Molecular Characterization and Functional Effect on Canine Peripheral Blood Mononuclear Cells of an Uncharacterized Major Egg Antigen EGR-01664 from <i>Echinococcus granulosus</i>.

Abstract

<h4>Background</h4>Cystic echinococcosis (CE) is a globally distributed zoonosis triggered by the larval stage of <i>Echinococcus granulosus</i> (<i>E. granulosus</i>), impacting humans and an extensive array of mammalian intermediate hosts. EGR-01664 is the major egg antigen of <i>E. granulosus</i>, but almost nothing is currently known about the function of EGR-01664 from <i>E. granulosus</i>.<h4>Methods</h4>This study aimed to investigate the <i>E. granulosus</i> EGR-01664 gene (GenBank ID: 36337379), and the recombinant EGR-01664 protein was expressed successfully. Next, the transcription of the EGR-01664 gene across various developmental stages of <i>E. granulosus</i> was analyzed. Its spatial expression patterns in adult worms and protoscoleces were characterized using both quantitative PCR (qPCR) and immunofluorescence assays. Furthermore, the immunomodulatory effects of rEGR-01664 on cell proliferation, nitric oxide production, and cytokine secretion were examined by co-culturing the recombinant protein with canine PBMCs.<h4>Results</h4>The rEGR-01664 could be recognized by sera from dogs infected with <i>E. granulosus</i>. Immunofluorescence assay (IFA) localization revealed the protein's presence in the epidermis of protoscoleces, the adult epidermis, and some parenchymal tissues. qPCR revealed that EGR-01664 mRNA levels were significantly higher in protoscoleces compared to adults (<i>p</i> < 0.0001). At a concentration of 20 μg/mL, rEGR-01664 could significantly activate the transcription and expression of IL-10, TGF-β1, IL-17A, and Bax in canine PBMCs. However, with an increase in concentration, it inhibited the expression of IFN-γ, Bcl-2, GSDMD, IL-18, and IL-1β. These results suggest that the EGR-01664 gene plays a crucial role in the development, parasitism, and reproduction of <i>E. granulosus.</i> In vitro studies have shown that rEGR-01664 protein regulates the immune regulation function of canine PBMCs, suggesting its potential as a vaccine adjuvant or immunotherapy target.<h4>Conclusions</h4>EGR-01664 may modulate canine PBMC functions to regulate host immune responses, thereby facilitating our understanding of how <i>E. granulosus</i> EGR-01664 contributes to the mechanism of parasitic immune evasion.