Molecular rationale for antibody-mediated targeting of the hantavirus fusion glycoprotein

The intricate lattice of Gn and Gc glycoprotein spike complexes on the hantavirus envelope facilitates host-cell entry and is the primary target of the neutralizing antibody-mediated immune response. Through study of a neutralizing monoclonal antibody termed mAb P-4G2, which neutralizes the zoonotic pathogen Puumala virus (PUUV), we provide a molecular-level basis for antibody-mediated targeting of the hantaviral glycoprotein lattice. Crystallographic analysis demonstrates that P-4G2 binds to a multi-domain site on PUUV Gc and may preclude fusogenic rearrangements of the glycoprotein that are required for host-cell entry. Furthermore, cryo-electron microscopy of PUUV-like particles in the presence of P-4G2 reveals a lattice-independent configuration of the Gc, demonstrating that P-4G2 perturbs the (Gn-Gc)4 lattice. This work provides a structure-based blueprint for rationalizing antibody-mediated targeting of hantaviruses.

Analytical Performance of the RIDASCREEN® Hantavirus Puumala IgG/IgM ELISA Assay

The National Reference Center for Hantavirus in Belgium is currently using the Hantavirus IgM/IgG ELISA Progen kit (Heidelberg, Germany) for the detection of the most prevalent Hantavirus in Western Europe, Puumala virus (PUUV). Two commercially available PUUV kits were compared: Progen and RIDASCREEN^® Hantavirus Puumala IgM/IgG ELISA assay (Darmstadt, Germany). Methods: The sensitivity was evaluated with a panel of 68 samples from patients with an acute infection (n = 44) or a past infection (n = 24). Specificity was evaluated with a panel of 62 samples from patients with potentially false borderline results (n = 7) (no seroconversion), seronegative samples (n = 25) and potentially cross reacting samples (n = 30). Discordances were resolved by immunoblot. Substantial agreement was calculated using Cohen kappa coefficient. Results: The RIDASCREEN^® kit showed a higher specificity (IgM: 94.3%; IgG: 94.4%) than the Progen kit (IgM: 77.0% IgG: 93.0%). The sensitivity for IgM ELISA was 100% for both assays. IgG sensitivity was, respectively, 98.3% and 100% for Progen and RIDASCREEN^®. A Cohen kappa coefficient of 0.76 and 0.90 was found between Puumala IgM and IgG, respectively. Conclusions: This study showed a higher specificity for the RIDASCREEN^® kit than the Progen kit, while the sensitivity was as good as for the Progen kit.

Relationship between circulating vascular endothelial growth factor and its soluble receptor in patients with hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome (HFRS) is characterized by endothelial dysfunction with capillary leakage without obvious cytopathology in the capillary endothelium. The aim of the study was to analyze the kinetics of vascular endothelial growth factor (VEGF) and its soluble receptor (sVEGFR-2) in HFRS patients infected with Dobrava (DOBV) or Puumala virus (PUUV). VEGF and sVEGFR-2 levels were measured in daily plasma and urine samples of 73 patients with HFRS (58 with PUUV, 15 with DOBV) and evaluated in relation to clinical and laboratory variables. In comparison with the healthy controls, initial samples (obtained in the first week of illness) from patients with HFRS had higher plasma and urine VEGF levels, whereas sVEGFR-2 levels were lower in plasma but higher in urine. VEGF levels did not differ in relation to hantavirus species, viral load, or the severity of HFRS. The comparison of VEGF dynamics in plasma and urine showed the pronounced secretion of VEGF in urine. Significant correlations were found between daily VEGF/sVEGFR-2 levels and platelet counts, as well as with diuresis: the correlations were positive for plasma VEGF/sVEGFR-2 levels and negative for urine levels. In addition, patients with hemorrhagic manifestations had very high plasma and urine VEGF, together with high urine sVEGFR-2. Measuring the local secretion of sVEGFR-2 in urine might be a useful biomarker for identifying HFRS patients who will progress to severe disease.

A multi-head intradermal electroporation device allows for tailored and increased dose DNA vaccine delivery to the skin

The identification of an effective and tolerable delivery method is a necessity for the success of DNA vaccines in the clinic. This manuscript describes the development and validation of a multi-headed intradermal electroporation device which would be applicable for delivering multiple DNA vaccine plasmids simultaneously but spatially separated. Reporter gene plasmids expressing green and red fluorescent proteins were used to demonstrate the impact of spatial separation on DNA delivery to increase the number of transfected cells and avoid interference through visible expression patterns. To investigate the impact of plasmid interference on immunogenicity, a disease target was investigated where issues with multi-valent vaccines had been previously described. DNA-based Hantaan and Puumala virus vaccines were delivered separately or as a combination and the effect of multi-valence was determined by appropriate assays. While a negative impact was observed for both antigenic vaccines when delivered together, these effects were mitigated when the vaccine was delivered using the multi-head device. We also demonstrate how the multi-head device facilitates higher dose delivery to the skin resulting in improved immune responses. This new multi-head platform device is an efficient, tolerable and non-invasive method to deliver multiple plasmid DNA constructs simultaneously allowing the tailoring of delivery sites for combination vaccines. Additionally, this device would allow the delivery of multi-plasmid vaccine formulations without risk of impacted immune responses through interference. Such a low-cost, easy to use device platform for the delivery of multi-agent DNA vaccines would have direct applications by the military and healthcare sectors for mass vaccination purposes.

NK cell activation in human hantavirus infection explained by virus-induced IL-15/IL15Rα expression

Clinical infection with hantaviruses cause two severe acute diseases, hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). These diseases are characterized by strong immune activation, increased vascular permeability, and up to 50% case-fatality rates. One prominent feature observed in clinical hantavirus infection is rapid expansion of natural killer (NK) cells in peripheral blood of affected individuals. We here describe an unusually high state of activation of such expanding NK cells in the acute phase of clinical Puumala hantavirus infection. Expanding NK cells expressed markedly increased levels of activating NK cell receptors and cytotoxic effector molecules. In search for possible mechanisms behind this NK cell activation, we observed virus-induced IL-15 and IL-15Rα on infected endothelial and epithelial cells. Hantavirus-infected cells were shown to strongly activate NK cells in a cell-cell contact-dependent way, and this response was blocked with anti-IL-15 antibodies. Surprisingly, the strength of the IL-15-dependent NK cell response was such that it led to killing of uninfected endothelial cells despite expression of normal levels of HLA class I. In contrast, hantavirus-infected cells were resistant to NK cell lysis, due to a combination of virus-induced increase in HLA class I expression levels and hantavirus-mediated inhibition of apoptosis induction. In summary, we here describe a possible mechanism explaining the massive NK cell activation and proliferation observed in HFRS patients caused by Puumala hantavirus infection. The results add further insights into mechanisms behind the immunopathogenesis of hantavirus infections in humans and identify new possible targets for intervention.

Hantaviruses cause severe clinical infections with up to 50% case-fatality rates. The diseases represent an important global health problem as no vaccine or specific treatment is available. The most prominent hallmark in patients is strong immune activation, reflected as massive CD8 T and NK cell expansion, accompanied by severe vascular leakage. The mechanisms behind this massive immune activation are still not fully understood. Here, we first assessed the expression of several activation markers and receptors on NK cells derived from hantavirus-infected patients using flow cytometry. High NK cell activation was observed during the acute phase of clinical infection. To address possible underlying mechanisms explaining this NK cell activation, we established an in vitro hantavirus infection model using human primary endothelial cells, the natural in vivo targets of the virus. We demonstrate hantavirus-induced IL-15/IL-15Rα on infected endothelial cells, and show that this results in NK cell activation, similar to the profile found in hantavirus-infected patients. Interestingly, these activated NK cells were able to kill uninfected endothelial cells despite their normal expression of HLA class I. The present data add further insights into hantavirus-induced pathogenesis and suggest possible targets for future therapeutical interventions in these severe diseases.

Identification of factors influencing the Puumala virus seroprevalence within its reservoir in aMontane Forest Environment

Puumala virus (PUUV) is a major cause of mild to moderate haemorrhagic fever with renal syndrome and is transmitted by the bank vole (Myodes glareolus). There has been a high cumulative incidence of recorded human cases in South-eastern Germany since 2004 when the region was first recognized as being endemic for PUUV. As the area is well known for outdoor recreation and the Bavarian Forest National Park (BFNP) is located in the region, the increasing numbers of recorded cases are of concern. To understand the population and environmental effects on the seroprevalence of PUUV in bank voles we trapped small mammals at 23 sites along an elevation gradient from 317 to 1420m above sea level. Generalized linear mixed effects models(GLMEM) were used to explore associations between the seroprevalence of PUUV in bank voles and climate and biotic factors. We found that the seroprevalence of PUUV was low (6%–7%) in 2008 and 2009, and reached 29% in 2010. PUUV seroprevalence was positively associated with the local species diversity and deadwood layer, and negatively associated with mean annual temperature, mean annual solar radiation, and herb layer. Based on these findings, an illustrative risk map for PUUV seroprevalence prediction in bank voles was created for an area of the national park. The map will help when planning infrastructure in the national park (e.g., huts, shelters, and trails).

[Variants of the immunoreactivity and infectious process in bank vole (Myodes glareolus) experimentally infected with the hantavirus Puumala (PUUV)]

As a result of a longitudinal study of the Puumala hantavirus (PUUV) in the experimentally infected bank voles (Myodes glareolus), we revealed three groups of the voles differing in the immunoreactivity and viral antigen concentration in the organs. The close correlation between these parameters suggested the existence of various mechanisms of the hantavirus persistence in the host.

Detection of Puumala hantavirus antigen in human intestine during acute hantavirus infection

Background

Puumala virus (PUUV) is the most important hantavirus species in Central Europe. Nephropathia epidemica (NE), caused by PUUV, is characterized by acute renal injury (AKI) with thrombocytopenia and frequently gastrointestinal symptoms.

Methods

456 patients with serologically and clinically confirmed NE were investigated at time of follow-up in a single clinic. The course of the NE was investigated using medical reports. We identified patients who had endoscopy with intestinal biopsy during acute phase of NE. Histopathological, immunohistochemical and molecular analyses of the biopsies were performed.

Results

Thirteen patients underwent colonoscopy or gastroscopy for abdominal pain, diarrhea, nausea and vomiting during acute phase of NE. Immunohistochemistry (IHC) revealed PUUV nucleocapsid antigen in 11 biopsies from 8 patients; 14 biopsies from 5 patients were negative for PUUV nucleocapsid antigen. IHC localized PUUV nucleocapsid antigen in endothelial cells of capillaries or larger vessels in the lamina propria. Rate of AKI was not higher and severity of AKI was not different in the PUUV-positive compared to the PUUV-negative group. All IHC positive biopsies were positive for PUUV RNA using RT-PCR. Phylogenetic reconstruction revealed clustering of all PUUV strains from this study with viruses previously detected from the South-West of Germany. Long-term outcome was favorable in both groups.

Conclusions

In patients with NE, PUUV nucleocapsid antigen and PUUV RNA was detected frequently in the intestine. This finding could explain frequent GI-symptoms in NE patients, thus demonstration of a more generalized PUUV infection. The RT-PCR was an effective and sensitive method to detect PUUV RNA in FFPE tissues. Therefore, it can be used as a diagnostic and phylogenetic approach also for archival materials. AKI was not more often present in patients with PUUV-positive IHC. This last finding should be investigated in larger numbers of patients with PUUV infection.

The use of chimeric virus-like particles harbouring a segment of hantavirus Gc glycoprotein to generate a broadly-reactive hantavirus-specific monoclonal antibody

Monoclonal antibodies (MAbs) against viral glycoproteins have important diagnostic and therapeutic applications. In most cases, the MAbs specific to viral glycoproteins are raised against intact virus particles. The biosynthesis of viral glycoproteins in heterologous expression systems such as bacteria, yeast, insect or mammalian cells is often problematic due to their low expression level, improper folding and limited stability. To generate MAbs against hantavirus glycoprotein Gc, we have used initially a recombinant yeast-expressed full-length Puumala virus (PUUV) Gc protein. However, this approach was unsuccessful. As an alternative recombinant antigen, chimeric virus-like particles (VLPs) harboring a segment of PUUV Gc glycoprotein were generated in yeast Saccharomyces cerevisiae. A 99 amino acid (aa)-long segment of Gc protein was inserted into the major capsid protein VP1 of hamster polyomavirus at previously defined positions: either site #1 (aa 80-89) or site #4 (aa 280-289). The chimeric proteins were found to self-assemble to VLPs as evidenced by electron microscopy. Chimeric VLPs induced an efficient insert-specific antibody response in immunized mice. Monoclonal antibody (clone #10B8) of IgG isotype specific to hantavirus Gc glycoprotein was generated. It recognized recombinant full-length PUUV Gc glycoprotein both in ELISA and Western blot assay and reacted specifically with hantavirus-infected cells in immunofluorescence assay. Epitope mapping studies revealed the N-terminally located epitope highly conserved among different hantavirus strains. In conclusion, our approach to use chimeric VLPs was proven useful for the generation of virus-reactive MAb against hantavirus Gc glycoprotein. The generated broadly-reactive MAb #10B8 might be useful for various diagnostic applications.

Puumala hantavirus outbreak among U.S. military health care beneficiaries, Stuttgart, Germany--2012

Hantaviruses are viruses of the family Bunyaviridae that are transmitted to humans via inhalation of the aerosolized excrement of rodents. The geographic distribution of hantavirus includes the Americas, Asia, and Europe. An outbreak of Puumala hantavirus infections among U.S. military health care beneficiaries was identified by the U.S. Army Public Health Command Region-Europe at U.S. Army installations in Stuttgart, Germany, during 2012. Overall, five cases (one probable and four confirmed) were identified in three service members, one U.S. civilian employee, and one dependent family member. Four cases were hospitalized, one of whom required dialysis. The outbreak investigation revealed that all cases exercised in forested areas and most were active smokers (4 out of 5). This report reviews the types of hantaviruses found worldwide and suggests that health care providers should suspect and consider possible hantavirus infections when evaluating patients with histories and clinical presentations consistent with such infections.

A model system for in vitro studies of bank vole borne viruses

The bank vole (Myodes glareolus) is a common small mammal in Europe and a natural host for several important emerging zoonotic viruses, e.g. Puumala hantavirus (PUUV) that causes hemorrhagic fever with renal syndrome (HFRS). Hantaviruses are known to interfere with several signaling pathways in infected human cells, and HFRS is considered an immune-mediated disease. There is no in vitro-model available for infectious experiments in bank vole cells, nor tools for analyses of bank vole immune activation and responses. Consequently, it is not known if there are any differences in the regulation of virus induced responses in humans compared to natural hosts during infection. We here present an in vitro-model for studies of bank vole borne viruses and their interactions with natural host cell innate immune responses. Bank vole embryonic fibroblasts (VEFs) were isolated and shown to be susceptible for PUUV-infection, including a wild-type PUUV strain (only passaged in bank voles). The significance of VEFs as a model system for bank vole associated viruses was further established by infection studies showing that these cells are also susceptible to tick borne encephalitis, cowpox and Ljungan virus. The genes encoding bank vole IFN-β and Mx2 were partially sequenced and protocols for semi-quantitative RT-PCR were developed. Interestingly, PUUV did not induce an increased IFN-β or Mx2 mRNA expression. Corresponding infections with CPXV and LV induced IFN-β but not Mx2, while TBEV induced both IFN-β and Mx2. In conclusion, VEFs together with protocols developed for detection of bank vole innate immune activation provide valuable tools for future studies of how PUUV and other zoonotic viruses affect cells derived from bank voles compared to human cells. Notably, wild-type PUUV which has been difficult to cultivate in vitro readily infected VEFs, suggesting that embryonic fibroblasts from natural hosts might be valuable for isolation of wild-type hantaviruses.

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.

[Serological characteristics of hantaviruses from clinical specimens analyzed in 1998-2008 in the Department of Virology, Public Health Institute, Ostrava]

In 1998 - 2008, serum samples from 464 patients, predominantly residents of the Moravia-Silesian Region, were examined in the Department of Virology, Public Health Institute in Ostrava, using Enzyme-Linked ImmunoSorbent Assay (ELISA) for the detection of specific anti-hantavirus antibodies. Seropositivity was ascertained in 41 persons (8.8%). More patients tested seropositive against Hantaan virus (24, i.e. 58.5%) than against Puumala virus (13, i.e. 31.7%). Four persons were reactive against both antigens. Clinical symptoms corresponding to hantavirus infection were observed in 19 seropositive patients. Fifteen of them had antibodies reactive with Hantaan virus antigen (cross-reactive with anti-Dobrava virus), 3 patients had antibodies against Puumala virus and 1 patient had both types of antibodies. Clinical data on the other seropositive persons were lacking. The higher rate of Dobrava virus infections in the Moravian-Silesian Region seems to be associated, among others, with the geographic distribution of striped field mouse (Apodemus agrarius) which is the main reservoir of Dobrava virus in Central Europe.

[Cloning and expression of the nucleoprotein gene of Puumala-like virus]

OBJECTIVE

In order to detect Hokkaido virus (HOKV), a recombinant baculovirus containing the nucleoprotein (NP) gene of HOKV was constructed, and then the NP was expressed in insect cell.

METHODS

The NP gene was cloned into plasmid PCR 2.1TA vector and then was ligated into baculovirus donor plasmid pFastBac after cutting by the restriction enzyme Kpn I and Not I. pFastBac 1 was subsequently transferred into the One Short TOP10 competent cells and then into DH1OBac E. coli competent cells, which contained the baculovirus shuttle vector (Bacmid) and the helper plasmid to generate a recombinant bacmid.

RESULTS

The NP gene was successfully expressed in Sf9 insect cell. The expressed recombinant nucleoprotein had been identified in the Sf9 insect cell by indirect immunofluorescence assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot. The results showed that the recombinant nucleoprotein appeared a molecular weight of 50 x 10(3) Mr, and could reacted with anti-recombinant Puumala virus (PUUV) nucleocapsid monoclonal antibodies and polyclonal antibodies against hantavirus.

CONCLUSION

Our results indicated that the recombinant nucleoprotein was successfully expressed and having the immunogenicity and reactivity of natural nucleoprotein of HOKV.

Genetic and antigenic analyses of a Puumala virus isolate as a potential vaccine strain

Puumala virus (PUUV), a causative agent of hemorrhagic fever with renal syndrome (HFRS), is prevalent in Europe and European Russia. No vaccine has been developed for PUUV-associated HFRS, primarily because of the low viral yield in cultured cells. A PUUV strain known as DTK/Ufa-97 was isolated in Russia and adapted for growth in Vero E6 cells maintained in serum-free medium. The DTK/Ufa-97 strain produced a higher viral titer in serum-free medium, suggesting that it may prove useful in the development of an HFRS vaccine. When PUUV-infected Vero E6 cells were grown in serum-free medium, the DTK/Ufa-97 strain yielded more copies of intracellular viral RNA and a higher viral titer in the culture fluid than did the Sotkamo strain. Phylogenetic analysis revealed that PUUVs can be classified into multiple lineages according to geographical origin, and that the DTK/Ufa-97 strain is a member of the Bashkiria-Saratov lineage. The deduced amino acid sequences of the small, medium, and large segments of the DTK/Ufa-97 strain were 99.2% to 100%, 99.3% to 99.8%, and 99.8% identical, respectively, to those of the Bashkirian PUUV strains and 96.9%, 92.6%, and 97.4% identical, respectively, to those of the Sotkamo strain, indicating that the PUUVs are genetically diverse. However, DTK/Ufa-97 and other strains of PUUV exhibited similar patterns of binding to a panel of monoclonal antibodies against Hantaan virus. In addition, diluted antisera (i.e., ranging from 1:160 to 1:640) specific to three strains of PUUV neutralized both homologous and heterologous viruses. These results suggest that the DTK/Ufa-97 strain is capable of extensive growth and is antigenically similar to genetically distant strains of PUUV.

[Immunogenicity of N-protein of Puumala hantavirus for noninbred mice in the intramuscular administration of its gene DNA]

The outbreaks of hantavirus infections in some regions of the Russian Federation in some years involve considerable material and social losses. In this connection, the designing of the most effective types of vaccines is an urgent task. The authors have created plasmid constructions containing the gene of hemorrhagic fever with renal syndrome virus, with whose Intramuscular injection there is a specific immune response and plasmid DNA is detectable in the adjacent tissues within a month after injection.

Passive immunization protects cynomolgus macaques against Puumala hantavirus challenge

BACKGROUND

Hantaviruses cause two severe and often fatal human diseases: haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Presently, there is no effective prevention available for HFRS or HPS. Here, we studied the effect of passive immunization on the course of infection in cynomolgus macaques challenged with wild-type Puumala hantavirus (PUUV-wt).

METHODS

A pool of serum drawn from previously PUUV-wt-infected monkeys was used for immunization; a pool of serum from the same monkeys that was obtained before infection was used as a control. Immunizations were administered 3 days before and 15 days after challenge with PUUV-wt. After challenge, monkeys were sampled once a week and analysed for PUUV-infection markers.

RESULTS

All three monkeys treated with non-immune serum became positive for PUUV RNA in plasma and showed PUUV nucleocapsid-specific immunoglobin M (IgM) responses after challenge. In contrast, no PUUV RNA or anti-PUUV-specific IgM response was detected in the three passively immunized monkeys. As seen in PUUV-infected humans, the control monkeys showed a marked decrease in the amount of platelets and increased levels of creatinine, interleukin (1L)-6, IL-10, and tumour necrosis factor (TNF) after inoculation. In contrast, no marked changes in the amount of platelets were observed in the immunized monkeys and they did not show increased levels of creatinine, IL-6, IL-10 and TNF after virus challenge.

CONCLUSION

The results show that passive immunization in monkeys, using serum from previously hantavirus-infected monkeys, can induce sterile protection and protect against pathogenesis. Convalescent-phase antibodies may represent a potential therapy that can induce immediate protection against HFRS and HPS.

[Detection of anti-hantavirus antibodies in forest workers in the north-east of Poland]

OBJECTIVE

To estimate exposition to hantaviruses in a high-risk population (forest workers) in the north-east of Poland.

METHODS

IgG antibodies against virus Puumala (PUUV) and Hantaan (HTNV) were detected by ELISA in sera of 59 forest workers from Podlaskie and Warmińsko-Mazurskie provinces (group I), as well as in 10 employees of Regional Forest Administration in Białystok (group II).

MAIN OBSERVATIONS

Anti-PUUV IgG antibodies were detected in 3 persons in group I and 1 in group II. Anti-HTNV IgG were present in 1 person in group I and 2 in group II, in one case accompanying strong reactivity towards PUUV.

RESULTS

Anti-PUUV IgG, suggestive of the history of non-diagnosed PUUV infection, were detected in 4 persons of 69 (5,7%). Isolated anti-HTNV IgG, which could indicate past infection with Saaremaa virus, antigenically related to HTNV, were present in 2 subjects (2,9%).

CONCLUSIONS

Non-diagnosed infections with Puumala and Saaremaa viruses seem to occur in the high risk groups in the north-east of Poland, with frequency comparable to other European countries. Most infections are probably mild or asymptomatic.

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.

Maternal antibodies postpone hantavirus infection and enhance individual breeding success

The transfer of maternal antibodies from mother to progeny is a well-known phenomenon in avian and mammalian species. Optimally, they protect the newborn against the pathogens in the environment. The effect of maternal antibodies on microparasite transmission dynamics may have important consequences for both the fitness of the host and the epizootic processes of the pathogens. However, there is a scarcity of studies examining these effects in free-living wild species. We studied the influence of maternal antibodies against the zoonotic Puumala hantavirus (PUUV) on the fitness of bank voles (Clethrionomys glareolus) and on PUUV transmission by exposing young maternal antibody-positive (MatAb+) and negative (MatAb-) bank voles (n=160) to PUUV in experimental populations. PUUV-specific maternal antibodies delayed the timing of infection. Females were more susceptible to PUUV infection than males. Interestingly, both the females and the males with maternal antibodies matured earlier than the other individuals in the population. Our results highlight the significance of maternal antibodies in the transmission of a pathogen and in the breeding success of the carriers.

[Prevalence of antibodies to hantavirus among hemodialysis patients with end-stage renal failure in Kaunas and its district]

The objective of this study was to investigate the prevalence of antibodies to hantaviruses among hemodialysis patients with end-stage renal failure in Kaunas and its district.

MATERIAL AND METHODS

Serums of 218 patients from four dialysis centers of Kaunas district were tested by using the immunoglobulin G antibody-capture enzyme-linked immunosorbent assay (ELISA). The reactivity of ELISA-positive sera was proven in Western blot tests using various hantavirus recombinant nucleocapsid proteins. The yeast-expressed nucleocapsid proteins were used for testing.

RESULTS

Antibodies against Dobrava/Hantaan and Puumala hantaviruses were found in 16 patients (seroprevalence 7.4%). Most of the sera were positive for Dobrava hantavirus (81%). The ratio of males to females was 1.2:1. Seroprevalence was significantly higher in older patients.

CONCLUSIONS

Results indicate that antibodies to two hantaviruses (Dobrava/Hantaan virus and Puumala virus) are prevalent among hemodialysis patients in Kaunas district with approximately the same seroprevalence as in neighboring countries.

[The cross and unspecific reactions in serological examination for antibodies against hantavirus Puumala]

A serological survey of 78 zoologist capturing small wild rodents in their environment, 9 patients with suspected hantavirus infections and 21 patients with acute renal dysfunction for antibodies to hantaviruses was conducted in Poland. Survey was done by the indirect ELISA with Puumala and Hantaan virus antigens. Out of the 78 mammalogists 15 were seropositive for hantavirus Puumala IgG without history of clinical illness. Analysis of relation between reactive zoologist's sera IgG with antigens of Puumala and Hantaan viruses suggests that these persons had contact with Puumala/Tula viruses rather than with Dobrava/Saaremaa complex. Analysis of results of IgG and IgM presence by ELISA test have confirmed correct interpretation criteria proposed by manufacturer for serological diagnosis of suspected hantavirus infection. Both cross and unspecific reactions in the some sera have been observed. Low number of patients with suspected hantavirus infection suggests the existence of underestimation in registration of data collected in Poland and existence of non-diagnosed infections with hantaviring.

[Occurrence of human hantavirus infections in Poland]

A spread of hantavirus infections causing hemorrhagic fever with renal syndrome is one of the rising epidemiological problems in the world. There is evidence that this type of viruses exists in almost all European countries. It is known that in Poland all the species of wild rodents hosting European hantaviruses are present. However, the data on hantavirus are very limited and information on incidence and prevalence of hantavirus infections among humans and animals in our country is lacking. Up to now, only one study in Poland has dealt with hantavirus infections in humans. Therefore the aim of the presented study was to show whether those infections are present in Poland and how prevalent they are. Two risk groups of hantavirus infection were investigated: group I--people with renal disorders (hospitalized patients with proteinuria and people suspected to hantavirus infection; n=30 people) and group II--healthy people employed at the universities, scientific institutions who due to their profession have contact with small rodents as well as students who captured those rodents when practicing or preparing their master theses (n=76) and forest workers (n=86). No one from the group of patients with renal disorders was positive for hantavirus Puumala IgG. Moreover, none of the forest workers had evidence of hantavirus infection. The hantavirus IgG were found only in the group of mammologists--19% persons were positive. Mammologists are an occupational subpopulation who remain in direct contact with host and/or with host excretions (virus is present in urine, feces, saliva of infected animals) and seem to be the most sensitive indicator of hantaviruses presence in environment. These results prove occurrence of hantavirus infections in Poland, however it seems that they are not very prevalent.

Development of novel immunoglobulin G (IgG), IgA, and IgM enzyme immunoassays based on recombinant Puumala and Dobrava hantavirus nucleocapsid proteins

Human infections with Asian and European hantaviruses can result in hemorrhagic fever with renal syndromes of differing severities characterized by renal dysfunction and sometimes by pulmonary symptoms. For the serological detection of human infections by hantaviruses relevant for Europe, we developed monoclonal antibody capture immunoglobulin G (IgG) and IgA enzyme-linked immunosorbent assays (ELISAs) based on yeast-expressed nucleocapsid proteins of Puumala and Dobrava hantaviruses. Moreover, for diagnosis of acute infections, mu-capture IgM ELISAs were established with nucleocapsid proteins expressed in Drosophila melanogaster Schneider S2 cells. The cutoff values of the ELISAs were determined by investigation of up to 500 human anti-hantavirus-negative serum samples. The specificities of the Puumala and Dobrava virus-specific IgM, IgA, and IgG ELISAs were found to be 100%. The sensitivities of these ELISAs were determined to be 100% with panels of characterized anti-Puumala or anti-Dobrava virus-positive human serum samples. In most cases, Puumala and Dobrava virus infections could be differentiated by ELISA reactivity alone, i.e., endpoint titration with homologous and heterologous antigens.

Dynamics of Puumala virus infection in bank voles in Ardennes department (France)

The hantaviruses (genus Hantavirus, family Bunyaviridae) include human pathogens and occur worldwide. In Western and Central Europe, the predominant serotype is Puumala (PUU) virus, which causes epidemic nephropathy. Voles are considered to be the main reservoir and the vector of PUU virus. A total of 719 rodents (mainly Clethrionomys glareolus, Apodemus sp.) trapped by capture-mark-recapture (CMR) in four sites in Ardennes department (France) between April 2004 and October 2005 were tested for the presence of PUU virus antibodies by enzyme-linked immunosorbent assay (ELISA). The predominant species, C. glareolus (86.5% [622 of 719]), also had the highest antibody prevalence (37.6% [291 of 773]). In C. glareolus, the antibody prevalence rate increased with age (weight) in site A, B and D, reaching more than 50% in the heaviest weight, and suggesting that horizontal infection may be important.

Production of hantavirus Puumala nucleocapsid protein in Saccharomyces cerevisiae for vaccine and diagnostics

The production of hantavirus Puumala nucleocapsid (N) protein for potential applications as a vaccine and for diagnostic purposes was investigated with Saccharomyces cerevisiae as a recombinant host. The N protein gene and the hexahistidine tagged N (h-N) protein gene were expressed intracellular from a 2-microm plasmid vectors under the control of a fused galactose inducible GAL10-PYK promoter. For monitoring the recombinant gene expression, a h-N and a GFP fusion protein was used. Different cultivation strategies and growth media compositions were tested in shake flasks and a 5 l bioreactor. When using defined YNB growth medium, we found the biomass yield to be unsatisfactorily low. Higher concentrated YNB medium, promoted cell growth but showed a pronounced inhibitory effect on heterologous gene expression. This phenomenon could not be attributed to plasmid losses, as we could demonstrate high stability of the vector under the applied cultivation conditions. Supplementation of YNB medium with extracts of plant origin resulted in increased biomass yields with concomitant high expression levels of the recombinant gene. The modified medium was used for fed-batch cultivations where basic metabolic features as well as growth parameters were determined in addition to recombinant gene expression. The maximal volumetric yield of N protein was 316 mg l(-1), the respective yield of h-N protein was 284 mg l(-1). Our study provides a basis for large-scale production of hantavirus vaccines, which satisfies economic efficiency as well as biosafety regulations for human applications.

Human leukocyte antigens B8-DRB1*03 in pediatric patients with nephropathia epidemica caused by Puumala hantavirus

In adults, HLA haplotype B8-DRB1*03 is clearly associated with a severe clinical course of nephropathia epidemica caused by Puumala hantavirus. We investigated whether the same applies in pediatric patients. This HLA haplotype was found in 20 of 39 (51%) of the patients, a significantly higher figure than in the Finnish population (19%). There were, however, no significant differences in the clinical picture between patients with and without HLA B8-DRB1*03.

Rapid field test for detection of hantavirus antibodies in rodents

Puumala virus (PUUV) is the causative agent of nephropathia epidemica, a mild form of haemorrhagic fever with renal syndrome. PUUV is transmitted to humans via aerosolized excreta of the infected bank vole (Clethrionomys glareolus). Current methods for screening of the PUUV prevalence among bank vole populations are laborious, combining sampling in the field and subsequent analyses in the laboratory. In order to facilitate animal testing, a new serological immunochromatographic rapid test was developed. The test uses PUUV nucleocapsid protein as antigen, and it detects anti-PUUV IgG antibodies in rodents. With fresh and undiluted bank-vole blood samples (n = 105) the efficacy of the test was 100%, and with frozen and diluted samples (n = 78) the efficacy was 91%. The test was also shown to detect related hantavirus infections in Norway lemmings and sibling voles (n = 31) with 99% efficacy. The test provides an applicable tool for studying PUUV and related hantavirus infections in arvicoline rodents.

Segments of Puumala Hantavirus Nucleocapsid Protein Inserted into Chimeric Polyomavirus-Derived Virus-Like Particles Induce a Strong Immune Response in Mice

Insertion of a short-sized epitope at four different sites of yeast-expressed hamster polyomavirus major capsid protein VP1 has been found to result in the formation of chimeric virus-like particles. Here, we demonstrate that the insertion of 45 or 120 amino acid-long segments from the N-terminus of Puumala hantavirus nucleocapsid protein into sites 1 (amino acids 80-89) and 4 (amino acids 288-295) of VP1 allowed the highly efficient formation of virus-like particles. In contrast, expression level and assembly capacity of fusions to sites 2 (amino acids 222-225) and 3 (amino acids 243-247) were drastically reduced. Immunization of BALB/c mice with chimeric virus-like particles induced a high-titered antibody response against the hantavirus nucleocapsid protein, even in the absence of any adjuvant. The strongest response was observed in mice immunized with virus-like particles harboring 120 amino acids of hantavirus nucleocapsid protein. According to the immunoglobulin subclass distribution of nucleocapsid protein-specific antibodies a mixed Th1/Th2 response was detected. The VP1 carrier itself also induced a mixed Th1/Th2 response, which was found to be reduced in mice immunized with virus-like particles harboring 120 amino acid-long inserts. In conclusion, hamster polyomavirus VP1 represents a promising carrier moiety for future vaccine development.

Quality control measures for the serological diagnosis of hantavirus infections

BACKGROUND

With society's rapidly increasing mobility, patients infected with severe viral infections can become seriously ill at any place in Europe and elsewhere. Improving the diagnostics of these infections is the most important step in detecting the pathogens and dealing with them, and for this purpose, quality control measures are essential tools.

OBJECTIVES

To assess the diagnostic reality for rare hantavirus infections in Europe by (1) running a pre-evaluation panel (four samples, sent out in 1999) to optimise sample preparation and shipping procedure and afterwards (2) starting an External Quality Assurance (EQA) program (20 samples, sent out in 2001).

STUDY DESIGN

All samples sent out had to be tested for the presence of specific IgG and IgM antibodies against hantavirus. For the pre-evaluation panel, four samples were distributed (two samples IgG+/IgM-, one sample IgG-borderline/IgM-, one sample IgG-/IgM-), for the EQA 20 samples (six samples IgG+/IgM+, eight samples IgG+/IgM-, one sample IgG-borderline/IgM-, five samples IgG-/IgM-). Thirteen laboratories took part in the pre-evaluation panel, 18 laboratories participated in the first EQA run.

RESULTS

For the pre-evaluation panel, the participants reported correct results for 64% of the IgG-positive samples (85% excluding borderline-positive sample), and 92% for the IgG-negative sample. IgM testing was correctly negative in all laboratories. For the EQA, the participants reported correct results for 76% of the IgG-positive samples, and 97% correct results for the IgG-negative samples. For the IgM-positive samples, 53% correct results were reported, and 98% correct results for the IgM-negative samples.

CONCLUSIONS

The results presented here prove the importance of quality measures also for viruses only rarely suspected, like hantavirus, and they clearly demonstrate the need for improvement of the existing test systems.

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.

Improvement of binding of Puumala virus neutralization site resembling peptide with a second-generation phage library

We have previously selected a peptide insert FPCDRLSGYWERGIPSPCVR recognizing the Puumala virus (PUUV) G2-glycoprotein-specific neutralizing monoclonal antibody (MAb) 1C9 with Kd of 2.85 x 10(-8) from a random peptide library X2CX14CX2 expressed on the pIII protein of the filamentous phage fd-tet. We have now created a second-generation phage-displayed peptide library in which each amino acid of the peptide was mutated randomly to another with a certain probability. Peptides were selected for higher affinity for MAb 1C9 and for a common binding motif for MAb 4G2 having an overlapping epitope with MAb 1C9 in G2 glycoprotein. The resulting peptides were synthesized as spots on cellulose membrane. Amino acid changes which improved the reactivity of the peptides to MAb 1C9 were combined in the peptide ATCDKLFGYYERGIPLPCAL with Kd of 1.49 x 10(-9) in biosensor measurements. Our results show that the binding properties of peptides, the affinity and the specificity can be improved and the binding specificity determining amino acids and structural factors can be analyzed by combining binding assays with synthetic peptides on membrane with the use of second-generation phage display libraries.

Lymphocyte Apoptosis during Hemorragic Fever with Renal Syndrome

Programmed cell death (PCD) is a fundamental process regulating immune homeostasis. During acute viral infections PCD of lymphocytes by apoptosis is necessary for removing the excess of activated antigen-reactive T cells and down-regulation of the immune response. On the other hand, apoptosis is the key mechanism of elimination of viral-infected cells. At the present time there is virtually no data on mechanisms of immune regulation during human hantavirus infections. In this study we examined the dynamic of PBL Fas and FasL expression, the first-step dead caspase-8, -2, -9 and effector caspase-3, -7 and -10 activity in freshly isolated PBL lysates, and anti-CD3-induced PBL mitogenic response and apoptosis in patients with Puumala virus (PUUV) associated hemorrhagic fever with the renal syndrome (HFRS). Data reported summarize the initial demonstration of increased Fas/FasL and activation of the initializing (caspase-2, -8 and -9) and the effector caspase-3, -7 and -10 in PBML during acute and convalescent phases of the hantavirus infection. The suppressed anti-CD3 mitogenic response and increased anti-CD3-induced apoptosis were also observed. Although more study needs to be done to determine the role of hantavirus and hantavirus induced pathways in PBML apoptosis, our data suggests that the immune system reacts to hantavirus infection, as to many other virus infections, by activation of apoptosis. These reactions of the immune system could be directed to preserve immune homeostasis, developing the most effective immune protection, and to eliminate cells infected with virus.

Hantavirus antibody occurrence in bank voles (Clethrionomys glareolus) during a vole population cycle

Puumala virus, genus Hantavirus, is the etiologic agent of nephropathia epidemica, a mild form of hemorrhagic fever with renal syndrome. The bank vole (Clethrionomys glareolus) is the natural reservoir species of this hantavirus. We initiated sampling of bank voles at sites of recently identified human nephropathia epidemica cases and paired control sites in the fall of 1995 in coastal areas of northern Sweden. Sites were trapped annually in spring and fall until 1999. Prevalence of antibody to Puumala virus was similar among local bank vole populations in the two types of sites over time. During peak years, however, the absolute number of bank voles was higher in case sites than control sites. Consequently, the likelihood of Puumala virus exposure was increased at case sites during population highs. This would imply that the risk of Puumala virus exposure to conspecifics and humans is habitat and site dependent with a temporal component.

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

Hantaviruses infecting humans in Eurasia include Hantaan, Seoul, Puumala and the closely related Dobrava and Saaremaa viruses. These viruses are causative agents of hemorrhagic fever with renal syndrome (HFRS), which is recognized as a severe health care problem in several countries. Diagnostics of hantavirus infections relies on serology, performed principally with enzyme immunoassay (EIA) or immunofluorescence assay (IFA). We developed four 5-min immunochromatographic IgM-antibody tests for diagnostics of acute Puumala, Dobrava and Hantaan virus infections and a similar combination test to detect all Eurasian pathogenic hantavirus infections. We evaluated the assays using 100 fingertip blood samples collected randomly from Finnish volunteers, 28 confirmed hantavirus IgM-negative sera, and 77 sera from patients with acute infections of various hantaviruses. The specificities and sensitivities of the Puumala-, Dobrava- and Hantaan virus -specific tests varied from 96 to 100%, whereas, the combination test showed 96% specificity and 80 to 93% sensitivity. Cross-reactions were observed commonly between the Dobrava and the Hantaan virus tests, but only rarely between the Puumala and the Hantaan virus, or the Puumala and the Dobrava virus, tests. Altogether, the rapid tests showed less cross-reactivity than the respective EIA tests. According to the results, the performance of these tests meets well the requirements for diagnostic use. Nevertheless, the specific one-antigen tests were markedly more sensitive than the combination test. However, if optimized, a combination test would be suitable for regions where several hantaviruses circulate.

[Grading the severity of disease in patients with Puumala or Dobrava virus infections from 1995 to 2000 in Croatia]

AIM

The aim of our study was to evaluate the proposed Croatian scale for grading the disease severity in patients with hemorrhagic fever with renal syndrome (HFRS). The aim was also to determine whether the infection with Dobrava virus (DOBV) in Croatia was associated with a more severe illness than the infection with Puumala virus (PUUV).

PATIENTS AND METHODS

To evaluate the scale, case records of 62 HFRS patients hospitalized at the University Hospital for Infectious Diseases in Zagreb from 1995 till 2000 were reviewed. ELISA IgM and IgG tests were used for the detection of specific IgM and IgG antibodies to PUUV or DOBV.

DISCUSSION

HFRS caused by hantaviruses is a zoonotic disease spread worldwide, posing a major public health problem of global dimensions. Recent epidemiologic studies show that almost all parts of Croatia are endemic regions for two hantaviruses, Puumala and Dobrava. The disease severity ranges from subclinical infection to severe illness with fatal outcome. Clinical picture is predominated by fever, myalgia, vomiting, hemorrhagic manifestation, visual impairment and kidney affection. There is still a lack of knowledge concerning all the parameters involved in the disease severity. Besides the type of virus and genetic material, host genes are also associated with the variable clinical course. HLA alleles B8, DR3, and DQ2 are strongly associated with severe outcome of PUUV infection, white HLA B27 allele is associated with a mild course. Whether similar genetic factors also operate in DOBV infection remains to be determined. Recently, a Croatian scale for grading the disease severity was proposed. The disease severity is graded by a scoring system (points attributed to specific clinical symptoms and laboratory findings) as 1--mild, 2--moderate, 3--severe, and 4--very severe. We found 60% of HFRS patients to be infected with PUUV and 40% with DOBV. In our study, 65% of patients infected with PUUV had mild, and 24% moderate disease. Severe and very severe disease was recorded in 11% of PUUV infected patients. In contrast, only 44% of patients infected with DOBV had mild disease, whereas 40% of patients showed a moderate clinical picture. Severe and very severe clinical picture was recorded in 16% of patients with DOBV infection. Statistical analysis showed a significant number of pa (p < 0.01) with PUUV infection to have mild disease, whereas a significant number of HFRS patients infected with DOBV had moderate (p < 0.01) and severe or very severe (p < 0.01) disease.

CONCLUSION

Our results clearly indicate that in Croatia DOBV infection is associated with a more severe disease than PUUV infection. However, we confirmed previous findings that even PUUV infection could lead to a severe disease. Our initial experience in the evaluation of the proposed grading scale for disease severity demonstrated the proposed Croatian scale to be a useful tool in grading disease severity in patients infected with PUUV or DOBV. Moreover, the proposed scale may also prove highly useful for the prognostic purpose.

[Hemorrhagic fever with renal syndrome: imported or native disease in the Zadar region]

AIM

The aim of the study is to warn of the need of clinical hemorrhagic fever with renal syndrome (HFRS) recognition and determination, and of the risk of its spread from a new focus of this natural zoonosis near Zadar (north Dalmatia), i.e., in the northern part (Lika) of the Zadar County.

METHOD

Clinical and epidemiologic characteristics of HFRS were analyzed in four patients. Patient sera were analyzed for Puumala (PUU) and Hantaan (HTN) viruses by immunofluorescence test (IFT) and immunoenzyme test (ELISA).

RESULTS

Epidemiologic studies confirmed the source of infection to be out of the area in three patients, whereas in one patient it was near Zadar area. Mild symptoms pointed to the disease. Pathologic findings showed pathologic leukocyte values (leukocytosis), two- to four-fold alanine aminotransferase, aspartate aminotransferase and creatinine increase in serum, proteinuria and erythrocyturia. A significant PUU antibody titer was found by serum IF and ELISA.

CONCLUSION

The occurrence of HFRS in the Zadar area was confirmed by clinical description and laboratory evidence. The newly identified focus was in the vicinity of this area could imply a risk for the disease epidemic in the Zadar area.

[Early diagnostics of hemorrhagic fever with renal syndrome on the basis of the use of Pumala virus recombinant nucleocapsid protein]

Pumala virus recombinant nucleocapsid protein was used for the early diagnosis of haemorrhagic fever with renal syndrome. Specific IgM in the sera of patients could be determined by the IEA technique as early as on days 2-3 from the onset of the disease. The diagnostic effectiveness of the test-system was 95% and its specificity was 98%.

[Serologic diagnosis of hemorrhagic fever with renal syndrome in Bosnia and Herzegovina in 2002]

AIM

Results of the serologic confirmation of hemorrhagic fever with renal syndrome (HFRS) in patients with clinical picture and overt symptoms of the disease from particular areas in Bosnia and Herzegovina during 2002 are presented.

METHODS

A total of 146 sera from 100 clinically suspected patients were tested. The sera were tested for the presence of specific IgM antibodies to Hantaan and Puumala antigens by Elisa IgM "capture" test, and for the presence of specific antibodies to Hantaan, Puumala and Dobrava antigens by Elisa IgG test.

DISCUSSION

Most of the positive IgM reactions were recorded as cross reactions to Hantaan and Puumala antigens, and most of the positive IgG reactions as cross reactions to Hantaan and Dobrava antigens. The finding of antibodies in the sera of patients from Europe that react with Hantaan antigen are not associated with the infection with Hantaan, but with the infection with viruses that are genetically related with Hantaan. To date, HFRS caused by Puumala and Dobrava viruses has been verified in Bosnia and Herzegovina.

CONCLUSION

Using Elisa IgM "capture" test, acute hantavirus infection was serologically confirmed in 38% of clinically suspected patients with manifested symptoms from different areas of Bosnia and Herzegovina in 2002. The distribution of human hantavirus infection in Bosnia and Herzegovina was confirmed by the presence of specific hantavirus antibodies in patient sera.

Mapping of B-cell epitopes in the nucleocapsid protein of Puumala hantavirus

Hantavirus nucleocapsid protein (N) has been proven to induce highly protective immune responses in animal models. The knowledge on the mechanisms behind N-induced protection is still limited, although recent data suggest that both cellular and humoral immune responses are of importance. For a detailed B-cell epitope mapping of Puumala hantavirus (PUUV) N, we used recombinant N derivatives of the Russian strain CG18-20 and the Swedish strain Vranica/Hällnäs, as well as overlapping synthetic peptides corresponding to the Finnish prototype strain Sotkamo. The majority of a panel of monoclonal antibodies (mAbs) reacted with proteins derived from all included PUUV strains demonstrating the antigenic similarity of these proteins. In line with previous results, the epitopes of most mAbs were mapped within the 80 N-terminal amino acids of N. The present study further revealed that the epitopes of four mAbs raised against native viral N were located within amino acids 14-45, whereas one mAb raised against recombinant N was mapped to amino acids 14-39. Differences between the reactivity of the PUUV strains Vranica/Hällnäs and CG18-20 N suggested the importance of amino acid position 35 for the integrity of the epitopes. In line with the patterns obtained by the truncated recombinant proteins, mapping by overlapping peptides (PEPSCAN) confirmed a complex recognition pattern for most analyzed mAbs. Together, the results revealed the existence of several, partially overlapping, and discontinuous B-cell epitopes. In addition, based on differences within the same competition group, novel epitopes were defined.

Serological study of hantavirus in man in the Autonomous Community of Madrid, Spain

Data relating to hantavirus infection in Spain are scarce and limited to rural areas. The aim of this work was to study the seroprevalence of hantavirus infection in the Autonomous Community of Madrid (ACM), a region containing both rural and urban populations in different ecological settings. Sera from 3852 individuals (1849 male, 2003 female) were screened by indirect inmunofluorescence, with Vero E6 cells infected with Puumala, Hantaan and Seoul viruses as antigens. Screen-positive results were confirmed by Western blot with recombinant Seoul virus nucleocapsid protein as antigen. Antibodies against hantavirus were detected in 12 sera (0.31%). No statistical differences were found according to sex and age. The highest prevalence was found in the southeastern area, significantly higher than the central and north-western areas. The most frequent serological pattern was reactivity against all three viruses used (33.3% of all positive sera). Therefore, this study confirms the presence of hantavirus infection in the ACM, including for the first time an urban area of Spain, but with the highest prevalence in a rural area. Serological evidence suggests that there is more than one circulating serotype.

Yeast-expressed Puumala hantavirus nucleocapsid protein induces protection in a bank vole model

Hantaviruses are rodent-borne agents that cause severe human diseases. The coding sequences for the authentic and a His-tagged Puumala hantavirus (PUUV) nucleocapsid (N) protein were expressed in yeast (Saccharomyces cerevisiae). N-specific monoclonal antibodies demonstrated native antigenicity of the two proteins. All bank voles vaccinated with the His-tagged N protein in Freund's adjuvant (n=12) were defined as completely protected against subsequent virus challenge, based on the absence of viral N protein, RNA and G2-specific antibodies. In the group vaccinated with the yeast-expressed authentic N protein in Freund's adjuvant, 2/6 animals were defined as completely protected and 4/6 as partially protected. Moreover, when animals were vaccinated with the His-tagged N protein in an adjuvant certified for human use (alum), all (n=8) were at least partially protected (six completely, two partially). The general advantages of the yeast expression system make the described recombinant proteins promising candidate vaccines against hantavirus infection.

Human leukocyte antigen-B8-DR3 is a more important risk factor for severe Puumala hantavirus infection than the tumor necrosis factor-alpha(-308) G/A polymorphism

The tumor necrosis factor (TNF)-alpha(-308) G/A polymorphism (TNF-2) is in linkage disequilibrium with the human leukocyte antigen (HLA)-B8-DR3 haplotype. Both factors have been associated with severe Puumala hantavirus-induced nephropathia epidemica (NE). To examine which part of this extended haplotype might show the strongest association with the outcome of NE, the HLA-B, HLA-DRB1, and TNF-alpha(-308) alleles in 116 hospital-treated patients with NE were analyzed. The findings pointing to clinically severe NE were strongly associated with HLA-B8-DR3 haplotype. There was a trend toward severe disease in persons positive for TNF-2. This was probably due to strong linkage disequilibrium with HLA-B8-DR3, since there were no differences in the clinical severity of NE when TNF-2-positive/B8-DR3-negative persons were compared with TNF-2-negative/B8-DR3-negative persons. It is concluded that the HLA-B8-DR3 haplotype is an important contributor to the course of NE. The data indicate that the TNF-2 allele is not an independent risk factor for severe NE but a passive component in the extended haplotype.

Long-lived memory T lymphocyte responses after hantavirus infection

Puumala virus (PUUV) is a hantavirus that causes hemorrhagic fever with renal syndrome (HFRS), which is an important public health problem in large parts of Europe. We examined the memory cytolytic T lymphocyte (CTL) responses in 13 Finnish individuals who had HFRS between 1984 and 1995. In seven of these donors, we detected virus-specific CTL responses against the PUUV nucleocapsid (N) protein after in vitro stimulation with PUUV. Six novel CD8(+) CTL epitopes were defined on the N protein and were found to be restricted by various HLA alleles including A2, A28, B7, and B8. This is the first demonstration of PUUV-specific CTL responses in humans, and the first identification of CTL epitopes on PUUV. In addition, this study provides one of the few characterizations of a human antiviral memory T cell response, without the complicating issues of virus persistence or reinfection. Interferon (IFN)-gamma ELISPOT analysis showed that memory CTL specific for these epitopes were present at high frequency in PUUV-immune individuals many years after acute infection in the absence of detectable viral RNA. The frequencies of PUUV-specific CTL were comparable to or exceeded those found in other viral systems including influenza, EBV and HIV, in which CTL responses may be boosted by periodic reinfection or virus persistence.

[Epidemic nephropathy. An important differential diagnosis of acute renal failure in Reutlingen, an endemic area]

BACKGROUND AND OBJECTIVE

Hantavirus ("epidemic") nephropathy (HN), or hemorrhagic fever with renal syndrome (WHO nomenclature), is an infection caused by strains (e.g. Puumala) of Hantavirus, which is often accompanied by acute renal failure. Although its typical symptomatology has been fully reported, it is rarely included in the differential diagnosis of renal nephropathy. This study investigated whether, in the presence of typical symptoms, specific search for a certain constellation of laboratory values in association with a typical history can more often provide the diagnosis of HN.

PATIENTS AND METHODS

18 patients (4 females, 14 males; average age 41 years) fulfilled the following inclusion criteria: abnormal values for creatinine, LDH and C-reactive protein, proteinuria and hematuria, as well as thrombocytopenia in conjunction with fever, back- and headache. After the diagnosis had been confirmed by demonstrating antibodies against the Puumala strain of hantavirus, follow-up included laboratory tests and clinical observation.

RESULTS

All patients fully recovered without any sequelae. There was a clearly increased frequency of cases at the Reutlingen Clinic compared with the previous years (maximally 7 cases per year in 1995-1999). The incidence in the Reutlingen region was probably at least 6.5/100 000 inhabitants.

CONCLUSION

At least in endemic regions HN is one of the most common causes of acute renal failure. The increase of cases can, among other reasons, be explained by the described prospective diagnostic schema. But climatic factors with changes in the density of the vector (bank vole) cannot be excluded.

Cross-protection against challenge with Puumala virus after immunization with nucleocapsid proteins from different hantaviruses

Hantaviruses are rodent-borne agents that cause hemorrhagic fever with renal syndrome or hantavirus pulmonary syndrome in humans. The nucleocapsid protein (N) is relatively conserved among hantaviruses and highly immunogenic in both laboratory animals and humans, and it has been shown to induce efficient protective immunity in animal models. To investigate the ability of recombinant N (rN) from different hantaviruses to elicit cross-protection, we immunized bank voles with rN from Puumala (PUUV), Topografov (TOPV), Andes (ANDV), and Dobrava (DOBV) viruses and subsequently challenged them with PUUV. All animals immunized with PUUV and TOPV rN were completely protected. In the group immunized with DOBV rN, 7 of 10 animals were protected, while only 3 of 8 animals were protected in the group immunized with ANDV rN, which is more closely related to PUUV rN than DOBV rN. Humoral and cellular immune responses after rN immunization were also investigated. The highest cross-reactive humoral responses against PUUV antigen were detected in sera from ANDV rN-immunized animals, followed by those from TOPV rN-immunized animals, and only very low antibody cross-reactivity was observed in sera from DOBV rN-immunized animals. In proliferation assays, T lymphocytes from animals immunized with all heterologous rNs were as efficiently recalled in vitro by PUUV rN as were T lymphocytes from animals immunized with homologous protein. In summary, this study has shown that hantavirus N can elicit cross-protective immune responses against PUUV, and the results suggest a more important role for the cellular arm of the immune response than for the humoral arm in cross-protection elicited by rN.

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.