A Novel α/β Hydrolase Domain Protein Derived From Haemonchus contortus Acts at the Parasite-Host Interface

Abstract

The α/β-hydrolase domain (ABHD) proteins belonging to α/β-hydrolase (ABH) superfamily are ubiquitously distributed throughout all the organisms, and their functional roles have been implicated in energy metabolism, cell signaling, growth and development. In our preliminary work, we identified a novel ABHD protein derived from Haemonchus contortus excretory-secretory (ES) proteins (HcESPs) that interacted with host T cells. Here, we demonstrated that H. contortus ABHD (HcABHD) protein, expressed in all life-cycle stages of H. contortus, is a mammalian ABHD17 homolog with immunodiagnostic utility and lipase activity. Given its catalytic activities and immunomodulatory potentials, we further investigated the functional diversity of HcABHD as an individual ES protein in parasite-host interactions. HcABHD protein may serve as depalmitoylase or thioesterase to suppress cell viability, inhibit cell proliferation, induce intrinsic and extrinsic T cell apoptosis, and cause cell cycle arrested at G1 phase. Moreover, recombinant HcABHD stimuli exerted critical controls on T cell cytokine production profiles, predominantly by inhibiting the secretions of interleukin (IL)-4, interferon-gamma (IFN-γ) and transforming growth factor-beta (TGF-β) 1, and promoting IL-10 production. As the immunomodulator acting at the parasite-host interface, HcABHD protein may have potential applications for the vaccine development of therapeutic intervention. Together, these findings may help illuminate the molecular and particularly immunomodulatory aspects of ES proteins and contribute to an enhanced understanding of parasite immune evasion in H. contortus-host biology.

Protection studies of an excretory–secretory protein HcABHD against Haemonchus contortus infection

“…Thus, in the parallel passive trial, anti-rHcABHD IgG were employed and elicited a protective capacity by generating a 51.5% reduction of cumulative FEC and a 73.8% reduction of total worm burden. Concurrently, circulating anti-rHcABHD IgG of challenged goats were maintained at considerably high levels throughout both active and passive immunization trials, which might inhibit the development and reproduction of H. contortus based on the pivotal role of HcABHD protein in energy metabolism and signaling [ 20 ]. As higher transcription level of the HcABHD gene in male adults rather than female adults was determined in our preliminary work [ 20 ], a stronger protective pattern of the immunization with rHcABHD antigen or anti-rHcABHD IgG targeting male worms of H. contortus was expected.…”

“…Protective type 2 immunity is characterized by amounting production of IL-4, IL-13 and IL-5, mediating the impairment of larval development and worm feeding and promoting worm expulsion [ 35 , 36 ]. In our preliminary work, the external stimuli of rHcABHD protein exhibited modulatory activities on cytokine secretion profiles in vitro and IL-4 secretion of host T cells was significantly inhibited by rHcABHD stimuli [ 20 ]. Consistent with this finding, a significantly increased level of IL-4 production was achieved by immunization with rHcABHD protein compared to that in the challenged adjuvant group at Day 42 of Trial 1, which might result from the neutralization of anti-rHcABHD IgG to native HcABHD antigen.…”

“…The production of rHcABHD proteins was performed as previously described [ 20 ]. Briefly, Escherichia coli BL21 (DE3) cells containing the reconstructed pET28a-HcABHD plasmid were incubated with Luria–Bertani medium containing kanamycin (100 µg/mL, Sigma-Aldrich, St. Louis, MO, USA) and then induced by isopropyl-β- d -thiogalactopyranoside (1 mM, Sigma-Aldrich) for rHcABHD expression.…”

“…In our preliminary studies, an ES protein, H. contortus α/β-hydrolase domain protein (HcABHD), was ascertained among 114 H. contortus ES proteins that interacted with goat T cells via integrated immunoproteomic and bioinformatics [ 19 ]. Subsequently, HcABHD was demonstrated as an immunomodulator that impaired host T cell functions via the disruption of T cell viability and proliferation, and the alteration of cytokine production profiles in vitro [ 20 ]. As immune factors engaging in the parasite-host interactions might be promising vaccine candidates, HcABHD protein expressed at multiple developmental stages may function as a protective antigen for the development of rational immunoprophylactics targeting H. contortus .…”

Fasciola gigantica tegumental calcium-binding EF-hand protein 4 exerts immunomodulatory effects on goat monocytes

“…Transcriptional analysis of the candidate gene was performed using the standard procedure for an ABI 7500 Real-Time PCR System (Applied Biosystems) and specific primers for the endogenous reference gene β-actin and target gene Fg - CaBP4 (Additional file 1 : Table S1). The relative transcription levels of Fg - CaBP4 were calculated using the 2 −ΔΔCt method [ 33 ]. This experiment was performed in triplicate.…”