Modification of endothelial cell functions by Hantaan virus infection: prolonged hyper-permeability induced by TNF-alpha of hantaan virus-infected endothelial cell monolayers

Disparate macrophage responses are linked to infection outcome of Hantan virus in humans or rodents

Hantaan virus (HTNV) is asymptomatically carried by rodents, yet causes lethal hemorrhagic fever with renal syndrome in humans, the underlying mechanisms of which remain to be elucidated. Here, we show that differential macrophage responses may determine disparate infection outcomes. In mice, late-phase inactivation of inflammatory macrophage prevents cytokine storm syndrome that usually occurs in HTNV-infected patients. This is attained by elaborate crosstalk between Notch and NF-κB pathways. Mechanistically, Notch receptors activated by HTNV enhance NF-κB signaling by recruiting IKKβ and p65, promoting inflammatory macrophage polarization in both species. However, in mice rather than humans, Notch-mediated inflammation is timely restrained by a series of murine-specific long noncoding RNAs transcribed by the Notch pathway in a negative feedback manner. Among them, the lnc-ip65 detaches p65 from the Notch receptor and inhibits p65 phosphorylation, rewiring macrophages from the pro-inflammation to the pro-resolution phenotype. Genetic ablation of lnc-ip65 leads to destructive HTNV infection in mice. Thus, our findings reveal an immune-braking function of murine noncoding RNAs, offering a special therapeutic strategy for HTNV infection.

Hantavirus: an overview and advancements in therapeutic approaches for infection

Hantaviruses are a significant and emerging global public health threat, impacting more than 200,000 individuals worldwide each year. The single-stranded RNA viruses belong to the Hantaviridae family and are responsible for causing two acute febrile diseases in humans: Hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). Currently, there are no licensed treatments or vaccines available globally for HTNV infection. Various candidate drugs have shown efficacy in increasing survival rates during the early stages of HTNV infection. Some of these drugs include lactoferrin, ribavirin, ETAR, favipiravir and vandetanib. Immunotherapy utilizing neutralizing antibodies (NAbs) generated from Hantavirus convalescent patients show efficacy against HTNV. Monoclonal antibodies such as MIB22 and JL16 have demonstrated effectiveness in protecting against HTNV infection. The development of vaccines and antivirals, used independently and/or in combination, is critical for elucidating hantaviral infections and the impact on public health. RNA interference (RNAi) arised as an emerging antiviral therapy, is a highly specific degrades RNA, with post-transcriptional mechanism using eukaryotic cells platform. That has demonstrated efficacy against a wide range of viruses, both in vitro and in vivo. Recent antiviral methods involve using small interfering RNA (siRNA) and other, immune-based therapies to target specific gene segments (S, M, or L) of the Hantavirus. This therapeutic approach enhances viral RNA clearance through the RNA interference process in Vero E6 cells or human lung microvascular endothelial cells. However, the use of siRNAs faces challenges due to their low biological stability and limited in vivo targeting ability. Despite their successful inhibition of Hantavirus replication in host cells, their antiviral efficacy may be hindered. In the current review, we focus on advances in therapeutic strategies, as antiviral medications, immune-based therapies and vaccine candidates aimed at enhancing the body's ability to control the progression of Hantavirus infections, with the potential to reduce the risk of severe disease.

OUP accepted manuscript

Hantavirus-induced diseases are emerging zoonoses with endemic appearances and frequent outbreaks in different parts of the world. In humans, hantaviral pathology is characterized by the disruption of the endothelial cell barrier followed by increased capillary permeability, thrombocytopenia due to platelet activation/depletion and an overactive immune response. Genetic vulnerability due to certain human leukocyte antigen haplotypes is associated with disease severity. Typically, two different hantavirus-caused clinical syndromes have been reported: hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). The primarily affected vascular beds differ in these two entities: renal medullary capillaries in HFRS caused by Old World hantaviruses and pulmonary capillaries in HCPS caused by New World hantaviruses. Disease severity in HFRS ranges from mild, e.g. Puumala virus-associated nephropathia epidemica, to moderate, e.g. Hantaan or Dobrava virus infections. HCPS leads to a severe acute respiratory distress syndrome with high mortality rates. Due to novel insights into organ tropism, hantavirus-associated pathophysiology and overlapping clinical features, HFRS and HCPS are believed to be interconnected syndromes frequently involving the kidneys. As there are no specific antiviral treatments or vaccines approved in Europe or the USA, only preventive measures and public awareness may minimize the risk of hantavirus infection. Treatment remains primarily supportive and, depending on disease severity, more invasive measures (e.g., renal replacement therapy, mechanical ventilation and extracorporeal membrane oxygenation) are needed.

A comprehensive screening of the whole proteome of hantavirus and designing a multi-epitope subunit vaccine for cross-protection against hantavirus: Structural vaccinology and immunoinformatics study

Hantaviruses are an emerging zoonotic group of rodent-borne viruses that are having serious implications on global public health due to the increase in outbreaks. Since there is no permanent cure, there is increasing interest in developing a vaccine against the hantavirus. This research aimed to design a robust cross-protective subunit vaccine using a novel immunoinformatics approach. After careful evaluation, the best predicted cytotoxic & helper T-cell and B-cell epitopes from nucleocapsid proteins, glycoproteins, RdRp proteins, and non-structural proteins were considered as potential vaccine candidates. Among the four generated vaccine models with different adjuvant, the model with toll-like receptor-4 (TLR-4) agonist adjuvant was selected because of its high antigenicity, non-allergenicity, and structural quality. The selected model was 654 amino acids long and had a molecular weight of 70.5 kDa, which characterizes the construct as a good antigenic vaccine candidate. The prediction of the conformational B-lymphocyte (CBL) epitope secured its ability to induce the humoral response. Thereafter, disulfide engineering improved vaccine stability. Afterwards, the molecular docking confirmed a good binding affinity of -1292 kj/mol with considered immune receptor TLR-4 and the dynamics simulation showed high stability of the vaccine-receptor complex. Later, the in silico cloning confirmed the better expression of the constructed vaccine protein in E. coli K12. Finally, in in silico immune simulation, significantly high levels of immunoglobulin M (IgM), immunoglobulin G1 (IgG1), cytotoxic & helper T lymphocyte (CTL & HTL) populations, and numerous cytokines such as interferon-γ (IFN-γ), interleukin-2 (IL-2) etc. were found as coherence with actual immune response and also showed faster antigen clearance for repeated exposures. Nonetheless, experimental validation can demonstrate the safety and cross-protective ability of the proposed vaccine to fight against hantavirus infection.

Dentin matrix protein 1 correlates with the severity of hemorrhagic fever with renal syndrome and promotes hyper-permeability of endothelial cells infected by Hantaan virus

Hantaviruses are the major causative agents of hemorrhagic fever with renal syndrome (HFRS) in humans, which is characterized by increased capillary permeability. Dentin matrix protein 1 (DMP1) has been shown to degrade components of the basal membrane and interendothelial junctions via matrix metalloproteinase-9. To study the changes of serum DMP1 in HFRS, we determined the concentration of DMP1 using sandwich enzyme-linked immunosorbent assay. We found that serum DMP1 concentrations increased significantly, and reached peak value during the oliguric phase and in the critical group in HFRS patients. Moreover, serum DMP1 concentrations were closely related to blood urea nitrogen, creatinine, cystatin C, and vascular endothelial growth factor (VEGF). We further explored the role of DMP1 in HTNV-infected human umbilical vein endothelial cells (HUVECs) model. Data from immunocytochemistry showed that VEGF and tumor necrosis factor-α (TNF-α) promoted the expression of DMP1 on HTNV-infected HUVECs. Results from transwell assays demonstrated that the permeability of HUVECs increased significantly after HTNV infection with the addition of DMP1, VEGF, and TNF-α. This study suggests that elevated DMP1 concentrations may be associated with disease stage, severity, and the degree of acute kidney injury. DMP1 is involved in the regulation of capillary permeability in HFRS caused by hantavirus infection.

What Do We Know about How Hantaviruses Interact with Their Different Hosts?

Hantaviruses, like other members of the Bunyaviridae family, are emerging viruses that are able to cause hemorrhagic fevers. Occasional transmission to humans is due to inhalation of contaminated aerosolized excreta from infected rodents. Hantaviruses are asymptomatic in their rodent or insectivore natural hosts with which they have co-evolved for millions of years. In contrast, hantaviruses cause different pathologies in humans with varying mortality rates, depending on the hantavirus species and its geographic origin. Cases of hemorrhagic fever with renal syndrome (HFRS) have been reported in Europe and Asia, while hantavirus cardiopulmonary syndromes (HCPS) are observed in the Americas. In some cases, diseases caused by Old World hantaviruses exhibit HCPS-like symptoms. Although the etiologic agents of HFRS were identified in the early 1980s, the way hantaviruses interact with their different hosts still remains elusive. What are the entry receptors? How do hantaviruses propagate in the organism and how do they cope with the immune system? This review summarizes recent data documenting interactions established by pathogenic and nonpathogenic hantaviruses with their natural or human hosts that could highlight their different outcomes.

Hantavirus-induced disruption of the endothelial barrier: neutrophils are on the payroll

Viral hemorrhagic fever caused by hantaviruses is an emerging infectious disease for which suitable treatments are not available. In order to improve this situation a better understanding of hantaviral pathogenesis is urgently required. Hantaviruses infect endothelial cell layers in vitro without causing any cytopathogenic effect and without increasing permeability. This implies that the mechanisms underlying vascular hyperpermeability in hantavirus-associated disease are more complex and that immune mechanisms play an important role. In this review we highlight the latest developments in hantavirus-induced immunopathogenesis. A possible contribution of neutrophils has been neglected so far. For this reason, we place special emphasis on the pathogenic role of neutrophils in disrupting the endothelial barrier.

Microvascular inflammation and acute tubular necrosis are major histologic features of hantavirus nephropathy

Hantavirus nephropathy (HVN) is an uncommon etiology of acute renal failure due to hantavirus infection. Pathological features suggestive of HVN historically reported are medullary interstitial hemorrhages in a background of acute interstitial nephritis (AIN). However, interstitial hemorrhages may be lacking because of medullary sampling error. This emphasizes that other pathological criteria may be of interest. We performed a retrospective clinicopathological study of 17 serologically proven HVN cases with renal biopsy from 2 nephrology centers in northern France. Histologic analysis was completed by immunohistochemistry with anti-CD3, anti-CD68, and anti-CD34 antibodies. Three control groups were not related to hantavirus infection: acute tubular necrosis (ATN) of ischemic or toxic etiology and AIN were used for comparison. Renal biopsy analysis showed that almost all HVN cases with medullary sampling (9/10) displayed interstitial hemorrhages, whereas focal hemorrhages were detected in 2 of the 7 "cortex-only" specimens. ATN was common, as it was present in 15 (88.2%) of 17 HVN cases. By contrast, interstitial inflammation was scarce with no inflammation or only slight inflammation, representing 15 (88.2%) of 17 cases. Moreover, HVN showed inflammation of renal microvessels with cortical peritubular capillaritis and medullary vasa recta inflammation; peritubular capillaritis was significantly higher in HVN after comparison with ischemic and toxic ATN controls (P = .0001 and P = .003, respectively), but not with AIN controls. Immunohistochemical studies highlighted the involvement of T cells and macrophages in renal microvascular inflammation related to HVN. Our study showed that microvascular inflammation, especially cortical peritubular capillaritis, and ATN are important histologic features of HVN.

Involvement of the Akt/NF-κB pathways in the HTNV-mediated increase of IL-6, CCL5, ICAM-1, and VCAM-1 in HUVECs

Background

Hantaan virus (HTNV) infection causes a severe form of HFRS(hemorrhagic fever with renal syndrome)in Asia. Although HTNV has been isolated for nearly forty years, the pathogenesis of HFRS is still unknown, and little is known regarding the signaling pathway that is activated by the virus.

Methodology/Principal Findings

Cardamonin was selected as a NF-κB inhibitor, and indirect immunofluorescence assays were used to detect the effect of cardamonin on HTNV-infected HUVECs. The effect of cardamonin on the HTNV-induced phosphorylation of Akt and DNA-binding activity of NF-κB were determined using Western blot analysis and electrophoretic mobility shift assays (EMSAs), respectively. Then, flow cytometric and quantitative real-time PCR analyses were performed to quantify the expression levels of the adhesion molecules ICAM-1 and VCAM-1, and the concentrations of IL-6, IL-8, and CCL5 in HUVEC supernatants were examined using ELISA. The results showed that cardamonin did not effect the proliferation of HUVECs or the replication of HTNV in HUVECs. Instead, cardamonin inhibited the phosphorylation of Akt and nuclear transduction of NF-κB and further reduced the expression of the adhesion molecules ICAM-1 and VCAM-1 in HTNV-infected HUVECs. Cardamonin also inhibited the secretion of IL-6 and CCL5, but not IL-8.

Conclusion/Significance

HTNV replication may not be dependent upon the ability of the virus to activate NF-κB in HUVECs. The Akt/NF-κB pathways may be involved in the pathogenesis of HFRS; therefore, cardamonin may serve as a potential beneficial agent for HFRS therapy.

Vascular events in viral hemorrhagic fevers: a comparative study of dengue and hantaviruses

Viral hemorrhagic diseases are a group of systemic viral infections with worldwide distribution and are significant causes of global mortality and morbidity. The hallmarks of viral hemorrhagic fevers are plasma leakage, thrombocytopenia, coagulopathy and hemorrhagic manifestations. The molecular mechanisms leading to plasma leakage in viral hemorrhagic fevers are not well understood. A common theme has emerged in which a complex interplay between pathogens, host immune response, and endothelial cells leads to the activation of endothelial cells and perturbation of barrier integrity. In this article, two clinically distinct viral hemorrhagic fevers caused by dengue viruses and hantaviruses are discussed to highlight their similarities and differences that may provide insights into the pathogenesis and therapeutic approach.

Establishment of SYBR green-based qPCR assay for rapid evaluation and quantification for anti-Hantaan virus compounds in vitro and in suckling mice

Hantaan viruses cause two severe diseases lacking efficient treatment, yet no effective prophylactic vaccines are available. Continued exploration of alternative antiviral agents to treat hantavirus-related syndromes remains compulsory. The fluorescence-based quantitative real-time PCR (qPCR) has become the touchstone for target gene quantification. In the present study, standard curves for Hantaan virus (HTNV), mouse, and human glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were generated by serial 10-fold dilutions of the constructed recombinant plasmid pGEM-T/HTNV, pGEM-T/mouse-GAPDH, and pGEM-T/human-GAPDH, respectively. Comparisons between the indirect immunofluorescence assay and qPCR assay in the detection of HTNV-infected Vero E6 cells showed improved detection limit and sensitivity of latter method. To characterize the inhibitory effect of several conventional antivirals (arbidol and ribavirin) and unconventional antivirals (indomethacin and curcumin) on HTNV, the levels of viral RNAs were measured for 4 days post-treatment of HTNV-infected Vero E6 cells and 18 days post-inoculation of HTNV-infected suckling mice. Our results validated that HTNV was sensitive to ribavirin and arbidol treatment, while indomethacin and curcumin may also be therapeutically effective in treating HTNV infection. As a result, the establishment and application of qPCR may be a useful tool for the evaluation of potential antivirals for Hantaan virus infection in vitro and in vivo.

Hantaan virus triggers TLR4-dependent innate immune responses

The innate immune response induced by Hantavirus is responsible for endothelial cell dysfunction and viral pathogenicity. Recent studies demonstrate that TLR4 expression is upregulated and mediates the secretion of several cytokines in Hantaan virus (HTNV)-infected endothelial cells. To examine viral interactions with host endothelial cells and characterize the innate antiviral responses associated with Toll-like receptors, we selected TLR4 as the target molecule to investigate anti-hantavirus immunity. TLR4 mRNA-silenced EVC-304 (EVC-304 TLR4-) cells and EVC-304 cells were used to investigate signaling molecules downstream of TLR4. The expression of the adaptor protein TRIF was higher in HTNV-infected EVC-304 cells than in EVC-304 TLR4- cells. However, there was no apparent difference in the expression of MyD88 in either cell line. The transcription factors for NF-κB and IRF-3 were translocated from the cytoplasm into the nucleus in HTNV-infected EVC-304 cells, but not in HTNV-infected EVC-304 TLR4- cells. Our results demonstrate that TLR4 may play an important role in the antiviral immunity of the host against HTNV infection through an MyD88-independent signaling pathway.

Pathogenesis of the hantavirus pulmonary syndrome

Hantavirus pulmonary syndrome caused by hantaviruses in the Americas presents as a broad clinical spectrum ranging from brief febrile prodrome with only thrombocytopenia to rapidly progressive fulminant pulmonary edema and shock. This vascular leak syndrome confined almost exclusively to the lung is initiated by the noncytolytic infection of capillary endothelial cells. A number of pathogenic mechanisms have been proposed, including immune cell-mediated injury, cytokine-mediated injury and enhanced VEGF responses from intercellular junctions resulting from highly specific virus–integrin interactions. This review examines evidence for each of these potential mechanisms, with relevant references to its sister syndrome, hemorrhagic fever with renal syndrome, in Eurasia. Any mechanism or combination of mechanisms must be able to explain the massive pulmonary capillary leak at the severe extreme of the spectrum, a disease manifestation without parallel in clinical medicine.

Cytokine expression during early and late phase of acute Puumala hantavirus infection

BACKGROUND

Hantaviruses of the family Bunyaviridae are emerging zoonotic pathogens which cause hemorrhagic fever with renal syndrome (HFRS) in the Old World and hantavirus pulmonary syndrome (HPS) in the New World. An immune-mediated pathogenesis is discussed for both syndromes. The aim of our study was to investigate cytokine expression during the course of acute Puumala hantavirus infection.

RESULTS

We retrospectively studied 64 patients hospitalised with acute Puumala hantavirus infection in 2010 during a hantavirus epidemic in Germany. Hantavirus infection was confirmed by positive anti-hantavirus IgG/IgM. Cytokine expression of IL-2, IL-5, IL-6, IL-8, IL-10, IFN-γ, TNF-α and TGF-β1 was analysed by ELISA during the early and late phase of acute hantavirus infection (average 6 and 12 days after onset of symptoms, respectively). A detailed description of the demographic and clinical presentation of severe hantavirus infection requiring hospitalization during the 2010 hantavirus epidemic in Germany is given. Acute hantavirus infection was characterized by significantly elevated levels of IL-2, IL-6, IL-8, TGF-β1 and TNF-α in both early and late phase compared to healthy controls. From early to late phase of disease, IL-6, IL-10 and TNF-α significantly decreased whereas TGF-β1 levels increased. Disease severity characterized by elevated creatinine and low platelet counts was correlated with high pro-inflammatory IL-6 and TNF-α but low immunosuppressive TGF-β1 levels and vice versa .

CONCLUSION

High expression of cytokines activating T-lymphocytes, monocytes and macrophages in the early phase of disease supports the hypothesis of an immune-mediated pathogenesis. In the late phase of disease, immunosuppressive TGF-β1 level increase significantly. We suggest that delayed induction of a protective immune mechanism to downregulate a massive early pro-inflammatory immune response might contribute to the pathologies characteristic of human hantavirus infection.

Pathogenic old world hantaviruses infect renal glomerular and tubular cells and induce disassembling of cell-to-cell contacts

Viral hemorrhagic fevers are characterized by enhanced permeability. One of the most affected target organs of hantavirus-induced hemorrhagic fever with renal syndrome is the kidney, and an infection often results in acute renal failure. To study the underlying cellular effects leading to kidney dysfunction, we infected human renal cell types in vitro that are critical for the barrier functions of the kidney, and we examined kidney biopsy specimens obtained from hantavirus-infected patients. We analyzed the infection and pathogenic effects in tubular epithelial and glomerular endothelial renal cells and in podocytes. Both epithelial and endothelial cells and podocytes were susceptible to hantavirus infection in vitro. The infection disturbed the structure and integrity of cell-to-cell contacts, as demonstrated by redistribution and reduction of the tight junction protein ZO-1 and the decrease in the transepithelial resistance in infected epithelial monolayers. An analysis of renal biopsy specimens from hantavirus-infected patients revealed that the expression and the localization of the tight junction protein ZO-1 were altered compared to renal biopsy specimens from noninfected individuals. Both tubular and glomerular cells were affected by the infection. Furthermore, the decrease in glomerular ZO-1 correlates with disease severity induced by glomerular dysfunction. The finding that different renal cell types are susceptible to hantaviral infection and the fact that infection results in the breakdown of cell-to-cell contacts provide useful insights in hantaviral pathogenesis.

T cells and pathogenesis of hantavirus cardiopulmonary syndrome and hemorrhagic fever with renal syndrome

We previously hypothesized that increased capillary permeability observed in both hantavirus cardiopulmonary syndrome (HCPS) and hemorrhagic fever with renal syndrome (HFRS) may be caused by hantavirus-specific cytotoxic T cells attacking endothelial cells presenting viral antigens on their surface based on clinical observations and in vitro experiments. In HCPS, hantavirus-specific T cell responses positively correlated with disease severity. In HFRS, in one report, contrary to HCPS, T cell responses negatively correlated with disease severity, but in another report the number of regulatory T cells, which are thought to suppress T cell responses, negatively correlated with disease severity. In rat experiments, in which hantavirus causes persistent infection, depletion of regulatory T cells helped infected rats clear virus without inducing immunopathology. These seemingly contradictory findings may suggest delicate balance in T cell responses between protection and immunopathogenesis. Both too strong and too weak T cell responses may lead to severe disease. It is important to clarify the role of T cells in these diseases for better treatment (whether to suppress T cell functions) and protection (vaccine design) which may need to take into account viral factors and the influence of HLA on T cell responses.

[Acute myopia]

This paper presents a case of ocular involvement during acute renal failure caused by hantavirus. A 34-year-old man suffered from sudden visual loss during acute onset fever with nausea and renal failure. The ophthalmologic examination showed myopia in both eyes and no signs of infection but virological studies revealed an infection with hantavirus. During treatment of the renal failure the myopia improved spontaneously. Transient myopia is a typical ocular involvement during infections with hantavirus which leads to renal failure.

Single HeLa and MCF-7 cell measurement using minimized impedance spectroscopy and microfluidic device

This study presents an impedance measurement system for single-cell capture and measurement. The microwell structure which utilizes nDEP force is used to single-cell capture and a minimized impedance spectroscopy which includes a power supply chip, an impedance measurement chip and a USB microcontroller chip is used to single-cell impedance measurement. To improve the measurement accuracy of the proposed system, Biquadratic fitting is used in this study. The measurement accuracy and reliability of the proposed system are compared to those of a conventional precision impedance analyzer. Moreover, a stable material, latex beads, is used to study the impedance measurement using the minimized impedance spectroscopy with cell-trapping device. Finally, the proposed system is used to measure the impedance of HeLa cells and MCF-7 cells. The impedance of single HeLa cells decreased from 9.55 × 10(3) to 3.36 × 10(3) Ω and the impedance of single MCF-7 cells decreased from 3.48 × 10(3) to 1.45 × 10(3) Ω at an operate voltage of 0.5 V when the excitation frequency was increased from 11 to 101 kHz. The results demonstrate that the proposed impedance measurement system successfully distinguishes HeLa cells and MCF-7 cells.

Integration of single-cell trapping and impedance measurement utilizing microwell electrodes

The ability to research individual cells has been seen as important in many kinds of biological studies. In the present study, cell impedance analysis is integrated into a single-cell trapping structure. For the purpose of precise positioning, a cell manipulation and measurement microchip, which uses an alternating current electrothermal effect (ACET) and a negative dielectrophoresis (nDEP) force to move a particle and cell on measurement electrodes, is developed. An ACET and an nDEP can be easily combined with subsequent analyses based on electric fields. A microwell presented in a previous study is separated into two parts, which are regarded as the measurement electrodes. The original structure is modified for precise positioning. Numerical simulations and analyses are conducted to compute and analyze the effects of the structural parameters. The results of simulations and analyses are used to obtain the optimum structure for the cell. The capture range of the microwell can be designed for cells of various sizes. In order to demonstrate the precision of the positioning, a particle is captured, measured, and released twice. The results show that the impedance error of the particle is about 3%. Finally, the developed structure is applied to trap and measure the impedance of a HeLa cell.

Elevated sICAM-1 levels in patients with hemorrhagic fever with renal syndrome caused by Hantaan virus

Increased vascular permeability and vascular leakage are characteristic pathological changes in hemorrhagic fever with renal syndrome (HFRS). Vascular endothelial cells are the main targets of Hantaan virus, the etiological agent of the severe form of HFRS. Hantaan virus can induce extensive damage of small blood vessels and capillaries. In vitro infection of human umbilical vein endothelial cells by Hantaan virus can induce the expression of intercellular adhesion molecule-1 (ICAM-1). The involvement of this molecule is implied in human HFRS. In the present study, serum-soluble ICAM-1 (sICAM-1) levels were determined and their relationships with the clinical course and disease severity were investigated in 112 HFRS patients and 30 healthy controls. The results showed that the serum levels of sICAM-1 in HFRS patients at fever, hypotensive, oliguric, and polyuric phases were significantly higher than those in controls (p < 0.001). However, no significant differences between the serum concentrations of sICAM-1 in the milder and more severe groups of patients were observed (p > 0.05). It is suggested that sICAM-1 was involved in the progression of HFRS. Time-dependent determinations of sICAM-1 levels may be indicators for the progression of disease, and elevated levels of sICAM-1 were not suggested to be correlated to disease severity.

Andes virus recognition of human and Syrian hamster beta3 integrins is determined by an L33P substitution in the PSI domain

Andes virus (ANDV) causes a fatal hantavirus pulmonary syndrome (HPS) in humans and Syrian hamsters. Human alpha(v)beta(3) integrins are receptors for several pathogenic hantaviruses, and the function of alpha(v)beta(3) integrins on endothelial cells suggests a role for alpha(v)beta(3) in hantavirus directed vascular permeability. We determined here that ANDV infection of human endothelial cells or Syrian hamster-derived BHK-21 cells was selectively inhibited by the high-affinity alpha(v)beta(3) integrin ligand vitronectin and by antibodies to alpha(v)beta(3) integrins. Further, antibodies to the beta(3) integrin PSI domain, as well as PSI domain polypeptides derived from human and Syrian hamster beta(3) subunits, but not murine or bovine beta(3), inhibited ANDV infection of both BHK-21 and human endothelial cells. These findings suggest that ANDV interacts with beta(3) subunits through PSI domain residues conserved in both Syrian hamster and human beta(3) integrins. Sequencing the Syrian hamster beta(3) integrin PSI domain revealed eight differences between Syrian hamster and human beta(3) integrins. Analysis of residues within the PSI domains of human, Syrian hamster, murine, and bovine beta(3) integrins identified unique proline substitutions at residues 32 and 33 of murine and bovine PSI domains that could determine ANDV recognition. Mutagenizing the human beta(3) PSI domain to contain the L33P substitution present in bovine beta(3) integrin abolished the ability of the PSI domain to inhibit ANDV infectivity. Conversely, mutagenizing either the bovine PSI domain, P33L, or the murine PSI domain, S32P, to the residue present human beta(3) permitted PSI mutants to inhibit ANDV infection. Similarly, CHO cells transfected with the full-length bovine beta(3) integrin containing the P33L mutation permitted infection by ANDV. These findings indicate that human and Syrian hamster alpha(v)beta(3) integrins are key receptors for ANDV and that specific residues within the beta(3) integrin PSI domain are required for ANDV infection. Since L33P is a naturally occurring human beta(3) polymorphism, these findings further suggest the importance of specific beta(3) integrin residues in hantavirus infection. These findings rationalize determining the role of beta(3) integrins in hantavirus pathogenesis in the Syrian hamster model.

Up-regulation of integrin beta3 expression in porcine vascular endothelial cells cultured in vitro by classical swine fever virus

Classical swine fever (CSF) caused by virulent strains of classical swine fever virus (CSFV) is a haemorrhagic disease of pigs, characterized by disseminated intravascular coagulation, thrombocytopenia and immunosuppression. The cell adhesion molecule, integrin beta3, plays a central role in maintaining and regulating vascular permeability. In view of the haemorrhagic pathology of the disease, the effect of CSFV infection on integrin beta3 expression was investigated using the swine umbilical vein endothelial cell (SUVEC) line, in conjunction with quantitative PCR and Western blotting techniques. Following infection, the expression levels of integrin beta3 were significantly up-regulated along with corresponding transcription levels. The infected endothelial cells adhered onto immobilized extracellular matrix (ECM) with more extensive spreading than that of the control, and such interaction was strongly inhibited by an anti-integrin beta3 monoclonal antibody (mAb). This study revealed the up-regulation of integrin beta3 in vascular endothelial cells by CSFV infection, and cell adhesion molecules of this kind possibly play an important role in the changes of haemostatic balance in haemorrhagic pathology of CSF.

Efficacy of arbidol on lethal hantaan virus infections in suckling mice and in vitro

AIM

Arbidol is an immunomodulator that was first developed in Russia. In this study, we report the antiviral activity of arbidol against Hantaan virus (HTNV) in vitro and in vivo.

METHODS

The antiviral activity of arbidol in vitro was determined by plaque-forming assay, ranging from 0.5 to 8 microg/mL. To investigate whether arbidol has an antiviral effect in vivo, suckling BALB/c mice infected with HTNV were treated with arbidol at 24 h before infection with a 5, 10 or 20 mg.kg(-1).d(-1), once per day, for 10 days. On day 12 and 28 post infection (pi), histopathological changes and viral antigen were detected. On days 4, 8, 12, and 16 pi, the viral load of target organs and serum TNF-alpha levels of arbidol-treated animals were determined.

RESULTS

Arbidol was found to have potent inhibitory activity against HTNV when added in vitro before or after viral infection, with a 50% inhibitory concentration (IC(50)) of 0.9 and 1.2 microg/mL, respectively. The 50% lethal dose (LD(50)) of arbidol for suckling mice was 78.42 mg.kg(-1).d(-1). Oral administration of arbidol increased both survival rate and mean time to death (MTD). Treatment with arbidol reduced histopathological changes, decreased viral load and viral antigen levels, and modulated the level of serum TNF-alpha.

CONCLUSION

Arbidol has the ability to elicit protective antiviral activity against HTNV in vivo and in vitro.Acta Pharmacologica Sinica (2009) 30: 1015-1024; doi: 10.1038/aps.2009.53; published online 8 June 2009.

Pathology of Puumala hantavirus infection in macaques

Hantaviruses are globally important human pathogens that cause hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. Capillary leakage is central to hantaviral diseases, but how it develops, has remained unknown. It has been hypothesized that the pathogenesis of hantavirus infection would be a complex interplay between direct viral effects and immunopathological mechanisms. Both of these were studied in the so far best model of mild hemorrhagic fever with renal syndrome, i.e. cynomolgus macaques infected with wild-type Puumala hantavirus. Viral RNA detected by in situ hybridization and nucleocapsid protein detected by immunohistochemical staining were observed in kidney, spleen and liver tissues. Inflammatory cell infiltrations and tubular damage were found in the kidneys, and these infiltrations contained mainly CD8-type T-cells. Importantly, these results are consistent with those obtained from patients with hantaviral disease, thus showing that the macaque model of hantavirus infection mimics human infection also on the tissue level. Furthermore, both the markers of viral replication and the T-cells appeared to co-localize in the kidneys to the sites of tissue damage, suggesting that these two together might be responsible for the pathogenesis of hantavirus infection.

The endothelium as a target for infections

The endothelial cells lining vascular and lymphatic vessels are targets of several infectious agents, including viruses and bacteria, that lead to dramatic changes in their functions. Understanding the pathophysiological mechanisms that cause the clinical manifestations of those infections has been advanced through the use of animal models and in vitro systems; however, there are also abundant studies that explore the consequences of endothelial infection in vitro without supporting evidence that endothelial cells are actual in vivo targets of infection in human diseases. This article defines criteria for considering an infection as truly endothelium-targeted and reviews the literature that offers insights into the pathogenesis of human endothelial-target infections.

Microfluidic device for cell capture and impedance measurement

This work presents a microfluidic device to capture physically single cells within microstructures inside a channel and to measure the impedance of a single HeLa cell (human cervical epithelioid carcinoma) using impedance spectroscopy. The device includes a glass substrate with electrodes and a PDMS channel with micro pillars. The commercial software CFD-ACE+ is used to study the flow of the microstructures in the channel. According to simulation results, the probability of cell capture by three micro pillars is about 10%. An equivalent circuit model of the device is established and fits closely to the experimental results. The circuit can be modeled electrically as cell impedance in parallel with dielectric capacitance and in series with a pair of electrode resistors. The system is operated at low frequency between 1 and 100 kHz. In this study, experiments show that the HeLa cell is successfully captured by the micro pillars and its impedance is measured by impedance spectroscopy. The magnitude of the HeLa cell impedance declines at all operation voltages with frequency because the HeLa cell is capacitive. Additionally, increasing the operation voltage reduces the magnitude of the HeLa cell because a strong electric field may promote the exchange of ions between the cytoplasm and the isotonic solution. Below an operating voltage of 0.9 V, the system impedance response is characteristic of a parallel circuit at under 30 kHz and of a series circuit at between 30 and 100 kHz. The phase of the HeLa cell impedance is characteristic of a series circuit when the operation voltage exceeds 0.8 V because the cell impedance becomes significant.

Association of chest radiography findings with host-related genetic factors in patients with nephropathia epidemica

Different host genetic factors causes imbalance in the immune response. The purpose of this study was to establish whether pathological findings in chest radiography are related to the various host-related immunological factors in nephropathia epidemica (NE). Chest radiography findings, human leukocyte antigen (HLA) alleles B8, DR3, B27, genotypes of the genes of tumour necrosis factor alpha (TNFalpha), interleukin -1alpha (IL-1alpha), IL1beta and IL-1 receptor antagonist (IL1RA) were analysed in 114 patients with serologically confirmed acute NE. Both the presence and severity of abnormal NE-related chest radiography findings associated with the B8, DR3 and TNF2 alleles are known to form a frequent extended HLA haplotype in European populations. Pleural effusion showed the strongest association with these genetic factors. Pathological findings in chest radiography are related to host genetic factors in NE. Pleural effusion is a sign of increased capillary permeability, an important feature in NE. Host genetic factors may contribute to increased capillary permeability observed in NE patients.

Immunopathogenesis of hantavirus pulmonary syndrome and hemorrhagic fever with renal syndrome: Do CD8+ T cells trigger capillary leakage in viral hemorrhagic fevers?

There are many viruses known to cause viral hemorrhagic fevers in humans. The mechanisms causing hemorrhage are likely to vary among viruses. Some viruses, such as Marburg virus, are directly cytopathic to infected endothelial cells, suggesting infection of endothelial cells alone can cause hemorrhage. On the other hand, there are viruses which infect endothelial cells without causing any cytopathic effects, suggesting the involvement of host immune responses in developing hemorrhage. Typical examples of these include viruses of the hantavirus species. We hypothesize that impairment of endothelial cell's defense mechanisms against cytotoxic CD8+ T cells is the mechanism of capillary leakage in hantavirus pulmonary syndrome and hemorrhagic fever with renal syndrome, which may be common to other viral hemorrhagic fevers. CD8+ T cells may be a potential target for therapy of some viral hemorrhagic fevers.

Endothelial cell infection and hemostasis

As an important component of the vasculature, endothelial cell lining covers the inner surface of blood vessels and provides an active barrier interface between the vascular and perivascular compartments. In addition to maintaining vasomotor equilibrium and organ homeostasis and communicating with circulating blood cells, the vascular endothelium also serves as the preferred target for a number of infectious agents. This review article focuses on the roles of interactions between vascular endothelial cells and invading pathogens and resultant endothelial activation in the pathogenesis of important human diseases with viral and bacterial etiologies. In this perspective, the signal transduction events that regulate vascular inflammation and basis for endothelial cell tropism exhibited by certain specific viruses and pathogenic bacteria are also discussed.

Tumor necrosis factor-alpha genetic predisposing factors can influence clinical severity in nephropathia epidemica

Severe human infection with Hantavirus is characterized by high fever, cold chills, thrombocytopenia, arterial hypotension, acute renal failure, and/or adult respiratory distress syndrome (ARDS)-like pulmonary involvement, but the clinical course varies greatly between individuals. We investigated whether genetically determined differences in tumor necrosis factor (TNF)-alpha production can influence the severity of Hantavirus disease. We studied a TNF-alpha single-nucleotide promoter polymorphism (SNP) at position -238 (a guanine [G]-to-adenine [A] transition) and ex vivo TNF-alpha production in a recall study of 36 Belgian patients who had a serologically proven form of Puumala virus-induced Hantavirus infection with the kidney as main target organ. In our study, the highest creatinine levels were found in patients with the lowest ex vivo TNF-alpha production. Creatinine levels correlated inversely with TNF-alpha production (R = -0.35, p < 0.05). The number of thrombocytes was significantly lower in patients with the GA-238 genotype (low TNF-alpha producers) compared with patients with the GG-238 genotype. In our study, genetically determined low production of TNF-alpha was associated with some parameters indicating a more severe clinical course of Puumala Hantavirus infection in humans, possibly by impaired activation of TNF-alpha-dependent antiviral mechanisms, which could in turn result in decreased clearance of Hantavirus.

Increased permeability of human endothelial cell line EA.hy926 induced by hantavirus-specific cytotoxic T lymphocytes

Hantavirus infection causes two human diseases, hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. The typical feature of these diseases is increased permeability in microvascular beds in the kidneys and the lungs, respectively. The mechanism of capillary leakage, however, is not understood. Some evidence suggests that hantavirus disease pathogenesis is immunologically mediated by cytotoxic T lymphocytes and other immune cells in target organs producing inflammatory cytokines. In this study we examined the roles of virus-specific cytotoxic T lymphocytes in increased permeability of human endothelial cells infected with hantavirus. We used a human CD8(+) hantavirus-specific cytotoxic T lymphocyte line, 1A-E2, specific for the HLA-A24-restricted epitope in Sin Nombre and Puumala virus G2 protein, and the human endothelial cell line, EA.hy926 that expresses HLA-A24 molecule. The cytotoxic T lymphocyte line recognized and lysed target cells infected with Sin Nombre virus, and in transwell permeability assays increased permeability of EA.hy926 cell monolayer infected with Sin Nombre virus or recombinant adenovirus expressing the Sin Nombre virus G2 protein. These results suggest that cytotoxic T lymphocyte activity contribute to capillary leakage observed in patients with hantavirus pulmonary syndrome or hemorrhagic fever with renal syndrome.

Dynamic changes of apoptosis-inducing ligands and Th1/Th2 like subpopulations in Hantaan virus-induced hemorrhagic fever with renal syndrome

The expression of the apoptosis-inducing ligands, TNF-alpha, FasL and TRAIL on peripheral blood mononuclear cells (PBMC) and the levels of their soluble form (TNF-alpha, sFasL and sTRAIL) in plasma from 40 hemorrhagic fever with renal syndrome (HFRS) patients as well as 26 healthy blood donors were determined by flow cytometry (FCM) analysis and sandwich ELISA, respectively. The status of Th1, Th2, Tc1 and Tc2 subsets in PBMC was evaluated by intracellular cytokine staining and FCM. Compared to controls, the expression of membrane bound FasL and TRAIL was up-regulated on surface of PBMC isolated from the HFRS patients, particularly on CD8+ T lymphocytes. The levels of TNF-alpha, sFasL and sTRAIL in plasma from the HFRS patients in the acute phase increase 4.7-fold, 6.0-fold and 1.8-fold, respectively, over those from the healthy donors. The percentage of Th1, Tc1 and Tc2 subsets in PBMC from the patients also increased significantly compared with those from healthy donors. These results indicate that dynamic changes occurred in both the membrane bound and soluble forms of apoptosis-inducing ligands (FasL, TRAIL and TNF-alpha) and proportions of Th1 and CTL in HFRS patients increased. Both factors may play an important role in the etiology of Hantaan virus infection in humans.

Hantaviruses: Immunology, Treatment, and Prevention

Hantaviruses are rodent-borne bunyaviruses that are associated with two main clinical diseases in humans: hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. It has been suggested that host-related immune mechanisms rather than direct viral cytopathology may be responsible for the principal abnormality (vascular dysfunction) in these syndromes. This review summarizes the current knowledge on hantaviral host immune responses, immune abnormalities, laboratory diagnosis, and antiviral therapy as well as the current approaches in vaccine development.