Metabolomics Analysis of Splenic CD19+ B Cells in Mice Chronically Infected With Echinococcus granulosus sensu lato Protoscoleces

The non-oral infection of larval Echinococcus granulosus induces immune and metabolic reprogramming in the colon of mice

Background

The intestinal tract serves as a critical regulator for nutrient absorption and overall health. However, its involvement in anti-parasitic infection and immunity has been largely neglected, especially when a parasite is not transmitted orally. The present study investigated the colonic histopathology and functional reprogramming in mice with intraperitoneal infection of the larval Echinococcus granulosus (E. granulosus).

Results

Compared with the control group, the E. granulosus-infected mice exhibited deteriorated secreted mucus, shortened length, decreased expression of tight junction proteins zonula occludens-1 (ZO-1), and occludin in the colon. Moreover, RNA sequencing was employed to characterize colonic gene expression after infection. In total, 3,019 differentially expressed genes (1,346 upregulated and 1,673 downregulated genes) were identified in the colon of infected mice. KEGG pathway and GO enrichment analysis revealed that differentially expressed genes involved in intestinal immune responses, infectious disease-associated pathways, metabolism, or focal adhesion were significantly enriched. Among these, 18 tight junction-relative genes, 44 immune response-associated genes, and 23 metabolic genes were annotated. Furthermore, mebendazole treatment could reverse the colonic histopathology induced by E. granulosus infection.

Conclusions

Intraperitoneal infection with E. granulosus induced the pathological changes and functional reprogramming in the colon of mice, and mebendazole administration alleviated above alternations, highlighting the significance of the colon as a protective barrier against parasitic infection. The findings provide a novel perspective on host-parasite interplay and propose intestine as a possible target for treating parasitic diseases that are not transmitted orally.

Transcriptomic Profiles of Splenic CD19+ B Cells in Mice Chronically Infected With the Larval Echinococcus granulosus

Background

We previously reported that the larval Echinococcus granulosus (E. granulosus) infection can expand the population of regulatory B cells in mice, thereby inhibiting the anti-infective immunity. However, the underlying mechanism is still largely unknown. This study further investigated the holistic transcriptomic profiles of total splenic B cells following the chronic infection of the parasite.

Methods

The infection model of larval E. granulosus was established by intraperitoneal inoculation with 2000 protoscolexes. Magnetic-Activated Cell Separation (MACS) was used to isolate the total splenic B cells. RNA sequencing was performed to screen the differentially expressed genes (DEGs) after infection. The expression of selected DEGs was verified using qRT-PCR. Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and Co-expression network analysis were applied to predict these DEGs' underlying biological processes, pathways, and interactions respectively.

Results

A total of 413 DEGs were identified in larval E. granulosus infected B cells, including 303 up- and 110 down-regulated genes. Notably, most DEGs related to inflammation and chemotaxis were significantly upregulated after infection. In line with these changes, significant expression upregulation of DEGs associated with fatty acid oxidation, lipid synthesis, lipolysis, lipid transport, and cholesterol biosynthesis, were observed in infected B cells. Co-expression network analysis showed an intimate interaction between these DEGs associated with immune and metabolism.

Conclusions

The present study revealed that the larval E. granulosus infection induces metabolic reprogramming of B cells, which provides a novel clue to clarify the immunoregulatory mechanism of B cells in parasitic infection.