Although mutations that remove glycosylation sites typically affect the stability and transport of glycoproteins, the F protein of RSV is an exception. Glycosylation site deletion variants of the F protein are still efficiently transported to the cell surface . However, RSV infection in Hep2 and Vero cell lines show different expression of ER stress genes from the PERK arm of the UPR . The RSV F protein is improperly glycosylated in Vero cells, suggesting differential glycosylation of RSV F is the driving factor distinguishing the two PERK responses . The mechanistic roles of glycosylation for UPR activation in RSV infection thus requires further attention.