Influence Of Toxocara Canis Infection On Blood Metabolome And Proteome As Well As The Lung Transcriptome Of Beagle Dogs

Toxocara canis,the common roundworm of dogs,is the primary causative agent of toxocariasis in humans.Infected individuals could show three major clinical forms of disease:visceral larva migrans(VLM),ocular larva migrans(OLM),or neurotoxocariasis(NT).Toxocariasis is one of the most important and neglected parasitic diseases.The seroprevalence of Toxocara spp.is reported from 12.14% to 44.83%.The average prevalence of T.canis infection in dogs in China's mainland is 17.34%.A number of “Omics” studies on T.canis have been reported,such as genomics,transcriptomics and proteomics studies.However,little is known about the molecular mechanism of Toxocara-host interaction.Therefore,in this study,we investigated the blood metabolomic and proteomic changes,and global transcriptomic profiling of lungs of Beagle dogs after infection with T.canis at different stages to reveale the influence of T.canis infection on definitive hosts.The metabolic changes of Beagle dogs' serum were examined at 24 h,10 d and 36 d after oral infection with 300 infectious T.canis eggs by LC-MS/MS.ROC curve analysis revealed five metabolite markers at 24 hpi(hour post-infection)to 36 dpi(day post-infection),with potential diagnostic value for toxocariasis.The levels of taurocholate,estradiol,prostaglandins and leukotriene were significantly changed.Primary bile acid biosynthesis pathway,steroid hormone biosynthesis pathway and biosynthesis of unsaturated fatty acids pathway were significantly altered by T.canis infection.In the present study,the proteomic alterations in the plasma of Beagle dogs induced by T.canis infection were studied by the quantitative mass spectrometry-based data-independent acquisition(DIA).At 24 hpi,the up-regulation of RARRES2 and the down-regulation of WDR1,moesin and filamin-A may participate in pro-inflammatory reaction or promote larvae migration.At 96 hpi,the up-regulation of protein C and FGL2 may participate in maintaining the stability of the coagulation system to protect the lung.At36 dpi,the up-regulation of CFHR5 and the down-regulation of CRP,FCN as well as multiple complements may affect the three traditional complement systems,including the classic pathway,lectin pathway and alternative pathway.ByRNA-Seq,we found that the expression level of manyRNAs were altered in infected dogs.The transcription level of SCGB1A1 was remarkably increased more than 100 times at the three infection stages,suggesting that SCGB1A1 could be an important roler in the lung tolerance during T.canis infection.The upregulation of FOXJ1 at 24 hpi,and the downregulation of IL-1B and IL-21 at 96 hpi seem to influence humoral immunity of dogs,and promote the development and migration of T.canis larvae.Also,some miRNAs,such as miRNA-150,miRNA-28,miRNA-423 a and miRNA-493,participated in T.canis infection at different stages.Further study on these altered metabolites,proteins orRNAs triggered by T.canis infection may discovery novel therapeutic or diagnostic targets for toxocariasis.