For Whom the Bell Tolls (and Nods): Spit-acular Saliva

Abstract

Having emerged during the early part of the Cretaceous period, ticks are an ancient group of hematophagous ectoparasites with significant veterinary and public health importance worldwide. The success of their life strategy can be attributed, in part, to saliva. As we enter into a scientific era where the collection of massive data sets and structures for biological application is possible, we suggest that understanding the molecular mechanisms that govern the life cycle of ticks is within grasp. With this in mind, we discuss what is currently known regarding the manipulation of Toll-like (TLR) and Nod-like (NLR) receptor signaling pathways by tick salivary proteins, and how these molecules impact pathogen transmission.

Message in a vesicle – trans-kingdom intercommunication at the vector–host interface

“…Blood-feeding arthropods secrete a vast arsenal of immunomodulatory molecules (Leitner et al, 2013;Shaw et al, 2016;Šimo et al, 2017). How these effector molecules affect immune signaling is another active area of investigation.…”

“…Recently, there has been a significant increase in research dedicated to the understanding of arthropods as vectors of diseases because these ailments disproportionately impact vulnerable populations around the world. Mosquitoes, ticks and sandflies, among other arthropods, secrete salivary proteins that contribute to microbial transmission (Leitner et al, 2013;Shaw et al, 2016;Šimo et al, 2017). One immune evasion strategy used by vector-borne pathogens to promote a successful infection is through the secretion of extracellular vesicles (Atayde et al, 2015;Babatunde et al, 2018;Lovo-Martins et al, 2018;Nogueira et al, 2015;Silverman et al, 2010a,b;Sisquella et al, 2017;Trocoli Torrecilhas et al, 2009).…”

Tick-host-pathogen systems immunobiology an interactive trio

“…Tick saliva impairs dendritic cell differentiation and expression of costimulatory molecules (106); diminishes their chemotactic responses; reduces stimulation of T lymphocytes (107); and, down regulates proinflammatory cytokine expression while increasing anti-inflammatory cytokine production (108). Among the best characterized molecular relationships between tick and host is the action of tick saliva on dendritic cell innate receptors, signal transduction pathways and inflammasome function (109,110,111).…”

Deviant Behavior: Tick-Borne Pathogens and Inflammasome Signaling

“…However, due to the space constraints of this review, we will limit our focus to tick-transmitted pathogens in the context of NLR and inflammasome signaling. More discussion on the immunosuppressive properties of tick saliva can be found in the following reviews [ 225 , 226 , 227 , 266 , 267 ].…”

“…of ticks ( scapularis , ricinus , pacificus and persulcatus ), and Ehrlichia spp. can be transmitted by Amblyomma americanum ( E. chaffeensis ) and I. scapularis ( E. muris -like) ticks [ 201 , 267 , 268 ]. Neither of these two bacteria have PAMPs that are known to bind Nod1/2 receptors or induce inflammasome activation; nevertheless, studies have reported that both induce NLR signaling.…”