Transcriptome and toxin family analysis of the paralysis tick, Ixodes holocyclus

Abstract

The Australian paralysis tick (Ixodes holocyclus) secretes neuropathic toxins into saliva that induce host paralysis. Salivary glands and viscera were dissected from fully engorged female I. holocyclus ticks collected from dogs and cats with paralysis symptoms. cDNA from both tissue samples were sequenced using Illumina HiSeq 100 bp pair end read technologies. Unique and nonredundant holocyclotoxin (HT) sequences were designated as HT2 to HT19, as none were identical to the previously described HT1. Specific binding to rat synaptosomes was determined for synthetic HTs, and their neurotoxic capacity was determined by neonatal mouse assay. They induced a powerful paralysis in neonatal mice, particularly HT4 which produced rapid and strong respiratory distress in all animals tested. This is the first known genomic database developed for the Australian paralysis tick. The database contributed to the identification and subsequent characterization of the holocyclotoxin family that will inform the development of novel anti-paralysis control methods.

Australian sugarcane soldier fly's salivary gland transcriptome in response to starvation and feeding on sugarcane crops

“…Similarly, chymotrypsin was highly upregulated in soldier fly salivary glands in response to feeding on sugarcane roots (Log 2 FC > 7). Chymotrypsin is a serine protease enzyme involved in many different pathways, especially in blood‐sucking insects [e.g., mosquitoes, assassin bugs ( Triatoma ) and the paralysis tick, Ixodes holocyclus ] (Rodriguez‐Valle et al ., ) where they degrade elastin and other components in extracellular matrix during feeding. Insect herbivores chymotrypsins can possibly be used to cleave internal peptide bonds in plant proteins.…”

Gene Expression in the Salivary Gland of Rhipicephalus (Boophilus) microplus Fed on Tick-Susceptible and Tick-Resistant Hosts

“…Motobu et al (2007) identified an H. longicornis SCP predominantly expressed in tick midgut upregulated in response to blood feeding, which has been described to play a role in hemoglobin degradation. SCPs were highly expressed in salivary glands and viscera from fully engorged Ixodes holocyclus female ticks (Rodriguez-Valle et al, 2018). The secretory/excretory proteome of helminths parasites identified SCPs that are part of a protein complex that regulates parasite-host interaction (Morassutti et al, 2012).…”

Tick paralysis in dogs and cats in Australia: treatment and prevention deliverables from 100 years of research

“…Again, in this second attempt at a vaccine using recombinant protein production methods, no product was commercialised . A third generation of a tick paralysis vaccine was recently reported using synthetic peptides based on expressed protein sequences found in late‐stage engorged ticks but only limited protective efficacy has been demonstrated to date . Vaccine development has always been competing against other preventative methods and the recent commercialisation of various isoxazoline compounds, their low cost and convenient dosing formulations makes it difficult to see an injectable vaccine ever be competitive.…”

“…A recombinant version of Holocyclotoxin 1 was successfully produced in yeast and published in 2017 but no mouse studies were described to support lethal in vivo biological activity . In another study published by the same group in 2018, a range of Holocyclotoxin peptides were synthesised based on patented sequences, injected into neonatal mice and paralytic effects were observed . The conclusions that can be reached based on all the studies to date are that the paralysis tick likely produces a swathe of peptides that may act synergistically or in varying proportions to induce paralysis of the host.…”