| Schistosomiasis japonica is one of the wide distributed and serious zoonotic parasitic diseases,once popular in southern China,12provinces (municipalities), autonomous regions, and a seriousimpact on the socio-economic and human health. More than half a century, schistosomiasis controlin China has made remarkable achievements, to the end of2010, the number of schistosomiasiscases had reduced from10,000,000to326,000cases. Schistosomiasis control situation in China isstill relatively severe, snails area has increased in some areas, the epidemic repeated. The maindifficulty for schistosomiasis control was that, the intermediate host snails is difficult to wipe out;many kinds of reservoir hosts exist, the manure of livestock (especially yellow cattle and waterbuffalo) is the most important source of infection. Repeated infections exist in humans andanimals, the chemotherapy-based control strategies alone can not effectively control thetransmission of schistosomiasis. To strengthen the research on schistosomiasis vaccine, becomingthe major demand of current control. Strengthening the studies on the relationship betweenschistosome and different suitability hosts, will provide an important basis for screening of theschistosome vaccine candidate molecules and new drug targets.As many as46species of mammals naturally infected with Schistosoma.japonicum, butdifferent mammals have different suitability for S. japonicum infection. According to the growthoutcome in their hosts and the relationship with hosts, the hosts are divided into suitable hostand non-suitable host. Microtus fortis is the only mammals of natural resistance to S. japonicum.Yellow cattle, water buffalo and goats are three most important natural reservoir hosts in endemicareas. Wistar rats, BALB/c mice and New Zealand white rabbits are experimental animals mostcommonly used in laboratory. The above criteria to be classified, yellow cattle, goats, BALB/cmice, New Zealand white rabbits are suitable hosts for S.japonicum infection; water buffalo,Wistar rats are non-suitable hosts for S.japonicum infection. Our group had gained some valuabledata or results in mechanisms of suitability for rats, mice and Microtus fortis infection withS.japonicum. This article focused on the mechanisms/reasons of infection differences in thenatural host, yellow cattle, water buffalo, goats, three different suitability natural hosts, thefollowing results were obtained:1. Development and pathogenicity of S japonicum in different suitability animal hostsArtificially infected with S japonicum cercariae under experimental conditions, yellow cattle,water buffalo, goat, Wistar rat, BALB/c mice and New Zealand white rabbits, parasites werecollected from them. There are significant differences in parasite recoveries of the six animals, theworm recovery rate in descending order: goats, BALB/c mice, New Zealand white rabbits, yellowcattle, water buffalo, Wistar rats. Difference also was observed in length and width of the worms,the length of worms in suitable hosts longer than that in non-suitable hosts, the length of femaleworms longer than that in the male worms(Wistar rat exceptions). Livers were covered with eggsnodules suitable host (yellow cattle, goats, BALB/c mice and New Zealand white rabbits) after 7w-infection, especially completely covered by white eggs nodules, the lesion is particularlyserious in New Zealand white rabbits and BALB/c mice; while only a few eggs nodules (waterbuffalo), or almost no eggs nodules (Wistar rat). The livers of infected yellow cattle and goatscontained significantly increased accumulation of inflammatory cells, and the schistosome eggswere surrounded with large amounts of eosinophil infiltration. In contrast, no hepatocyte swellingor lymphocyte infiltration, and fewer white blood cells, was observed in water buffalo.Observation of ultrastructure showed that worms from water buffalo have collapsed and loosedsurface with less spines and sensory papillae, organelles of cytoplasm were dissolved and morevacuole structures in the male worm tegument, the female worms from water buffalo had noobvious difference in the tegument, but internal microvilli were showed shorter and fewer thanthose from yellow cattle.2. Immune responses in natural hosts of S.japonicum, yellow cattle and water buffaloIn this study, yellow cattle and water buffalo were artificially infected with S. japonicumcercariae, and at different times post infection(0weeks [w],2w,4w,7w), the CD4+and CD8+Tcell subsets and the intracellular cytokines interferon-γ(IFN-γ) and interleukin-4(IL-4) in theperipheral blood, as well as specific serum IgG antibodies, were detected and analyzed. The studywill provide useful information for the design of a vaccine and its delivery procedure.The percentage of CD4+T cells was higher in yellow cattle, while the percentage of CD8+Tcells was higher in water buffalo from pre-infection to7w post infection. The CD4/CD8ratioswere decreased in both species after challenge with schistosomes. Comparing with water buffalo,the IFN-γ level was higher and decreased significantly, while the IL-4level was lower andincreased gradually in yellow cattle from pre-infection to7w post infection. The specific serumIgG antibody was detected by ELISA in yellow cattle and water buffalo pre and post infectionwith S. japonicum. The results showed that the antibody response in water buffalo was at a lowlevel until7w post infection; while the level of SEA specific IgG antibodies was increasedgradually in yellow cattle after infection with schistosomes in yellow cattle and and reached ahigher level at7w post infection. Immunological analysis suggested that CD4+T cells might be anintegral component of the immune response and might associate with worm development inyellow cattle and Th1dominated the immune response during early infection, then the responseshifted to Th2-type polarized immunity at6–7weeks, but no obvious shift of Th1-type toTh2-type polarized immunity was observed in schistosome-infected water buffalo. This study willprovide scientific basis for schistosome vaccine design in future.3. Microarray analysis of gene expression in schistosomes derived from different natural hostsBy using high-throughput microarray technology to compare the gene expression profiles ofadult schistosomes obtained from three natural hosts, yellow cattle, water buffalo and goats,66differentially expressed genes were found between schistosomes from water buffalo and from goat(p<0.05, FC>2),491were found between schistosomes from water buffalo and goats(p<0.05,FC>2),46were the common differentially expressed genes found in schictosomes from water buffalo compared to those from yellow cattle and goats. The pattern analysis of the differentiallyexpressed genes suggested that some protein phosphatase/kinase (PP2A,CDK6), neural regulationassociated genes(protocadherin, Rab3interacting molecule–related, lim-homeobox familytranscription factor),development associated genes(iroquois homeobox family transcriptionfactor, lim-homeobox family transcription factor), nucleotide metabolism associatedgenes(NDK6,EIF3,histone h4-like, Pumilio), elongase of very long chain fatty acids,apoptosis-inducing genes(TSP-1)up-regulated in schistosome from water buffalo; while somecellular structure-associated genes (eggshell protein, spectrin, ciliary rootlet, cell wall protein,gamma-tubulin complex, macroglobulin), apoptosis-associated protein kinase genes(tyrosine-protein kinase, serine threonine protein kinase Akt, MAPK/ERK kinase4, MAPK/ERKkinase1), reproduction and embryonic development associated Dlx homeobox, neuralregulation associated genes(taurine transporter, glutamate receptor, glutamic acid-rich protein),development associated genes(distal-less/Dlx homeobox), epidermal growth factor receptor,muitifunctional signal transduction-related leucine-rich repeat motif and zinc finger protein genes,down-regulated in schistosomes from water buffalo.Here we found that,first, some apoptosis-associated protein kinases became the differentiallyexpressed genes(serine threonine protein kinase Akt, MAPK/ERK kinase4, MAPK/ERK kinase1,tyrosine-protein kinase), up-regulated in schistosome-susceptible host, goats, andapoptosis-inducing genes(TSP-1) up-regulated in schistosome from water buffalo, these resultsremind us that apoptosis may be a reseason for difference of worm development in their hostenvironment. Second, neural regulation associated genes (protocadherin, Rab3interactingmolecule–related, lim-homeobox family transcription factor, glutamate receptor, taurine transporter)were differentially expressed, also suggesting that neuromodulation might be a key difference forschistosome infecting different suitable hosts. Third, development and cell structure associatedgenes were differentially expressed, precisely because of the different development outcomecaused by three different natural animal hosts. These differentially genes further analyzed byKEGG pathway suggested that they involved in many critical cellular events, including neulotidemetabolism, lipid metabolism, energy metabolism, genetic information processing andimmune-ralated system and Wnt signaling pathway etc. These genes we found may be more criticaland important for parasite growth and development, and worthy of further attention.The study first compared and analyzed the gene expression difference in schistosomes fromthree natural hosts, yellow cattle, water buffalo and goats, will be helpful for analysis andidentification of worm genes affecting growth and development, and will provide basis forscreening the schistosomes vaccine candidate molecules.4. Microarray analysis of gene expression in peripheral blood from yellow cattle and waterbuffalo pre and post infection with S.japonicumIn this paper, the bos taurus genome-wide gene chip was used to analyze and compare theoverall gene expression profiles of peripheral blood from yellow cattle and water buffalo pre and post infection with S.japonicum. Before infection, there are5740differentially expressed genes (p<0.05, FC>2) between yellow cattle and water buffalo, and4185were still exist after infection,accounting for72.9%. After7w infection with S.japonicum, there are6353differentially expressedgenes between the two hosts, and the2168differentially expressed genes were newly presentedafter infection, included with the differentially expressed genes in yellow cattle and water buffaloassociated with S.japonicum infection. After infection7w with S.japonicum, yellow cattle andwater buffalo respectively showed different changes compared to pre-infection, the differences intheir gene expression were mostly unique, yellow cattle unique to78.5%, water buffalo unique to96.2%, the common changes in their gene expression were less, only83. In yellow cattle, the totaldifferentially expressed genes497, the unique390(accounting for78.5%of the total differentiallyexpressed genes) pre and post infection; while the non-suitable host water buffalo showed muchmore differentially expressed genes, total2197after infection, the unique2114(accounting for96.2%of the total differentially expressed genes) pre and post infection.Further analysis showed that the new presenting differentially expressed genes between twohosts maily associated with innate immune system, immune regulation, hematopoietic cells, p53signaling pathway, purine metabolism etc., mostly under-expressed in water buffalo compared toyellow cattle. The pathway enrichment analysis results have much in common with the result fordifferentially expressed genes pre infection between two hosts, indicated that the native differencein the two hosts precisely continued to affect the infection of S.japonicum, especially theunder-expressed genes in water buffalo compared to yellow cattle.It will increase our understanding of the relationship between parasites and differentsuitability natural hosts, and will likely find some of the key mechanisms or host target moleculesassociated with the suitability for S.japonicum infection.5. Microsatellite analysis and screening/verification on characteristic differentially expressedgenes of schistosomes from different hostsThe study selected7pairs microsatellite primers from related research papers, and used themto analyze the genetic polymorphism in schistosomes from six different animal hosts. The resultsshowed that the microsatellite primers could not discriminate the different host-derivedschistosomes. One pair of primers used to hierarchical clustering analysis, could separate theexperimental animal host-derived worms from the natural host-derived worms.From results of microarray for schistosomes from three natural hosts and by using Real-timePCR method, we get2characteristic differentially expressed genes of S. japonicum from yellowcattle,3from water buffalo and5from goats. The ten characteristic differentially expressed genesof S. japonicum from three reservoir hosts might be used as molecular markers to identify thevarious sources of reservoir hosts for S. japonicum.This study first compared and analyzed the overall gene expression profiles in schistosomesfrom three different suitability hosts(yellow cattle,water buffalo and goats) and in peripheralblood from yellow cattle and water buffalo pre and post infection with S.japonicum. Some important parasite-derived and host-derived molecules associated with worm growth anddevelopment had been screened and analyzed. It accumulated valuable information andknowledge of relationship between different suitablility natural hosts with schistosomes, andprovided new ideas for the screening schistosome vaccine candidate molecules or new drug targetsfor livestock. |
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