Macrophage Migration Inhibitory Factor in Psoroptes ovis: Molecular Characterization and Potential Role in Eosinophil Accumulation of Skin in Rabbit and Its Implication in the Host-Parasite Interaction.

Psoroptes ovis, a common surface-living mite of domestic and wild animals worldwide, results in huge economic losses and serious welfare issues in the animal industry. P. ovis infestation rapidly causes massive eosinophil infiltration in skin lesions, and increasing research revealed that eosinophils might play an important role in the pathogenesis of P. ovis infestation. Intradermal injection of P. ovis antigen invoked massive eosinophil infiltration, suggesting that this mite should contain some relative molecules involved in eosinophil accumulation in the skin. However, these active molecules have not yet been identified. Herein, we identified macrophage migration inhibitor factor (MIF) in P. ovis (PsoMIF) using bioinformatics and molecular biology methods. Sequence analyses revealed that PsoMIF appeared with high similarity to the topology of monomer and trimer formation with host MIF (RMSD = 0.28 angstroms and 2.826 angstroms, respectively) but with differences in tautomerase and thiol-protein oxidoreductase active sites. Reverse transcription PCR analysis (qRT-PCR) results showed that PsoMIF was expressed throughout all the developmental stages of P. ovis, particularly with the highest expression in female mites. Immunolocalization revealed that MIF protein located in the ovary and oviduct of female mites and also localized throughout the stratum spinosum, stratum granulosum, and even basal layers of the epidermis in skin lesions caused by P. ovis. rPsoMIF significantly upregulated eosinophil-related gene expression both in vitro (PBMC: CCL5, CCL11; HaCaT: IL-3, IL-4, IL-5, CCL5, CCL11) and in vivo (rabbit: IL-5, CCL5, CCL11, P-selectin, ICAM-1). Moreover, rPsoMIF could induce cutaneous eosinophil accumulation in a rabbit model and increased the vascular permeability in a mouse model. Our findings indicated that PsoMIF served as one of the key molecules contributing to skin eosinophil accumulation in P. ovis infection of rabbits.

Molecular characterization of four novel serpins in Psoroptes ovis var. cuniculi and their implications in the host-parasite interaction.

Psoroptes ovis var. cuniculi infestation rapidly causes skin lesion, cutaneous inflammatory and subsequent adaptive immune response in rabbits. To success feeding and survive on the host skin, this mite should product bioactive molecules to confront host tissue repair and immune defense, but these molecules of this mite remains mostly unknown. Serpins have been proved to involve in diverse biological functions including parasite reproduction, survival and modulating host defense. Limited information is currently available on serpins from Psoroptes mites. Herein, we identified four novel serpins (PsoSP3-PsoSP6) in P. ovis var. cuniculi using bioinformatics and molecular biology techniques. Sequence analysis revealed that PsoSP3-PsoSP6 comprised the common features of typical serpins superfamily including serpin domains, signature or the reactive centre loop (RCL) domain. The recombinant PsoSP4-PsoSP6 (rPsoSP4-rPsoSP6) revealed variable potency inhibition on trypsin, chymotrypsin and elastase except for rPsoSP3 in inhibitory activity assays. By quantitative RT-PCR, the expressions of PsoSP3 and PsoSP4 were higher in juvenile mites (larva and nymph) than in adult mites, however, PsoSP5 and PsoSP6 appeared near-exclusive expression in adult female mites. Immunolocalization showed that native PsoSP4 protein was localized in uterus, whilst native PsoSP3, PsoSP5 and PsoSP6 were specifically localized in the ovarian nutritive cell (ONC) in ovary. Our findings indicated that PsoSP3-PsoSP6 might play critical roles in development and reproduction physiologies. rPsoSP4-rPsoSP6 might participate in modulating host inflammation, immune response and tissue repair.