MALDI-MS can also be applied for O-glycan analysis (Canis et al. 2010; Franc et al. 2013); however, it has not been widely used in the virology field and only a few examples of O-glycoprofiling of viral glycoproteins using MALDI-MS exist (Schmitt et al. 1999; Collar et al. 2016). It can probably be explained by lower interest in viral O-glycosylation as opposed to N-glycosylation, primarily due to poorly characterized functions of viral O-glycans and the presumption that most viral glycoproteins are not heavily O-glycosylated. In addition, more sophisticated methods allowing simultaneous determination of modified amino acids have rapidly taken over, which have in the recent years been widely used for analysis of viral O-glycosylation.