Intracerebral infection with dengue-3 virus induces meningoencephalitis and behavioral changes that precede lethality in mice

<p>Abstract</p> <p>Background</p> <p>Dengue, one of the most important arboviral diseases of humans, may cause severe systemic disease. Although dengue virus (DENV) has been considered to be a non-neurotropic virus, dengue infection has been associated recently with a series of neurological syndromes, including encephalitis. In this work, we evaluated behavioral changes and inflammatory parameters in C57BL/6 mice infected with non-adapted dengue virus 3 (DENV-3) genotype I.</p> <p>Methods</p> <p>C57BL/6 mice received 4 × 10³PFU of DENV-3 by an intracranial route. We evaluated the trafficking of leukocytes in brain microvasculature using intravital microscopy, and evaluated chemokine and cytokine profiling by an ELISA test at 3 and 6 days post infection (p.i.). Furthermore, we determined myeloperoxidase activity and immune cell populations, and also performed histopathological analysis and immunostaining for the virus in brain tissue.</p> <p>Results</p> <p>All animals developed signs of encephalitis and died by day 8 p.i. Motor behavior and muscle tone and strength parameters declined at day 7 p.i. We observed increased leukocyte rolling and adhesion in brain microvasculature of infected mice at days 3 and 6 p.i. The infection was followed by significant increases in IFN-γ, TNF-α, CCL2, CCL5, CXCL1, and CXCL2. Histological analysis showed evidence of meningoencephalitis and reactive gliosis. Increased numbers of neutrophils, CD4⁺and CD8⁺T cells were detected in brain of infected animals, notably at day 6 p.i. Cells immunoreactive for anti-NS-3 were visualized throughout the brain.</p> <p>Conclusion</p> <p>Intracerebral infection with non-adapted DENV-3 induces encephalitis and behavioral changes that precede lethality in mice.</p

A Model of DENV-3 Infection That Recapitulates Severe Disease and Highlights the Importance of IFN-γ in Host Resistance to Infection

There are few animal models of dengue infection, especially in immunocompetent mice. Here, we describe alterations found in adult immunocompetent mice inoculated with an adapted Dengue virus (DENV-3) strain. Infection of mice with the adapted DENV-3 caused inoculum-dependent lethality that was preceded by several hematological and biochemical changes and increased virus dissemination, features consistent with severe disease manifestation in humans. IFN-γ expression increased after DENV-3 infection of WT mice and this was preceded by increase in expression of IL-12 and IL-18. In DENV-3-inoculated IFN-γ−/− mice, there was enhanced lethality, which was preceded by severe disease manifestation and virus replication. Lack of IFN-γ production was associated with diminished NO-synthase 2 (NOS2) expression and higher susceptibility of NOS2−/− mice to DENV-3 infection. Therefore, mechanisms of protection to DENV-3 infection rely on IFN-γ-NOS2-NO-dependent control of viral replication and of disease severity, a pathway showed to be relevant for resistance to DENV infection in other experimental and clinical settings. Thus, the model of DENV-3 infection in immunocompetent mice described here represents a significant advance in animal models of severe dengue disease and may provide an important tool to the elucidation of immunopathogenesis of disease and of protective mechanisms associated with infection

TNFR1 absence protects against memory deficit induced by sepsis possibly through.

The involvement of TNF-α type 1 receptor (TNFR1) in memory deficits induced by sepsis was explored by using TNFR1 knockout (KO) mice. We reported that wild type (WT) mice presented memory deficits in the novel object recognition test 10 days after sepsis induced by cecumligation and perforation (CLP). These deficits were not observed in TNFR1 KO mice. The involvement of serum and brain cytokines TNF-α, IL-1β, IL-6, IFN-γ and IL-10 was then investigated. TNFR1 KO mice had higher serum levels of TNF-α and IL-1β, and brain levels of TNF-α than WT mice. After CLP, the brain levels of TNF-α, IL-1β, IL-6 and IFN-γ increased in both WT and KO mice. Our next step was to determine the expression of inflammatory cytokines, BDNF and TrKb in the hippocampus. The absence of TNFR1 inmice subjected to polymicrobial sepsis resulted in higher BDNF expression in the hippocampus. In conclusion, after CLP, memory is preserved in the absence of TNFR1. This finding was associated with increased BDNF expression in the hippocampus

Leukocyte recruitment and cfDNA levels in BALF after IAV infection upon OmCI and Zileuton treatment.

<p>C57BL/6J mice were infected intranasally with 10⁴ PFU of Influenza A/WSN/33 H1N1, or received PBS intranasally (Mock group). The 5-LO inhibitor Zileuton (30 mg/kg) was given alone or in combination with OmCI. Mice received the treatment prior to the infection and daily until day 5 after infection, while vehicle group received PBS both, via i.p, Zileuton was given by oral gavage. At the sixth day after infection, mice were euthanized, BAL performed and lungs were harvested. A) Total number of leukocytes; B) number of neutrophils; C) cfDNA levels measured in BALF. Data are presented as Mean ± SEM. * and *** for p<0.05 and p<0.001 respectively, when compared to Mock group; # and ## for p<0.05, p<0.01 respectively, when compared to Vehicle group (One-way ANOVA, Newman-Keuls Multiple Comparison test).</p

Effects of C5 activation inhibitor OmCI during IAV infection on leukocyte transmigration and protein leakage.

<p>C57BL/6J mice were infected intranasally with influenza or Mock infected as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064443#pone-0064443-g001" target="_blank">Figure 1</a>. OmCI treated mice received the protein prior to IAV infection and daily thereafter, while vehicle group received PBS, until one day before the indicated time point. At the 1, 3 and 6 days after infection, mice were euthanized and BAL performed. A) Total number of leukocytes, B) number of neutrophils and C) number of macrophages, D) number of lymphocytes recovered from the airways; E) total protein quantification in BALF. Data are presented as Mean ± SEM. *, ** and *** for p<0.05, p<0.01 and p<0.001 respectively, when compared to Mock group; # and ## for p<0.05, p<0.01 respectively, when compared to Vehicle group sampled on the same day (One-way ANOVA, Newman-Keuls Multiple Comparison test).</p

Neutrophil accumulation in lung parenchyma of vehicle and OmCI treated mice.

<p>C57BL/6J mice were infected and assigned to treatment groups as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064443#pone-0064443-g002" target="_blank">Figure 2</a>. At 1, 3 and 6 days after infection, mice were euthanized, lungs harvested and MPO assayed, to measure neutrophil accumulation in tissue. A) Relative numbers of neutrophils in lungs. At day 6, lungs were harvested for assessment of neutrophil infiltration by analysis of H&E stained lung slides. B) Pathologic score (0–5) of neutrophil accumulation in lungs performed by a pathologist. Representative slides of H&E stained lungs of a C) mock mouse; D) vehicle mouse; E) OmCI treated mouse. Asterisks indicate areas with neutrophils infiltration and arrowheads indicate bronchial epithelial damage. Data are presented as Mean ± SEM. * and *** for p<0.05 and p<0.001, respectively, when compared to Mock group (One-way ANOVA, Newman-Keuls Multiple Comparison test). Bars represent 100 µm.</p