Ultrastructural Features of Human Liver Specimens from Patients Who Died of Dengue Hemorrhagic Fever

Abstract

Recent advances in electron microscopy and tomography have revealed distinct virus-induced endoplasmic reticulum (ER) structures unique for dengue virus (DV) and other flaviviruses in cell culture models, including hepatocytes. These altered ultrastructures serve as sites for viral replication. In this study, we used transmission electron microscopy to investigate whether such structures were present in the liver of fatal dengue hemorrhagic fever (DHF) autopsy cases. In parallel, electron microscopic examination of suckling mouse brains experimentally infected with DV was performed as an in vivo model of acute DV infection. Typical features of ER changes containing abundance of replicative virions were observed in neurons and microglia of DV-infected suckling mouse brains (SMB). This indicated that the in vivo DV infection could induce similar viral replication structures as previously described in the in vitro DV-infected cell model. Nevertheless, liver tissues from autopsy of patients who died of DHF showed scant changes of ER membrane structures and rare particles of virions in hepatocytes, despite overwhelming evidence for the presence of viral antigens and RNA–indicating active virus replication. Instead hepatocytes contained an abundance of steatotic vesicles and structural damages. This lack of structural changes indicative of virus replication in human hepatocytes is discussed.

Quo vadis? Central Rules of Pathogen and Disease Tropism

“…Mitochondrial damage is also observed in Herpes Simplex Virus-1 (HSV-1)-infected myenteric neurons ( Khoury-Hanold et al., 2016 ) and during L. monocytogenes epithelial cell infection ( Stavru et al., 2011 ), suggesting that this is a common alteration that may be caused by the metabolic stress of infection, pathogen mechanisms to avoid host cell apoptosis, or avoidance of other host defense mechanisms ( Stavru et al., 2011 ). Examples of other sites of subcellular structural alterations include the endoplasmic reticulum, Golgi and nucleus during dengue virus infection ( Win et al., 2019 ). Subcellular sites of disease tropism may be sites of direct contact with host structures, as in T. cruzi infection, in which cytoplasmic parasites interact with the mitochondria via parasite flagella ( Lentini et al., 2018 ).…”

Dengue Immunopathogenesis: A Crosstalk between Host and Viral Factors Leading to Disease: PART II - DENV Infection, Adaptive Immune Responses, and NS1 Pathogenesis

“…Controversially, DENV-ADE for other considered immune cells such as endothelial cells [116,117] have been also described in vitro and in vivo [118][119][120][121]. However, histochemistry of autopsy samples from fatal dengue cases and in vitro assays using peripheral blood cells revealed that macrophages/monocytes are primary targets for DENV infection and not endothelial cells [122][123][124][125][126][127].…”

“…The plasma leakage syndrome, is defined as the extensive extravasation and accumulation of fluids out of blood vessels into the surrounding tissues and serous cavities, causing serositis which includes pleural effusion, and pericardial and peritoneal ascites, leading to hemoconcentration, hypotension, organ disfunction, and life-threatening shock [6,214]. In DENV infection, the transient nature of plasma leakage, its association with the late febrile phase and the paucity of structural damage to the vasculature identified by autopsy studies initially suggested that circulating factors were primarily responsible for this phenomenon [5,125,126,205].…”

Dengue Immunopathogenesis: A Crosstalk between Host and Viral Factors Leading to Disease: Part I - Dengue Virus Tropism, Host Innate Immune Responses, and Subversion of Antiviral Responses

“…Numerous in vitro studies have shown that DENV is able to infect a variety of cell types including epithelial cells, endothelial cells, hepatocytes, muscle cells, dendritic cells, monocytes, B cells, and mast cells [65,66,[111][112][113][114][115][116][117]. Several autopsies and ex vivo studies have found the presence of DENV antigens (e.g., envelope protein, NS3) in some tissues such as the skin, liver, spleen, lymph node, kidney, bone marrow, lung, thymus, and brain [56,67,68,[118][119][120][121][122]. However, infectious virus particles have not always been isolated from all these organs but only from the liver and peripheral blood mononuclear cells (PBMCs), suggesting that: (a) the presence of DENV antigens such as the structural proteins E, pre-M, and C in several organs may not always be associated with the evidence of productive viral infection and severe organ pathology and (b) the immune cells and liver may be the main targets for DENV replication during the dengue disease [67].…”