Immunogenic and cross-reactive carbohydrate determinants in ticks and other arthropods

Ticks are parasites that feed on the blood of humans and animals, using it as their sole source of food. Due to their lifestyle, ticks at each life stage transmit various tick-borne pathogens while feeding on their hosts. Unlike mosquitoes - another important group of pathogen-transmitting arthropods - ticks can feed on the same host for prolonged periods, which underscores the importance of tick mechanisms that inhibit or reduce the host's defence mechanisms and, consequently, allow the transmission of pathogens. This unique tick-host-pathogen triangle requires the involvement of various tick molecules to mediate interactions with both host and pathogen molecules at multiple levels. This review highlights the glycan molecules identified in various tick species that can trigger an immune response and thus primarily affect the interaction with the host. As the enzymes involved in Golgi-mediated glycan maturation differ between ticks, insects, and their vertebrate hosts, these differences contribute to the glycan profiles observed in ticks. These differences in glycan structures influence the interactions ticks have with their hosts and pathogens. On one hand, they may participate in molecular mimicry and mechanisms that lower the host's immune reaction, blood clotting, and other defence mechanisms due to their different structures, but on the other hand they may also trigger the host's defence mechanisms, such as participating in delayed red meat allergy and facilitating the transmission of pathogens. Tick glycobiology remains largely unexplored and deserves more attention, especially considering the potential of glycans and glycoproteins as targets for anti-tick vaccines.