Abstract
During host-parasite interactions, binding of excretory/secretory proteins (ESPs) on the host immune cells is considered the fundamental phase for regulation of immune responses. In this study, gene encoding Haemonchus contortus tropomyosin (Hc-TpMy), was successfully cloned and expressed, and the recombinant protein after host cell surface attachment was evaluated for immune functional analysis with goat peripheral blood mononuclear cells (PBMCs) in vitro. The isopropyl-β-D-thiogalactopyranoside (IPTG)-induced recombinant protein was successfully recognized by the sera of rat experimentally infected with rHc-TpMy. The immunofluorescence assay detected attachment of rHc-TpMy on the surface of host PBMCs. Furthermore, immunoregulatory roles of rHc-TpMy on cytokines expression, PBMC proliferation, migration, nitric oxide (NO) production, apoptosis and monocytes phagocytosis were observed. The results showed that expression of IL-4 and IFN-γ cytokines, cell proliferation, NO production and PBMC migration were significantly suppressed by goat PBMCs after co-incubation with rHc-TpMy protein. However, the productions of IL-10, IL-17 and TGF-β1 cytokines, PBMCs apoptosis and monocytes phagocytosis were elevated at dose dependent manner. Our findings indicated that rHc-TpMy is an important ES binding protein exhibit distinct immuno-suppressive roles on goat PBMCs which might be a potential molecular target to control haemonchosis in future.
Highlights
The gastrointestinal nematode parasite Haemonchus contortus is a serious worldwide problem, in the goat and sheep industry, where it causes mortality in young animals due to its blood feeding behavior in abomasal mucosa [1]
Bioinformatics searching tools for similarity of Haemonchus contortus tropomyosin (Hc-TpMy) to other known invertebrate tropomyosins revealed that Hc-TpMy sequence had 100% homology with H. contortus (CDJ92091), Heligmosomoides polygyrus (ABV44405) and Teladorsagia circumcincta (ADB27966), whereas, high similarity was found with Trichostrongylus colubriformis 99% (P15846), Caenorhabditis elegans 53% (NP_001300454), Ascaris lumbricoides 97% (ABS82498), Anisakis simplex 96% (Q9NAS5), Heterodera glycines 93% (AAQ12016)
Immunoblot analysis showed that rHc-TpMy protein could be recognized by antibodies in sera from goats infected with H. contortus (Figure 1B)
Summary
The gastrointestinal nematode parasite Haemonchus contortus is a serious worldwide problem, in the goat and sheep industry, where it causes mortality in young animals due to its blood feeding behavior in abomasal mucosa [1]. The existing control strategies for nematode infection through widespread use of antihelmintics have resulted in serious drug resistance in domestic. The emergence of drug resistance demands for novel anti-parasitic drugs and vaccines, and development of powerful immunological approaches to control nematode infections [4]. A deep insight into developmental biology of H. contortus at a molecular level might determine some key antigens as new drug targets, which could provide promising vaccine candidates against haemonchosis. The use of H. contortus excretory and secretory proteins (HcESPs)-induced protective immunity against parasite and recombinant antigens have been under extensive investigation as a control strategy against haemonchosis [5,6]. Helminth infections, including nematodes, are habitually associated with increased IgE levels and type I hypersensitivity reactions, which in turn are responsible for the expression of interleukins and T helper cell type 2 (Th2) immune responses induced by ES antigens [7]
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