Dengue infection in mice inoculated by the intracerebral route: neuropathological effects and identification of target cells for virus replication

Abstract

Dengue is an important arboviral infection, causing a broad range symptom that varies from lifethreatening mild illness to severe clinical manifestations. Recent studies reported the impairment of the central nervous system (CNS) after dengue infection, a characteristic previously considered as atypical and underreported. However, little is known about the neuropathology associated to dengue. Since animal models are important tools for helping to understand the dengue pathogenesis, including neurological damages, the aim of this work was to investigate the effects of intracerebral inoculation of a neuroadapted dengue serotype 2 virus (DENV2) in immunocompetent BALB/c mice, mimicking some aspects of the viral encephalitis. Mice presented neurological morbidity after the 7 th day post infection. At the same time, histopathological analysis revealed that DENV2 led to damages in the CNS, such as hemorrhage, reactive gliosis, hyperplastic and hypertrophied microglia, astrocyte proliferation, Purkinje neurons retraction and cellular infiltration around vessels in the pia mater and in neuropil. Viral tropism and replication were detected in resident cells of the brain and cerebellum, such as neurons, astrocyte, microglia and oligodendrocytes. Results suggest that this classical mice model might be useful for analyzing the neurotropic effect of DENV with similarities to what occurs in human. Dengue is one of the most important diseases caused by an arbovirus, the dengue virus (DENV), which affects 96 million people annually worldwide, with 396 million estimated infections 1. The disease has a broad range manifestation, varying from a life-threatening mild flu-like illness, known as dengue fever, to severe dengue 2. The virus belongs to the family Flaviviridae, genus Flavivirus, and consists of four antigenically distinct serotypes (DENV 1-4) 3. Although DENV is classically characterized as a non-neurotropic virus, in the last decades several studies led to a different understanding of the clinical profile of the dengue disease. In addition to a variety of non-specific signs and symptoms, the disease may also present manifestations including neurological involvements 4. The emergence of neurological signs in human patients infected with DENV was first reported in 1976 5. Nowadays, encephalitis and encephalopathy stand out as the most common neurological signs resulting from DENV infection 6 .

CNS Immune Profiling in a Dengue Virus-Infected Immunocompetent Outbred ICR Mice Strain

“…The construction animal models of DENV infection with neural complications are urgently needed for further investigation. According to our current work, which is similar to that of previous works using immunocompetent BALB/c mice (Amorim et al, 2019 ) or C57BL/6 mice (Chen et al, 2004 ), viral RNA was significantly increased in the brain 1 week after DENV was inoculated through intravenous and intracerebral routes of infection. These infection models demonstrated the successful viral infection and replication in the CNS, indicating a viral enhancement in immunocompetent mice under precise immune-privileged conditions.…”

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and glial cells: Insights and perspectives

“…However, activation of microglial cells following viral infection in the CNS can also have deleterious effects as we previously showed ( Amorim et al., 2019 ; Salomão et al., 2020 ). Although both in physiological and pathological contexts, microglial cells are supposed to support neuronal development and survival and clear debris and dysfunctional synapses ( Tremblay et al., 2011 ; Yanuck, 2019 ), when overactivated during viral or bacterial infection, those cells can directly induce neuronal damage ( Chen et al., 2010 ; Klein et al., 2019 ; Mukherjee et al., 2019 ; Trzeciak et al., 2019 ).…”

Tree Shrew as a New Animal Model for the Study of Dengue Virus

“…SCID mice have also been used to assess vaccine effectiveness after DENV challenge (33)(34)(35). Symptoms of human related clinical diseases have not been observed in immunocompetent mouse models, but neurotropic disease could be developed (36,37). A research group also tried to develop new mouse models by knocking in human STING, which is susceptible to cleavage by the DENV NS2B-NS3 protease, and more susceptible to DENV infection (19,20,38,39).…”

“…Central nervous system (CNS) impairment was reported in DENV infection of mice and human ( 36 ). The bleeding lesions, local subarachnoid hemorrhage, local proliferation of glial cells in the cortex and parenchymal hemorrhage of brain tissue were found in the brain tissues of tree shrews infected by DENV-3 ( Figure 4B ).…”