Diagnostic rapid tests for acute hantavirus infections: specific tests for Hantaan, Dobrava and Puumala viruses versus a hantavirus combination test

Comparison of simulation and predictive efficacy for hemorrhagic fever with renal syndrome incidence in mainland China based on five time series models

Background

Hemorrhagic fever with renal syndrome (HFRS) is a zoonotic infectious disease commonly found in Asia and Europe, characterized by fever, hemorrhage, shock, and renal failure. China is the most severely affected region, necessitating an analysis of the temporal incidence patterns in the country.

Methods

We employed Autoregressive Integrated Moving Average (ARIMA), Long Short-Term Memory (LSTM), Convolutional Neural Network (CNN), Nonlinear AutoRegressive with eXogenous inputs (NARX), and a hybrid CNN-LSTM model to model and forecast time series data spanning from January 2009 to November 2023 in the mainland China. By comparing the simulated performance of these models on training and testing sets, we determined the most suitable model.

Results

Overall, the CNN-LSTM model demonstrated optimal fitting performance (with Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE), and Mean Absolute Error (MAE) of 93.77/270.66, 7.59%/38.96%, and 64.37/189.73 for the training and testing sets, respectively, lower than those of individual CNN or LSTM models).

Conclusion

The hybrid CNN-LSTM model seamlessly integrates CNN's data feature extraction and LSTM's recurrent prediction capabilities, rendering it theoretically applicable for simulating diverse distributed time series data. We recommend that the CNN-LSTM model be considered as a valuable time series analysis tool for disease prediction by policy-makers.

Hantavirus in humans: a review of clinical aspects and management

Hantavirus infections are part of the broad group of viral haemorrhagic fevers. They are also recognised as a distinct model of an emergent zoonotic infection with a global distribution. Many factors influence their epidemiology and transmission, such as climate, environment, social development, ecology of rodent hosts, and human behaviour in endemic regions. Transmission to humans occurs by exposure to infected rodents in endemic areas; however, Andes hantavirus is unique in that it can be transmitted from person to person. As hantaviruses target endothelial cells, they can affect diverse organ systems; increased vascular permeability is central to pathogenesis. The main clinical syndromes associated with hantaviruses are haemorrhagic fever with renal syndrome (HFRS), which is endemic in Europe and Asia, and hantavirus cardiopulmonary syndrome (HCPS), which is endemic in the Americas. HCPS and HFRS are separate clinical entities, but they share several features and have many overlapping symptoms, signs, and pathogenic alterations. For HCPS in particular, clinical outcomes are highly associated with early clinical suspicion, access to rapid diagnostic testing or algorithms for presumptive diagnosis, and prompt transfer to a facility with critical care units. No specific effective antiviral treatment is available.

Abdominal CT findings in Puumala hantavirus-infected patients

BACKGROUND

Previous clinical studies have reported abdominal findings on ultrasonography or MRI in Puumala hantavirus-infected patients.

PURPOSE

To determine if abdominal computed tomography (CT) can lead to a diagnosis of Puumala virus infection in the presence of a suggestive clinical picture.

MATERIAL AND METHODS

CT findings were studied retrospectively in 30 patients who presented to the emergency department of two (Belgian) hospitals with serologically confirmed Puumala hantavirus infection.

RESULTS

The most frequent finding was perirenal fascial thickening (90%), followed by perirenal fat stranding (87%). Retroperitoneal fat stranding was found in 19 patients (64%) in the perivesical spaces along the fascia of the external iliac vessels with or without involvement of the presacral fat. Half of the patients had pelvic ascites, and pleural fluid was found in 7 of them. The right and left mean pole-to-pole kidney's lengths were respectively 125.7 mm and 127.8 mm in 28 patients.

CONCLUSION

Retroperitoneal fat stranding, perirenal fascial thickening and/or perirenal fat stranding were found in most patients with acute Puumala virus infection who have undergone CT. Although nonspecific, these findings may help to suggest Puumala hantavirus infection in the right clinical settings.

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.

Comparison of indirect immunofluorescence and western blot method in the diagnosis of hantavirus infections

BACKGROUND

Serologic cross-reactivity between hantaviruses often complicates the interpretation of the results.

AIM

To analyze the diagnostic value of indirect immunofluorescence assay (IFA) and western blot (WB) in the diagnosis of hantavirus infections.

METHODS

One hundred eighty-eight serum samples from Puumala (PUUV) and Dobrava (DOBV) orthohantavirus infected patients were analyzed. Serology was performed using commercial tests (Euroimmun, Lübeck, Germany).

RESULTS

Using IFA, 49.5% of acute-phase samples showed a monotypic response to PUUV, while 50.5% cross-reacted with other hantaviruses. The overall cross-reactivity was higher for immunoglobulin G (IgG) (50.0%) than for immunoglobulin M (IgM) (25.5%). PUUV IgM/IgG antibodies showed low/moderate reactivity with orthohantaviruses Hantaan (12.3%/31.5%), Seoul (7.5%/17.8%), DOBV (5.4%/ 28.1%), and Saaremaa (4.8%/15.7%). Both DOBV IgM and IgG antibodies were broadly reactive with Hantaan (76.2%/95.2%), Saaremaa (80.9%/83.3%), and Seoul (78.6%/85.7%) and moderate with PUUV (28.5%/38.1%). Using a WB, serotyping was successful in most cross-reactive samples (89.5%).

CONCLUSION

The presented results indicate that WB is more specific than IFA in the diagnosis of hantavirus infections, confirming serotype in most IFA cross-reactive samples.

Amplicon-Based, Next-Generation Sequencing Approaches to Characterize Single Nucleotide Polymorphisms of Orthohantavirus Species

Whole-genome sequencing (WGS) of viruses from patient or environmental samples can provide tremendous insight into the epidemiology, drug resistance or evolution of a virus. However, we face two common hurdles in obtaining robust sequence information; the low copy number of viral genomes in specimens and the error introduced by WGS techniques. To optimize detection and minimize error in WGS of hantaviruses, we tested four amplification approaches and different amplicon pooling methods for library preparation and examined these preparations using two sequencing platforms, Illumina MiSeq and Oxford Nanopore Technologies MinION. First, we tested and optimized primers used for whole segment PCR or one kilobase amplicon amplification for even coverage using RNA isolated from the supernatant of virus-infected cells. Once optimized we assessed two sources of total RNA, virus-infected cells and supernatant from the virus-infected cells, with four variations of primer pooling for amplicons, and six different amplification approaches. We show that 99-100% genome coverage was obtained using a one-step RT-PCR reaction with one forward and reverse primer. Using a two-step RT-PCR with three distinct tiling approaches for the three genomic segments (vRNAs), we optimized primer pooling approaches for PCR amplification to achieve a greater number of aligned reads, average depth of genome, and genome coverage. The single nucleotide polymorphisms identified from MiSeq and MinION sequencing suggested intrinsic mutation frequencies of ~10-5-10-7 per genome and 10-4-10-5 per genome, respectively. We noted no difference in the coverage or accuracy when comparing WGS results with amplicons amplified from RNA extracted from infected cells or supernatant of these infected cells. Our results show that high-throughput diagnostics requiring the identification of hantavirus species or strains can be performed using MiSeq or MinION using a one-step approach. However, the two-step MiSeq approach outperformed the MinION in coverage depth and accuracy, and hence would be superior for assessment of genomes for epidemiology or evolutionary questions using the methods developed herein.

Puumala hantavirus: an imaging review

Puumala virus (PUUV) is the most common hantavirus in Europe. It is known to cause nephropathia epidemica, which is considered a mild type of hemorrhagic fever with renal syndrome. However, it does not only involve the kidneys and is rarely accompanied by symptomatic hemorrhage. We review the imaging abnormalities caused by PUUV infection, from head to pelvis, emphasizing the broad spectrum of possible findings and bringing further support to a previously suggested denomination "Hantavirus disease" that would encompass all clinical manifestations. Although non-specific, knowledge of radiological appearances is useful to support clinically suspected PUUV infection, before confirmation by serology.

Identification and validation of specific B-cell epitopes of hantaviruses associated to hemorrhagic fever and renal syndrome

Background

Orthohantavirus infection is a neglected global health problem affecting approximately 200,000 people/year, spread by rodent hosts and associated to fatal human diseases, such as hemorrhagic fever with renal syndrome (HFRS) and orthohantavirus cardiopulmonary syndrome (HCPS). Circulation of HFRS-associated orthohantaviruses, such as Seoul, Gou, Amur, Dobrava and Hantaan, are supposed to be restricted to Eurasian countries even though their hosts can be a worldwide distribution. Few confirmed HFRS orthohantavirus infections in humans have been reported in American countries, but due to lower medical awareness of the symptoms of this zoonosis, it could be associated to viral underreporting or to misdiagnosis with several tropical hemorrhagic diseases. Serological evidence of orthohantavirus infections, using enzyme-linked immunosorbent assay for the presence of immunoglobulin M and G against recombinant nucleoprotein protein, remains as an essential assay for viral surveillance. In this study, we aimed to identify in silico immunogenic B-cell linear epitopes present on orthohantavirus nucleoprotein that are exclusive to HFRS-related species.

Methodology/Principal findings

In silico analysis were performed using Seoul orthohantavirus nucleoprotein (SHNP) sequence as a model. Linear B-cell-epitopes on SHNP and its immunogenicity were predicted by BepiPred-2.0 and Vaxijen algorithms, respectively. The conservancy of predicted epitopes was compared with the most clinically relevant HFRS or HCPS-associated orthohantavirus, aiming to identify specific sequences from HFRS-orthohantavirus. Peptide validation was carried out by ELISA using Balb/c mice sera immunized with purified recombinant rSHNP. Peptides cross-reactivity against HCPS orthohantavirus were evaluated using immunized sera from mice injected with recombinant Juquitiba orthohantavirus nucleoprotein (rJHNP).

Conclusion/Significance

In silico analysis revealed nine potential immunogenic linear B-cell epitopes from SHNP; among them, SHNP_(G72-D110) and SHNP_(P251-D264) showed a high degree of sequence conservation among HFRS-related orthohantavirus and were experimentally validated against rSHNP-IMS and negatively validated against rJHNP-IMS. Taken together, we identified and validated two potential antigenic B-cell epitopes on SHNP, which were conserved among HFRS-associated orthohantavirus and could be applied to the development of novel immunodiagnostic tools for orthohantavirus surveillance.

Orthohantaviruses are the etiological agents of serious rodent-borne neglected human diseases named as hemorrhagic fever with renal syndrome (HFRS) and orthohantavirus cardiopulmonary syndrome (HCPS). These distinct clinical manifestations of disease are related to specific orthohantavirus species and it is believed that HFRS-associated orthohantavirus mainly circulate into Old World (Asia and Europe) whereas HCPS-associated orthohantaviruses are predominant into New World countries (Americas). However, since Seoul orthohantavirus, associated with HFRS, was isolated in America and its natural host (Rattus norvegicus) are widely distributed around the world, it raised the question if the viral underreporting is associated to lower medical awareness of the symptoms or if it is associated to misdiagnosis with other tropical hemorrhagic diseases (leptospirosis, yellow fever). In this context, considering that the HFRS are clinically indistinguishable from order hemorrhagic diseases, and that serological tests are predominantly based on serology tests against nucleoprotein, a highly conserved protein among different orthohantavirus, we hypothesize that current available tests do not detect all HFRS-associated orthohantavirus. In this sense; we aimed to identify B-cell linear epitopes exclusively conserved on HFRS-associated orthohantavirus nucleoprotein, using a combination of in silico and experimental approaches, to identify targets that could be applied in the development of novel immunodiagnostic tools able to identify different HFRS orthohantavirus species.

Cytotoxic Lesion of the Corpus Callosum Caused by Puumala Hantavirus Infection

We report the case of a 45-year-old male referred to our hospital with fever, asthenia, visual disturbances and increasing headaches. Diffusion-weighted imaging of the brain showed high signal intensity in the splenium of corpus callosum with low apparent diffusion coefficient values. Diagnosis of cytotoxic lesion of corpus callosum was made with Puumala Hantavirus infection serologically confirmed and should not be mistaken for ischemia. Patient was discharged 8 days after admission and imaging findings had resolved 3 weeks later.

Development and evaluation of a bioinformatics approach for designing molecular assays for viral detection

BACKGROUND

Viruses belonging to the Flaviviridae and Bunyaviridae families show considerable genetic diversity. However, this diversity is not necessarily taken into account when developing diagnostic assays, which are often based on the pairwise alignment of a limited number of sequences. Our objective was to develop and evaluate a bioinformatics workflow addressing two recurrent issues of molecular assay design: (i) the high intraspecies genetic diversity in viruses and (ii) the potential for cross-reactivity with close relatives.

METHODOLOGY

The workflow developed herein was based on two consecutive BLASTn steps; the first was utilized to select highly conserved regions among the viral taxon of interest, and the second was employed to assess the degree of similarity of these highly-conserved regions to close relatives. Subsequently, the workflow was tested on a set of eight viral species, including various strains from the Flaviviridae and Bunyaviridae families.

PRINCIPAL FINDINGS

The genetic diversity ranges from as low as 0.45% variable sites over the complete genome of the Japanese encephalitis virus to more than 16% of variable sites on segment L of the Crimean-Congo hemorrhagic fever virus. Our proposed bioinformatics workflow allowed the selection-based on computing scores-of the best target for a diagnostic molecular assay for the eight viral species investigated.

CONCLUSIONS/SIGNIFICANCE

Our bioinformatics workflow allowed rapid selection of highly conserved and specific genomic fragments among the investigated viruses, while considering up to several hundred complete genomic sequences. The pertinence of this workflow will increase in parallel to the number of sequences made publicly available. We hypothesize that our workflow might be utilized to select diagnostic molecular markers for higher organisms with more complex genomes, provided the sequences are made available.

Kidney disease in Puumala hantavirus infection

Acute kidney injury (AKI) remains a predominant clinical expression of nephropathia epidemica (NE). Its pathogenesis is not yet fully understood. Here, we describe the tissue injury comprehensively and present new data aimed to characterize the injury and explain its pathophysiology. When compared to tubulointerstitial nephritis of a wide variety of other aetiologies, a high degree of proteinuria is a distinguished trait of NE, a finding that is also helpful in the clinical suspicion of the disease. Recently, novel biomarkers for the prediction of severe AKI, including neutrophil gelatinase-associated lipocalin (NGAL), have been identified and ultrastructural tissue changes have been more accurately described. A role for soluble urokinase-type plasminogen activator (suPAR) in the pathogenesis of NE has been suggested, and data on gene polymorphisms, in relation to the severity of AKI have been presented. Smoking is a risk factor for NE and smoking is also associated with aggravated AKI in NE. Although no specific treatment is in sight, recent case reports concerning therapy directed against vascular permeability and vasodilation are of interest. In fact, future work trying to explain the pathophysiology of AKI might need concentrated efforts towards the mechanisms of increased vascular permeability and vasodilatation, which irrespective of organ manifestation, are two major determinants of NE.

Proteomic-based biomarker discovery for development of next generation diagnostics

In the post-genome age, proteomics is receiving significant attention because they provide an invaluable source of biological structures and functions at the protein level. The search for disease-specific biomarkers for diagnostic and/or therapeutic applications is one of the areas that proteomics is having a significant impact. Thus, the identification of a "good" biomarker enables a more accurate early diagnosis and prognosis of disease. Rapid advancements in mass spectrometry (MS) instrumentation, liquid chromatography MS (LCMS), protein microarray technology, and other protein profiling methodologies have a substantial expansion of our toolbox to identify disease-specific protein and peptide biomarkers. This review covers a selection of widely used proteomic technologies for biomarker discovery. In addition, we describe the most commonly used approaches for diagnosis based on proteomic biomarkers and further discuss trends and critical challenges during development of cost-effective rapid diagnostic tests and microfluidic diagnostic systems based on proteomic biomarkers.

Hantavirus infections

Over the past few decades understanding and recognition of hantavirus infection has greatly improved worldwide, but both the amplitude and the magnitude of hantavirus outbreaks have been increasing. Several novel hantaviruses with unknown pathogenic potential have been identified in a variety of insectivore hosts. With the new hosts, new geographical distributions of hantaviruses have also been discovered and several new species were found in Africa. Hantavirus infection in humans can result in two clinical syndromes: haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS) caused by Old World and New World hantaviruses, respectively. The clinical presentation of HFRS varies from subclinical, mild, and moderate to severe, depending in part on the causative agent of the disease. In general, HFRS caused by Hantaan virus, Amur virus and Dobrava virus are more severe with mortality rates from 5 to 15%, whereas Seoul virus causes moderate and Puumala virus and Saaremaa virus cause mild forms of disease with mortality rates <1%. The central phenomena behind the pathogenesis of both HFRS and HCPS are increased vascular permeability and acute thrombocytopenia. The pathogenesis is likely to be a complex multifactorial process that includes contributions from immune responses, platelet dysfunction and the deregulation of endothelial cell barrier functions. Also a genetic predisposition, related to HLA type, seems to be important for the severity of the disease. As there is no effective treatment or vaccine approved for use in the USA and Europe, public awareness and precautionary measures are the only ways to minimize the risk of hantavirus disease.

Lateral flow test using Echinococcus granulosus native antigen B and comparison of IgG and IgG4 dipsticks for detection of human cystic echinococcosis

Cystic echinococcosis (CE) caused by infection with Echinococcus granulosus is of major concern for humans in many parts of the world. Antigen B was prepared from E. granulosus hydatid fluid, and Western blots confirmed eight batches showing a band corresponding to the 8-/12-kDa subunit with positive serum and no low-molecular mass band (< 15 kDa) with negative serum. The batches were pooled and used to prepare lateral flow immunoglobulin G4 (IgG4) and IgG dipsticks. Diagnostic sensitivity was determined using serum samples from 21 hydatidosis patients, and diagnostic specificity was established using sera from 17 individuals infected with other parasites and 15 healthy people. IgG4 dipstick had a diagnostic sensitivity of 95% (20 of 21) and a specificity of 100% (32 of 32). The IgG dipstick had a sensitivity of 100% (21 of 21) and a specificity of 87.5% (28 of 32). Thus, both IgG and IgG4 dipsticks had high sensitivities, but IgG4 had greater specificity for the diagnosis of human CE.

The pathogenesis of nephropathia epidemica: new knowledge and unanswered questions

Puumala virus (PUUV) causes an acute hemorrhagic fever with renal syndrome (HFRS), a zoonosis also called nephropathia epidemica (NE). The reservoir host of PUUV is the bank vole (Myodes glareolus). Herein we review the main clinical manifestations of NE, acute kidney injury, increased vascular permeability, coagulation abnormalities as well as pulmonary, cardiac, central nervous system and ocular manifestations of the disease. Several biomarkers of disease severity have recently been discovered: interleukin-6, pentraxin-3, C-reactive protein, indoleamine 2,3-dioxygenase, cell-free DNA, soluble urokinase-type plasminogen activator, GATA-3 and Mac-2 binding protein. The role of cytokines, vascular endothelial growth hormone, complement, bradykinin, cellular immune response and other mechanisms in the pathogenesis of NE as well as host genetic factors will be discussed. Finally therapeutic aspects and directions for further research will be handled.

Antibody levels to hantavirus in inhabitants of western Santa Catarina State, Brazil

Hantavirus cardiopulmonary syndrome (HCPS) is an infectious disease caused by hantaviruses of the family Bunyaviridae, and is transmitted by aerosols of excreta of infected rodents. The aim of the present study was to determine antibody levels to hantavirus in the population that lives at frontier of Brazil and Argentina. Participated of the study 405 individuals living in the municipalities of Bandeirante, Santa Helena, Princesa and Tunapolis, state of Santa Catarina, Brazil. IgG antibodies to hantavirus were analyzed in sera by an ELISA that uses a recombinant N protein of Araraquara hantavirus as antigen. The results were also confirmed by immunofluorescent test. Eight individuals showed antibodies to hantavirus (1.97% positivity), with serum titers ranging from 100 to 800. Six seropositives were males, older than 30 years and farmers. Our results reinforce previous data on hantavirus circulation and human infections in the southern border of Brazil with Argentina.

Rodent-borne hantaviruses in Cambodia, Lao PDR, and Thailand

In order to evaluate the circulation of hantaviruses present in southeast Asia, a large scale survey of small mammal species was carried out at seven main sites in the region (Cambodia, Lao People's Democratic Republic, and Thailand). Small scale opportunistic trapping was also performed at an eighth site (Cambodia). Using a standard IFA test, IgG antibodies reacting to Hantaan virus antigens were detected at six sites. Antibody prevalence at each site varied from 0 to 5.6% with antibodies detected in several rodent species (Bandicota indica, B. savilei, Maxomys surifer, Mus caroli, M. cookii, Rattus exulans, R. nitidius, R. norvegicus, and R. tanezumi). When site seroprevalence was compared with site species richness, seropositive animals were found more frequently at sites with lower species richness. In order to confirm which hantavirus species were present, a subset of samples was also subjected to RT-PCR. Hantaviral RNA was detected at a single site from each country. Sequencing confirmed the presence of two hantavirus species, Thailand and Seoul viruses, including one sample (from Lao PDR) representing a highly divergent strain of Seoul virus. This is the first molecular evidence of hantavirus in Lao PDR and the first reported L segment sequence data for Thailand virus.

Expression of recombinant Araraquara Hantavirus nucleoprotein in insect cells and its use as an antigen for immunodetection compared to the same antigen expressed in Escherichia coli

Background

Antigens for Hantavirus serological tests have been produced using DNA recombinant technology for more than twenty years. Several different strategies have been used for that purpose. All of them avoid the risks and difficulties involved in multiplying Hantavirus in the laboratory. In Brazil, the Araraquara virus is one of the main causes of Hantavirus Cardio-Pulmonary Syndrome (HCPS).

Methods

In this investigation, we report the expression of the N protein of the Araraquara Hantavirus in a Baculovirus Expression System, the use of this protein in IgM and IgG ELISA and comparison with the same antigen generated in E. coli.

Results

The protein obtained, and purified in a nickel column, was effectively recognized by antibodies from confirmed HCPS patients. Comparison of the baculovirus generated antigen with the N protein produced in E. coli showed that both were equally effective in terms of sensitivity and specificity.

Conclusions

Our results therefore indicate that either of these proteins can be used in serological tests in Brazil.

Experience with extrarenal manifestations of hemorrhagic fever with renal syndrome in a tertiary care hospital in South Korea

Reports on the clinical entity of hemorrhagic fever with renal syndrome (HFRS) have focused on acute renal failure. Data on the extrarenal manifestations are limited primarily to case reports. In this study, protean extrarenal manifestations involving the major organs occurred in one-third of patients with HFRS during various stages (i.e., febrile phase through diuretic phase). Pancreatobiliary manifestations and major bleeding occurred in 11% and 10% of patients, respectively. Cardiovascular and central nervous system manifestations developed during the febrile or oliguric phase, whereas pancreatobiliary manifestations and major bleeding were detected even in the diuretic phase. Thus, close monitoring of and additional knowledge about various extrarenal manifestations are needed.

Characterization of monoclonal antibodies against hantavirus nucleocapsid protein and their use for immunohistochemistry on rodent and human samples

Monoclonal antibodies are important tools for various applications in hantavirus diagnostics. Recently, we generated Puumala virus (PUUV)-reactive monoclonal antibodies (mAbs) by immunisation of mice with chimeric polyomavirus-derived virus-like particles (VLPs) harbouring the 120-amino-acid-long amino-terminal region of the PUUV nucleocapsid (N) protein. Here, we describe the generation of two mAbs by co-immunisation of mice with hexahistidine-tagged full-length N proteins of Sin Nombre virus (SNV) and Andes virus (ANDV), their characterization by different immunoassays and comparison with the previously generated mAbs raised against a segment of PUUV N protein inserted into VLPs. All of the mAbs reacted strongly in ELISA and western blot tests with the antigens used for immunization and cross-reacted to varying extents with N proteins of other hantaviruses. All mAbs raised against a segment of the PUUV N protein presented on chimeric VLPs and both mAbs raised against the full-length AND/SNV N protein reacted with Vero cells infected with different hantaviruses. The reactivity of mAbs with native viral nucleocapsids was also confirmed by their reactivity in immunohistochemistry assays with kidney tissue specimens from experimentally SNV-infected rodents and human heart tissue specimens from hantavirus cardiopulmonary syndrome patients. Therefore, the described mAbs represent useful tools for the immunodetection of hantavirus infection.

Hantavirus infection: a neglected diagnosis in thrombocytopenia and fever?

Thrombocytopenia, fever, and acute renal failure are characteristic features of nephropathia epidemica, the predominant hantavirus infection in Europe. However, clinical presentation and blood cell counts may point to other disorders, such as a hematologic disease, particularly when impairment of renal function is not evident. This differential diagnosis often results in further extensive and unnecessary testing. We describe 3 patients with hantavirus infection with no renal failure, in whom a hematologic disorder was initially suspected. Serologic testing of hantavirus finally unraveled the mystery, and outcome of the patients was excellent. It is conceivable that similar cases often remain undiagnosed. Thus, testing for hantavirus should always be considered in cases of thrombocytopenia and fever of unknown origin, especially in areas endemic for the infection.

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.

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.

Use of Saccharomyces cerevisiae-expressed recombinant nucleocapsid protein to detect Hantaan virus-specific immunoglobulin G (IgG) and IgM in oral fluid

Hantaan virus is the causative agent of severe hemorrhagic fever with renal syndrome. Clinical surveillance for Hantaan virus infection is unreliable, and laboratory verification is essential. The detection of virus-specific immunoglobulin M (IgM) and IgG in serum is most commonly used for the diagnosis of hantavirus infection. Testing of oral fluid samples instead of serum offers many advantages for surveillance. However, commercial tests for hantavirus-specific antibodies are unavailable. For the detection of Hantaan virus in the oral fluid of humans, we have developed a monoclonal antibody-based capture enzyme-linked immunosorbent IgM assay (IgM capture ELISA) and indirect enzyme-linked immunosorbent IgG and IgM assays (indirect IgG and IgM ELISAs) for paired serum and oral fluid samples using the Saccharomyces cerevisiae yeast-expressed nucleocapsid protein of the Hantaan-Fojnica virus. The sensitivity and specificity of the oral fluid IgM capture ELISA in comparison with the results of the serum Hantaan virus IgM assay were 96.7% and of 94.9%, respectively. Thus, data on the overall performance of the oral fluid IgM capture ELISA are in close agreement with those of the serum IgM assay, and the method exhibits the potential to serve as an easily transferable tool for large-scale epidemiological studies. Data on the indirect IgM ELISA also showed close agreement with the serum IgM assay data; however, the indirect IgG ELISA displayed a lower sensitivity and a lower specificity. In conclusion, the IgM capture ELISA can be used with oral fluid instead of serum samples for the diagnosis of Hantaan virus infection.

Detection and typing of human pathogenic hantaviruses by real-time reverse transcription-PCR and pyrosequencing

BACKGROUND

Because the clinical course of human infections with hantaviruses can vary from subclinical to fatal, rapid and reliable detection of hantaviruses is essential. To date, the diagnosis of hantavirus infection is based mainly on serologic assays, and the detection of hantaviral RNA by the commonly used reverse transcription (RT)-PCR is difficult because of high sequence diversity of hantaviruses and low viral loads in clinical specimens.

METHODS

We developed 5 real-time RT-PCR assays, 3 of which are specific for the individual European hantaviruses Dobrava, Puumala, or Tula virus. Two additional assays detect the Asian species Hantaan virus together with Seoul virus and the American species Andes virus together with Sin Nombre virus. Pyrosequencing was established to provide characteristic sequence information of the amplified hantavirus for confirmation of the RT-PCR results or for a more detailed virus typing.

RESULTS

The real-time RT-PCR assays were specific for the respective hantavirus species and optimized to run on 2 different platforms, the LightCycler and the ABI 7900/7500. Each assay showed a detection limit of 10 copies of a plasmid containing the RT-PCR target region, and pyrosequencing was possible with 10 to 100 copies per reaction. With this assay, viral genome could be detected in 16 of 552 (2.5%) specimens of suspected hantavirus infections of humans and mice.

CONCLUSIONS

The new assays detect, differentiate, and quantify hantaviruses in clinical specimens from humans and from their natural hosts and may be useful for in vitro studies of hantaviruses.

Rapid immunochromatographic test for hantavirus andes contrasted with capture-IgM ELISA for detection of andes-specific IgM antibodies

Hantavirus is associated with hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). The clinical diagnosis of hantavirus infections has been confirmed routinely by the immunofluorescence antibody assay (IFA) or enzyme-linked immunosorbent assay (ELISA). A rapid and easy diagnostic test for hantavirus infection is required. A new immunochromatographic assay for hantavirus, POC-PUU, useful for the diagnosis of epidemic nephrophaty associated with hantavirus Puumala in Europe, was evaluated in Chile. This test is based on recombinant N-protein of hantavirus Puumala, and cross-reacts with other hantaviruses. Eighty human sera were selected at random from patients from Southern Chile who were suspected with HPS. The hantavirus capture-IgM ELISA was compared with a commercially available POC-PUU test (POC PUUMALA, Reagena Ltd., Toivala, Finland). The test sensitivity and specificity of the POC-PUU test were 97 and 90%, respectively. It is important to note that although the test is not specific for Andes virus the sensitivity and specificity were above 90%, which indicates good reactivity to the Puumala nucleoprotein antigen. As this test is cost-effective, with a high negative value, rapid and easy to carry out, specialized personnel are not necessary, nor does it require specialized equipment. Its usefulness for diagnosis is important in hospitals far from reference centers and areas with a high incidence of HPS cases.

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.

Identification of Dobrava, Hantaan, Seoul, and Puumala viruses by one-step real-time RT-PCR

We developed four assays for specifically identifying Dobrava (DOB), Hantaan (HTN), Puumala (PUU), and Seoul (SEO) viruses. The assays are based on the real-time one-step reverse transcriptase polymerase chain reaction (RT-PCR) with the small segment used as the target sequence. The detection limits of DOB, HTN, PUU, and SEO assays were 25, 25, 25, and 12.5 plaque-forming units, respectively. The assays were evaluated in blinded experiments, each with 100 samples that contained Andes, Black Creek Canal, Crimean-Congo hemorrhagic fever, Rift Valley fever and Sin Nombre viruses in addition to DOB, HTN, PUU and SEO viruses. The sensitivity levels of the DOB, HTN, PUU, and SEO assays were 98%, 96%, 92% and 94%, respectively. The specificity of DOB, HTN and SEO assays was 100% and the specificity of the PUU assay was 98%. Because of the high levels of sensitivity, specificity, and reproducibility, we believe that these assays can be useful for diagnosing and differentiating these four Old-World hantaviruses.

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.

Hantavirus infection in children

PURPOSE OF REVIEW

This article focuses on recent developments in knowledge about hantavirus infections and hantavirus cardiopulmonary syndrome in children. We highlight clinical characterization, epidemiology, pathogenesis, diagnostic techniques, and current alternatives for treatment and prevention.

RECENT FINDINGS

After the first description of hantavirus pulmonary syndrome (HPS) in 1993 in the United States, new cases of HPS and new hantavirus species have been described throughout the Americas. The factors involved in the expression of hantavirus disease have, in part, been recognized, but there have been descriptions of newer viruses and newer rodent reservoirs. Several seroprevalence studies suggest that the virus-host interaction has been taking place for many years, and changes in human behavior and wild rodent ecology, sometimes secondary to industrial progress, facilitate the clinical recognition of disease. Sin nombre virus (SNV) and Andes virus (ANDV) are examples of the same disease with differences in the virus virulence and in the host response. The North American syndrome and the Southern HPS differ in epidemiologic patterns and in the spectrum of disease.

SUMMARY

Currently, no Food and Drug Administration (FDA)-approved antiviral drugs, vaccines, or immunotherapeutic agents are available for treatment of the disease, and therapy is primarily supportive. Intensive care medicine has played an outstanding role in decreasing the lethality of HPS. A ribavirin trial in the United States did not support the use of the drug in fully developed HCPS. Recently published data suggest that a strong neutralizing antibody response may be a predictor of effective clearance of and recovery from SNV infection. This has raised the possibility that passive immunotherapy may be useful in HCPS. Extensive work has been done to develop a hantavirus vaccine, but at present it seems unlikely that a vaccine will be in commercial development in the near future.

Tropical dermatology: viral tropical diseases

Viruses are important pathogens in tropical areas; most of them, especially the tropical hemorrhagic fevers, produce mucocutaneous manifestations. More than any other kind of pathogen, viruses have the possibility for being widespread, since they have a greater probability of mutation than do bacteria, can cross species barriers easily, and infect both human beings and animals in habitats with a great biodiversity. Tropical habitats also have been subject to major ecologic changes in the last few decades, exposing humans to direct contact with these viruses and allowing hemorrhagic fevers due to new emergent viruses such as flaviviruses, filoviruses, arenaviruses, and hantaviruses to become major threats to public health. The collapse of eradication programs in many countries, as well as population increases and ecologic modifications, have led to the spread of dengue and yellow fever to large portions of the world owing to the dissemination of vectors, especially mosquitoes, with broad ecologic ranges. Viruses previously restricted to some geographic areas, such as Rift Valley fever, Crimean-Congo hemorrhagic fever, West Nile fever, and monkeypox are now affecting new countries and populations. Other viruses such as herpes B infection often affect travelers and animal handlers in most parts of the world. Dermatologic lesions occur in all these diseases and can facilitate a rapid diagnosis, leading to control of the virus and helping prevent possible outbreaks.