Changes And Preliminary Study In MicroRNA Expression Profile In Mouse Brains Infected With Rabies Virus

The rabies virus (RABV), a non-segmented, single-stranded antisense RNA virusof the family Rhabdoviridae, genus Lyssavirus, is a highly neurotropic virus that cancause a fatal infection in central nervous systems (CNS) of warm-blooded animals.The World Health Organization (WHO) has estimated that the number of humandeaths from rabies was55,000annually worldwide, with56%of the death in Asia and44%in Africa. At present, China has the second-highest number of human rabies caseall over the world, after India. Although significant advances have been made in rabiesprevention and control, rabies remains a major threat to public health.Rabies is an ancient Zoonoses which experienced a long history of severalthousand years, and the rabies virus has been studied over hundred years, but theexact pathogenic mechanism underlying rabies virus infection remains unknown. Inorder to understand the viral pathogenic mechanism, study the host-virus interactionat the cellular and molecular level has been seen as an important way. Recent reportsindicate that RNA interference (RNAi) represents a vital component of the innateanti-viral immune response in plants and invertebrate animals. it serves as a hostgene-regulation mechanism that is triggered by the expression of highly structuredmiRNA molecules.However, role of cellular miRNAs in the defense against viralinfection in mammalian organisms has thus far remained elusive. A large number ofresearch reports have shown that the intracellular miRNA can affect tropism,virulence and pathogenicity of the virus. It has been proposed that cellular miRNAsmay have a substantial efect on viral evolution and have the potential to regulate thetissue tropism of viruses. Hence, miRNAs play a crucial role in the host-virusinteraction networks. Understanding on the interaction between host and RABV,especially on changes in miRNA expression profile and biological functions of hostinfected with RABV is very limited.miRNA microarray technology，in combination with bioinformatics to predictmiRNA target genes, has proved to be a very efficient high-throughput detection toestablish miRNA expression pattern, to complete functional clustering, pathway and network enrichment of target genes of differentially expressed miRNA, mutualauthentication between qRT-PCR and DNA microarray results and so on, and it offersan efficient and accurate access to uncover the host response to viral infection processthe miRNA and its related information. Understanding the miRNA expression profileof host upon RABV infection at pan-genomic level, which is very important toexplain the pathogenic mechanisms of rabies virus infection.In the current study, we created an expression profile of cellular miRNAs in theCNS of mice infected with different RABV strains and performed target predictionand functional enrichment of miRNAs found to be differentially expressed. Finally,we performed gene microarray analysis and qRT-PCR to verify the expression levelsof the predicted targets of the modulated miRNAs in these pathways. SeveralmiRNAs were modulated in RABV-infected mouse brains. Functional enrichmentrevealed that many of the predicted targets of these miRNAs are likely to play keyroles in immune response. This study is mainly divided into three parts:Part1. Changes in microRNA expression profile in mouse brains infected with ERArabies virus strain. To determine changes in miRNA expression in mouse brains inresponse to RABV infection, we evaluated miRNA expression profiles that tenmiRNAs, miR-1894-5p, miR-290-3p, miR-1901, miR-207, miR-1896, miR-715,miR-3470b, miR-146b*, miR-203, and miR-770-5p, were found to be significantlyup-regulated, and six miRNAs, miR-200a,miR-200b, miR-200c, miR-182, miR-183,and miR-429, were significantly down-regulated upon RABV infection. For thesesixteen differentially expressed miRNAs, all three systems-----miRand, TargetScanand MicroCosm predicted6200target genes. Gene ontology and KEGG Pathwaysanalyses were performed by DAVID database. Network analysis of the differentiallyexpressed miRNAs in response to RABV were performed by Ingenuity PathwayAnalysis and the results indicated that the target genes of differentially expressedmiRNAs are mainly involved in JAK-STAT signaling pathway, antigen processingand presentation, ubiquitin mediated proteolysis and complement cascades. Thisexperiment suggested that the cellular miRNA can directly or indirectly regulatedownstream gene expression during RABV infection.Part2. Changes in microRNA expression profile in mouse brains infected with streetrabies virus strain. To determine changes in miRNA expression in mouse brains inresponse to RABV infection, we evaluated miRNA expression profiles that nine miRNAs, miR-691, miR-377, miR-1935, miR-190, miR-1902, miR-135a*, miR-203,miR-2138, and miR-290-5p, were found to be significantly up-regulated. However,only one miRNAs, miR-145, was found to be down-regulated upon RABV infection.This indicates that host miRNAs were modulated in the CNS upon infection withstreet rabies virus. For these nine differentially expressed miRNAs, all three systems-----miRand, TargetScan and MicroCosm predicted3038target genes. Gene ontologyand KEGG Pathways analyses were performed by DAVID database.The predictedtarget genes miRNA were found to be involved in immune-related pathways, such asthe Jak-STAT signaling pathway, MAPK signaling pathway, Fc gamma R-mediatedphagocytosis and cytokine-cytokine receptor interactions. Present experiment showedthat miRNAs play an important role in the process of rabies virus infection, miRNAsexpression levels of cellular changes may be associated with virulence andpathogenicity.Part3. Comparative Analysis in microRNA expression profile in mouse brainsinfected with of different strains. In this study, based on comprehensive examinationof miRNA expression profiles from brains infected with FJDRV, a acute street rabiesvirus, and ERA, a non-lethal laboratory-adopted rabies virus, relative to thenon-infected mice, we identified a group of miRNAs that were differentiallyexpressed. To our knowledge, this is the first report on cellular miRNA in response toRABV infections. We found that RABV infection led to alteration of cellular miRNAsin mice and intriguingly, distinct expression pattern of host miRNAs were observed inmice infected with different strains of RABV.Analysis of microRNA expression changes in different strains of RABVinfection of the central nervous system, deepen the understanding of RABVpathogenesis. This is the first study the RABV intracranial infection can lead to braintissue of mice microRNA expression changes. miRNAs regarded as importantregulatory molecules of the host physiological or pathological processes may beinvolved in RABV-host interactions. The results of this study can lay the foundationfor exploring rabies prevention and treatment strategies.