Ixodes scapularis Tick Saliva Proteins Sequentially Secreted Every 24 h during Blood Feeding

Abstract

Ixodes scapularis is the most medically important tick species and transmits five of the 14 reportable human tick borne disease (TBD) agents in the USA. This study describes LC-MS/MS identification of 582 tick- and 83 rabbit proteins in saliva of I. scapularis ticks that fed for 24, 48, 72, 96, and 120 h, as well as engorged but not detached (BD), and spontaneously detached (SD). The 582 tick proteins include proteases (5.7%), protease inhibitors (7.4%), unknown function proteins (22%), immunity/antimicrobial (2.6%), lipocalin (3.1%), heme/iron binding (2.6%), extracellular matrix/ cell adhesion (2.2%), oxidant metabolism/ detoxification (6%), transporter/ receptor related (3.2%), cytoskeletal (5.5%), and housekeeping-like (39.7%). Notable observations include: (i) tick saliva proteins of unknown function accounting for >33% of total protein content, (ii) 79% of proteases are metalloproteases, (iii) 13% (76/582) of proteins in this study were found in saliva of other tick species and, (iv) ticks apparently selectively inject functionally similar but unique proteins every 24 h, which we speculate is the tick's antigenic variation equivalent strategy to protect important tick feeding functions from host immune system. The host immune responses to proteins present in 24 h I. scapularis saliva will not be effective at later feeding stages. Rabbit proteins identified in our study suggest the tick's strategic use of host proteins to modulate the feeding site. Notably fibrinogen, which is central to blood clotting and wound healing, was detected in high abundance in BD and SD saliva, when the tick is preparing to terminate feeding and detach from the host. A remarkable tick adaptation is that the feeding lesion is completely healed when the tick detaches from the host. Does the tick concentrate fibrinogen at the feeding site to aide in promoting healing of the feeding lesion? Overall, these data provide broad insight into molecular mechanisms regulating different tick feeding phases. These data set the foundation for in depth I. scapularis tick feeding physiology and TBD transmission studies.

Tick attachment cement – reviewing the mysteries of a biological skin plug system

“…Nevertheless it became clear that the sheer quantity of proteins and other products of the salivary glands (Alarcon‐Chaidez, 2014) make assignment to particular functions such as cement formation difficult. To address this problem, temporary expression patterns of the salivary glands were analysed (Radulovic et al ., 2014; Kim et al ., 2016; Bullard, Williams & Karim, 2016), showing which salivary products were produced at certain points during feeding. These subsets of proteins were then tested for their functions by specific inactivation in living ticks and verification in feeding trials (Kim, Curran & Mulenga, 2014).…”

“…Recently, two chitinases have been identified from the saliva of Ixodes scapularis Say, 1821, one of them inactive and with 64–65% similarity to the chitinase‐like proteins from Amblyomma americanum . However, the role of these proteins was not investigated (Kim et al ., 2016). …”

“…It was suggested that the latter might be the result of degenerating processes of the salivary glands at that point (Kim et al ., 2016). Further analysis of tick cement composition used Fourier transform infrared spectroscopy attenuated total reflectance (FTIR‐ATR) to obtain information about the secondary structures of proteins at the surface of the cement cone (Bullard et al ., 2016).…”

Heparan sulfate/heparin glycosaminoglycan binding alters inhibitory profile and enhances anticoagulant function of conserved Amblyomma americanum tick saliva serpin 19

“…Tick saliva proteomes (Kim et al, 2016b; Tirloni et al, 2015), immunoproteomes (Radulović et al, 2014), and western blotting analysis approaches (Chalaire et al, 2011; Ibelli et al, 2014; Kim et al, 2015) have confirmed that ticks do inject serpins into animals during feeding. Several studies have established that some tick saliva serpins have inhibitory functions against host defense system proteases (Chmelar et al, 2011; Ibelli et al, 2014; Kim et al, 2015; Mulenga et al, 2013; Prevot et al, 2006, 2009; Xu et al, 2016).…”

Host Immune Evasion by Lyme and Relapsing Fever Borreliae: Findings to Lead Future Studies for Borrelia miyamotoi

“…Ixodes saliva contains adaptive and innate immunomodulatory and anticomplement proteins (165, 178–183). A recent study demonstrated changes in the salivary protein profile over the course of a feeding, which has implications for the efficacy of the host immune response at the feeding pit and for transmitting spirochetes (168). Currently, several members of the anticomplement family of proteins have been characterized from I. scapularis, I. ricinus , and I. persulcatus including Salp15, Salp20, Isac, Irac I, Irac II, and Ixac-B1, -2, -3, -4, -5.…”