Unveiling of brain transcriptome of masked palm civet (Paguma larvata) with chronic infection of Toxoplasma gondii

Multiomics and bioinformatics identify differentially expressed effectors in the brain of Toxoplasma gondii infected masked palm civet

Introduction

The masked palm civet (Paguma larvata) serves as a reservoir in transmitting pathogens, such as Toxoplasma gondii, to humans. However, the pathogenesis of T. gondii infection in masked palm civets has not been explored. We studied the molecular changes in the brain tissue of masked palm civets chronically infected with T. gondii ME49.

Methods

The differentially expressed proteins in the brain tissue were investigated using iTRAQ and bioinformatics.

Results

A total of 268 differential proteins were identified, of which 111 were upregulated and 157 were downregulated. KEGG analysis identified pathways including PI3K-Akt signaling pathway, proteoglycans in cancer, carbon metabolism, T-cell receptor signaling pathway. Combing transcriptomic and proteomics data, we identified 24 genes that were differentially expressed on both mRNA and protein levels. The top four upregulated proteins were REEP3, REEP4, TEP1, and EEPD1, which was confirmed by western blot and immunohistochemistry. KEGG analysis of these 24 genes identified signaling cascades that were associated with small cell lung cancer, breast cancer, Toll-like receptor signaling pathway, Wnt signaling pathways among others. To understand the mechanism of the observed alteration, we conducted immune infiltration analysis using TIMER databases which identified immune cells that are associated with the upregulation of these proteins. Protein network analysis identified 44 proteins that were in close relation to all four proteins. These proteins were significantly enriched in immunoregulation and cancer pathways including PI3K-Akt signaling pathway, Notch signaling pathway, chemokine signaling pathway, cell cycle, breast cancer, and prostate cancer. Bioinformatics utilizing two cancer databases (TCGA and GEPIA) revealed that the four genes were upregulated in many cancer types including glioblastoma (GBM). In addition, higher expression of REEP3 and EEPD1 was associated with better prognosis, while higher expression of REEP4 and TEP1 was associated with poor prognosis in GBM patients.

Discussion

We identified the differentially expressed genes in the brain of T. gondii infected masked palm civets. These genes were associated with various cellular signaling pathways including those that are immune- and cancer-related.

Transcriptome analysis of a newly established mouse model of Toxoplasma gondii pneumonia

BACKGROUND

Toxoplasmosis is a zoonotic parasitic disease caused by Toxoplasma gondii. Toxoplasma gondii infection of the lungs can lead to severe pneumonia. However, few studies have reported Toxoplasma pneumonia. Most reports were clinical cases due to the lack of a good disease model. Therefore, the molecular mechanisms, development, and pathological damage of Toxoplasma pneumonia remain unclear.

METHODS

A mouse model of Toxoplasma pneumonia was established by nasal infection with T. gondii. The model was evaluated using survival statistics, lung morphological observation, and lung pathology examination by hematoxylin and eosin (H&E) and Evans blue staining at 5 days post-infection (dpi). Total RNA was extracted from the lung tissues of C57BL/6 mice infected with T. gondii RH and TGME49 strains at 5 dpi. Total RNA was subjected to transcriptome analysis by RNA sequencing (RNA-seq) followed by quantitative real-time polymerase chain reaction (qRT-PCR) validation. Transcript enrichment analysis was performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases to assess the biological relevance of differentially expressed transcripts (DETs).

RESULTS

C57BL/6 mice infected with T. gondii via nasal delivery exhibited weight loss, ruffled fur, and respiratory crackles at 5 dpi. The clinical manifestations and lethality of RH strains were more evident than those of TGME49. H&E staining of lung tissue sections from mice infected with T. gondii at 5 dpi showed severe lymphocytic infiltration, pulmonary edema, and typical symptoms of pneumonia. We identified 3167 DETs and 1880 DETs in mice infected with the T. gondii RH and TGME49 strains, respectively, compared with the phosphate-buffered saline (PBS) control group at 5 dpi. GO and KEGG enrichment analyses of DETs showed that they were associated with the immune system and microbial infections. The innate immune, inflammatory signaling, cytokine-mediated signaling, and chemokine signaling pathways displayed high gene enrichment.

CONCLUSION

In this study, we developed a new mouse model for Toxoplasma pneumonia. Transcriptome analysis helped to better understand the molecular mechanisms of the disease. These results provided DETs during acute T. gondii lung infection, which expanded our knowledge of host immune defenses and the pathogenesis of Toxoplasma pneumonia.