In the assay developed here, infection of cells with the lentivirus vector and expression of the Gluc reporter did not induce ER stress in and of itself as evaluated by XBP-1 message splicing (Fig 5A), BiP levels and phosphorylated eIF2alpha (Fig. 5B), nor did it effect cell viability as assessed by tetrazolium salt, WST-1 cell proliferation assay (Roche Diagnostics GmbH, Mannheim, Germany) evaluated 48 hrs after infection of >95% of cells (data not shown). This evidence concerns the gene XBP1 and infection.