title: Nitric oxide synthase expression correlates with death in an experimental mouse model of dengue with CNS involvement.
abstract: BACKGROUND
  The clinical presentation of dengue is classified by the World Health Organization into dengue without warning signs, dengue with warning signs and severe dengue. Reports of neurological disease caused by Dengue virus (DENV) are becoming frequent, with symptoms that include reduced consciousness, severe headache, neck stiffness, focal neurological signs, tense fontanelle and convulsions. However, the immune mechanisms involved in neurovirulence remain poorly understood. Here we present a mouse model in which one genotype of DENV is inoculated by the intracranial route and infects C57/BL6 mice and replicates in the brain, causing death of mice.
  
  
  METHODS
  Mice were infected with different serotypes/genotypes of DENV by the intracranial route to evaluate viral replication, host cytokine and nitric oxide synthase 2 (Nos2) expression in the brain via real-time PCR. Histological analysis of the brain tissues was also performed. An analysis of which cells were responsible for the expression of cytokines and Nos2 was performed using flow cytometry. Survival curves of infected animals were also generated
  
  
  RESULTS
  DENV 3 genotype I infected mice and replicated in the brain, causing death in our murine model. The increased levels of NOS2 could be the cause of the death of infected mice, as viral replication correlates with increased Nos2 and cytokine expression in the brain of C57BL/6 mice. In Nos2-/- mice that were infected with DENV, no clinical signs of infection were observed and cytokines were expressed at low levels, with the exception of interferon gamma (Ifng). Additionally, the Ifng-/- mice infected with DENV exhibited a severe and lethal disease, similar to the disease observed in C57BL/6 mice, while the DENV- infected Nos2-/- mice did not display increased mortality. Analyses of the brains from infected C57BL/6 mice revealed neuronal degeneration and necrosis during histopathologic examination. IFNg and NOS2 were produced in the brains of infected mice by CD4+ T cells and macrophages, respectively.
  
  
  CONCLUSIONS
  The neurovirulence of DENV 3 genotype I is associated with a deleterious role of NOS2 in the brain, confirming this murine model as an appropriate tool to study DENV neurovirulence.
authors: Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil. marcoasc@cpqrr.fiocruz.br.
authors: Kátia Paulino Ribeiro
authors: KP
authors: de Souza
authors: Emanuele Guimarães
authors: EG
authors: Silva
authors: Eliseu Soares
authors: ES
authors: de Oliveira Rocha
authors: Leandra Barcelos
authors: LB
authors: Figueiredo
authors: Camila Megale
authors: CM
authors: de Almeida-Leite
authors: Rosa Maria Esteves
authors: RM
authors: Arantes
authors: Juliana
authors: J
authors: de Assis Silva Gomes
authors: Gustavo Portela
authors: GP
authors: Ferreira
authors: Jaquelline Germano
authors: JG
authors: de Oliveira
authors: Erna Geessien
authors: EG
authors: Kroon
authors: Marco Antônio
authors: MA
authors: Campos
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology; D003715:Dengue / Q000473:pathology*; D004195:Disease Models, Animal; D020869:Gene Expression Profiling; D006651:Histocytochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D016019:Survival Analysis
chemical_list: D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse
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