All cells other than Human Foreskin Fibroblasts (HFF) (ATCC cell line CRL-2522) were grown in Glasgow Modified Eagles Medium supplemented with 10% foetal bovine serum, 4 mM glutamine, 100 units/ml penicillin and 100 ug/ml streptomycin. HFF cells were grown in Dulbecco modified Eagles medium supplemented as described above but with the addition of 1x MEM non-essential amino acids.