Infection of the central nervous system with dengue virus 3 genotype I causing neurological manifestations in Brazil

Dengue virus 3 genotype I (GI) lineage 1 (L1) isolates elicit differential cytopathic effect with syncytium formation in human glioblastoma cells (U251)

BACKGROUND

Dengue virus (DENV) is a Flaviviridae member classified into four antigenically distinct serotypes (DENV 1, 2, 3, and 4) and further subdivided genotypes. DENV3 is subdivided into four or five genotypes, depending on the classification adopted. Despite their high genetic proximity, as revealed by phylogenetic complete polyprotein analysis, DENV3 MG-20 and DENV3 PV_BR showed different neurovirulence in mice models. Our group identified six amino acid mutations in protein E, including the E62K and E123Q, which may affect interactions of hydrophobic clusters on domain II, thus leading to the observed differences in the studied viruses.

METHODS

Human glioblastoma cells (U251) derived from a malignant glioblastoma tumor by explant technique were infected by the DENV3 GIL1 isolates DENV3 MG-20 and DENV3 PV_BR and analyzed by plaque assays and titration, optical, immunofluorescence, and transmission electronic microscopy.

RESULTS

The two isolates showed different cytopathic effects (CPE) and fusogenic patterns, further confirmed by indirect immunofluorescence. Transmission electron microscopy revealed intense cytopathic effects in DENV3 MG-20 infected U251 cells, displaying endoplasmic reticulum hypertrophy and turgid vesicles with proteins and multiple viruses, distinct from DENV3 PV_BR infected cells. It is hypothesized that the different amino acids in the DENV3 MG-20 isolate are related to an increased membrane fusion ability in viral infection, thus facilitating immune system evasion and increased chances of central nervous system cell infection.

CONCLUSION

These results emphasize the biological differences between the isolates, which could be a critical factor in host-virus interaction and severe dengue development. Our study presents comparative results of highly similar isolates with the potential to generate more subsidies for a deeper understanding of the DENV pathogenesis. The neurotropism of the isolate DENV3 MG-20 (belonging to the DENV3 GI L1 genotype) showing infection of nervous system cells (U251) could contribute to understanding neurological dengue disease.

Wild-type Yellow fever virus in cerebrospinal fluid from fatal cases in Brazil, 2018

Yellow fever virus (YFV) is the causative agent of yellow fever (YF), a hemorrhagic and viscerotropic acute disease. Severe YF has been described in approximately 15-25% of YF patients, with 20-50% of severe YF cases being fatal. Here we analyzed cerebrospinal fluid (CSF) samples collected during the YF outbreak in Brazil in 2018, aiming to investigate CNS neuroinvasion in fatal YFV cases. YFV RNA was screened by RT-qPCR targeting the 3'UTR region of the YFV genome in CSF. CSF samples were tested for the presence of anti-YFV IgM and neutralizing antibodies, coupled with routine laboratory examinations. Among the 13 patients studied, we detected anti-YFV IgM in CSF from eight patients and YFV RNA in CSF from five patients. YFV RNA genomic load in CSF samples ranged from 1.75×103 to 5.42×103 RNA copies/mL. We genotyped YFV from three CSF samples that grouped with other YFV samples from the 2018 outbreak in Brazil within the South-American I genotype. Even though descriptions of neurologic manifestations due to wild type YFV (WT-YFV) infection are rare, since the last YF outbreak in Brazil in 2017-2018, a few studies have demonstrated WT-YFV RNA in CSF samples from YF fatal cases. Serological tests indicated the presence of IgM and neutralizing antibodies against YFV in CSF samples from two patients. Although the presence of viral RNA, IgM and neutralizing antibodies in CSF samples could indicate neuroinvasiveness, further studies are needed to better elucidate the role of YFV neuroinvasion and possible impacts in disease pathogenesis.

Virological Surveillance of Aedes aegypti Vectors Identifies All Four Dengue Serotypes in a Hyperendemic Region

Dengue virus (DENV) 1-4 is the etiological agent of dengue, the most important viral infection transmitted by Aedes spp mosquitoes to humans. Our goal was to identify the circulating DENV in Aedes aegypti collected in an area of Brazil where all four DENV serotypes had already been detected in humans, understand the epidemiology better, and to test the vector as a virological surveillance tool. Twenty-eight larvae pools and 174 females of Aedes aegypti were screened by reverse transcriptase quantitative polymerase chain reaction and semi-nested PCR assays. PCR products were sequenced, and phylogenetic analyses were performed. Nine larvae pools (32.1%) were positive for DENV, four (44.4%) with DENV-3, and five (55.6%) with more than one serotype. Fifteen females (8.6%) were positive for any DENV serotype. DENV-1 isolates belong to genotype V, DENV-2 to American-Asian genotype, DENV-3 to genotypes I and III, and DENV-4 to genotypes I and II. We demonstrate for the first time the co-circulation of all four DENV serotypes in larvae pools and adult Aedes aegypti in a hyperendemic area. This scenario represents a challenge for disease control and reinforces the importance of virological surveillance in the vector as a tool for predicting circulating DENV serotypes in humans.

Dengue virus 3 genotype I shows natural changes in heparan sulphate binding sites, cell interactions, and neurovirulence in a mouse model

Dengue virus (DENV) is the most prevalent pathogen of the Flaviviridae family. Due to the considerable increase in DENV incidence and spread, symptoms such as CNS involvement have increased. Heparan sulphate (HS) was the first molecule identified as an adhesion factor for DENV in mammalian cells. Viral phenotypes with different HS interactions are associated with various clinical symptoms, including neurological alterations. Here, using in silico analyses, in vitro studies, and the in vivo mouse model, we characterized two natural circulating DENV3 genotype I (GI) lineage 1 (L1) in Brazil-DENV3 MG-20 (from Minas Gerais) and DENV3 PV_BR (from Rondônia) that present divergent neurovirulent profiles and sensitivity to sulphated molecules. We identified substitutions at the viral envelope (E) in positions 62 and 123 as likely responsible for the differences in neurovirulence. The E62K and E123Q substitutions in DENV3 MG-20 and DENV3 PV_BR, respectively, greatly influenced in silico electrostatic density and heparin docking results. In vivo, mice inoculated with DENV3 MG-20 died, but not those infected with DENV3 PV_BR. The clinical symptoms, such as paralysis of the lower limbs and meningoencephalitis, and histopathology, also differed between the inoculated groups. In vitro heparin and heparinases assays further demonstrated the biological impact of these substitutions. Other characteristics that have been previously associated with alterations in cell tropism and neurovirulence, such as changes in the size of lysis plaques and differences in cytopathic effects in glioblastoma cells, were also observed.

Cytokines and Soluble HLA-G Levels in the Acute and Recovery Phases of Arbovirus-Infected Brazilian Patients Exhibiting Neurological Complications

Severe neurological complications following arbovirus infections have been a major concern in seasonal outbreaks, as reported in the Northeast region of Brazil, where the same mosquito transmitted Zika (ZIKV), Dengue (DENV), and Chikungunya (CHIKV) viruses. In this study, we evaluated the levels of 36 soluble markers, including cytokines, chemokines, growth factors, and soluble HLA-G (Luminex and ELISA) in: i) serum and cerebrospinal fluid (CSF), during the acute phase and two years after the infection (recovery phase, only serum), ii) the relationship among all soluble molecules in serum and CSF, and iii) serum of infected patients without neurological complications, during the acute infection. Ten markers (sHLA-G, IL-10, IL-22, IL-8, MIP-1α, MIP-1β, MCP-1, HGF, VEGF, and IL-1RA) exhibited differential levels between the acute and recovery phases, with pronounced increases in MIP-1α (P<0.0001), MCP-1 (P<0.0001), HGF (P= 0.0001), and VEGF (P<0.0001) in the acute phase. Fourteen molecules (IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-13, IL-15, IL-17A, IFN-α, TNF, and G-CSF) exhibited distinct levels between arbovirus patients presenting or not neurological complications. IL-8, EGF, IL-6, and MCP-1 levels were increased in CSF, while RANTES and Eotaxin levels were higher in serum. Soluble serum (IL-22, RANTES, Eotaxin) and CSF (IL-8, EGF, IL-3) mediators may discriminate putative risks for neurological complications following arbovirus infections. Neurological complications were associated with the presence of a predominant inflammatory profile, whereas in non-complicated patients an anti-inflammatory profile may predominate. Mediators associated with neuroregeneration (EGF and IL-3) may be induced in response to neurological damage. Broad spectrum immune checkpoint molecules (sHLA-G) interact with cytokines, chemokines, and growth factors. The identification of soluble markers may be useful to monitor neurological complications and may aid in the development of novel therapies against neuroinflammation.

Complete genome analysis and characterization of neurotropic dengue virus 2 cosmopolitan genotype isolated from the cerebrospinal fluid of encephalitis patients

Dengue virus (DENV) infection remains a major public health concern in many parts of the world, including Southeast Asia and the Americas. Sri Lanka experienced its largest dengue outbreak in 2017. Neurological symptoms associated with DENV infection have increasingly been reported in both children and adults. Here, we characterize DENV type 2 (DENV-2) strains, which were isolated from cerebrospinal fluid (CSF) and/or serum of patients with dengue encephalitis. Acute serum and CSF samples from each patient were subjected to dengue-specific non-structural protein 1 (NS1) antigen test, IgM and IgG enzyme-linked immunosorbent assay (ELISA), virus isolation, conventional and real-time polymerase chain reaction (PCR), and next-generation sequencing (NGS). Among the 5 dengue encephalitis patients examined, 4 recovered and 1 died. DENV-2 strains were isolated from serum and/or CSF samples of 3 patients. The highest viral genome levels were detected in the CSF and serum of the patient who succumbed to the illness. A phylogenetic tree revealed that the DENV-2 isolates belonged to a new clade of cosmopolitan genotype and were genetically close to strains identified in China, South Korea, Singapore, Malaysia, Thailand, and the Philippines. According to the NGS analysis, greater frequencies of nonsynonymous and synonymous mutations per gene were identified in the nonstructural genes. The full genomes of serum- and CSF-derived DENV-2 from the same patient shared 99.7% similarity, indicating that the virus spread across the blood-brain barrier. This is the first report to describe neurotropic DENV-2 using whole-genome analysis and to provide the clinical, immunological, and virological characteristics of dengue encephalitis patients during a severe dengue outbreak in Sri Lanka in 2017.

Flaviviruses as agents of childhood central nervous system infections in Brazil

Flaviviruses are agents of a major emerging human public health issue and members of this genus have been associated with central nervous system (CNS) infections. In Brazil, a country endemic for some arboviruses, the most clinically relevant neurotropic flaviviruses include Dengue virus and Zika virus. Flaviviruses cause diseases ranging from mild or sub-clinical infections to severe cases as CNS infections. There is a lack of data about the incidence of flaviviruses in the CNS of children in Brazil. In this review, we provide a general overview of several flaviviruses that cause CNS infections in Brazilian children and explore the importance of epidemiological surveillance of CNS infections in cases of flavivirus infections.

Flaviviruses as agents of childhood central nervous system infections in Brazil

Flaviviruses are agents of a major emerging human public health issue, and members of the Flavivirus genus have been associated with central nervous system (CNS) infections. In Brazil, a country endemic for some arboviruses, the most clinically relevant neurotropic flaviviruses include dengue virus and Zika virus. Flaviviruses cause diseases ranging from mild or subclinical infections to severe cases as CNS infections. There is a lack of data about the incidence of flaviviruses in the CNS of children in Brazil. In this review, we provide a general overview of several flaviviruses that cause CNS infections in Brazilian children and explore the importance of epidemiologic surveillance of CNS infections in cases of Flavivirus infections.

Isolation and complete genome analysis of neurotropic dengue virus serotype 3 from the cerebrospinal fluid of an encephalitis patient

Although neurological manifestations associated with dengue viruses (DENV) infection have been reported, there is very limited information on the genetic characteristics of neurotropic DENV. Here we describe the isolation and complete genome analysis of DENV serotype 3 (DENV-3) from cerebrospinal fluid of an encephalitis paediatric patient in Jakarta, Indonesia. Next-generation sequencing was employed to deduce the complete genome of the neurotropic DENV-3 isolate. Based on complete genome analysis, two unique and nine uncommon amino acid changes in the protein coding region were observed in the virus. A phylogenetic tree and molecular clock analysis revealed that the neurotropic virus was a member of Sumatran-Javan clade of DENV-3 genotype I and shared a common ancestor with other isolates from Jakarta around 1998. This is the first report of neurotropic DENV-3 complete genome analysis, providing detailed information on the genetic characteristics of this virus.

Dengue viruses (DENV) are viruses that can cause asymptomatic infection to life-threatening haemorrhagic fever disease. Although DENV are not classically known to infect and invade central nervous system (CNS) in human, numerous cases of DENV infection in the CNS have been reported with limited information about the characteristics of the infecting virus. Here, we report the isolation and first complete genome analysis of DENV serotype 3 (DENV-3) from cerebrospinal fluid of a patient diagnosed with dengue encephalitis in Jakarta, Indonesia. By using next-generation sequencing strategy, we recovered the complete genome of the virus isolate and identified unique amino acid changes not found in any other recovered DENV-3 strains. The virus was determined to be closely related to isolates from Jakarta, Indonesia, which have been circulating for almost four decades.

Neurological manifestations of dengue in Central Brazil

INTRODUCTION:

The incidence of dengue has increased throughout the 2000s with a consequent global increase in atypical clinical forms.

METHODS:

This study reports a series of cases of neurological dengue out of 498 confirmed cases of laboratory dengue in Goiânia, Brazil. Cases were confirmed based on viral RNA detection via polymerase chain reaction or IgM antibody capture.

RESULTS:

Neurological symptoms occurred in 5.6% of cases, including paresthesia (3.8%), encephalitis (2%), encephalopathy (1%), seizure (0.8%), meningoencephalitis (0.4%), and paresis (0.4%). DENV-3 was the predominant circulating serotype (93%).

CONCLUSIONS:

We reported dengue cases with neurological manifestations in endemic area.

Zika virus: what do we know about the viral structure, mechanisms of transmission, and neurological outcomes?

The Zika virus epidemic that started in Brazil in 2014 has spread to >30 countries and territories in Latin America, leading to a rapid rise in the incidence of microcephalic newborns and adults with neurological complications. At the beginning of the outbreak, little was known about Zika virus morphology, genome structure, modes of transmission, and its potential to cause neurological malformations and disorders. With the advancement of basic science, discoveries of the mechanisms of strain variability, viral transfer to the fetus, and neurovirulence were published. These will certainly lead to the development of strategies to block vertical viral transmission, neuronal invasion, and pathogenesis in the near future. This paper reviews the current literature on Zika virus infections, with the aim of gaining a holistic insight into their etiology and pathogenesis. We discuss Zika virus history and epidemiology in Brazil, viral structure and taxonomy, old and newly identified transmission modes, and neurological consequences of infection.