Amblyomma americanum ticks utilizes countervailing pro and anti-inflammatory proteins to evade host defense

Abstract

Feeding and transmission of tick-borne disease (TBD) agents by ticks are facilitated by tick saliva proteins (TSP). Thus, defining functional roles of TSPs in tick evasion is expected to reveal potential targets in tick-antigen based vaccines to prevent TBD infections. This study describes two types of Amblyomma americanum TSPs: those that are similar to LPS activate macrophage (MΦ) to express pro-inflammation (PI) markers and another set that suppresses PI marker expression by activated MΦ. We show that similar to LPS, three recombinant (r) A. americanum insulin-like growth factor binding-related proteins (rAamIGFBP-rP1, rAamIGFBP-rP6S, and rAamIGFBP-rP6L), hereafter designated as PI-rTSPs, stimulated both PBMC -derived MΦ and mice RAW 267.4 MΦ to express PI co-stimulatory markers, CD40, CD80, and CD86 and cytokines, TNFα, IL-1, and IL-6. In contrast, two A. americanum tick saliva serine protease inhibitors (serpins), AAS27 and AAS41, hereafter designated as anti-inflammatory (AI) rTSPs, on their own did not affect MΦ function or suppress expression of PI markers, but enhanced expression of AI cytokines (IL-10 and TGFβ) in MΦ that were pre-activated by LPS or PI-rTSPs. Mice paw edema test demonstrated that in vitro validated PI- and AI-rTSPs are functional in vivo since injection of HEK293-expressed PI-rTSPs (individually or as a cocktail) induced edema comparable to carrageenan-induced edema and was characterized by upregulation of CD40, CD80, CD86, TNF-α, IL-1, IL-6, and chemokines: CXCL1, CCL2, CCL3, CCL5, and CCL11, whereas the AI-rTSPs (individually and cocktail) were suppressive. We propose that the tick may utilize countervailing PI and AI TSPs to regulate evasion of host immune defenses whereby TSPs such as rAamIGFBP-rPs activate host immune cells and proteins such as AAS27 and AAS41 suppress the activated immune cells.

Iripin-3, a New Salivary Protein Isolated From Ixodes ricinus Ticks, Displays Immunomodulatory and Anti-Hemostatic Properties In Vitro

“…Serpins secreted in tick saliva can facilitate blood meal uptake not only by inhibiting coagulation but also by suppressing host inflammatory responses ( 37 , 72 , 74 ). Therefore, we next investigated whether Iripin-3 attenuates pro-inflammatory cytokine production by LPS-stimulated BMDMs.…”

“…The decreased IL-6 production was probably caused by the inhibition of Il6 transcription and not by reduced viability of macrophages, since the metabolic activity of macrophages remained unchanged in the presence of Iripin-3. Several tick serpins have been shown to inhibit IL-6 transcription and secretion ( 37 – 39 , 74 , 98 ), which can occur as a result of serpin-mediated inhibition of proteases such as cathepsin G and cathepsin B ( 37 ). However, the inhibition of pro-inflammatory cytokine production does not have to be dependent on serpin anti-protease activity because some serpins, like Iris and α-1-antitrypsin, can alter pro-inflammatory cytokine production by binding to immune cells via exosites ( 98 , 99 ).…”

Roles of three putative salmon louse (Lepeophtheirus salmonis) prostaglandin E2 synthases in physiology and host–parasite interactions

“…Scientific approaches to understand the interaction between the fish and this resilient ectoparasite has included searches for parasite substances that manipulate the host. Following the identification of PGE 2 in lice secretory/excretory products, a pivotal role of PGE 2 as a salmon louse immune-dampening substance was suggested [ 36 ] based on its role in immunomodulation by other endo- and ectoparasites [ 24 , 26 , 28 – 30 , 67 ]. However, the exact role of PGE 2 in the salmon louse host–parasite interaction remains elusive due to technical difficulties obtaining pure secretions from salmon lice glands.…”

“…However, uncovering the role of PGs is complicated by their diverse roles and the fact that these compounds are produced by both the host and the parasite [ 27 ]. In blood-feeding arthropods such as ticks, PGs are suggested to be involved in vasodilation and immune modulation in the host, as high concentrations of PGE 2 are found in tick saliva [ 28 – 30 ]. Both PGE 2 and PGD 2 have been detected in gland secretions from the fish tapeworm Diphyllobothrium dendriticum when incubated in serum from a host fish [ 24 ], and in vitro studies have suggested that PGE 2 derived from the tapeworm Schistocephalus solidus have the potential to modulate host leukocyte viability and reactive oxygen species production [ 31 ].…”

Borrelia burgdorferi infection modifies protein content in saliva of Ixodes scapularis nymphs

“…We found five IGFBP-rP sequences, three of which were suppressed, and two that were enhanced. We have recently shown that some of the tick IGFBP-rPs, which bind insulin [ 191 ], are involved in tick evasion of host inflammation defense [ 192 ]. Interestingly, RNAi silencing mediated disruption of A. americanum IGFBP-rP1 and IGFBP-rP6S and L significantly affected tick fitness and feeding success [ 193 ] demonstrating the significance of this protein in tick feeding physiology.…”