Pathogenesis of puumala and other hantavirus infections

High pentraxin-3 plasma levels associate with thrombocytopenia in acute Puumala hantavirus-induced nephropathia epidemica

Our aim was to investigate whether plasma levels of the long pentraxin-3 (PTX3) associate with the severity of Puumala hantavirus-induced nephropathia epidemica (NE). Sixty-one prospectively identified consecutively hospitalized NE patients were examined. Plasma PTX3, interleukin (IL)-6, terminal complement complex SC5b-9, complement component C3, C-reactive protein (CRP), creatinine, sodium, kynurenine, and tryptophan levels, as well as the blood cell count, were determined for up to five consecutive days after hospitalization. Receiver operating characteristic (ROC) analysis revealed that the maximum PTX3 level >101.6 ng/ml (high PTX3) showed a sensitivity of 71% and a specificity of 89% for detecting platelet level <50 × 10(9)/l, with an area under the curve (AUC) value of 0.78 (95% confidence interval [CI] 0.63-0.94). High PTX3 level was also associated with several other variables reflecting the severity of the disease: patients with high PTX3 level had higher maximum blood leukocyte (16.1 vs. 9.7 × 10(9)/l, p < 0.001), plasma IL-6 (16.9 vs. 9.0 pg/ml, p = 0.007), and creatinine (282 vs. 124 μmol/l, p = 0.007) levels than patients with low maximum PTX3 level. They also had longer hospital stays (8 vs. 5 days, p = 0.015) compared to patients with low PTX3 level. High plasma PTX3 levels are associated with thrombocytopenia and the overall severity of NE.

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.

Puumala virus infection in Syrian hamsters (Mesocricetus auratus) resembling hantavirus infection in natural rodent hosts

The mechanism of hantavirus persistent infection in natural hosts is poorly understood due to a lack of laboratory animal models. Herein, we report that Syrian hamsters (Mesocricetus auratus) infected with Puumala virus (PUUV) at 4 weeks old show persistent infection without clinical symptoms for more than 2 months. IgG and IgM antibodies against the viral nucleocapsid protein and neutralizing antibody were first detectable at 14 days postinoculation (dpi) and maintained through 70 dpi. Viral RNA was first detected from 3 dpi in lungs and blood clots, and was detected in all tissues tested at 7 dpi. The viral RNA persisted for at least 70 days in the lungs, kidney, spleen, heart, and brain. The highest level of RNA copies was observed at 14 dpi in the lungs. Slight inflammatory reactions were observed in the lungs, adrenal glands, and brain. Immunohistochemical analysis revealed that PUUV antigen persisted until 56 dpi in the kidneys and adrenal glands. Infected hamsters showed no body weight loss or clinical signs. These results indicate that PUUV infection in hamsters is quite similar to the hantavirus infection of natural host rodents.

High activity of indoleamine 2,3-dioxygenase is associated with renal insufficiency in Puumala hantavirus induced nephropathia epidemica

Nephropathia epidemica (NE) is a hemorrhagic fever with renal syndrome caused by Puumala hantavirus. The severity of NE varies greatly. The aim of the present study was to evaluate whether serum indoleamine 2,3-dioxygenase (IDO) activity is associated with the severity of NE. A prospectively collected cohort of 102 consecutive patients with acute serologically confirmed NE was examined. Serum kynurenine, tryptophan, creatinine, CRP, and blood cell count were measured for up to 5 consecutive days after admission. The kynurenine to tryptophan (kyn/trp) ratio reflecting IDO activity was calculated. A maximum kyn/trp ratio >202 µmol/mmol had a sensitivity of 85% and a specificity of 75% for detecting maximum serum creatinine values >250 µmol/L by receiver operating characteristic (ROC) analysis. A maximum kyn/trp ratio >202 µmol/mmol (high IDO level) was also associated with other parameters reflecting the severity of the disease and renal impairment. Patients with high IDO levels had higher maximum serum creatinine (379 vs. 102 µmol/L, P<0.001), plasma C-reactive protein (104.1 vs. 72.1 mg/L, P=0.029), and blood leukocyte values (11.9 vs. 9.0 × 10(9) /L, P<0.001) compared to patients with kyn/trp ratio ≤ 202 µmol/mmol. They also had lower minimum urinary output (1,100 vs. 1,900 ml/day, P<0.001) and longer hospital stays (8 vs. 5 days, P<0.001). In conclusion, high serum IDO activity was associated with increased disease severity and renal impairment in NE.

Hantavirus pulmonary syndrome: a concise clinical review

In 1978, hantaviruses were first described as the etiological agent of hemorrhagic fever with renal syndrome (HFRS) in Korea. Since then, numerous related, enveloped, negative-stranded RNA viruses have been identified, forming the genus Hantavirus within the family Bunyaviridae. These pathogens are distributed worldwide and thus can be classified, on the basis of phylogenetic origins, into Old World viruses or New World viruses (ie North, Central, and South America). Similarly, these viruses cause two major types of syndromes, corresponding respectively to their phylogenies: the original HFRS or the more recently described hantavirus pulmonary syndrome (HPS). As the hantavirus pulmonary syndrome is the primary hantaviral disease in North America, it will thus be the focus of this review.

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.

A global perspective on hantavirus ecology, epidemiology, and disease

Hantaviruses are enzootic viruses that maintain persistent infections in their rodent hosts without apparent disease symptoms. The spillover of these viruses to humans can lead to one of two serious illnesses, hantavirus pulmonary syndrome and hemorrhagic fever with renal syndrome. In recent years, there has been an improved understanding of the epidemiology, pathogenesis, and natural history of these viruses following an increase in the number of outbreaks in the Americas. In this review, current concepts regarding the ecology of and disease associated with these serious human pathogens are presented. Priorities for future research suggest an integration of the ecology and evolution of these and other host-virus ecosystems through modeling and hypothesis-driven research with the risk of emergence, host switching/spillover, and disease transmission to humans.

The severity of Puumala hantavirus induced nephropathia epidemica can be better evaluated using plasma interleukin-6 than C-reactive protein determinations

Background

Nephropathia epidemica (NE) is a Scandinavian type of hemorrhagic fever with renal syndrome caused by Puumala hantavirus. The clinical course of the disease varies greatly in severity. The aim of the present study was to evaluate whether plasma C-reactive protein (CRP) and interleukin (IL)-6 levels associate with the severity of NE.

Methods

A prospectively collected cohort of 118 consecutive hospital-treated patients with acute serologically confirmed NE was examined. Plasma IL-6, CRP, and creatinine, as well as blood cell count and daily urinary protein excretion were measured on three consecutive days after admission. Plasma IL-6 and CRP levels higher than the median were considered high.

Results

We found that high IL-6 associated with most variables reflecting the severity of the disease. When compared to patients with low IL-6, patients with high IL-6 had higher maximum blood leukocyte count (11.9 vs 9.0 × 10⁹/l, P = 0.001) and urinary protein excretion (2.51 vs 1.68 g/day, P = 0.017), as well as a lower minimum blood platelet count (55 vs 80 × 10⁹/l, P < 0.001), hematocrit (0.34 vs 0.38, P = 0.001), and urinary output (1040 vs 2180 ml/day, P < 0.001). They also stayed longer in hospital than patients with low IL-6 (8 vs 6 days, P < 0.001). In contrast, high CRP did not associate with severe disease.

Conclusions

High plasma IL-6 concentrations associate with a clinically severe acute Puumala hantavirus infection, whereas high plasma CRP as such does not reflect the severity of the disease.

Hormonal deficiencies during and after Puumala hantavirus infection

Previous reports have described panhypopituitarism associated with severe cases of hemorrhagic fever with renal syndrome (HFRS), but the prevalence of hormonal deficiencies after nephropathia epidemica (NE), a milder form of HFRS, has not been studied. This study was conducted in order to determine the prevalence of hormonal defects in patients with acute NE and during long-term follow-up. Fifty-four patients with serologically confirmed acute NE were examined by serum hormonal measurements during the acute NE, after 3 months, and after 1 to 10 (median 5) years. Thirty out of 54 (56%) patients had abnormalities of the gonadal and/or thyroid axis during the acute NE. After a median follow-up of 5 years, 9 (17%) patients were diagnosed with a chronic, overt hormonal deficit: hypopituitarism was found in five patients and primary hypothyroidism in five patients. In addition, chronic subclinical testicular failure was found in five men. High creatinine levels and inflammatory markers during NE were associated with the acute central hormone deficiencies, but not with the chronic deficiencies. Hormonal defects are common during acute NE and, surprisingly, many patients develop chronic hormonal deficiencies after NE. The occurrence of long-term hormonal defects cannot be predicted by the severity of acute NE.

Inhibition of TNF-alpha-induced activation of NF-kappaB by hantavirus nucleocapsid proteins

Hantaviruses cause two human diseases thought to be immune-mediated: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). We recently reported that the nucleocapsid (N) protein of HFRS-causing Hantaan virus (HTNV) inhibits tumor necrosis factor-alpha (TNF-alpha) activation of nuclear factor-kappaB (NF-kappaB). Here we measured the ability of other hantaviral N proteins to similarly interfere with the inflammatory process of TNF-alpha. We found that like HTNV N, the N proteins of HFRS-causing Seoul and Dobrava viruses inhibited TNF-alpha activation of NF-kappaB and translocation of the NF-kappaB p65 subunit, but did not interfere with degradation of inhibitor of NF-kappaB (IkappaB). In contrast, the HFRS-causing Puumala virus and the HPS-causing Andes and Sin Nombre viruses did not prevent TNF-alpha activation of NF-kappaB or nuclear translocation of p65. These studies provide evidence that hantaviruses differ in their abilities to interfere with host innate immune responses.

Electrocardiographic changes in patients with haemorrhagic fever with renal syndrome

The purpose of the study was to assess the incidence, type and dynamics of electrocardiography (ECG) alterations in patients with haemorrhagic fever with renal syndrome (HFRS) according to different stages of the disease. 79 patients hospitalized at the University Hospital for Infectious Diseases in Zagreb during the large HFRS outbreak in Croatia in 2002 were retrospectively analysed. HFRS diagnosis was confirmed by enzyme-linked immunosorbent assay. A 12-lead resting ECG was obtained. 30 (38%) patients had abnormal ECG findings, most frequently in the oliguric stage. Increased levels of urea and creatinine were observed in all patients with abnormal ECG, along with abnormal chest X-ray in nearly 50% of cases. Sinus tachycardia was the most frequent ECG disorder in the febrile stage, and bradycardia in the oliguric stage. During the course of disease, some other ECG disorders were recorded: bundle branch conduction defects, non-specific ventricular repolarization disturbances, supraventricular and ventricular extrasystoles, prolonged QT interval, low voltage of the QRS complexes in standard limb leads, atrioventricular block first-degree, and atrial fibrillation. Myocarditis was present in 3 patients. In conclusion, abnormal ECG was found in more than one-third of HFRS patients with the most common findings during the oliguric stage. All ECG changes were transient.

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.

Experience with intravenous ribavirin in the treatment of hemorrhagic fever with renal syndrome in Korea

Results of a clinical study using intravenous (IV) ribavirin for treating Department of Defense personnel with hemorrhagic fever with renal syndrome (HFRS) acquired in Korea from 1987 to 2005 were reviewed to determine the clinical course of HFRS treated with IV ribavirin. A total of 38 individuals enrolled in the study had subsequent serological confirmation of HFRS. Four of the 38 individuals received three or fewer doses of ribavirin and were excluded from treatment analysis. Of the remaining 34 individuals, oliguria was present in one individual at treatment initiation; none of the remaining 33 subjects developed oliguria or required dialysis. The mean peak serum creatinine was 3.46 mg/dl and occurred on day 2 of ribavirin therapy. Both the peak serum creatinine and the onset of polyuria occurred on mean day 6.8 of illness. Reversible hemolytic anemia was the main adverse event of ribavirin, with a >or=25% decrease in hematocrit observed in 26/34 (76.5%) individuals. While inability to adjust for all baseline variables prevents comparison to historical cohorts in Korea where oliguria has been reported in 39-69% cases and dialysis required in approximately 40% HFRS cases caused by Hantaan virus, the occurrence of 3% oliguria and 0% dialysis requirement in the treatment cohort is supportive of a previous placebo-controlled HFRS trial in China where IV ribavirin given early resulted in decreased occurrence of oliguria and decreased severity of renal insufficiency.

Hantaan virus nucleocapsid protein binds to importin alpha proteins and inhibits tumor necrosis factor alpha-induced activation of nuclear factor kappa B

Hantaviruses such as Hantaan virus (HTNV) and Andes virus cause two human diseases, hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome, respectively. For both, disease pathogenesis is thought to be immunologically mediated and there have been numerous reports of patients with elevated levels of proinflammatory and inflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha), in their sera. Multiple viruses have developed evasion strategies to circumvent the host cell inflammatory process, with one of the most prevalent being the disruption of nuclear factor kappa B (NF-kappaB) activation. We hypothesized that hantaviruses might also moderate host inflammation by interfering with this pathway. We report here that the nucleocapsid (N) protein of HTNV was able to inhibit TNF-alpha-induced activation of NF-kappaB, as measured by a reporter assay, and the activation of endogenous p65, an NF-kappaB subunit. Surprisingly, there was no defect in the degradation of the inhibitor of NF-kappaB (IkappaB) protein, nor was there any alteration in the level of p65 expression in HTNV N-expressing cells. However, immunofluorescence antibody staining demonstrated that cells expressing HTNV N protein and a green fluorescent protein-p65 fusion had limited p65 nuclear translocation. Furthermore, we were able to detect an interaction between HTNV N protein and importin alpha, a nuclear import molecule responsible for shuttling NF-kappaB to the nucleus. Collectively, our data suggest that HTNV N protein can sequester NF-kappaB in the cytoplasm, thus inhibiting NF-kappaB activity. These findings, which were obtained using cells transfected with cDNA representing the HTNV N gene, were confirmed using HTNV-infected cells.

How to diagnose hantavirus infections and detect them in rodents and insectivores

Hantaviruses are carried by rodents and insectivores in which they cause persistent and generally asymptomatic infections. Several hantaviruses can infect humans and many of them cause either haemorrhagic fever with renal syndrome (HFRS) in Eurasia or hantavirus cardiopulmonary syndrome (HCPS) in the Americas. In humans hantavirus infections are diagnosed using IgM-capture tests but also by RT-PCR detection of viral RNA. For detection of hantavirus infections in rodents and insectivores, serology followed by immunoblotting of, for example, lung tissue, and RT-PCR detection of viral RNA may be used, and if of interest followed by sequencing and virus isolation. For sero/genotyping of hantavirus infections in humans and carrier animals neutralisation tests/RNA sequencing are required. Hantaviruses are prime examples of emerging and re-emerging infections and it seems likely that many new hantaviruses will be detected in the near future.

Hantaviruses direct endothelial cell permeability by sensitizing cells to the vascular permeability factor VEGF, while angiopoietin 1 and sphingosine 1-phosphate inhibit hantavirus-directed permeability

Hantaviruses infect human endothelial cells and cause two vascular permeability-based diseases: hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. Hantavirus infection alone does not permeabilize endothelial cell monolayers. However, pathogenic hantaviruses inhibit the function of alphav beta3 integrins on endothelial cells, and hemorrhagic disease and vascular permeability deficits are consequences of dysfunctional beta3 integrins that normally regulate permeabilizing vascular endothelial growth factor (VEGF) responses. Here we show that pathogenic Hantaan, Andes, and New York-1 hantaviruses dramatically enhance the permeability of endothelial cells in response to VEGF, while the nonpathogenic hantaviruses Prospect Hill and Tula have no effect on endothelial cell permeability. Pathogenic hantaviruses directed endothelial cell permeability 2 to 3 days postinfection, coincident with pathogenic hantavirus inhibition of alphav beta3 integrin functions, and hantavirus-directed permeability was inhibited by antibodies to VEGF receptor 2 (VEGFR2). These studies demonstrate that pathogenic hantaviruses, similar to alphav beta3 integrin-deficient cells, specifically enhance VEGF-directed permeabilizing responses. Using the hantavirus permeability assay we further demonstrate that the endothelial-cell-specific growth factor angiopoietin 1 (Ang-1) and the platelet-derived lipid mediator sphingosine 1-phosphate (S1P) inhibit hantavirus directed endothelial cell permeability at physiologic concentrations. These results demonstrate the utility of a hantavirus permeability assay and rationalize the testing of Ang-1, S1P, and antibodies to VEGFR2 as potential hantavirus therapeutics. The central importance of beta3 integrins and VEGF responses in vascular leak and hemorrhagic disease further suggest that altering beta3 or VEGF responses may be a common feature of additional viral hemorrhagic diseases. As a result, our findings provide a potential mechanism for vascular leakage after infection by pathogenic hantaviruses and the means to inhibit hantavirus-directed endothelial cell permeability that may be applicable to additional vascular leak syndromes.

Hantavirus causing hemorrhagic fever with renal syndrome enters from the apical surface and requires decay-accelerating factor (DAF/CD55)

The Old World hantaviruses, members of the family Bunyaviridae, cause hemorrhagic fever with renal syndrome (HFRS). Transmission to humans occurs via inhalation of aerosols contaminated with the excreta of infected rodents. The viral antigen is detectable in dendritic cells, macrophages, lymphocytes, and, most importantly, microvascular endothelial cells. However, the site and detailed mechanism of entry of HFRS-causing hantaviruses in polarized epithelial cells have not yet been defined. Therefore, this study focused on the entry of the pathogenic hantaviruses Hantaan and Puumala into African green monkey kidney epithelial cells and primary human endothelial cells. The polarized epithelial and endothelial cells were found to be susceptible to hantavirus infection exclusively from the apical surface. Treatment with phosphatidylinositol-specific phospholipase C, which removes glycosylphosphatidylinositol (GPI)-anchored proteins from the cell surface, protects cells from infection, indicating that hantaviruses require a GPI-anchored protein as a cofactor for entry. Decay-accelerating factor (DAF)/CD55 is a GPI-anchored protein of the complement regulatory system and serves as a receptor for attachment to the apical cell surface for a number of viruses. Infection was reduced by the pretreatment of hantaviral particles with human recombinant DAF. Moreover, the treatment of permissive cells with DAF-specific antibody blocked infection. These results demonstrate that the Old World hantaviruses Hantaan and Puumala enter polarized target cells from the apical site and that DAF is a critical cofactor for infection.

[Emerging zoonoses: Hantavirus infections]

Among the emerging viruses, hantaviruses are being focused on more and more due to their increasing number and worldwide distribution. Transmission occurs via inhalation of aerosolized infected rodent excreta. The symptoms and course of disease vary with the infecting hantavirus species. The distribution of the different hantavirus species correlates with the geographical distribution of the virus-type-specific rodent host. Hantaviruses in Europe and Asia cause hemorrhagic fever with renal syndrome (HFRS). Infection with Puumala, the prevalent virus type in Germany, results in a more moderate form of HFRS, nephropathia epidemica. Infections with virus species on the American continents lead to a clinical picture with predominantly pulmonary pathology (hantaviral pulmonary syndrome). No specific antiviral therapy or approved vaccines are available for any hantavirus species. Controlling the rodent populations and avoiding contact with rodent excrement are the only measures that can be undertaken to contain and prevent infection.

Human CD8+ T cell memory generation in Puumala hantavirus infection occurs after the acute phase and is associated with boosting of EBV-specific CD8+ memory T cells

The induction and maintenance of T cell memory is incompletely understood, especially in humans. We have studied the T cell response and the generation of memory during acute infection by the Puumala virus (PUUV), a hantavirus endemic to Europe. It causes a self-limiting infection with no viral persistence, manifesting as hemorrhagic fever with renal syndrome. HLA tetramer staining of PBMC showed that the CD8(+) T cell response peaked at the onset of the clinical disease and decreased within the next 3 wk. Expression of activation markers on the tetramer-positive T cells was also highest during the acute phase, suggesting that the peak population consisted largely of effector cells. Despite the presence of tetramer-positive T cells expressing cytoplasmic IFN-gamma, PUUV-specific cells producing IFN-gamma in vitro were rare during the acute phase. Their frequency, as well as the expression of IL-7R alpha mRNA and surface protein, increased during a follow-up period of 6 wk and probably reflected the induction of memory T cells. Simultaneously with the PUUV-specific response, we also noted in seven of nine patients an increase in EBV-specific T cells and the transient presence of EBV DNA in three patients, indicative of viral reactivation. Our results show that in a natural human infection CD8(+) memory T cells are rare during the peak response, gradually emerging during the first weeks of convalescence. They also suggest that the boosting of unrelated memory T cells may be a common occurrence in human viral infections, which may have significant implications for the homeostasis of the memory T cell compartment.

Hantavirus infection in East Asia

Hantaviruses are enveloped RNA viruses that belong to the Hantavirus genus of the family Bunyaviridae. These viruses persistently infect their rodent reservoirs without causing disease. The virus is transmitted to humans via the inhalation of infectious aerosols generated from contaminated animal secretions or through the contaminated saliva of animal bites. Hantaviruses cause haemorrhagic fever with renal syndrome in Euro-Asia, and hantavirus pulmonary syndrome (HPS) in North and South America. Here, we review the epidemiology and epizootiology of hantavirus infection in Asian countries.

Evaluation of the efficacy of disinfectants against Puumala hantavirus by real-time RT-PCR

Puumala virus, a hantavirus belonging to the Bunyaviridae family, causes a human disease known as nephropathia epidemica, a mild form of hemorrhagic fever with renal syndrome. The implementation of effective decontamination procedures is critical in hantavirus research to minimize the risk of personnel exposure. This study investigated the efficacy of Clidox^®, Dettol^®, ethanol, Halamid-d^®, peracetic acid, sodium hypochloride and Virkon^®S for inactivating Puumala virus. A real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was used to quantify Puumala virus before and after treatment with these products. Inactivation of Puumala virus was effective after 10 min with all products except ethanol. Inactivation with absolute ethanol was effective only after 30 min. Using the qRT-PCR method, this study has shown that the commercially available products Clidox^®, Halamid-d^® and Virkon^®S in particular represent a rapid and safe way to decontaminate surfaces with possible Puumala virus contamination. These products can be used in solutions of 1–2%, with contact times greater than 10 min, for inactivating effectively Puumala virus.

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.

Viral zoonoses in Europe

A number of new virus infections have emerged or re-emerged during the past 15 years. Some viruses are spreading to new areas along with climate and environmental changes. The majority of these infections are transmitted from animals to humans, and thus called zoonoses. Zoonotic viruses are, as compared to human-only viruses, much more difficult to eradicate. Infections by several of these viruses may lead to high mortality and also attract attention because they are potential bio-weapons. This review will focus on zoonotic virus infections occurring in Europe.

HFRS causing hantaviruses do not induce apoptosis in confluent Vero E6 and A-549 cells

Hantaviruses are known to cause little or no cytopathic effect in vitro, but have been suggested to cause apoptosis. To determine whether different hantaviruses would induce apoptosis to varying degrees, confluent Vero E6 cells were infected with the hemorrhagic fever with renal syndrome (HFRS) causing viruses Hantaan, Dobrava, Saaremaa, and Puumala. However, no difference was found in the percentage of adherent cells, or of cells with condensed nuclei, between non-infected and virus-infected cells at 3, 6, 9, or 12 days after infection. Furthermore, no differences in the percentage of cells with inter-nucleosomal cleavage of DNA between uninfected and Hantaan infected cells could be detected using the TUNEL assay. Possibly, slightly more apoptotic cells, but never more than 5%, were detected after Hantaan infection of non-confluent cells as compared to the negative control. Earlier reported results that Tula hantavirus induces significant apoptosis on Vero E6 cells were also verified, suggesting that non-pathogenic hantaviruses might differ from HFRS-causing strains regarding induction of apoptosis. In conclusion, the results indicated that the HFRS-causing hantaviruses might induce a very low level of apoptosis in dividing cells, but not at all in confluent cells.

Tula hantavirus infection of Vero E6 cells induces apoptosis involving caspase 8 activation

Hantaviruses are known to cause two severe human diseases: haemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. The mechanisms of pathogenesis of these two diseases are progressively becoming understood. Recently, two hantaviruses, Hantaan and Prospect Hill were reported to cause programmed cell death of Vero E6 cells. This study shows that Tula hantavirus (TULV) infection efficiently triggers an apoptotic programme in infected Vero E6 cells, and that the replication of TULV is required for the activation of caspase 3 and the cleavage of poly (ADP-ribose) polymerase, two molecular hallmarks of apoptosis. The enforced treatment of infected Vero E6 cells with tumour necrosis factor alpha (TNF-alpha), but not interferon alpha (IFN-alpha), advanced the time course of apoptosis. Furthermore, caspase 8 was activated on day 4 post-infection, the same day when caspase 3 was activated. TNF receptor 1 was induced during a late stage of TULV infection. These data suggest that, unlike during influenza A virus infection, TNF-alpha, but not type I IFN-alpha/beta, may contribute significantly to apoptosis in a synergistic manner with TULV propagation. Interestingly, pretreatment with a broad-spectrum caspase inhibitor, z-VAD-fmk, efficiently inhibited apoptosis of TULV-infected Vero E6 cells. Taken together, these results suggest that TULV replication initiates a typical apoptotic programme involving caspase 8 activation.

Identification and analysis for cross-reactivity among hantaviruses of H-2b-restricted cytotoxic T-lymphocyte epitopes in Sin Nombre virus nucleocapsid protein

Sin Nombre virus (SNV) causes hantavirus pulmonary syndrome (HPS), with a high rate of mortality in humans who are infected by the transmission of virus from the natural rodent host. In humans, cytotoxic T lymphocytes (CTL) specific for SNV appear to play an important role in the pathogenicity of HPS. There is a correlation between the frequencies of SNV-specific CTLs and the severity of HPS disease. In order to create a mouse model to study the role of SNV-specific T cells in vivo, T cell responses to SNV nucleocapsid (N) protein in B6.PL Thy1(a)/Cy mice (H-2(b)) immunized with plasmid DNA or recombinant vaccinia virus expressing SNV N protein were examined. Four peptides, NC94-101, NC175-189, NC217-231 and NC331-345, were recognized by CD8(+) T cells in CTL and ELISPOT assays in SNV N-immunized mice. Interestingly, two of these epitopes are located in the central region of the SNV N protein, where several human CD8(+) T-cell epitopes have been defined in Puumala virus and SNV. CTL lines specific for these four epitopes were cross-reactive to corresponding Puumala virus peptides, but only one of them was cross-reactive to Hantaan virus peptides. These results will enable the analysis of the roles of CTL in immunopathology of HPS in experimental mouse models of HPS.

Urinary excretion of interleukin-6 correlates with proteinuria in acute Puumala hantavirus-induced nephritis

BACKGROUND

Nephropathia epidemica (NE) is a mild type of hemorrhagic fever with renal syndrome caused by Puumala Hantavirus. Cytokines are thought to have an important role in the pathogenesis of NE. The aim of this study is to evaluate whether cytokines contribute to renal involvement in NE.

METHODS

Overnight urinary excretion of interleukin-1beta (IL-1beta), IL-1 receptor antagonist (IL-1Ra), IL-6, tumor necrosis factor-alpha (TNF-alpha), albumin, immunoglobulin G (IgG), and alpha1-microglobulin and quantitative 24-hour urinary protein excretion were measured for 3 consecutive days from 70 hospitalized patients with acute NE (49 men, 21 women; age, 15 to 70 years; median age, 39 years). Plasma levels of the respective cytokines also were measured. Urinary collections were repeated after 1 year. The control group for blood samples included 400 healthy blood donors.

RESULTS

Maximum median urinary IL-6 excretion in the acute phase of NE was increased compared with values detected after 1 year (49.5 versus 0.7 pg/min; P < 0.001). Correspondingly, maximum median plasma IL-6 concentration in patients was increased compared with controls (14.6 versus 1.2 pg/mL; P < 0.001). Urinary IL-6 excretion correlated with urinary albumin, IgG, and protein excretion (r = 0.79; P < 0.001; r = 0.76; P < 0.001; and r = 0.65; P < 0.001, respectively), but not plasma IL-6 levels (r = 0.18; P = 0.148).

CONCLUSION

Plasma IL-6 concentrations and urinary IL-6 excretion were markedly increased in patients with acute NE, but there was no correlation between plasma and urinary IL-6 levels. The high urinary IL-6 levels might reflect local production of this proinflammatory cytokine in the kidneys during acute infection.

Bovine aortic endothelial cells are susceptible to hantavirus infection; a new aspect in hantavirus ecology

Hantaviruses are enveloped RNA viruses that belong to the family Bunyaviridae. They are the causative agents of hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Hantaviruses show a worldwide distribution with specific rodent species as natural hosts. It is known that rodents can transmit the virus via feces, urine, saliva, or bites to humans. Additionally, antibodies against different hantaviruses were also found in domestic animals, For example, Danes et al. documented hantavirus-specific IgG titers in 2% of examined cattle [Ceskoslov. Epidemiol. Mikrobiol. Imunol. 41 (1992) 15]. In order to clarify the possibility of a nonrodent and nonhuman hantavirus infection, the susceptibility of bovine aortic endothelial cells (BAEC) to Hantavirus serotype Puumala infection was investigated. The hantaviral nucleocapsid protein was detected in 95% of infected BAEC at the fourth cell culture passage 12 weeks after initial infection by immunofluorescence assay (IFA). The presence of Puumala virus (PUU) nucleocapsid protein and the viral glycoproteins G1 and G2 in infected cells were additionally confirmed by Western blot analysis. The viral RNA genome was identified in infected BAEC cultures and in cell-free culture medium at the fourth passage by reverse transcription polymerase chain reaction (RT-PCR), verified by cDNA nucleotide sequence analysis, showing a 98-100% homology to the input virus. The infected BAEC cultures were shown to express alpha(V)beta(3)-integrin surface receptors that are known to mediate virus entry in human cells and revealed no major cytopathic effects (CPEs) as assayed by immunofluorescence staining of the cytoskeletal components actin and microtubules. In the present study, we documented for the first time that a nonrodent and nonhuman aortic endothelial cell culture of bovine origin (BAEC) can be efficiently infected with a hantavirus. This finding is of particular importance because it adds new aspects to questions dealing with host species barrier, viral reservoir, virus transmission, and ecology of hantaviruses.

Bovine aortic endothelial cells are susceptible to Hantaan virus infection

Hantavirus serotype Hantaan (HTN) is one of the causative agents of hemorrhagic fever with renal syndrome (HFRS, lethality up to 10%). The natural host of HTN is Apodemus agrarius. Recent studies have shown that domestic animals like cattle are sporadically seropositive for hantaviruses. In the present study, the susceptibility of bovine aortic endothelial cells (BAEC) expressing alpha(V)beta(3)-integrin to a HTN infection was investigated. Viral nucleocapsid protein and genomic RNA segments were detected in infected BAEC by indirect immunofluorescence assay, Western blot analysis, and reverse transcription-polymerase chain reaction (RT-PCR), respectively. The results of this study strongly support our previous observation on Puumala virus (PUU) that has been propagated efficiently in BAEC. These findings open a new window to contemplate the ecology of hantavirus infection and transmission route from animal to man.

Immune responses to Puumala virus infection and the pathogenesis of nephropathia epidemica

Puumala virus, causative agent of a mild form of hemorrhagic fever with renal syndrome, also known as nephropathia epidemica, induces long-lasting humoral and cellular immunity in patients. The virus itself is not cytopathic, and the immune responses to the virus may be involved in teh pathogenesis of the disease.

Bacillus anthracis lethal toxin induces TNF-alpha-independent hypoxia-mediated toxicity in mice

Bacillus anthracis lethal toxin (LT) is the major virulence factor of anthrax and reproduces most of the laboratory manifestations of the disease in animals. We studied LT toxicity in BALB/cJ and C57BL/6J mice. BALB/cJ mice became terminally ill earlier and with higher frequency than C57BL/6J mice. Timed histopathological analysis identified bone marrow, spleen, and liver as major affected organs in both mouse strains. LT induced extensive hypoxia. Crisis was due to extensive liver necrosis accompanied by pleural edema. There was no evidence of disseminated intravascular coagulation or renal dysfunction. Instead, analyses revealed hepatic dysfunction, hypoalbuminemia, and vascular/oxygenation insufficiency. Of 50 cytokines analyzed, BALB/cJ mice showed rapid but transitory increases in specific factors including KC, MCP-1/JE, IL-6, MIP-2, G-CSF, GM-CSF, eotaxin, FasL, and IL-1beta. No changes in TNF-alpha occurred. The C57BL/6J mice did not mount a similar cytokine response. These factors were not induced in vitro by LT treatment of toxin-sensitive macrophages. The evidence presented shows that LT kills mice through a TNF-alpha-independent, FasL-independent, noninflammatory mechanism that involves hypoxic tissue injury but does not require macrophage sensitivity to toxin.

Hantavirus infections in Spain: analysis of sera from the general population and from patients with pneumonia, renal disease and hepatitis

BACKGROUND

Hantaviruses are rodent borne viruses in the family Bunyaviridae that cause significant morbidity in large areas of Europe. There are only a few reports available on hantavirus infections from Spain. Although the results of these earlier studies indicated the presence of hantavirus infections, no confirmative or serotype-specific analyses have been performed.

OBJECTIVES

To investigate whether hantaviruses cause human infection/disease in Spain.

STUDY DESIGN

Ten thousand, four hundred and eighteen serum samples from the general population and 599 sera from 492 patients with potential hantavirus infections (renal disease, pneumonia or hepatitis) were initially screened by immunofluorescence assay (IFA) using Hantaan, Seoul and Puumala hantavirus antigens. Altogether 193 suspicious samples (165 from healthy people and 28 from patients) were selected for confirmation by quality-assured assays.

RESULTS AND CONCLUSIONS

Of the 165 pre-screened serum samples from healthy individuals, only five could be confirmed by IFA for hantavirus-reactive antibodies (using Dobrava, Saaremaa, Hantaan or Puumala virus antigens). In addition, one serum was found weakly positive for hantavirus-reactive IgG by ELISA using recombinant Saaremaa virus (SAAV) nucleocapsid (N) antigen, and subsequently confirmed by immunoblotting. Thus, the results indicated a low (0.06%) total antibody prevalence to hantaviruses in Spain. Of 28 pre-screened serum samples from hospitalized patients, eight reacted as positive or showed border-line reactivities for hantavirus-specific IgM by ELISA using recombinant Saaremaa and Puumala virus N antigens. The IFA/ELISA reactive/border-line samples were subsequently analyzed by a focus reduction neutralization test, which revealed low titers (1:80) against SAAV in two samples from a patient with hepatic disease. The nature of the hantavirus(es) potentially involved remain, however, unknown, since none of the positive samples showed neutralizing titers of the expected range to any of the known European hantaviruses.

Hantaviruses induce cytopathic effects and apoptosis in continuous human embryonic kidney cells

Hantaviruses are maintained in nature in persistently infected rodents and can also persistently infect cultured mammalian cells, causing little or no cytopathology. An unexpected outcome of this study was the observation of cytopathic effects (CPE) in the hantavirus-infected human embryonic kidney cell line HEK293. It was confirmed that hantaviruses induce apoptosis in HEK293 cells, although apoptosis appeared mostly in uninfected, bystander cells and rarely in infected HEK293 cells. Although studies by others suggest that the nucleocapsid protein of Puumala virus interacts with the Fas-mediated apoptosis enhancer Daxx at the gene expression level, it was determined that members of the TNF receptor superfamily did not contribute to the apoptosis observed in infected HEK293 cells. The observation of CPE in HEK293 cells might lead to a better understanding of the mechanisms of persistence and pathogenesis in hantavirus infections.

Genetic characterization of new Dobrava hantavirus isolate from Greece

The first complete genome sequence of Dobrava hantavirus isolated from yellow-necked mouse Apodemus flavicollis trapped in the northeastern Greece is described. The S, M, and L segments of the Greek isolate of Dobrava virus are 1673, 3635, and 6532 nucleotides (nt) long, respectively, and encode the nucleocapsid (N) protein of 429 amino acids (aa), glycoprotein precursor of 1135 aa, and the L protein of 2151 aa. N protein contains three cysteine residues conserved in all known hantaviruses, as well as structural domains responsible for the RNA binding and presumable interaction with the apoptosis enhancer Daxx. All cysteine residues and glycosylation sites that are conserved among G1G2 sequences of all hantaviruses species were also found in the Greek isolate. The L protein contains all the polymerase motifs and structural domains found in other hantavirus polymerases. Comparison of the Greek isolate of Dobrava virus with other hantaviruses showed the highest level of sequence homology with Dobrava virus isolate from Slovenia. Other hantaviruses carried by Murinae rodents (Saaremaa, Hantaan, Seoul, and Thailand viruses) were more divergent and hantaviruses carried by Arvicolinae or Sigmodontinae rodents showed the highest genetic diversity with the Greek isolate of Dobrava. The results of phylogenetic analyses confirmed these observations and showed a monophily of all the Dobrava virus strains that, in turn, shared more ancient ancestors first with Saaremaa virus and then with other Murinae-borne hantaviruses.

Rodent host specificity of European hantaviruses: evidence of Puumala virus interspecific spillover

In order to investigate rodent host specificity of European hantaviruses, experimental infection of colonized and wild-trapped rodents was performed. In addition to the natural rodent reservoir, Clethrionomys glareolus, Puumala hantavirus (PUUV) could infect colonized Microtus agrestis and Lemmus sibiricus, but not Syrian hamsters or Balb/C mice. Neither C. glareolus, nor M. agrestis, could be readily infected by Tula hantavirus (TULV). Wild-trapped Apodemus flavicollis and A. agrarius, the natural reservoirs of Dobrava (DOBV) and Saaremaa (SAAV) hantaviruses, respectively, could both be infected by SAAV. NMRI mice could also be infected by SAAV, but with lower efficiency as compared to Apodemus mice. Balb/C and NMRI laboratory mice, but not C. glareolus, could be infected by DOBV. To our knowledge, this is the first time DOBV and SAAV have been shown to infect adult laboratory mice. Moreover, potential hantavirus spillover infections were investigated in wild-trapped rodents. In addition to the natural host C. glareolus, we also found M. arvalis and A. sylvaticus with a history of PUUV infection. We did not find any C. glareolus or A. sylvaticus infected with TULV, a hantavirus which is known to circulate in the same geographical regions of Belgium.

The in vitro and in vivo protective activity of monoclonal antibodies directed against Hantaan virus: potential application for immunotherapy and passive immunization

Hantaan virus (HTNV), a member of the genus Hantavirus, family Bunyaviridae, is an etiologic agent causing a serious human disease, hemorrhagic fever with renal syndrome (HFRS), with a mortality as high as 15% and is also a potential bioterrorism agent. It is urgently needed to develop anti-HTNV-neutralizing monoclonal antibodies (MAbs) for treatment and prevention of HTNV infection. In the present study, 18 murine MAbs directed against HTNV strain Chen were generated and characterized. Among these MAbs, 13 were directed against viral nucleocapsid protein (NP), four recognized the viral envelope glycoprotein G2 and one reacted with both NP and G2. Only those MAbs that recognize the epitopes on G2 were positive in hemagglutination inhibition (HI) test and had in vitro virus-neutralizing activity and in vivo protective activity against HTNV infection of susceptible mice. Since all the mice were protected by administration of the virus-neutralizing MAbs one day before and two days after HTNV challenge, these neutralizing MAbs are potentially useful for pre- and post-exposure prophylaxis and for immunotherapy of HTNV infection. Phase II clinical trials of these neutralizing MAbs for emergent treatment of patients with HTNV infection in early stages of HRFS are carried out in endemic areas in China.

Hantavirus infection of dendritic cells

Dendritic cells (DCs) play a pivotal role as antigen-presenting cells in the antiviral immune response. Here we show that Hantaan virus (HTNV), which belongs to the Bunyaviridae family (genus Hantavirus) and causes hemorrhagic fever with renal syndrome, productively infects human DCs in vitro. In the course of HTNV infection, DCs did not show any cytopathic effect and viral replication did not induce cell lysis or apoptosis. Furthermore, HTNV did not affect apoptosis-inducing signals that are important for the homeostatic control of mature DCs. In contrast to immunosuppressive viruses, e.g., human cytomegalovirus, HTNV activated immature DCs, resulting in upregulation of major histocompatibility complex (MHC), costimulatory, and adhesion molecules. Intriguingly, strong upregulation of MHC class I molecules and an increased intercellular cell adhesion molecule type 1 expression was also detected on HTNV-infected endothelial cells. In addition, antigen uptake by HTNV-infected DCs was reduced, another characteristic feature of DC maturation. Consistent with these findings, we observed that HTNV-infected DCs stimulated T cells as efficiently as did mature DCs. Finally, infection of DCs with HTNV induced the release of the proinflammatory cytokines tumor necrosis factor alpha and alpha interferon. Taken together, our findings indicate that hantavirus-infected DCs may significantly contribute to hantavirus-associated pathogenesis.

Hantaan virus infection causes an acute neurological disease that is fatal in adult laboratory mice

Hantaan virus, the etiological agent of Korean hemorrhagic fever, is transmitted to humans from persistently infected mice (Apodemus agrarius), which serve as the primary reservoir. Here we demonstrate that several strains of adult Mus musculus domesticus (C57BL/6, BALB/c, AKR/J, and SJL/J) were susceptible to Hantaan virus infection when infected intraperitoneally. First clinical signs were loss of weight, ruffled fur, and reduced activity, which were followed by neurological symptoms, such as paralyses and convulsions. Within 2 days of disease onset, the animals died of acute encephalitis. PCR analysis indicated a systemic infection with viral RNA present in all major organs. Immunohistochemical and in situ hybridization analyses of postmortem material detected viral antigen and RNA in the central nervous system (predominantly brain), liver, and spleen. In the central nervous system, viral antigen and RNA colocalized with perivascular infiltrations, the predominant pathological finding. To investigate the involvement of the interferon system in Hantaan virus pathogenesis, we infected alpha/beta interferon receptor knockout mice. These animals were more susceptible to Hantaan virus infection, indicating an important role of interferon-induced antiviral defense mechanisms in Hantaan virus pathogenesis. The present model may help to overcome shortcomings in the development of therapeutic and prophylactic measurements against hantavirus infections.

Viral agents as biological weapons and agents of bioterrorism

Multiple viral agents have been classified by the CDC as potential weapons of mass destruction or agents for biologic terrorism. Agents such as smallpox, viral hemorrhagic fever viruses, agents of viral encephalitis, and others are of concern because they are highly infectious and relatively easy to produce. Although dispersion might be difficult, the risk is magnified by the fact that large populations are susceptible to these agents and only limited treatment and vaccination strategies exist. Although the risk of large-scale bioterrorism using viral agents is small, public health programs and health care providers must be prepared for this potentially devastating impact on public health.

Hantavirus nucleocapsid protein interacts with the Fas-mediated apoptosis enhancer Daxx

Hantaviruses cause two severe diseases, haemorrhagic fever with renal syndrome in Eurasia and hantavirus pulmonary syndrome in the Americas. To understand more about the molecular mechanisms that lead to these diseases, the associations of Puumala virus nucleocapsid protein (PUUV-N) with cellular proteins were studied by yeast two-hybrid screening. Daxx, known as an apoptosis enhancer, was identified from a HeLa cDNA library and its interaction with PUUV-N was confirmed by GST pull-down assay, co-immunoprecipitation and co-localization studies. Furthermore, domains of interaction were mapped to the carboxyl-terminal region of 142 amino acids in Daxx and the carboxyl-terminal 57 residues in PUUV-N, respectively. In pepscan assays, the binding sites of Daxx to PUUV-N were mapped further to two lysine-rich regions, of which one overlaps the sequence of the predicted nuclear localization signal of Daxx. These data suggest a direct link between host cell machinery and a hantavirus structural component.

Generation of recombinant vaccinia viruses expressing Puumala virus proteins and use in isolating cytotoxic T cells specific for Puumala virus

Puumala (PUU) virus causes a form of hemorrhagic fever with renal syndrome (HFRS), called nephropathia epidemica (NE), in Europe. HFRS is characterized by an increased capillary permeability, which we hypothesize is caused by hyperactivation of the host immune system, especially cellular immune responses. To identify cytotoxic T lymphocytes (CTLs) specific for the PUU virus from NE patients, we have made recombinant vaccinia viruses expressing PUU virus proteins, the nucleocapsid (N) and two surface glycoproteins, G1 and G2. Recombinant vaccinia viruses carrying the N or the first half of the G2 cDNA under the control of a strong synthetic promoter were made. To express G1 and the second half of the G2 proteins, however, we needed to use a T7 expression system, where the T7 RNA polymerase is produced from another recombinant vaccinia virus co-infecting the same cells. These recombinant vaccinia viruses were used to detect and clone PUU virus-specific CTLs from the peripheral blood mononuclear cells of NE patients. An HLA-A24-restricted CTL line recognizing the G2 protein was isolated and its 9-mer epitope was determined.

Increased glomerular permeability in patients with nephropathia epidemica caused by Puumala hantavirus

BACKGROUND

Nephropathia epidemica (NE) is the Scandinavian type of haemorrhagic fever with renal syndrome. Usually heavy transient proteinuria is present at the onset of the disease.

METHODS

We investigated glomerular permeability in eight patients with acute NE and in eight healthy controls. Six patients were followed for 1 year. The glomerular filtration rate (GFR) was determined by inulin clearance and effective renal plasma flow (ERPF) by para-aminohippurate clearance.

RESULTS

GFR and ERPF were significantly reduced in NE patients during the acute phase compared with those in controls (P<0.001 and P<0.001, respectively). The filtration fraction (FF) was thus high, 0.37. The fractional clearances of albumin, IgG, and IgG(4) were markedly increased. As a sign of tubular dysfunction, increased urinary excretion of alpha(1)-microglobulin was observed in all patients. After 1 year, the GFR of the patients no longer differed from that of the controls. ERPF was lower and FF higher than those in controls (P=0.014 and P=0.009, respectively). The fractional clearances of albumin, IgG, and IgG(4) remained increased. The high-molecular fractional dextran clearances in the patients were significantly increased compared with controls during the acute phase. Computed analysis of glomerular membrane-pore structure showed that the "shunt-flow" was increased in the patients during the acute phase compared with the controls. There was a positive correlation between the FF and the shunt (r=0.768, P=0.026). In addition, fractional clearances of albumin and IgG correlated significantly with the shunt (r=0.810, P=0.015 and r=0.762, P=0.028, respectively).

CONCLUSIONS

Renal involvement in the acute phase of NE is characterized by a markedly decreased GFR and ERPF. Increased glomerular permeability is associated with impairment of both the size- and charge-selectivity properties of the glomerular filter.

Wild-type Puumala hantavirus infection induces cytokines, C-reactive protein, creatinine, and nitric oxide in cynomolgus macaques

Hantaviruses cause two severe human diseases: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Approximately 200,000 cases are reported annually, and there is to date no specific treatment available. A major obstacle in studying the medical aspects of HFRS and HPS has been the lack of an adequate animal model. Here we show that infection of cynomolgus macaques by wild-type Puumala hantavirus resulted in typical signs of HFRS including lethargy, anorexia, proteinuria, and/or hematuria, in addition to cytokine (interleukin 6 [IL-6], IL-10, and tumor necrosis factor alpha), C-reactive protein, creatinine, and nitric oxide responses. Viral RNA was detected in plasma from days 3 to 7 postinoculation until days 24 to 28 postinoculation, infectious virus was recovered, and the virus-specific immune responses (immunoglobulin M [IgM], IgG, and neutralizing antibodies) mimicked those seen in humans. The results indicated that the monkey model will provide a valuable tool for studies of pathogenesis, candidate vaccines, and antivirals for hantavirus disease.