The Innate Immune Response in DENV- and CHIKV-Infected Placentas and the Consequences for the Fetuses: A Minireview.

Dengue virus (DENV) and chikungunya (CHIKV) are arthropod-borne viruses belonging to the Flaviviridae and Togaviridae families, respectively. Infection by both viruses can lead to a mild indistinct fever or even lead to more severe forms of the diseases, which are characterized by a generalized inflammatory state and multiorgan involvement. Infected mothers are considered a high-risk group due to their immunosuppressed state and the possibility of vertical transmission. Thereby, infection by arboviruses during pregnancy portrays a major public health concern, especially in countries where epidemics of both diseases are regular and public health policies are left aside. Placental involvement during both infections has been already described and the presence of either DENV or CHIKV has been observed in constituent cells of the placenta. In spite of that, there is little knowledge regarding the intrinsic earlier immunological mechanisms that are developed by placental cells in response to infection by both arboviruses. Here, we approach some of the current information available in the literature about the exacerbated presence of cells involved in the innate immune defense of the placenta during DENV and CHIKV infections.

Capybara Oil Improves Renal Pathophysiology and Inflammation in Obese Mice.

Obesity is an inflammatory disease associated with secondary diseases such as kidney disease, which can cause lipotoxicity, inflammation and loss of organ function. Polyunsaturated fatty acids act in the production of lipid mediators and have anti-inflammatory characteristics. In this work, the objective was to evaluate renal histopathology in obese mice and the effects of treatment with capybara oil (CO) (5000 mg/kg/day for 4 weeks). Parameters such as body mass, lipid profile, systolic blood pressure, urinary creatinine and protein excretion, structure and ultrastructure of the renal cortex, fibrosis, tissue inflammation and oxidative stress were analyzed. CO treatment in obese mice showed improvement in the lipid profile and reduction in systolic blood pressure levels, in addition to beneficial remodeling of the renal cortex. Our data demonstrated that CO decreased inflammation, oxidative stress and renal fibrosis, as evidenced by quantifying the expression of TNF-α, IL-10, CAT, SOD, α-SMA and TGF-ß. Although treatment with CO did not show improvement in renal function, ultrastructural analysis showed that the treatment was effective in restoring podocytes and pedicels, with restructuring of the glomerular filtration barrier. These results demonstrate, for the first time, that treatment with CO is effective in reducing kidney damage, being considered a promising treatment for obesity.

Liver immunopathogenesis in fatal cases of dengue in children: detection of viral antigen, cytokine profile and inflammatory mediators.

Introduction: Dengue virus (DENV), the etiologic agent of dengue fever illness, represents a global public health concern, mainly in tropical and subtropical areas across the globe. It is well known that this acute viral disease can progress to severe hemorrhagic stages in some individuals, however, the immunopathogenic basis of the development of more severe forms by these patients is yet to be fully understood. Objective: In this context, we investigated and characterized the histopathological features as well as the cytokine profile and cell subpopulations present in liver tissues from three fatal cases of DENV in children. Methods: Hematoxylin and Eosin, Periodic Acid Schiff and Picro Sirius Red staining were utilized for the histopathological analysis. Immunohistochemistry assay was performed to characterize the inflammatory response and cell expression patterns. Results: Vascular dysfunctions such as hemorrhage, vascular congestion and edema associated with a mononuclear infiltrate were observedin all three cases. Liver tissues exhibited increased presence of CD68+ and TCD8+ cells as well as high expression of MMP-9, TNF-a, RANTES, VEGFR-2 mediators. Viral replication was confirmed by the detection of NS3 protein. Conclusion: Taken together, these results evidenced key factors that may be involved in the development of severe alterations in liver tissues of children in response to DENV infection.

The Innate Defense in the Zika-Infected Placenta.

Zika virus (ZIKV) is an arthropod-borne virus that belongs to the Flaviviridae family, genus Flavivirus and was first isolated 1947 in Uganda, Africa, from the serum of a sentinel Rhesus monkey. Since its discovery, the virus was responsible for major outbreaks in several different countries, being linked to severe complications in pregnant women, neonatal birth defects and the congenital zika syndrome. Maternal-fetal transmission of ZIKV can occur in all trimesters of pregnancy, and the role of the placenta and its cells in these cases is yet to be fully understood. The decidua basalis and chorionic villi, maternal-fetal components of the placenta, contain a rich immunological infiltrate composed by Hofbauer cells, mastocytes, dendritic cells and macrophages, primary cells of the innate immune response that have a role that still needs to be better investigated in ZIKV infection. Recent studies have already described several histopathological features and the susceptibility and permissiveness of placenta cells to infection by the Zika virus. In this review, we address some of the current knowledge on the innate immune responses against ZIKV, especially in the placenta.

Immunopathology of Renal Tissue in Fatal Cases of Dengue in Children.

Dengue virus (DENV) infection represents a worldwide public health concern and can cause damage to multiple organs, including the kidney. In this work, we investigated the histopathological changes caused by dengue virus infection along with the detection of inflammatory mediators, cytokines, and cell expression patterns in the renal tissue of three fatal cases in children. Hematoxylin and Eosin staining was performed to analyze these histopathological changes. Immunohistochemistry allowed for the detection of immunological inflammatory markers in renal tissues that were quantified and further analyzed. Vascular congestion, edema and glomerular infiltrate were observed in the three cases, in addition to the thickening of the matrix area around the glomerular capillaries and mononuclear infiltrate associated with vascular congestion in the medullary region. The renal tissues exhibited collagen deposition and high expression of CD68+ Mø, CD8+ T, CD56+ cells and MMP-9, and the cytokine profile was mainly characterized by the expression of IFN-γ and TNF-α. Additionally, the expression of RANTES, VEGFR-2 and VCAM-1 were observed. The replication of DENV was evidenced by the detection of the NS3 protein. These results contributed to clarifying the main factors that may be involved in changes in the renal tissue of fatal cases of dengue in children.

Histopathological and immunological characteristics of placentas infected with chikungunya virus.

Although vertical transmission of CHIKV has been reported, little is known about the role of placenta in the transmission of this virus and the effects of infection on the maternal-fetal interface. In this work we investigated five placentas from pregnant women who became infected during the gestational period. Four formalin-fixed paraffin-embedded samples of placenta (cases 1-4) were positive for CHIKV by RT-PCR. One (case 5) had no positive test of placenta, but had positive RT-PCR for CHIKV in the serum of the mother and the baby, confirming vertical transmission. The placentas were analyzed regarding histopathological and immunological aspects. The main histopathological changes were: deciduitis, villous edema, deposits, villous necrosis, dystrophic calcification, thrombosis and stem vessel obliteration. In infected placentas we noted increase of cells (CD8+ and CD163+) and pro- (IFN-γ and TNF-α) and anti-inflammatory (TGF-ß and IL-10) cytokines compared to control placentas. Moreover, CHIKV antigen was detected in decidual cell, trophoblastic cells, stroma villi, Hofbauer cells, and endothelial cells. In conclusion, CHIKV infection seems to disrupt placental homeostasis leading to histopathological alterations in addition to increase in cellularity and cytokines overproduction, evidencing an altered and harmful environment to the pregnant woman and fetus.

SARS-CoV-2 Is Persistent in Placenta and Causes Macroscopic, Histopathological, and Ultrastructural Changes.

SARS-CoV-2 is a virus that belongs to the Betacoronavirus genus of the Coronaviridae family. Other coronaviruses, such as SARS-CoV and MERS-CoV, were associated with complications in pregnant women. Therefore, this study aimed to report the clinical history of five pregnant women infected with SARS-CoV-2 (four symptomatic and one asymptomatic who gave birth to a stillborn child) during the COVID-19 pandemic. They gave birth between August 2020 to January 2021, a period in which there was still no vaccination for COVID-19 in Brazil. In addition, their placental alterations were later investigated, focusing on macroscopic, histopathological, and ultrastructural aspects compared to a prepandemic sample. Three of five placentas presented SARS-CoV-2 RNA detected by RT-PCRq at least two to twenty weeks after primary pregnancy infection symptoms, and SARS-CoV-2 spike protein was detected in all placentas by immunoperoxidase assay. The macroscopic evaluation of the placentas presented congested vascular trunks, massive deposition of fibrin, areas of infarctions, and calcifications. Histopathological analysis showed fibrin deposition, inflammatory infiltrate, necrosis, and blood vessel thrombosis. Ultrastructural aspects of the infected placentas showed a similar pattern of alterations between the samples, with predominant characteristics of apoptosis and detection of virus-like particles. These findings contribute to a better understanding of the consequences of SARS-CoV-2 infection in placental tissue, vertical transmission.

Placental Alterations in a Chikungunya-Virus-Infected Pregnant Woman: A Case Report.

Chikungunya virus (CHIKV) is an arthropod-borne virus first isolated in Tanzania, Africa. The virus has spread to Asia as well as South and Central America through infected Aedes mosquitoes. Vertical transmission may also occur, and was first documented during a chikungunya outbreak in La Réunion Island in 2005. Since then, some authors have been discussing the role of the placenta in maternal-fetal CHIKV transmission. CHIKV infection is characterized by fever, headache, rash, and arthralgia. However, atypical manifestations and clinical complications, including neurological, cardiac, renal, ocular, and dermal, may occur in some cases. In this report, we describe the case of a pregnant woman infected by CHIKV during the third trimester of gestation, who presented with severe dermatological manifestations during the epidemic in Rio de Janeiro, Brazil in 2019. CHIKV RNA and antigens were detected in the placental tissue, which presented with histopathological (deciduitis, fibrin deposition, edema, fetal vessel thickening, and chorioamnionitis) and ultrastructural alterations (cytotrophoblast with mitochondrial swelling and dilated cisterns in endoplasmic reticulum, vesicles in syncytiotrophoblasts, and thickening of the basement membrane of the endothelium).

Cytokines and inflammatory mediators: Markers involved in interstitial damage to the pancreas in two dengue fever cases associated with acute pancreatitis.

Dengue viral (DENV) infections can lead to acute pancreatitis and associated tissue damage. This study examined the pancreas from two fatal cases of DENV for histopathological changes as well as for the detection of cytokines, and other inflammatory mediators. Tissue sections were prepared for examination by ultrastructural and histopathological techniques. Sections from the pancreas of non-infected individuals were prepared in parallel as a control. The presence of viral replication in macrophages was detected by co-staining for the proteins NS3 and CD68 by immunofluorescence. Immunohistochemistry was used to detect cells that expressed cytokines and inflammatory mediators to characterize the inflammatory response. Edema, acinar necrosis and fibrosis areas associated with a mononuclear infiltrate were found in infected tissues. The major site of virus replication appeared to be macrophages based on their exclusive presentation of the viral protein NS3. Pancreatic tissues from the infected individuals also displayed increased levels of high mobility group box-1, caspase-3, gelatinase B and tumor necrosis factor alpha compared to controls. The presence of virus replicating macrophages in the pancreas was associated with multiple changes in tissue structure that included elevated levels of cytokines and inflammatory markers that may differentiate acute pancreatitis due to DENV infections from other causes.

Evaluating Dengue Virus Pathogenesis in Mice and Humans by Histological and Immunohistochemistry Approaches.

The analysis of dengue virus (DENV) infected tissues in mice experimental model and in human biopsies/autopsies may support the pathogenesis studies. Through such models, it is possible to investigate possible histopathological changes caused by the infection and detections of different targets of interest, such as viral antigens, immune cells, and cytokines. In this chapter, we showed a brief review of how histological and immunohistochemistry approaches may improve the knowledge in this field.

Histopathological and immunological characteristics of placentas infected with chikungunya virus

Although vertical transmission of CHIKV has been reported, little is known about the role of placenta in the transmission of this virus and the effects of infection on the maternal-fetal interface. In this work we investigated five placentas from pregnant women who became infected during the gestational period. Four formalin-fixed paraffin-embedded samples of placenta (cases 1–4) were positive for CHIKV by RT-PCR. One (case 5) had no positive test of placenta, but had positive RT-PCR for CHIKV in the serum of the mother and the baby, confirming vertical transmission. The placentas were analyzed regarding histopathological and immunological aspects. The main histopathological changes were: deciduitis, villous edema, deposits, villous necrosis, dystrophic calcification, thrombosis and stem vessel obliteration. In infected placentas we noted increase of cells (CD8+ and CD163+) and pro- (IFN-γ and TNF-α) and anti-inflammatory (TGF-β and IL-10) cytokines compared to control placentas. Moreover, CHIKV antigen was detected in decidual cell, trophoblastic cells, stroma villi, Hofbauer cells, and endothelial cells. In conclusion, CHIKV infection seems to disrupt placental homeostasis leading to histopathological alterations in addition to increase in cellularity and cytokines overproduction, evidencing an altered and harmful environment to the pregnant woman and fetus.

Spontaneous Abortion and Chikungunya Infection: Pathological Findings.

Intrauterine transmission of the Chikungunya virus (CHIKV) during early pregnancy has rarely been reported, although vertical transmission has been observed in newborns. Here, we report four cases of spontaneous abortion in women who became infected with CHIKV between the 11th and 17th weeks of pregnancy. Laboratorial confirmation of the infection was conducted by RT-PCR on a urine sample for one case, and the other three were by detection of IgM anti-CHIKV antibodies. Hematoxylin and eosin (H&E) staining and an electron microscopy assay allowed us to find histopathological, such as inflammatory infiltrate in the decidua and chorionic villi, as well as areas of calcification, edema and the deposition of fibrinoid material, and ultrastructural changes, such as mitochondria with fewer cristae and ruptured membranes, endoplasmic reticulum with dilated cisterns, dispersed chromatin in the nuclei and the presence of an apoptotic body in case 1. In addition, by immunohistochemistry (IHC), we found a positivity for the anti-CHIKV antibody in cells of the endometrial glands, decidual cells, syncytiotrophoblasts, cytotrophoblasts, Hofbauer cells and decidual macrophages. Electron microscopy also helped in identifying virus-like particles in the aborted material with a diameter of 40-50 nm, which was consistent with the size of CHIKV particles in the literature. Our findings in this study suggest early maternal fetal transmission, adding more evidence on the role of CHIKV in fetal death.

Pancreatic steatosis in adult rats induced by nicotine exposure during breastfeeding.

PURPOSE: Maternal nicotine exposure negatively impacts offspring's health and metabolism, leading to obesity and insulin resistance. Here we investigated the pancreatic islet function, glycemic homeostasis, and insulin signaling in adult rat offspring that were nicotine-exposed during breastfeeding. METHODS: For this, lactating Wistar rat dams were divided into two groups: Nicotine (implanted with osmotic minipumps containing 6 mg/Kg, NIC) and Control (saline, CON). Solutions were released from postnatal (PN) day 2-16. At PN110 and PN170, 10 offspring per litter/sex/group were submitted to the oral glucose tolerance test (OGTT). PN180 offspring were killed and glycemia, insulinemia, adiponectinemia, pancreas morphology as well as pancreatic islet protein expression (related to insulin secretion) and skeletal muscle (related to insulin action) were evaluated. Males and females were compared to their respective controls. RESULTS: Adult NIC offspring of both sexes showed glucose intolerance in the OGTT. Despite normoglycemia, NIC males showed hyperinsulinemia while females, although normoinsulinemic, had hyperglycemia. Both sexes showed increased IRI, reduced adiponectin/visceral fat mass ratio and higher ectopic deposition of lipids in the pancreatic tissue adipocytes. In pancreatic islets, NIC males showed lower PDX-1 expression while females had higher PDX-1 and GLUT2 expressions plus lower α2 adrenergic receptor. In the muscle, NIC offspring of both sexes showed reduction of GLUT4 expression; NIC males also had lower insulin receptor and pAKT expressions. CONCLUSIONS: Thus, glycemic homeostasis and peripheral insulin signaling in adult offspring of both sexes are affected by nicotine exposure through the milk, increasing the risk for type 2 diabetes development.

Aliskiren Reduces the Adrenal Zona Glomerulosa Apoptosis and Autophagy in Wistar Rats with 2K1C Hypertension.

Hypertension is a disease classified as primary or secondary, manifested not only by elevation of blood pressure but also involved in structural and functional changes of target organs. Renal artery stenosis is a leading factor of secondary hypertension, and its progress is associated with overactivation of the renin-angiotensin-aldosterone system (RAAS). Aliskiren is a renin inhibiting drug that suppresses RAAS and culminates in decreased renin release, plasma angiotensin II concentration, and inhibition of aldosterone secretion. In this sense, the aim of the present study was to analyze the structural and ultrastructural morphophysiology of the adrenal glomerular zone, after treatment with aliskiren in Wistar rats with 2K1C hypertension. Parameters as structure and ultrastructure of the adrenal glomerular zone, cellular apoptosis, nuclear cell proliferation, and AT1 receptor expression were analyzed by immunostaining and electron microscopy. Our results showed that the hypertensive animals treated with aliskiren presented a reestablishment of AT1 receptor expression and decrease in apoptosis and autophagy. In addition, treatment with aliskiren improves the cell aspects in the adrenal glomerular zone, evidenced by ultrastructural analysis through preserved nuclei and well-developed mitochondria. Therefore, our evidence suggests that aliskiren has a beneficial effect on the adrenal glomerular zone remodeling in animals with renovascular hypertension.

Zika Induces Human Placental Damage and Inflammation.

In Brazil, an epidemic of Zika virus (ZIKV) infections was declared in 2015 that coincided with alarming reports of microcephaly in newborns associated with mother infection. Although the virus has placental tropism, changes in the tissue morphology and immunity of infected patients have not yet been elucidated. Here, we investigated the histopathological and ultrastructural changes along with the immunological profile and the BDNF expression in rare placental material. Tissues were obtained in the 2015-2016 Brazilian epidemic, of ten ZIKV-infected patients during pregnancy, five resulting in cases of fetal microcephaly and five non-microcephaly, compared to five non-infected control placentae. Viral antigens were only detected in samples from the ZIKV infected patients. Infected placentae presented histopathological severe damage, while the ultrastructural evaluation showed abnormal organelles, such as clusters of virus-like particles consistent with the ZIKV dimensions. Increased infiltration of CD68+ and TCD8+ cells, expression of MMPs, cytokines (IFN-γ and TNF-α) and other immunological mediators (RANTES/CCL5 and VEGFR-2) confirmed excessive inflammation and vascular permeability dysfunction. An evaluation of BDNF showed a decrease that could modulate neuronal damage in the developing fetus. The placental changes caused by ZIKV are not pathognomonic, however, the data provide evidence that this infection leads to severe placental injury.

Fatal Dengue Cases Reveal Brain Injury and Viral Replication in Brain-Resident Cells Associated with the Local Production of Pro-Inflammatory Mediators.

Dengue is an arboviral disease caused by dengue virus (DENV), which is transmitted to humans by Aedes aegypti mosquitoes. Infection by DENV most commonly results in a mild flu-like illness; however, the disease has been increasingly associated with neurological symptomatology. This association draws attention to further investigations on the impact of DENV infection in the host's central nervous system. Here, we analyzed brain samples of three fatal dengue cases that occurred in 2002 during an outbreak in Rio de Janeiro, Brazil. Brain tissues of these cases were marked by histopathological alterations, such as degenerated neurons, demyelination, hemorrhage, edema, and increased numbers of astrocytes and microglial cells. Samples were also characterized by lymphocytic infiltrates mainly composed of CD8 T cells. DENV replication was evidenced in neurons, microglia and endothelial cells through immunohistochemistry and in situ hybridization techniques. Pro-inflammatory cytokines, such as TNF-α and IFN-γ were detected in microglia, while endothelial cells were marked by the expression of RANTES/CCL5. Cytoplasmic HMGB1 and the production of nitric oxide were also found in neurons and microglial cells. This work highlights the possible participation of several local pro-inflammatory mediators in the establishment of dengue neuropathogenesis.

Zika Virus Infects Human Placental Mast Cells and the HMC-1 Cell Line, and Triggers Degranulation, Cytokine Release and Ultrastructural Changes.

Zika virus (ZIKV) is an emergent arthropod-borne virus whose outbreak in Brazil has brought major public health problems. Infected individuals have different symptoms, including rash and pruritus, which can be relieved by the administration of antiallergics. In the case of pregnant women, ZIKV can cross the placenta and infect the fetus leading to congenital defects. We have identified that mast cells in the placentae of patients who had Zika during pregnancy can be infected. This led to our investigation on the possible role of mast cells during a ZIKV infection, using the HMC-1 cell line. We analyzed their permissiveness to infection, release of mediators and ultrastructural changes. Flow cytometry detection of ZIKV-NS1 expression 24 h post infection in 45.3% of cells showed that HMC-1 cells are permissive to ZIKV infection. Following infection, ß-hexosaminidase was measured in the supernatant of the cells with a notable release at 30 min. In addition, an increase in TNF-α, IL-6, IL-10 and VEGF levels were measured at 6 h and 24 h post infection. Lastly, different intracellular changes were observed in an ultrastructural analysis of infected cells. Our findings suggest that mast cells may represent an important source of mediators that can activate other immune cell types during a ZIKV infection, which has the potential to be a major contributor in the spread of the virus in cases of vertical transmission.

Aliskiren improves renal morphophysiology and inflammation in Wistar rats with 2K1C renovascular hypertension.

Hypertension is characterized by persistent elevated blood pressure levels, one of the leading causes of death in the world. Renovascular hypertension represents the most common cause of secondary hypertension, and its progress is associated with overactivation of the renin angiotensin aldosterone system (RAAS), causing systemic and local changes. Aliskiren is a renin-inhibiting drug that optimizes RAAS suppression. In this sense, the objective of the present study was to analyze the morphophysiology of the left kidney in Wistar rats with renovascular hypertension after treatment with Aliskiren. Parameters such as systolic blood pressure, urinary creatinine and protein excretion, renal cortex structure and ultrastructure, fibrosis and tissue inflammation were analyzed. Our results showed that the hypertensive animals treated with Aliskiren presented a reestablishment of blood pressure, expression of renin, and renal function, as well as a remodeling of morphological alterations through the reduction of fibrosis. The treatment regulated the laminin expression and decreased pro-inflammatory cytokines, restoring the integrity of the glomerular filtration barrier. Therefore, our findings suggest that Aliskiren has a renoprotective effect acting on the improvement of the morphology, physiology and pathology of the renal cortex of animals with renovascular hypertension.

Renal Injury in DENV-4 Fatal Cases: Viremia, Immune Response and Cytokine Profile.

Dengue virus (DENV) infections may result in asymptomatic cases or evolve into a severe disease, which involves multiple organ failure. Renal involvement in dengue can be potentially related to an increased mortality. Aiming to better understand the role of DENV in renal injury observed in human fatal cases, post-mortem investigations were performed in four DENV-4 renal autopsies during dengue epidemics in Brazil. Tissues were submitted to histopathology, immunohistochemistry, viral quantification, and characterization of cytokines and inflammatory mediators. Probably due the high viral load, several lesions were observed in the renal tissue, such as diffuse mononuclear infiltration around the glomerulus in the cortical region and in the medullary vessels, hyalinosis arteriolar, lymphocytic infiltrate, increased capsular fibrosis, proximal convoluted tubule (PCT) damage, edema, PCT debris formation, and thickening of the basal vessel membrane. These changes were associated with DENV-4 infection, as confirmed by the presence of DENV-specific NS3 protein, indicative of viral replication. The exacerbated presence of mononuclear cells at several renal tissue sites culminated in the secretion of proinflammatory cytokines and chemokines. Moreover, it can be suggested that the renal tissue injury observed here may have been due to the combination of both high viral load and exacerbated host immune response.

A Stillborn Multiple Organs' Investigation from a Maternal DENV-4 Infection: Histopathological and Inflammatory Mediators Characterization.

Dengue virus (DENV) is an emerging virus involved in outbreaks in Brazil. The association between the virus and vertical transmission, with disorders in the placenta, has raised a worldwide concern. On the 29th gestational week, a pregnant woman presented severe complications due to a DENV infection leading to maternal and fetus death. Postmortem analysis of fetal organs demonstrated the presence of DENV using reverse transcriptase polymerase chain reaction (RT-PCR) in the fetal brain and DENV non-structural protein 3 (NS3) staining in placenta and several peripheral fetal tissues, such as the brain, liver, lungs, and spleen. Histological analysis of the placenta and fetal organs revealed different types of tissue abnormalities, which included inflammation, hemorrhage, edema, and necrosis in placenta and tissue disorganization in the fetus, such as spongiform parenchyma, microglial inflammation, steatosis, hyalinose arteriolar, inflammatory cells in the alveolar septa, and disorganization of the lymphoid follicle. Increased cellularity (macrophage, Hofbauer cells and TCD8+ lymphocytes) and up-regulation of inflammatory mediators such as IFN-γ, TNF-α, RANTES/CCL5, MCP1/CCL2, and VEGF/R2 were detected in the liver, lung, spleen, brain, and placenta, supporting placental and fetus peripheral tissues inflammation. Maternal infection leading to the production of those vascular mediators may alter the vascular permeability, facilitating the virus entry and tissue and barrier dysfunction.