate dendritic cells from CD34  precursors. MATERIALS AND METHODS Mobilization and collection of peripheral blood stem cells (PBSC). 23 samples of PBSC were collected from 22 MM patients during haematological steady state (two patients) or after mobilization with cyclophosphamide (CY) (4 g/m 2 )  GM-CSF (three patients), melphalan (MEL) (70 g/m 2 )  G-CSF (four patients) or cyclophosphamide (4 g/m 2 )  G-CSF (14 patients). Growth factors were administered subcutaneously at a dose of 5±10 mg/kg/d within 24 h after completion of chemotherapy and continued daily until PBSC collections were completed. Leukapheresis procedures were performed using the CS 3000 blood cell separator (Fenwall Laboratories, Baxter). During each procedure 10 litres of blood were processed. After buffy coat preparation, the PBSC products were frozen and stored in liquid nitrogen according to standard operating procedures. Enrichment and ex vivo expansion of CD34  cells. In four cases PBSC obtained after mobilization with cyclo- phosphamide  G-CSF were used for CD34  cell isolation. For that purpose the Isolex TM 300 device (Baxter) was used. After thawing, enriched CD34  cells were cultured for 12 d in RPMI±10% FCS with a combination of the following cytokines: recombinant human interleukin 1b (rh-IL-1b) (Boehringer Mannheim) at 5ng/ml; rh-IL-3 (PeproTech, Sanvertech) at 50ng/ml; rh-IL-6 (PeproTech, Sanvertech) at 10 ng/ml; stem cell factor (rh-SCF) (Amgen) at 50 ng/ml; granulocyte macrophage-colony stimulating factor British Journal of Haematology , 1999, 106, 1033±1036 1033 q 1999 Blackwell Science Ltd Correspondence: Dr Catherine De Greef, Department of Haematology-Immunology, Free University Brussels (VUB), Laarbeeklaan 103E, 1090 Brussels, Belgium.