Lymphoblastoid cell lines with integrated human herpesvirus type 6.

Objective: Attempts were made to establish stable in vitro cell lines latently infected with human herpesvirus type 6 (HHV-6).

Study design/methods: We previously studied a patient with B-cell acute lymphoblastic leukemia infected with HHV-6. The peripheral blood mononuclear cells (PBMCs) from this patient were immortalized by infection with Epstein-Barr virus (EBV) and herpesvirus saimiri (HVS).

Results: Infection of the PBMCs with EBV and HVS gave rise to B- and T-lymphoblastoid cell lines, respectively. Both cell lines were positive for HHV-6 DNA, as confirmed by polymerase chain reaction (PCR) and Southern blot hybridization. Fluorescence in situ hybridization (FISH) demonstrated integration of HHV-6 in these cell lines. Only one integrated site of viral DNA was detected in metaphase chromosome spreads, and it was preferentially located at the long arm of chromosome 1 (1q44). HHV-6 appeared latent in the infected cells, since neither the HHV-6 immediate-early gene transcript nor virion-associated protein was detected.

Conclusions: The HHV-6-positive lymphoblastoid cell lines would be useful for study of the mechanism of HHV-6 integration.