Cell culture
The human T cell lines A3.01 and PM1 (NIBSC, UK) and the human myeloid cell line U937 (NIBSC, UK) were grown in complete RPMI 1640 medium supplemented with 10% fetal bovine serum, 2 mM l-glutamine and 100 U/ml penicillin–streptomycin. The human hepatic cell lines HepG2 and Huh7 (kindly provided by Dr Thomas Pietschmann, Department of Molecular Virology, University of Heidelberg) as well as HeLa cells were maintained in Dulbecco's high glucose modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum, 2 mM l-glutamine and 100 U/ml penicillin–streptomycin. Cells lines were incubated at 37°C with 100% humidity in 5–7% CO2 and passaged using standard cell culture techniques.