The real-life invertebrate vampires and how proteins in their saliva enable them to consume blood

Haematophagous animals rely on the blood of vertebrates for nutrition, egg development, and survival. To obtain blood meals, these organisms have evolved salivary constituents that potently circumvent the host haemostatic response, which otherwise prevents blood loss through the formation of a blood clot. These salivary proteins can directly affect platelet aggregation, induce vasodilation and inhibit proteinases of the clotting cascade. There are over >15,000 species of blood-feeding invertebrates, and the sialome of several of these animals has been characterised. Within these sialomes, antihaemostatic proteins have been isolated and developed as antithrombotic therapeutics. Consequently, examining the saliva of neglected haematophagous invertebrates could be pharmacologically relevant and provide further insight into evolutionary adaptations to blood-feeding.

Using proteotranscriptomic analyses, I aim to explore the salivary gland venom composition of underexplored haematophagous arthropods, including Australian native horseflies (family Tabanidae), Australian native ticks such as the eastern paralysis tick Ixodes holocyclus, southern paralysis tick Ixodes cornuatus, and ornate kangaroo tick Amblyomma triguttatum, and the only native Australian kissing bug, Triatoma leopoldi. By examining their saliva, I hope to identify coagulotoxic molecules which allow them to overcome host haemostatic systems. Since venom peptides from non-haematophagous animals have also been shown to potently modulate haemostatic systems, I will test a range of peptides from venomous invertebrates for coagulotoxicity against mammalian blood and invertebrate haemolymph. Finally, I will characterise identified molecules both structurally and functionally to gain further knowledge into their role in the saliva of blood-feeding invertebrates. This research will expand the knowledge available on the salivary toxins of blood-feeding invertebrates, and discover new molecules with potential as therapeutics for thromboembolic disorders.