Taenialarvae possess distinct acetylcholinesterase profiles with implications for host cholinergic signalling
Authors: de Lange Anja , Prodjinotho Ulrich Fabien , Tomes Hayley , Hagen Jana , Jacobs Brittany-Amber , Smith Katherine , Horsnell William , Sikasunge Chummy , Selkirk Murray E. , da Costa Clarissa Prazeres , Raimondo Joseph Valentino 
Published: June 2020

Larvae of the cestodesTaenia soliumandTaenia crassicepsinfect the central nervous system of humans.Taenia soliumlarvae in the brain cause neurocysticercosis, the leading cause of adult-acquired epilepsy worldwide. Relatively little is understood about how cestode-derived products modulate host neural and immune signalling. Acetylcholinesterases, a class of enzyme that degrade acetylcholine, are produced by a host of parasitic worms to aid their survival in the host. Acetylcholine is an important signalling molecule in both the human nervous and immune systems, with powerful modulatory effects on the excitability of cortical networks. Therefore, it is important to establish whether cestode derived acetylcholinesterases may alter host neuronal cholinergic signalling. Here we make use of multiple techniques to profile acetylcholinesterase activity in different extracts of bothTaenia crassicepsandTaenia soliumlarvae. We find that the larvae of both species contain substantial acetylcholinesterase activity. However, acetylcholinesterase activity is lower inTaenia soliumas compared toTaenia crassicepslarvae. Further, whilst we observed acetylcholinesterase activity in all fractions ofTaenia crassicepslarvae, including on the membrane surface and in the excreted/secreted extracts, we could not identify acetylcholinesterases on the membrane surface or in the excreted/secreted extracts ofTaenia soliumlarvae. Finally, using whole-cell patch clamp recordings in rat hippocampal brain slice cultures, we demonstrate thatTaenialarval derived acetylcholinesterases can modify neuronal responses to acetylcholine. Together, these findings highlight the possibility thatTaenialarval acetylcholinesterases can interfere with cholinergic signalling in the host, potentially contributing to pathogenesis in neurocysticercosis.

Author summary

Infection of the human nervous system with larvae of the parasiteTaenia soliumis a significant cause of acquired epilepsy worldwide. Despite this, the precise cellular and molecular mechanisms underlying epileptogenesis in neurocysticercosis remain unclear. Acetylcholinesterases are a family of enzymes widely produced by helminthic parasites. These enzymes facilitate the breakdown of acetylcholine, which is also a major neurotransmitter in the human nervous system. IfT. soliumlarvae produce acetylcholinesterases, this could potentially disrupt host cholinergic signalling, which may in turn contribute to seizures and epilepsy. We therefore set out to investigate the presence and activity of acetylcholinesterases inT. soliumlarvae, as well as inTaenia crassicepslarvae, a species commonly used as a model parasite in neurocysticercosis research. We found that bothT. crassicepsandT. soliumlarvae produce acetylcholinesterases with substantial activity. We further demonstrate that the acetylcholinesterase activity in the products of these parasites is sufficient to disrupt cholinergic signalling in an ex vivo brain slice model. This study provides evidence thatTaenialarvae produce acetylcholinesterases and that these can interfere with cholinergic signalling in the host and potentially contribute to pathogenesis in neurocysticercosis.