Glycosylation in invertebrate immunity: Host response and pathogen evasion strategies

Glycosylation, a key post-translational protein modification, has been found central to host-pathogen interactions, underpinning numerous critical interactions mediated by carbohydrate structures (glycans). Glycan-dependent interactions regulate pathogen adhesion, recognition, invasion, and immune evasion. Invertebrates represent the largest and most diverse group of species on Earth, from established classical model organisms such as Drosophila and Caenorhabditis, to medically relevant parasites and disease-carrying vectors. However, glycan-mediated interactions between invertebrates and their pathogens remain far less studied compared to vertebrate systems. This review summarizes current knowledge on the role of invertebrate glycosylation, including N- and O-glycans and glycosaminoglycans, in defense against diverse pathogens, and the immune-evasive role of glycosylation employed by invertebrate (or invertebrate-borne) pathogens during host infection. While current research highlights the critical importance of glycosylation in these interactions, some key gaps persist: a lack of comprehensive glycomic and glycoproteomics analysis across representative invertebrate species, and poor understanding of receptor molecules and signaling mechanisms for these glycans and glycoproteins. We hope this review will stimulate further research into this critical yet underexplored facet of invertebrate-pathogen interactions.