MRI features in dengue encephalitis: A case series in South Indian tertiary care hospital

Roles of NS1 Protein in Flavivirus Pathogenesis

Flaviviruses such as dengue, Zika, and West Nile viruses are highly concerning pathogens that pose significant risks to public health. The NS1 protein is conserved among flaviviruses and is synthesized as a part of the flavivirus polyprotein. It plays a critical role in viral replication, disease progression, and immune evasion. Post-translational modifications influence NS1's stability, secretion, antigenicity, and interactions with host factors. NS1 protein forms extensive interactions with host cellular proteins allowing it to affect vital processes such as RNA processing, gene expression regulation, and cellular homeostasis, which in turn influence viral replication, disease pathogenesis, and immune responses. NS1 acts as an immune evasion factor by delaying complement-dependent lysis of infected cells and contributes to disease pathogenesis by inducing endothelial cell damage and vascular leakage and triggering autoimmune responses. Anti-NS1 antibodies have been shown to cross-react with host endothelial cells and platelets, causing autoimmune destruction that is hypothesized to contribute to disease pathogenesis. However, in contrast, immunization of animal models with the NS1 protein confers protection against lethal challenges from flaviviruses such as dengue and Zika viruses. Understanding the multifaceted roles of NS1 in flavivirus pathogenesis is crucial for effective disease management and control. Therefore, further research into NS1 biology, including its host protein interactions and additional roles in disease pathology, is imperative for the development of strategies and therapeutics to combat flavivirus infections successfully. This Review provides an in-depth exploration of the current available knowledge on the multifaceted roles of the NS1 protein in the pathogenesis of flaviviruses.

Multisystem Failure in Fatal Dengue: Associations between the Infectious Viral Serotype and Clinical and Histopathological Findings

Dengue is the most important arthropod-borne viral infection of humans. However, its viral pathogenesis is still unknown. The information collected from dengue fatal cases is crucial for understanding the complex interactions between virulence and host factors. This study aimed to establish possible associations between the clinical characteristics, histopathological changes, replication, and tissue location of viral serotypes in dengue fatal cases. Clinical and histopathological characterizations, antigen localization in tissue, and detection of the infecting serotype and replication using real-time polymerase chain reaction were all performed on the dengue fatal cases. The majority of the cases involved people under the age of 20. Bleeding (48.3%), abdominal pain (44.8%), myalgia (52.9%), and headache (48.3%) were the most common clinical manifestations in the cases. There was multiorgan pathology, with histopathological changes primarily in the liver, spleen, and lung. Similarly, the viral antigen was found primarily in these organs; however, there were no associations between tissue changes, viral location, infecting serotypes, and replication processes. Dengue infection should be considered a multiorgan disease, the outcome of which is possibly not associated with the infecting viral serotype.

Blood in the Brain on Susceptibility-Weighted Imaging

Intraparenchymal brain hemorrhage is not uncommon and results from a wide variety of causes ranging from trauma to tumor. Many a time, it is not possible to determine the exact cause of non-traumatic hemorrhage on conventional magnetic resonance imaging (MRI). Susceptibility-weighted imaging (SWI) is a high-resolution (3D) gradient-echo sequence. It is extremely sensitive to the inhomogeneity of the local magnetic field and highly useful in identifying the small amount of hemorrhage, which may be inapparent on other MR pulse sequences. In this review, we present different pattern of an intra-parenchymal brain hemorrhage on SWI with emphasis on differential diagnosis.

The Spectrum of MRI Findings in Dengue Encephalitis

Background

In this study, we aimed to describe eight cases of dengue encephalitis along with their magnetic resonance imaging (MRI) findings. Dengue encephalitis is caused by an arbovirus that has four strains DENV1-DENV4. The dengue virus is usually non-neurotropic but DENV2 & DENV3 are neurotropic. Dengue encephalitis is characterized by headaches, seizures, and altered consciousness.

Methodology

At our facility, we performed 3T MRI on eight suspected cases of dengue encephalitis using the criteria established by Varatharaj et al. We were able to diagnose dengue encephalitis based on the proposed criteria which included symptoms, serology, cerebrospinal fluid (CSF) analysis results, MRI findings, and routine blood laboratory workup in dengue encephalitis. Because numerous brain regions are potentially impacted in severe cases of dengue encephalitis, an MRI of the brain can reveal the severity of the condition. In deteriorating situations, it may detect whether or not further regions are being impacted. Hence, MRI should be done in all suspected cases of dengue encephalitis.

Results

The changes observed on MRI of the eight cases were in the supra-tentorium (deep periventricular white matter, subcortical white matter, and deep gray matter of the brain, which includes basal ganglia and thalami), infra-tentorium (cerebellar white matter and brainstem, which includes pons), and occasionally in cortical gray matter. The MRI showed mild-to-moderate hyperintensities on T2-weighted images and fluid-attenuated inversion recovery sequence (FLAIR); diffusion restriction is seen on diffusion-weighted images. The neurological clinical features included non-localizing signs and symptoms such as altered mental status, headache with vomiting, and fever.

Conclusions

The commonly affected areas of the brain in dengue encephalitis are the basal ganglia, thalamus, brainstem, cerebellum, cortical white matter, periventricular white matter, and cortical gray matter, which are all hyperintense on T2-weighted images and FLAIR. The lesions are iso or hypointense on T1-weighted images and micro-hemorrhages appear as blooming on susceptibility-weighted MRI. MRI is a crucial initial investigation in suspected cases of dengue encephalitis and known cases of dengue fever experiencing worsening neurological conditions.

Acute Dengue Hemorrhagic Encephalitis in a Child: A Case Report

Expanded dengue syndrome includes unusual or atypical manifestations of dengue fever by involving various organ systems. There have been increasing reports of dengue fever with unusual manifestations. Even though dengue virus is considered as a non-neurotropic virus, central nervous system complications have been reported. We are reporting a 4-year-old child who presented with acute dengue hemorrhagic encephalitis along with classical features of dengue infection and magnetic resonance imaging findings, suggestive of hemorrhage in the thalamus and cerebellum.

A systematic review on phytochemicals for the treatment of dengue

Dengue fever is prevalent in subtopic regions, producing mortality and morbidity worldwide, which have been of major concern to different governments and World Health Organization. The search of new anti-dengue agents from phytochemicals was assumed to be highly emergent in past. The phytochemicals have been used in wide distribution of vector ailments such as malaria. The demand of the phytochemicals is based on the medicines which are mostly considered to be safer, less harmful than synthetic drugs and nontoxic. This review mentions majorly about the phytochemicals potentially inhibiting dengue fever around the world. The phytochemicals have been isolated from different species, have potential for the treatment of dengue. Different crude extracts and essential oils obtained from different species showed a broad activity against different phytochemicals. The current studies showed that natural products represent a rich source of medicines toward the dengue fever. Furthermore, ethnobotanical surveys and laboratory investigation established identified natural plants species in the development of drug discovery to control the dengue fever.

Flavivirus NS1 Triggers Tissue-Specific Vascular Endothelial Dysfunction Reflecting Disease Tropism

Flaviviruses cause systemic or neurotropic-encephalitic pathology in humans. The flavivirus nonstructural protein 1 (NS1) is a secreted glycoprotein involved in viral replication, immune evasion, and vascular leakage during dengue virus infection. However, the contribution of secreted NS1 from related flaviviruses to viral pathogenesis remains unknown. Here, we demonstrate that NS1 from dengue, Zika, West Nile, Japanese encephalitis, and yellow fever viruses selectively binds to and alters permeability of human endothelial cells from lung, dermis, umbilical vein, brain, and liver in vitro and causes tissue-specific vascular leakage in mice, reflecting the pathophysiology of each flavivirus. Mechanistically, each flavivirus NS1 leads to differential disruption of endothelial glycocalyx components, resulting in endothelial hyperpermeability. Our findings reveal the capacity of a secreted viral protein to modulate endothelial barrier function in a tissue-specific manner both in vitro and in vivo, potentially influencing virus dissemination and pathogenesis and providing targets for antiviral therapies and vaccine development.

Puerta-Guardo et al. discover that five flavivirus NS1 proteins trigger hyperpermeability and vascular dysfunction in human endothelial cells and mice in a manner reflecting disease tropism. This tissue-specific tropism is partially determined by the capacity of NS1 to bind endothelial cells and is characterized by disruption of endothelial glycocalyx components.