RESUMO
Although chronic gastrointestinal dysmotility syndromes are a common worldwide health problem, underlying causes for these disorders are poorly understood. We show that flavivirus infection of enteric neurons leads to acute neuronal injury and cell death, inflammation, bowel dilation, and slowing of intestinal transit in mice. Flavivirus-primed CD8+ T cells promote these phenotypes, as their absence diminished enteric neuron injury and intestinal transit delays, and their adoptive transfer reestablished dysmotility after flavivirus infection. Remarkably, mice surviving acute flavivirus infection developed chronic gastrointestinal dysmotility that was exacerbated by immunization with an unrelated alphavirus vaccine or exposure to a non-infectious inflammatory stimulus. This model of chronic post-infectious gastrointestinal dysmotility in mice suggests that viral infections with tropism for enteric neurons and the ensuing immune response might contribute to the development of bowel motility disorders in humans. These results suggest an opportunity for unique approaches to diagnosis and therapy of gastrointestinal dysmotility syndromes.
Assuntos
Infecções por Flavivirus/patologia , Flavivirus/patogenicidade , Motilidade Gastrointestinal , Intestinos/patologia , Animais , Linfócitos T CD8-Positivos/imunologia , Flavivirus/genética , Infecções por Flavivirus/imunologia , Infecções por Flavivirus/virologia , Intestinos/virologia , Leucócitos/citologia , Leucócitos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/patologia , Neurônios/ultraestrutura , RNA Viral/isolamento & purificação , RNA Viral/metabolismo , SíndromeRESUMO
Flaviviruses such as Zika virus and West Nile virus have the potential to cause severe neuropathology if they invade the central nervous system. The type I interferon response is well characterized as contributing to control of flavivirus-induced neuropathogenesis. However, the interferon-stimulated gene (ISG) effectors that confer these neuroprotective effects are less well studied. Here, we used an ISG expression screen to identify Shiftless (SHFL, C19orf66) as a potent inhibitor of diverse positive-stranded RNA viruses, including multiple members of the Flaviviridae (Zika, West Nile, dengue, yellow fever, and hepatitis C viruses). In cultured cells, SHFL functions as a viral RNA-binding protein that inhibits viral replication at a step after primary translation of the incoming genome. The murine ortholog, Shfl, is expressed constitutively in multiple tissues, including the central nervous system. In a mouse model of Zika virus infection, Shfl-/- knockout mice exhibit reduced survival, exacerbated neuropathological outcomes, and increased viral replication in the brain and spinal cord. These studies demonstrate that Shfl is an important antiviral effector that contributes to host protection from Zika virus infection and virus-induced neuropathological disease.
Assuntos
Proteínas de Ligação a RNA/metabolismo , Infecção por Zika virus/patologia , Zika virus/metabolismo , Animais , Linhagem Celular , Efeito Citopatogênico Viral , Modelos Animais de Doenças , Suscetibilidade a Doenças/metabolismo , Suscetibilidade a Doenças/virologia , Flavivirus/genética , Infecções por Flavivirus/genética , Infecções por Flavivirus/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fármacos Neuroprotetores/metabolismo , Proteínas de Ligação a RNA/genética , Replicação Viral/fisiologia , Zika virus/patogenicidade , Infecção por Zika virus/genéticaRESUMO
Flaviviruses encode one, two, or no N-linked glycosylation sites on their envelope proteins. Glycosylation can impact virus interactions with cell surface attachment factors and also may impact virion stability and virus replication. Envelope protein glycosylation has been identified as a virulence determinant for multiple flaviviruses, but the mechanisms by which glycosylation mediates pathogenesis remain unclear. In this Gem, we summarize current knowledge on flavivirus envelope protein glycosylation and its impact on viral infection and pathogenesis.
Assuntos
Infecções por Flavivirus/metabolismo , Flavivirus , Proteínas do Envelope Viral/metabolismo , Replicação Viral , Animais , Flavivirus/patogenicidade , Flavivirus/fisiologia , Infecções por Flavivirus/patologia , Glicosilação , HumanosRESUMO
Tembusu virus (TMUV) is a flavivirus responsible for panzootic outbreaks of severe egg-drop and fatal encephalitis of domestic waterfowl in China. Although TMUV can be attenuated by in vitro passaging, experimental evidence supporting the role of specific genetic changes in virulence attenuation is currently lacking. Here, we performed site-directed mutagenesis on five envelope (E) protein amino acid residues in accordance with the attenuated TMUV generated in our recent study. Our results showed that the Thr-to-Lys mutation of residue 367 in E protein (E367) plays a predominant role in viral cell adaptation and virulence attenuation in ducks compared with mutations in other residues. We further demonstrated that the positively charged basic amino acid substitution at E367 enhanced the viral binding affinity for glycosaminoglycans (GAGs) and reduced viremia levels and the efficiency of replication in major target organs in subcutaneously inoculated ducks. Interestingly, the T367K mutation increased viral neutralization sensitivity to the early immune sera. Together, our findings provide the first evidence that a basic amino acid substitution at E367 strongly impacts the in vitro and in vivo infection of TMUV.IMPORTANCE Outbreaks of Tembusu virus (TMUV) infection have caused huge economic losses in the production of domestic waterfowl since the virus was first recognized in China in 2010. To control TMUV infection, a live-attenuated vaccine candidate of TMUV was developed in our previous study, but the mechanisms of virulence attenuation are not fully understood. Here, we found that the Thr-to-Lys substitution at E367 is a crucial determinant of TMUV virulence attenuation in ducks. We demonstrated that the T367K mutation attenuates TMUV through reducing viral replication in the blood, brain, heart (ducklings), and ovaries. These data provide new insights into understanding the pathogenesis of TMUV and the rational development of novel TMUV vaccines.
Assuntos
Substituição de Aminoácidos , Infecções por Flavivirus/imunologia , Infecções por Flavivirus/virologia , Flavivirus/genética , Proteínas do Envelope Viral/genética , Substituição de Aminoácidos/imunologia , Animais , Anticorpos Neutralizantes , Linhagem Celular , China/epidemiologia , Patos/virologia , Feminino , Infecções por Flavivirus/epidemiologia , Infecções por Flavivirus/patologia , Mutagênese Sítio-Dirigida , Mutação , Doenças das Aves Domésticas/imunologia , Doenças das Aves Domésticas/mortalidade , Doenças das Aves Domésticas/patologia , Doenças das Aves Domésticas/virologia , Carga Viral , Virulência , Replicação ViralRESUMO
According to modern classification, tick-borne flaviviruses have been divided into a mammalian tick-borne virus group and a seabird tick-borne virus group (STBVG). The STBVG includes the Tyuleniy virus, Meaban virus, Saumarez Reef virus, and the recently discovered Kama virus (KAMV). The latter was isolated from Ixodes lividus, an obligate parasitic tick of the sand martin (Riparia riparia), in 1989 in the central part of the Russian Plain. In 2014, based on molecular genetic analysis, it was shown that KAMV is a new virus belonging to STBVG, genus Flavivirus, fam. Flaviviridae. Very little is known about the Kama virus concerning its range, vectors, and reservoir hosts. GenBank contains a single sequence of the complete genome of this virus. In the present study, the complete genome sequences of two strains, isolated in 1983 in the Omsk region (Western Siberia) from gamasid mites in the nests of rooks (Corvus frugilegus), have been determined. Phylogenetic analyses of their genomes showed a close relationship both with each other (approx. 98.9% nucleotide identity) and with KAMV isolated in European Russia (approx. 98.4% nucleotide identity). The ecological features of KAMV that are due to the species of the vector (gamasid mites) and its hosts (colonial birds of the mainland of Eurasia) indicate that KAMV is an atypical representative STBVG.
Assuntos
Vírus da Encefalite Transmitidos por Carrapatos/genética , Infecções por Flavivirus/genética , Flavivirus/genética , Genoma Viral/genética , Animais , Antígenos Virais/genética , Aves , Vírus da Encefalite Transmitidos por Carrapatos/patogenicidade , Flavivirus/patogenicidade , Infecções por Flavivirus/patologia , Infecções por Flavivirus/virologia , Humanos , Ixodes/genética , Ixodes/virologia , Conformação de Ácido NucleicoRESUMO
BCL2 family proteins including pro-survival proteins, BH3-only proteins and BAX/BAK proteins control mitochondria-mediated apoptosis to maintain cell homeostasis via the removal of damaged cells and pathogen-infected cells. In this study, we examined the roles of BCL2 proteins in the induction of apoptosis in cells upon infection with flaviviruses, such as Japanese encephalitis virus, Dengue virus and Zika virus. We showed that survival of the infected cells depends on BCLXL, a pro-survival BCL2 protein due to suppression of the expression of another pro-survival protein, MCL1. Treatment with BCLXL inhibitors, as well as deficient BCLXL gene expression, induced BAX/BAK-dependent apoptosis upon infection with flaviviruses. Flavivirus infection attenuates cellular protein synthesis, which confers reduction of short-half-life proteins like MCL1. Inhibition of BCLXL increased phagocytosis of virus-infected cells by macrophages, thereby suppressing viral dissemination and chemokine production. Furthermore, we examined the roles of BCLXL in the death of JEV-infected cells during in vivo infection. Haploinsufficiency of the BCLXL gene, as well as administration of BH3 mimetic compounds, increased survival rate after challenge of JEV infection and suppressed inflammation. These results suggest that BCLXL plays a crucial role in the survival of cells infected with flaviviruses, and that BCLXL may provide a novel antiviral target to suppress propagation of the family of Flaviviridae viruses.
Assuntos
Flavivirus/patogenicidade , Proteína bcl-X/fisiologia , Animais , Apoptose/genética , Apoptose/fisiologia , Linhagem Celular , Sobrevivência Celular/genética , Sobrevivência Celular/fisiologia , Chlorocebus aethiops , Vírus da Dengue/patogenicidade , Vírus da Dengue/fisiologia , Vírus da Encefalite Japonesa (Espécie)/patogenicidade , Vírus da Encefalite Japonesa (Espécie)/fisiologia , Flavivirus/fisiologia , Infecções por Flavivirus/genética , Infecções por Flavivirus/patologia , Infecções por Flavivirus/fisiopatologia , Técnicas de Inativação de Genes , Células HEK293 , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/fisiologia , Humanos , Imunidade Inata , Camundongos , Camundongos Knockout , Modelos Biológicos , Proteína de Sequência 1 de Leucemia de Células Mieloides/antagonistas & inibidores , Proteína de Sequência 1 de Leucemia de Células Mieloides/genética , Proteína de Sequência 1 de Leucemia de Células Mieloides/fisiologia , Células U937 , Células Vero , Replicação Viral/fisiologia , Zika virus/patogenicidade , Zika virus/fisiologia , Proteína bcl-X/antagonistas & inibidores , Proteína bcl-X/genéticaRESUMO
Owing to the large-scale epidemic of Zika virus disease and its association with microcephaly, properties that allow flaviviruses to cause nervous system diseases are an important area of investigation. At present, although potential pathogenic mechanisms of flaviviruses in the nervous system have been examined, they have not been completely elucidated. In this paper, we review the possible mechanisms of blood-brain barrier penetration, the pathological effects on neurons, and the association between virus mutations and neurotoxicity. A hypothesis on neurotoxicity caused by the Zika virus is presented. Clarifying the mechanisms of virulence of flaviviruses will be helpful in finding better antiviral drugs and optimizing the treatment of symptoms.
Assuntos
Pesquisa Biomédica/tendências , Infecções do Sistema Nervoso Central/patologia , Infecções do Sistema Nervoso Central/fisiopatologia , Infecções por Flavivirus/patologia , Infecções por Flavivirus/fisiopatologia , Flavivirus/patogenicidade , Humanos , VirulênciaRESUMO
The duck Tembusu virus (DTMUV) is a mosquito-borne flavivirus. It causes severe symptoms of egg-drop, as well as neurological symptoms and brain damage in ducks. However, the specific molecular mechanisms of DTMUV-induced neurovirulence and host responses in the brain remain obscure. To better understand the host-pathogen and neuro-immune interactions of DTMUV infection, we conducted high-throughput RNA-sequencing to reveal the transcriptome profiles of DTMUV-infected duck brain. Totals of 117, 212, and 150 differentially expressed genes (DEGs) were identified at 12, 24, and 48 h post infection (hpi). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses uncovered genes and pathways related to the nervous system and immune responses in duck brain. Neuro-related genes, including WNT3A, GATA3, and CHRNA6, were found to be significantly downregulated. RIG-I-like receptors (DHX58, IFIH1) and Toll-like receptors (TLR2 and TLR3) were activated, inducing the expression of 22 interferon stimulated genes (ISGs) and antigen-processing and -presenting genes (TAP1 and TAP2) in the brain. Our research provides comprehensive information for the molecular mechanisms of neuro-immune and host-pathogen interactions of DTMUV.
Assuntos
Encéfalo/metabolismo , Infecções por Flavivirus/imunologia , Infecções por Flavivirus/veterinária , Flavivirus/imunologia , Perfilação da Expressão Gênica/veterinária , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/fisiologia , Neuroimunomodulação/genética , Membro 2 da Subfamília B de Transportadores de Cassetes de Ligação de ATP/genética , Membro 2 da Subfamília B de Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 3 da Subfamília B de Transportadores de Cassetes de Ligação de ATP/genética , Animais , Encéfalo/imunologia , Encéfalo/patologia , Encéfalo/virologia , Patos/genética , Patos/imunologia , Flavivirus/patogenicidade , Infecções por Flavivirus/metabolismo , Infecções por Flavivirus/patologia , Fator de Transcrição GATA3/genética , Fator de Transcrição GATA3/metabolismo , Interações Hospedeiro-Patógeno/imunologia , Interferons/metabolismo , Neuroimunomodulação/imunologia , Receptores Nicotínicos/genética , Receptores Nicotínicos/metabolismo , Receptores do Ácido Retinoico/genética , Receptores do Ácido Retinoico/metabolismo , Receptores Toll-Like/genética , Receptores Toll-Like/metabolismo , Transcriptoma , Proteína Wnt3A/genética , Proteína Wnt3A/metabolismoRESUMO
West Nile Virus, Usutu virus, Bagaza virus, Israel turkey encephalitis virus and Tembusu virus currently constitute the five flaviviruses transmitted by mosquito bites with a marked pathogenicity for birds. They have been identified as the causative agents of severe neurological symptoms, drop in egg production and/or mortalities among avian hosts. They have also recently shown an expansion of their geographic distribution and/or a rise in cases of human infection. This paper is the first up-to-date review of the pathology of these flaviviruses in birds, with a special emphasis on the difference in susceptibility among avian species, in order to understand the specificity of the host spectrum of each of these viruses. Furthermore, given the lack of a clear prophylactic approach against these viruses in birds, a meta-analysis of vaccination trials conducted to date on these animals is given to constitute a solid platform from which designing future studies.
Assuntos
Doenças das Aves/transmissão , Doenças das Aves/virologia , Infecções por Flavivirus/veterinária , Flavivirus/classificação , Flavivirus/isolamento & purificação , Mosquitos Vetores/virologia , Animais , Doenças das Aves/patologia , Aves , Transmissão de Doença Infecciosa , Infecções por Flavivirus/patologia , Infecções por Flavivirus/transmissãoRESUMO
Studies have demonstrated cross-reactivity of anti-dengue virus (DENV) antibodies in human sera against Zika virus (ZIKV), promoting increased ZIKV infection in vitro. However, the correlation between in vitro and in vivo findings is not well characterized. Thus, we evaluated the impact of heterotypic flavivirus immunity on ZIKV titers in biofluids of rhesus macaques. Animals previously infected (≥420 days) with DENV2, DENV4, or yellow fever virus were compared to flavivirus-naïve animals following infection with a Brazilian ZIKV strain. Sera from DENV-immune macaques demonstrated cross-reactivity with ZIKV by antibody-binding and neutralization assays prior to ZIKV infection, and promoted increased ZIKV infection in cell culture assays. Despite these findings, no significant differences between flavivirus-naïve and immune animals were observed in viral titers, neutralizing antibody levels, or immune cell kinetics following ZIKV infection. These results indicate that prior infection with heterologous flaviviruses neither conferred protection nor increased observed ZIKV titers in this non-human primate ZIKV infection model.
Assuntos
Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Infecções por Flavivirus/imunologia , Infecção por Zika virus/imunologia , Animais , Reações Cruzadas/imunologia , Ensaio de Imunoadsorção Enzimática , Flavivirus/imunologia , Infecções por Flavivirus/patologia , Macaca mulatta , Reação em Cadeia da Polimerase , Zika virus/imunologia , Infecção por Zika virus/patologiaRESUMO
Etiologic diagnosis is uncertain in 35% to 50% of patients with encephalitis, despite its substantial global prevalence and disease burden. We report on 2 adult female patients with fatal leukoencephalitis associated with human pegivirus-1 (HPgV-1) brain infection. Neuroimaging showed inflammatory changes in cerebral white matter. Brain-derived HPgV-1 RNA sequences clustered phylogenetically with other pegiviruses despite an 87-nucleotide deletion in the viral nonstructural (NS)2 gene. Neuropathology disclosed lymphocyte infiltration and gliosis predominantly in brain white matter. HPgV-1 NS5A antigen was detected in lymphocytes as well as in astrocytes and oligodendrocytes. HPgV-1 neuroadaptation should be considered in the differential diagnosis of progressive leukoencephalitis in humans. Ann Neurol 2018;84:789-795.
Assuntos
Encefalite/patologia , Encefalite/virologia , Infecções por Flavivirus/patologia , Leucoencefalopatias/patologia , Leucoencefalopatias/virologia , Evolução Fatal , Feminino , Flavivirus , Humanos , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Tembusu virus (TMUV) usually affects adult ducks, causing a severe drop of egg production. It has also been shown to be pathogenic in commercial Pekin ducklings below 7 weeks of age. Here, we report a TMUV-caused neurological disease in young egg-type ducklings and the pathogenicity of the egg-type duck-origin TMUV isolates in meat-type Pekin ducklings. RESULTS: The disease occurred in 25 to 40-day-old Jinding ducklings in China, and was characterized by paralysis. Gross lesions were lacking and microscopic lesions appeared chiefly in brain and spleen. Inoculation in embryonated duck eggs resulted in isolation of TMUV Y and GL. The clinical signs and microscopic lesions observed in the spontaneously infected egg-type ducks were repeated in Pekin ducklings by experimental infection. Notably, both Y and GL strains caused 100% mortality in the case of 2-day-old inoculation by intracerebral route. High mortalities (80 and 70%) also occurred following infection of the Y virus at 2 days of age by intramuscular route and at 9 days of age by intracerebral route. CONCLUSIONS: These findings demonstrate that the egg-type duck-origin TMUVs exhibit high pathogenicity in Pekin ducklings, and that the severity of the disease in ducklings is dependent on the infection route and the age of birds at the time of infection. The availability of the highly pathogenic TMUV strains provides a useful material with which to begin investigations into the molecular basis of TMUV pathogenicity in ducks.
Assuntos
Infecções por Flavivirus/veterinária , Flavivirus/patogenicidade , Doenças das Aves Domésticas/virologia , Fatores Etários , Animais , Linhagem Celular , Cricetinae , Vias de Administração de Medicamentos/veterinária , Patos/virologia , Flavivirus/genética , Infecções por Flavivirus/patologia , Infecções por Flavivirus/virologia , Paralisia/veterinária , Paralisia/virologia , Doenças das Aves Domésticas/patologiaRESUMO
Flaviviruses are positive, single-stranded, enveloped cytoplasmic sense RNA viruses that cause a variety of important diseases worldwide. Among them, Zika virus, West Nile virus, Japanese encephalitis virus, and Dengue virus have the potential to cause severe disease. Extensive studies have been performed to elucidate the structure and replication strategies of flaviviruses, and current studies are aiming to unravel the complex molecular interactions between the virus and host during the very early stages of infection. The outcomes of viral infection and rapid establishment of the antiviral state, depends on viral detection by pathogen recognition receptors and rapid initiation of signalling cascades to induce an effective innate immune response. Extracellular and intracellular pathogen recognition receptors play a crucial role in detecting flavivirus infection and inducing a robust antiviral response. One of the main hallmarks of flaviviral nonstructural proteins is their multiple strategies to antagonise the interferon system. In this chapter, we summarize the molecular characteristics of flaviviral proteins and discuss how viral proteins target different components of the interferon signalling pathway by blocking phosphorylation, enhancing degradation, and downregulating the expression of major components of the Janus kinase/signal transducer and activator of transcription pathway. We also discuss how the interactions of viral proteins with host proteins facilitate viral pathogenesis. Due to the lack of antivirals or prophylactic treatments for many flaviviral infections, it is necessary to fully elucidate how these viruses disrupt cellular processes to influence pathogenesis and disease outcomes.
Assuntos
Infecções por Flavivirus/imunologia , Flavivirus/imunologia , Imunidade Inata , Interferons/imunologia , Transdução de Sinais/imunologia , Proteínas não Estruturais Virais/imunologia , Animais , Flavivirus/patogenicidade , Infecções por Flavivirus/patologia , Humanos , Janus Quinases/imunologiaRESUMO
Virus infections of the central nervous system (CNS) can manifest in various forms of inflammation, including that of the brain (encephalitis) and spinal cord (myelitis), all of which may have long-lasting deleterious consequences. Although the knowledge of how different viruses affect neural cells is increasing, understanding of the mechanisms by which cells respond to neurotropic viruses remains fragmented. Several virus types have the ability to infect neural tissue, and astrocytes, an abundant and heterogeneous neuroglial cell type and a key element providing CNS homeostasis, are one of the first CNS cell types to get infected. Astrocytes are morphologically closely aligned with neuronal synapses, blood vessels, and ventricle cavities, and thereby have the capacity to functionally interact with neurons and endothelial cells. In this review, we focus on the responses of astrocytes to infection by neurotropic flaviviruses, including tick-borne encephalitis virus (TBEV), Zika virus (ZIKV), West Nile virus (WNV), and Japanese encephalitis virus (JEV), which have all been confirmed to infect astrocytes and cause multiple CNS defects. Understanding these mechanisms may help design new strategies to better contain and mitigate virus- and astrocyte-dependent neuroinflammation.
Assuntos
Astrócitos/metabolismo , Astrócitos/virologia , Infecções por Flavivirus/metabolismo , Infecções por Flavivirus/virologia , Flavivirus/fisiologia , Animais , Vírus da Encefalite Japonesa (Espécie)/fisiologia , Encefalite Japonesa/virologia , Infecções por Flavivirus/patologia , Infecções por Flavivirus/transmissão , Humanos , Tropismo Viral , Febre do Nilo Ocidental/metabolismo , Febre do Nilo Ocidental/patologia , Febre do Nilo Ocidental/virologia , Vírus do Nilo Ocidental/fisiologiaRESUMO
BACKGROUND: The breeding consequences of virus infections have rarely been studied in avian natural breeding populations. In this paper we investigated the links between humoral immunity following a natural flavivirus infection and reproduction in a wild bird population of collared flycatcher (Ficedula albicollis). We analyzed plasma from 744 birds for antibodies and correlated these results to a number of reproductive components. RESULTS: Nearly one third (27.8%) of the sampled collared flycatchers were found seropositive for flavivirus. Males had significantly more frequently flavivirus antibodies (32.3%) than females (25.1%). Seropositive females differed significantly from seronegative females in four traits: they had earlier lay date, higher body weight, higher survival rate and were older than seronegative females. The females did not differ in clutch size, number of fledged young or number of recruited young. Seropositive males had female partners with earlier lay date, i.e. the males bred earlier and they also produced more fledged young than seronegative males. In contrast, the males did not differ in clutch size, number of recruited young, male weight, age or survival. Interestingly, seropositive males had larger ornament, forehead badge size, than seronegative males. CONCLUSIONS: Collared flycatchers with an antibody response against flavivirus were more successful than birds with no antibody response, for any of the measured life history traits. The positive link between flavivirus antibody presence and life-history trait levels suggest that it is condition dependent in the collared flycatcher.
Assuntos
Flaviviridae/fisiologia , Infecções por Flavivirus/patologia , Reprodução/fisiologia , Aves Canoras/virologia , Animais , Anticorpos Antivirais/sangue , Especificidade de Anticorpos/imunologia , Feminino , Infecções por Flavivirus/sangue , Infecções por Flavivirus/imunologia , Genoma Viral , Modelos Lineares , Masculino , Aves Canoras/sangue , Aves Canoras/imunologiaRESUMO
BACKGROUND: Flaviviruses are a group of diverse and emerging arboviruses and an immense global health problem. A number of flaviviruses are neurotropic, causing severe encephalitis and even death. Type I interferons (IFNs) are the first line of defense of the innate immune system against flavivirus infection. IFNs elicit the concerted action of numerous interferon-stimulated genes (ISGs) to restrict both virus infection and replication. Viperin (virus-inhibitory protein, endoplasmic reticulum-associated, IFN-inducible) is an ISG with broad-spectrum antiviral activity against multiple flaviviruses in vitro. Its activity in vivo restricts neurotropic infections to specific regions of the central nervous system (CNS). However, the cell types in which viperin activity is required are unknown. Here we have examined both the regional and cell-type specificity of viperin in the defense against infection by several model neurotropic flaviviruses. METHODS: Viral burden and IFN induction were analyzed in vivo in wild-type and viperin-/- mice infected with Langat virus (LGTV). The effects of IFN pretreatment were tested in vitro in primary neural cultures from different brain regions in response to infection with tick-borne encephalitis virus (TBEV), West Nile virus (WNV), and Zika virus (ZIKV). RESULTS: Viperin activity restricted nonlethal LGTV infection in the spleen and the olfactory bulb following infection via a peripheral route. Viperin activity was also necessary to restrict LGTV replication in the olfactory bulb and the cerebrum following CNS infection, but not in the cerebellum. In vitro, viperin could restrict TBEV replication in primary cortical neurons, but not in the cerebellar granule cell neurons. Interferon-induced viperin was also very important in primary cortical neurons to control TBEV, WNV, and ZIKV. CONCLUSIONS: Our findings show that viperin restricts replication of neurotropic flaviviruses in the CNS in a region- and cell-type-specific manner. The most important sites of activity are the olfactory bulb and cerebrum. Activity within the cerebrum is required in the cortical neurons in order to restrict spread. This study exemplifies cell type and regional diversity of the IFN response within the CNS and shows the importance of a potent broad-spectrum antiviral ISG.
Assuntos
Antivirais/metabolismo , Infecções por Flavivirus/patologia , Flavivirus/fisiologia , Regulação Viral da Expressão Gênica/fisiologia , Proteínas/metabolismo , Animais , Antivirais/uso terapêutico , Astrócitos/patologia , Astrócitos/virologia , Células Cultivadas , Cérebro/patologia , Cérebro/virologia , Modelos Animais de Doenças , Interferon-alfa/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/patologia , Neurônios/virologia , Bulbo Olfatório/efeitos dos fármacos , Bulbo Olfatório/patologia , Bulbo Olfatório/virologia , Proteínas/genética , Proteínas/uso terapêutico , Replicação Viral/efeitos dos fármacosRESUMO
Viruses of intermediate virulence are defined as isolates causing an intermediate morbidity/mortality rate in a specific animal model system, involving specific host and inoculation parameters (e.g. dose and route). Therefore, variable disease phenotype may exist between animals that develop severe disease or die and those that are asymptomatic or survive after infection with these isolates. There may also be variability amongst animals within each of these subsets. Such potential variability may confound the use of time-point sacrifice experiments to investigate pathogenesis of this subset of virus strains, as uniformity in disease outcome is a fundamental assumption for time-course sacrifice experiments. In the current study, we examined the disease phenotype, neuropathology, neural infection and glial cell activity in moribund/dead and surviving Swiss white (CD-1) mice after intraperitoneal infection with various Australian flaviviruses, including West Nile virus (WNV) strains of intermediate virulence (WNVNSW2011 and WNVNSW2012), and highly virulent Murray Valley encephalitis virus (MVEV) isolates. We identified notable intragroup variation in the end-point disease in mice infected with either WNVNSW strain, but to a lesser extent in mice infected with MVEV strains. The variable outcomes associated with WNVNSW infection suggest that pathogenesis investigations using time-point sacrifice of WNVNSW-infected mice may not be the best approach, as the assumption of uniformity in outcomes is violated. Our study has therefore highlighted a previously unacknowledged challenge to investigating pathogenesis of virus isolates of intermediate virulence. We have also set a precedent for routine examination of the disease phenotype in moribund/dead and surviving mice during survival challenge experiments.
Assuntos
Modelos Animais de Doenças , Vírus da Encefalite do Vale de Murray/fisiologia , Infecções por Flavivirus/patologia , Infecções por Flavivirus/virologia , Vírus do Nilo Ocidental/fisiologia , Animais , Histocitoquímica , Injeções Intraperitoneais , Camundongos , Sistema Nervoso/patologia , Sistema Nervoso/virologia , Reprodutibilidade dos Testes , Análise de Sobrevida , Carga Viral , VirulênciaRESUMO
We report a widespread Usutu virus outbreak in birds in the Netherlands. Viral presence had been detected through targeted surveillance as early as April 2016 and increased mortality in common blackbirds and captive great grey owls was noticed from August 2016 onwards. Usutu virus infection was confirmed by post-mortem examination and RT-PCR. Extensive Usutu virus activity in the Netherlands in 2016 underlines the need to monitor mosquito activity and mosquito-borne infections in 2017 and beyond.
Assuntos
Doenças das Aves/virologia , Aves , Surtos de Doenças/veterinária , Infecções por Flavivirus/patologia , Infecções por Flavivirus/veterinária , Flavivirus/isolamento & purificação , Animais , Animais Selvagens/virologia , Antígenos Virais/análise , Sequência de Bases , Doenças das Aves/epidemiologia , Doenças das Aves/patologia , Culicidae/virologia , Flavivirus/genética , Flavivirus/patogenicidade , Infecções por Flavivirus/epidemiologia , Infecções por Flavivirus/virologia , Países Baixos/epidemiologia , RNA Viral/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa/veterináriaRESUMO
UNLABELLED: Suppressors of cytokine signaling (SOCS) proteins are intracellular proteins that inhibit cytokine signaling in a variety of cell types. A number of viral infections have been associated with SOCS upregulation; however, not much is known about the mechanisms regulating SOCS expression during viral infection. In this study, we used two pathologically distinct intracerebral (i.c.) infection models to characterize temporal and spatial aspects of SOCS expression in the virus-infected central nervous system (CNS), and by employing various knockout mouse models, we sought to identify regulatory mechanisms that may underlie a virus induced upregulation of SOCS in the CNS. We found that i.c. infection with either lymphocytic choriomeningitis virus (LCMV) or yellow fever virus (YF) results in gradual upregulation of SOCS1/3 mRNA expression peaking at day 7 postinfection (p.i.). In the LCMV model, SOCS mRNA was expressed in brain resident cells, including astrocytes and some neurons, and for SOCS1 in particular this upregulation was almost entirely mediated by gamma interferon (IFN-γ) produced by infiltrating T cells. After infection with YF, we also found SOCS expression to be upregulated in brain resident cells with a peak on day 7 p.i., but in this model, the upregulation was only partially dependent on IFN-γ and T cells, indicating that at least one other mediator was involved in the upregulation of SOCS following YF infection. We conclude that virus-induced inflammation of the CNS is associated with upregulation of SOCS1/3 mRNA expression in brain resident cells and that at least two distinctive pathways can lead to this upregulation. IMPORTANCE: In the present report, we have studied the induction of SOCS1 and SOCS3 expression in the context of virus-induced CNS infection. We found that both a noncytolytic and a cytolytic virus induce marked upregulation of SOCS1 and -3 expression. Notably, the kinetics of the observed upregulation follows that of activity within proinflammatory signaling pathways and, interestingly, type II interferon (IFN), which is also a key inducer of inflammatory mediators, seems to be essential in initiating this counterinflammatory response. Another key observation is that not only cells of the immune system but also CNS resident cells are actively involved in both the pro- and the counterinflammatory immune circuits; thus, for example, astrocytes upregulate both C-X-C-motif chemokine 10 (CXCL10) and SOCS when exposed to type II IFN in vivo.
Assuntos
Infecções por Arenaviridae/patologia , Encefalite Viral/patologia , Infecções por Flavivirus/patologia , Coriomeningite Linfocítica/imunologia , Vírus da Coriomeningite Linfocítica/imunologia , Proteínas Supressoras da Sinalização de Citocina/biossíntese , Animais , Infecções por Arenaviridae/imunologia , Infecções por Arenaviridae/virologia , Encefalite Viral/imunologia , Encefalite Viral/virologia , Infecções por Flavivirus/imunologia , Infecções por Flavivirus/virologia , Perfilação da Expressão Gênica , Interferon gama/imunologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , RNA Mensageiro/análise , Linfócitos T/imunologia , Fatores de Tempo , Regulação para CimaRESUMO
UNLABELLED: The mosquito-borne West Nile virus (WNV) is responsible for outbreaks of viral encephalitis in humans, horses, and birds, with particularly virulent strains causing recent outbreaks of disease in eastern Europe, the Middle East, North America, and Australia. Previous studies have phylogenetically separated WNV strains into two main genetic lineages (I and II) containing virulent strains associated with neurological disease. Several WNV-like strains clustering outside these lineages have been identified and form an additional five proposed lineages. However, little is known about whether these strains have the potential to induce disease. In a comparative analysis with the highly virulent lineage I American strain (WNVNY99), the low-pathogenicity lineage II strain (B956), a benign Australian strain, Kunjin (WNVKUN), the African WNV-like Koutango virus (WNVKOU), and a WNV-like isolate from Sarawak, Malaysia (WNVSarawak), were assessed for neuroinvasive properties in a murine model and for their replication kinetics in vitro. While WNVNY99 replicated to the highest levels in vitro, in vivo mouse challenge revealed that WNVKOU was more virulent, with a shorter time to onset of neurological disease and higher morbidity. Histological analysis of WNVKOU- and WNVNY99-infected brain and spinal cords demonstrated more prominent meningoencephalitis and the presence of viral antigen in WNVKOU-infected mice. Enhanced virulence of WNVKOU also was associated with poor viral clearance in the periphery (sera and spleen), a skewed innate immune response, and poor neutralizing antibody development. These data demonstrate, for the first time, potent neuroinvasive and neurovirulent properties of a WNV-like virus outside lineages I and II. IMPORTANCE: In this study, we characterized the in vitro and in vivo properties of previously uncharacterized West Nile virus strains and West Nile-like viruses. We identified a West Nile-like virus, Koutango virus (WNVKOU), that was more virulent than a known virulent lineage I virus, WNVNY99. The enhanced virulence of WNVKOU was associated with poor viral clearance and the induction of a poor neutralizing antibody response. These findings provide new insights into the pathogenesis of West Nile virus.