Molecular Characterization and Serodiagnostic Potential of Two Serpin Proteins in Psoroptes Ovis

Background: Psoroptes ovis a common ectoparasite of wild and domestic animals, leads to cutaneous inflammation, extreme pruritus, scaly lesions, and causes an economically devastating loss of animal husbandry and animal welfare issues. Serine proteinase inhibitor (Serpin) is present in almost all organisms that are involved in host-pathogen interactions, inflammatory responses, and reproductive development, etc. However, the research on P. ovis serpins is still limited.Methods: In this study, two serpins of P. ovis (PsoSP1 and PsoSP2) were cloned, and the molecular characterization was analyzed by bioinformatics. The transcriptional profiles and tissue localization of PsoSP1 and PsoSP2 in P. ovis were investigated by quantitative real-time PCR and immunohistochemistry, respectively. The potential function of recombinant PsoSP1 and PsoSP2 (rPsoSP1 and rPsoSP2) in the serodiagnosis of P. ovis infestation in rabbits were evaluated by indirect enzyme-linked immunosorbent assay (iELISA). Results: Both of the 523 residue PsoSP1 and the 240 residue PsoSP2 proteins contained typical serpin domains and signatures. Both PsoSP1 and PsoSP2 expressed throughout the life cycle, more specifically, significantly higher expression in female mites than the larva, nymph, and male mites (p < 0.001). The native PsoSP1 and PsoSP2 proteins localized in ovary and mouthpart of adult female mites, respectively. Compared to rPsoSP2, the rPsoSP1 displayed better diagnostic efficiency with higher values of sensitivity, specificity and the area under the receiver operating characteristic curve (AUC) than rPsoSP1 by iELISA (rPsoSP1 - rPsoSP2: 96.0% - 90.0%; 90.91% - 78.18%; 0.988 - 0.964, respectively). Moreover, the rPsoSP1 showed seropositive in 80% rabbits as early as the 2nd week post-infestation (p.i.), prior to visible clinical signs and microscopy-positive of skin scrapings. Conclusions: These results suggested that these two serpins may play essential roles in reproductive development, blood-feeding, and pathogenicity of P. ovis. Compared to PsoSP2, PsoSP1 appeared as a potential antigen for serodiagnosis of P. ovis infestation in rabbits, especially at the early stage of infestation.