Severity Biomarkers in Puumala Hantavirus Infection

Annually, over 10,000 cases of hemorrhagic fever with renal syndrome (HFRS) are diagnosed in Europe. Puumala hantavirus (PUUV) causes most of the European HFRS cases. PUUV causes usually a relatively mild disease, which is rarely fatal. However, the severity of the infection varies greatly, and factors affecting the severity are mostly unrevealed. Host genes are known to have an effect. The typical clinical features in PUUV infection include acute kidney injury, thrombocytopenia, and increased vascular permeability. The primary target of hantavirus is the endothelium of the vessels of different organs. Although PUUV does not cause direct cytopathology of the endothelial cells, remarkable changes in both the barrier function of the endothelium and the function of the infected endothelial cells occur. Host immune or inflammatory mechanisms are probably important in the development of the capillary leakage. Several immunoinflammatory biomarkers have been studied in the context of assessing the severity of HFRS caused by PUUV. Most of them are not used in clinical practice, but the increasing knowledge about the biomarkers has elucidated the pathogenesis of PUUV infection.     

Hantavirus Research in Finland: Highlights and Perspectives

Finland has the highest incidence of hantavirus infections globally, with a significant impact on public health. The large coverage of boreal forests and the cyclic dynamics of the dominant forest rodent species, the bank vole Myodes glareolus, explain most of this. We review the relationships between Puumala hantavirus (PUUV), its host rodent, and the hantavirus disease, nephropathia epidemica (NE), in Finland. We describe the history of NE and its diagnostic research in Finland, the seasonal and multiannual cyclic dynamics of PUUV in bank voles impacting human epidemiology, and we compare our northern epidemiological patterns with those in temperate Europe. The long survival of PUUV outside the host and the life-long shedding of PUUV by the bank voles are highlighted. In humans, the infection has unique features in pathobiology but rarely long-term consequences. NE is affected by specific host genetics and risk behavior (smoking), and certain biomarkers can predict the outcome. Unlike many other hantaviruses, PUUV causes a relatively mild disease and is rarely fatal. Reinfections do not exist. Antiviral therapy is complicated by the fact that when symptoms appear, the patient already has a generalized infection. Blocking vascular leakage measures counteracting pathobiology, offer a real therapeutic approach.     

The hantaviruses causing hemorrhagic fever with renal syndrome and pulmonary syndrome

The goal of this review is to provide basic information on hantaviruses as causative agents of Hemorrhagic Fever with Renal Syndrome (HFRS) and Hantavirus Pulmonary Syndrome (HPS), two zoonotic diseases widely distributed in Asia/Europe, and the American continent, respectively. Hantaviruses are rodent-borne and transmitted to humans by direct contact with infected rodents or their secretions (urine, feces and saliva). Both, HFRS and HPS share some clinical aspects, however, hemorrhage and renal failure are the hallmark of HFRS, while respiratory problems are distinctive signs and symptoms of patients with HPS. Studies on hantavirus infection in rodents from Mexico are included, some recomendations to prevent or avoid contact with rodents are mentioned, and some determinant ecologic factors of hantaviruses distribution and their natural rodents, are also included.     

The Association between Hantavirus Infection and Selenium Deficiency in Mainland China

Hemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses and transmitted by rodents is a significant public health problem in China, and occurs more frequently in selenium-deficient regions. To study the role of selenium concentration in HFRS incidence we used a multidisciplinary approach combining ecological analysis with preliminary experimental data. The incidence of HFRS in humans was about six times higher in severe selenium-deficient and double in moderate deficient areas compared to non-deficient areas. This association became statistically stronger after correction for other significant environment-related factors (low elevation, few grasslands, or an abundance of forests) and was independent of geographical scale by separate analyses for different climate regions. A case-control study of HFRS patients admitted to the hospital revealed increased activity and plasma levels of selenium binding proteins while selenium supplementation in vitro decreased viral replication in an endothelial cell model after infection with a low multiplicity of infection (MOI). Viral replication with a higher MOI was not affected by selenium supplementation. Our findings indicate that selenium deficiency may contribute to an increased prevalence of hantavirus infections in both humans and rodents. Future studies are needed to further examine the exact mechanism behind this observation before selenium supplementation in deficient areas could be implemented for HFRS prevention.     

Prevalence of Antibodies against Hantaviruses in Serum and Saliva of Adults Living or Working on Farms in Yorkshire,United Kingdom

Hantaviruses are an established cause of haemorrhagic fever with renal syndrome (HFRS) in Europe. Following a confirmed case of HFRS in the UK, in an individual residing on a farm in North Yorkshire and the Humber, a tidal estuary on the east coast of Northern England, and the subsequent isolation of a Seoul hantavirus from rats trapped on the patient’s farm, it was considered appropriate to further investigate the public health risk of this virus in the region. Of a total 119 individuals tested, nine (7.6%) were seropositive for hantavirus antibodies. Seven of the seropositive samples showed a stronger reaction to Seoul and Hantaan compared to other clinically relevant hantaviruses. Observation of rodents during the day, in particular mice, was associated with a reduced risk of seropositivity. In addition to one region known to be at risk following an acute case, five further potential risk areas have been identified. This study supports recently published evidence that hantaviruses are likely to be of public health interest in the region.     

Hormonal Defects Are Common during Puumala Hantavirus Infection and Associate with Disease Severity and Biomarkers of Altered Haemostasis

Central and peripheral hormone deficiencies have been documented during and after acute hantavirus infection. Thrombocytopenia and coagulation abnormalities are common findings in haemorrhagic fever with renal syndrome (HFRS). The associations between coagulation and hormonal abnormalities in HFRS have not been studied yet. Forty-two patients diagnosed with Puumala virus (PUUV) infection were examined during the acute phase and on a follow-up visit approximately one month later. Hormonal defects were common during acute PUUV infection. Overt (clinical) hypogonadism was identified in 80% of the men and approximately 20% of the patients had overt hypothyroidism. At the one-month follow-up visit, six patients had central hormone deficits. Acute peripheral hormone deficits associated with a more severe acute kidney injury (AKI), longer hospital stay and more severe thrombocytopenia. Half of the patients with bleeding symptoms had also peripheral hormonal deficiencies. Patients with free thyroxine levels below the reference range had higher D-dimer level than patients with normal thyroid function, but no thromboembolic events occurred. Acute phase hormonal abnormalities associate with severe disease and altered haemostasis in PUUV infection.     

Immunogenetic Factors Affecting Susceptibility of Humans and Rodents to Hantaviruses and the Clinical Course of Hantaviral Disease in Humans

We reviewed the associations of immunity-related genes with susceptibility of humans and rodents to hantaviruses, and with severity of hantaviral diseases in humans. Several class I and class II HLA haplotypes were linked with severe or benign hantavirus infections, and these haplotypes varied among localities and hantaviruses. The polymorphism of other immunity-related genes including the C4A gene and a high-producing genotype of TNF gene associated with severe PUUV infection. Additional genes that may contribute to disease or to PUUV infection severity include non-carriage of the interleukin-1 receptor antagonist (IL-1RA) allele 2 and IL-1β (-511) allele 2, polymorphisms of plasminogen activator inhibitor (PAI-1) and platelet GP1a. In addition, immunogenetic studies have been conducted to identify mechanisms that could be linked with the persistence/clearance of hantaviruses in reservoirs. Persistence was associated during experimental infections with an upregulation of anti-inflammatory responses. Using natural rodent population samples, polymorphisms and/or expression levels of several genes have been analyzed. These genes were selected based on the literature of rodent or human/hantavirus interactions (some Mhc class II genes, Tnf promoter, and genes encoding the proteins TLR4, TLR7, Mx2 and β3 integrin). The comparison of genetic differentiation estimated between bank vole populations sampled over Europe, at neutral and candidate genes, has allowed to evidence signatures of selection for Tnf, Mx2 and the Drb Mhc class II genes. Altogether, these results corroborated the hypothesis of an evolution of tolerance strategies in rodents. We finally discuss the importance of these results from the medical and epidemiological perspectives.     

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.     

肾综合征出血热发病机制的研究进展

肾综合征出血热(hemorrhagic fever with renal syndrome, HFRS)是由汉坦病毒感染引起的以发热、休克、出血和肾脏损害为主要特征的急性自然疫源性疾病。汉坦病毒主要感染人血管内皮细胞,引起小血管和毛细血管广泛损伤。血管通透性增加是HFRS临床表现的病理基础。国内外学者尽管在汉坦病毒致病机制方面开展了诸多研究,如病毒诱导的免疫病理反应、宿主遗传与细胞凋亡、血小板减少与功能障碍、血管内皮损伤等,但HFRS发病机制仍未完全阐明,也无特效治疗药物,深入探讨汉坦病毒致病的分子机制,寻找有效治疗药物仍是汉坦病毒/HFRS领域的研究热点。本文结合近年来国内外相关研究,阐述HFRS发病机制的研究进展。     

肾综合征出血热抗病毒治疗及疫苗研发进展

肾综合征出血热(hemorrhagic fever with renal syndrome, HFRS)是由汉坦病毒感染引起的一种自然疫源性疾病,在世界范围内广泛流行,我国一直是流行高发区,患者占所有HFRS患者一半以上,其主要临床特征为发热、出血、低血压休克和肾脏损害,严重危害人类健康。尽管抗病毒治疗和疫苗免疫接种可以防治汉坦病毒感染,但目前尚无特效抗病毒药物。近年来,随着医学科技进步,汉坦病毒的抗病毒治疗和疫苗研发有了新的进展。本文基于近年体内外研究及临床试验结果,对HFRS抗病毒治疗和疫苗研发进展作一综述。     

肾综合征出血热流行过程及其影响因素研究进展

肾综合征出血热（hemorrhagic fever with renal syndrome, HFRS）是由汉坦病毒（hantavirus）感染引起的一种乙类传染病,可引发急性肾损伤,病死率较高。汉坦病毒型别与选择性宿主转换和地区适应密切相关,并由此不断以基因重组等方式进化,不同型别汉坦病毒所致疾病严重程度不同。全球环境变化及宿主动物习性改变加速了汉坦病毒基因组变异;同时,我国大规模土地改造、基础设施建设也使人群与病毒宿主和疾病传播媒介的接触机会增加,一定程度上增大了人群患病风险。本文综述了肾综合征出血热流行过程的主要特征及其相关影响因素,为有效防控该疾病的发生和流行提供参考依据。     

Detection of Human Hantavirus Infections in Lithuania

Abstract Background: In Europe certain hantaviruses are known to cause hemorrhagic fever with renal syndrome of different severity. The objective of the present investigation was to study the presence of hantavirus infections in Lithuania. Material and Methods: Two different serum panels from cancer patients (n = 438) and blood donors (n = 299) from Lithuania were tested by monoclonal antibody capture IgG ELISA using yeast-expressed recombinant nucleocapsid (rN) proteins of Puumala virus (PUUV), Hantaan virus (HTNV) and Dobrava virus (DOBV). The reactivity of ELISA-positive sera was proven in Western blot tests using various hantavirus rN proteins. Selected serum samples were further analyzed by focus reduction neutralization assays. Results: In the IgG ELISA 39 sera from the cancer patients and four sera from blood donors were found to be reactive with at least one of the rN proteins. By immunoblot using the three yeast-expressed rN proteins, the ELISA reactivity of 36 of 39 and two of four serum samples from cancer patients and blood donors, respectively, was confirmed; this corresponds to a seroprevalence of 8.2% and 0.7%, respectively. In ELISA, the majority of the samples reacted exclusively with rN proteins of HTNV and DOBV (31 of 36 and one of two in the two groups). In the group of sera selected for serotyping by focus reduction neutralization assay, this dominance was confirmed by the identification of eight DOBV but only four PUUV infections. No infection by HTNV or another hantavirus besides DOBV and PUUV was verified. Anti-hantavirus-positive human sera were detected in all seven investigated counties of Lithuania. Conclusion: In Lithuania at least two hantaviruses, DOBV and PUUV, circulate and cause human infections. Additional investigations are needed to study the seroprevalence more precisely and to search for clinical cases of hantavirus infections.     

Pathophysiology of hantavirus pulmonary syndrome in rhesus macaques

The pathophysiology of hantavirus pulmonary syndrome (HPS) remains unclear because of a lack of surrogate disease models with which to perform pathogenesis studies. Nonhuman primates (NHP) are considered the gold standard model for studying the underlying immune activation/suppression associated with immunopathogenic viruses such as hantaviruses; however, to date an NHP model for HPS has not been described. Here we show that rhesus macaques infected with Sin Nombre virus (SNV), the primary etiological agent of HPS in North America, propagated in deer mice develop HPS, which is characterized by thrombocytopenia, leukocytosis, and rapid onset of respiratory distress caused by severe interstitial pneumonia. Despite establishing a systemic infection, SNV differentially activated host responses exclusively in the pulmonary endothelium, potentially the mechanism leading to acute severe respiratory distress. This study presents a unique chronological characterization of SNV infection and provides mechanistic data into the pathophysiology of HPS in a closely related surrogate animal model. We anticipate this model will advance our understanding of HPS pathogenesis and will greatly facilitate research toward the development of effective therapeutics and vaccines against hantaviral diseases.Hantavirus pulmonary syndrome (HPS), otherwise referred to as “hantavirus cardiopulmonary syndrome,” is an acute respiratory disorder that was described initially in 1993 during an outbreak in the Four Corners region of the United States (1). The etiological agent was identified quickly as a novel hantavirus and subsequently was named “Sin Nombre virus” (SNV) (2). Over the last two decades several species of hantaviruses have been documented throughout the Americas, many of which are etiological agents of HPS (3). More than 2,000 cases of HPS have been reported with mortality rates ranging from 30 to 50% (4). Although HPS often occurs as isolated and sporadic incidents, outbreaks have been documented, most recently in Yosemite National Park, which resulted in nine cases of HPS with three deaths and an international public health response (5–8). The Yosemite outbreak highlights the importance of developing effective medical counter measures against HPS; none are currently available.The genus Hantavirus (family Bunyaviridae) comprises a unique group of viruses that are maintained in nature and transmitted to humans from specific small-mammal reservoirs (4). In addition to HPS, pathogenic hantaviruses also cause hemorrhagic fever with renal syndrome (HFRS), which can result from infection with Old World hantaviruses. Hantavirus infections are associated with vascular leakage that is believed to be primarily immune mediated, although the target organs for each syndrome differ; HPS primarily affects the lung, whereas HFRS targets the kidneys. Our understanding of the pathogenesis of these viruses is limited, in large part because of a lack of animal models (4, 9, 10). Currently the only model of lethal hantavirus disease is the Syrian hamster, which, after infection with Andes virus, develops severe disease that faithfully recapitulates the cardiopulmonary phase of HPS in humans (11–13). Nonhuman primates (NHPs) often are viewed as the gold-standard model for the study of emerging viral pathogens, especially those that are immunopathogenic, because these animals are believed to recapitulate most accurately the underlying deleterious host immune responses associated with disease progression in humans. To date, attempts at developing an NHP model for HPS or HFRS have largely been unsuccessful (14, 15). The lone NHP model for hantavirus infection is a mild HFRS-like disease that follows infection of cynomolgus macaques with Puumala virus propagated in bank voles (16). Cynomolgus monkeys develop mild signs of disease including lethargy, proteinuria, and microhematuria, indicative of acute nephropathy (17, 18). Here we have developed an NHP model for HPS based on infection of rhesus macaques with SNV passaged in deer mice. This model provided the first, to our knowledge, in-depth pathogenesis study in the nearest surrogate host and identified virus replication, systemic hematologic abnormalities, and lung-specific proinflammatory responses as hallmarks of HPS pathogenesis. This model will advance the development of intervention strategies combating infections with HPS-causing hantaviruses.     

汉坦病毒激发人胃上皮细胞病变和凋亡

目的证实人胃粘膜上皮细胞是否为汉坦病毒属(HV)汉滩病毒型(HTN)和汉城病毒型(SEO)病毒的靶细胞,病毒对其是否有致细胞病变效应(CPE)和促凋亡作用。方法建立人胃上皮细胞(HGEC)离体培养;用HVN8、76118、Z37、Seoul8039株感染HGEC,观察细胞CPE,用直接免疫荧光法(IFA)检测病毒感染细胞和感染灶;用AnnexinV FITCkit观察HV的致HGEC凋亡和坏死作用。结果HTNV和SEOV可以感染离体培养的HGEC,形成感染灶并出现CPE;与模拟感染细胞相比,N8、76118、Z37、Seoul8039株感染的HGEC凋亡和坏死细胞比例明显增高,HTNV较SEOV促凋亡和坏死作用更强。结论HGEC可作为HTNV和SEOV感染的靶细胞,致CPE并促进细胞凋亡和坏死,在急性肾综合征出血热病人胃粘膜损害机制中起重要作用。     

Central Nervous System and Ocular Manifestations in Puumala Hantavirus Infection

Puumala hantavirus (PUUV), carried and spread by the bank vole (Myodes glareolus), causes a mild form of hemorrhagic fever with renal syndrome (HFRS) called nephropathia epidemica (NE). Acute high fever, acute kidney injury (AKI), thrombocytopenia, and hematuria are typical features of this syndrome. In addition, headache, blurred vision, insomnia, vertigo, and nausea are commonly associated with the disease. This review explores the mechanisms and presentations of ocular and central nervous system involvement in acute NE.     

Recent Evidence of Hantavirus Circulation in the American Tropic

Hantaan virus was discovered in Korea during the 1970s while other similar viruses were later reported in Asia and Europe. There was no information about hantavirus human infection in the Americas until 1993 when an outbreak was described in the United States. This event promoted new studies to find hantaviruses in the Americas. At first, many studies were conducted in Brazil, Argentina, Chile, Uruguay and Paraguay, while other Latin American countries began to report the presence of these agents towards the end of the 20th century. More than 30 hantaviruses have been reported in the Western Hemisphere with more frequent cases registered in the southern cone (Argentina, Chile, Uruguay, Paraguay, Bolivia and Brazil). However there was an important outbreak in 2000 in Panama and some rare events have been described in Peru, Venezuela and French Guiana. Since hantaviruses have only recently emerged as a potential threat in the tropical zones of the Americas, this review compiles recent hantavirus reports in Central America, the Caribbean islands and the northern region of South America. These studies have generated the discovery of new hantaviruses and could help to anticipate the presentation of possible future outbreaks in the region.     

Hantaviruses in the americas and their role as emerging pathogens

The continued emergence and re-emergence of pathogens represent an ongoing, sometimes major, threat to populations. Hantaviruses (family Bunyaviridae) and their associated human diseases were considered to be confined to Eurasia, but the occurrence of an outbreak in 1993-94 in the southwestern United States led to a great increase in their study among virologists worldwide. Well over 40 hantaviral genotypes have been described, the large majority since 1993, and nearly half of them pathogenic for humans. Hantaviruses cause persistent infections in their reservoir hosts, and in the Americas, human disease is manifest as a cardiopulmonary compromise, hantavirus cardiopulmonary syndrome (HCPS), with case-fatality ratios, for the most common viral serotypes, between 30% and 40%. Habitat disturbance and larger-scale ecological disturbances, perhaps including climate change, are among the factors that may have increased the human caseload of HCPS between 1993 and the present. We consider here the features that influence the structure of host population dynamics that may lead to viral outbreaks, as well as the macromolecular determinants of hantaviruses that have been regarded as having potential contribution to pathogenicity.     

High prevalence of hantavirus infection in a group of Chinese patients with acute hepatitis of unknown aetiology

In southwestern China, small but substantial numbers of patients with acute hepatitis were found without known hepatropic viral infections (hepatitisA, B, C, D or E, cytomegalovirus, Epstein–Barr virus) and were receiving no hepatotoxic drugs. Prevalence of antibodies, both neutralizing and specific immunoglobulin (Ig)M and IgG, to Hantaan virus were evaluated in a cohort of 136 such patients: 83 were of unknown aetiology, 53 had known viral hepatitis and 59 healthy subjects acted as controls. The results showed that the incidence of neutralizing antibody to Hantaan virus in acute hepatitis patients with non-hepatitisA–E virus infections (13 of 83) was significantly higher than in those with A–E infections (0 of 53, P <0.01). Furthermore, the incidence of specific IgM antibody to Hantaan virus in acute hepatitis patients with non-hepatitisA–E virus infections (6 of 83) was significantly higher than in those with A–E infections (0 of 53, P <0.05) and in healthy subjects (0 of 59, P <0.05). These findings suggest that Hantaan virus may be an important agent, contributing, at least in southwestern China, to a significant number of the cases of acute hepatitis of unknown aetiology. This hantavirus infection resulted in an acute hepatitis, differing from the typical diseases: haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS).     

Hantavirus Immunology of Rodent Reservoirs: Current Status and Future Directions

Hantaviruses are hosted by rodents, insectivores and bats. Several rodent-borne hantaviruses cause two diseases that share many features in humans, hemorrhagic fever with renal syndrome in Eurasia or hantavirus cardiopulmonary syndrome in the Americas. It is thought that the immune response plays a significant contributory role in these diseases. However, in reservoir hosts that have been closely examined, little or no pathology occurs and infection is persistent despite evidence of adaptive immune responses. Because most hantavirus reservoirs are not model organisms, it is difficult to conduct meaningful experiments that might shed light on how the viruses evade sterilizing immune responses and why immunopathology does not occur. Despite these limitations, recent advances in instrumentation and bioinformatics will have a dramatic impact on understanding reservoir host responses to hantaviruses by employing a systems biology approach to identify important pathways that mediate virus/reservoir relationships.