Glycosylation of viral proteins has complex links with UPR activation, being important only for a subset of viral glycoproteins and glycosylation sites. This is unsurprising, given the complex and diverse roles played by site-specific glycosylation in protein folding and function. Our limited understanding of the complex interactions between viral protein glycosylation and the UPR highlight the need for further research. In particular, although research into the surface glycoproteins of the IAV HA and CoV S glycoproteins is extensive, knowledge of the surface glycoproteins of other respiratory viruses remains comparatively inadequate. For instance the E3-19K glycoprotein of AdV is known to specifically trigger IRE1 while having no effect on the two remaining signalling cascades , although the mechanisms behind this specific activation are unclear. As these viral glycoproteins often activate specifc arms of the UPR, they represent one mechanism viruses can use to subvert the UPR to their advantage. Collectively, the surface glycoproteins of respiratory viruses are the major -but not only -means by which these viruses modulate the UPR.