Characterization of a human herpes virus-6 (HHV-6) and epstein-barr virus (EBV) associated leukemic cell line, J6-1

This report characterizes the J6-1 cell line derived from a Chinese acute myelomonocytic leukemia patient and previoulsy reported to be associated with EBV. These studies showed that J6-1 cells were also infected with HHV-6 as demonstrate at the DNA level by PCR and Southern blot hybridization and by expression of HHV-6 early membrane antigen on the J6-1 cell surface. Further characterization showed J6-1 was co-infected with EBV type 2. Generally, cells infected with EBV type 2 do not grow well in vitro, However, J6-1, although difficult to maintain in vitro, has been growth for 15 years. Possibly, co-infection with HHV-6 confers this property. In this regard, J6-1 cells exhibited density dependent growth which could be inhibited with an anti-HHV-6-MA monoclonal antibody (MAb). In contrast, anti-HHV-6-VCA MAb stimulate the J6-1 cell proliferation. Electron microscopic analysis showed that, morphologically, there were two types of J6-1 cell, one with lymphoblastoid features and one with a monocytoid appearance. Accordingly, the flow profile of the J6-1 cell line showed heterogeneity with two populations comprised of CD15-, CD19+cells with low light scatter (small cells) and a population with greater light scatter (larger cells) which was CD15+, CD19+, The population was negative for progenitor cell markers (CD33, 34), and T cell markers. Southern analysis showed no T cell receptor rearrangement, however there was a clonal J_H and kappa light chain expressing population. Glycocytochemical analysis showed several endogenous lectin receptors on the J6-1 cell surface: BSA-Xylose, BSA-Rhamnose, BSA-Gal, BSA-Lac. This cell line shares many characteristics with other monocytic/lymphoblastoid cell lines isolated elsewhere and provides circumstantial evidence linking Herpes viruses, as least as co-factors, to leukemia cell growth.