Structural Basis for a Neutralizing Antibody Response Elicited by a Recombinant Hantaan Virus Gn Immunogen

Hantaviruses are a group of emerging pathogens capable of causing severe disease upon zoonotic transmission to humans. The mature hantavirus surface presents higher-order tetrameric assemblies of two glycoproteins, Gn and Gc, which are responsible for negotiating host cell entry and constitute key therapeutic targets. Here, we demonstrate that recombinantly derived Gn from Hantaan virus (HTNV) elicits a neutralizing antibody response (serum dilution that inhibits 50% infection [ID₅₀], 1:200 to 1:850) in an animal model. Using antigen-specific B cell sorting, we isolated monoclonal antibodies (mAbs) exhibiting neutralizing and non-neutralizing activity, termed mAb HTN-Gn1 and mAb nnHTN-Gn2, respectively. Crystallographic analysis reveals that these mAbs target spatially distinct epitopes at disparate sites of the N-terminal region of the HTNV Gn ectodomain. Epitope mapping onto a model of the higher order (Gn-Gc)₄ spike supports the immune accessibility of the mAb HTN-Gn1 epitope, a hypothesis confirmed by electron cryo-tomography of the antibody with virus-like particles. These data define natively exposed regions of the hantaviral Gn that can be targeted in immunogen design. IMPORTANCE The spillover of pathogenic hantaviruses from rodent reservoirs into the human population poses a continued threat to human health. Here, we show that a recombinant form of the Hantaan virus (HTNV) surface-displayed glycoprotein, Gn, elicits a neutralizing antibody response in rabbits. We isolated a neutralizing (HTN-Gn1) and a non-neutralizing (nnHTN-Gn2) monoclonal antibody and provide the first molecular-level insights into how the Gn glycoprotein may be targeted by the antibody-mediated immune response. These findings may guide rational vaccine design approaches focused on targeting the hantavirus glycoprotein envelope.

Nlrc3 Knockout Mice Showed Renal Pathological Changes After HTNV Infection

Hantaan virus (HTNV) infects humans and causes hemorrhagic fever with renal syndrome (HFRS). The development of well-characterized animal models of HFRS could accelerate the testing of vaccine candidates and therapeutic agents and provide a useful tool for studying the pathogenesis of HFRS. Because NLRC3 has multiple immunoregulatory roles, we investigated the susceptibility of Nlrc3-/- mice to HTNV infection in order to establish a new model of HFRS. Nlrc3-/- mice developed weight loss, renal hemorrhage, and tubule dilation after HTNV infection, recapitulating many clinical symptoms of human HFRS. Moreover, infected Nlrc3-/- mice showed higher viral loads in serum, spleen, and kidney than wild type C57BL/6 (WT) mice, and some of them manifested more hematological disorders and significant pathological changes within multiple organs than WT mice. Our results identify that HTNV infected Nlrc3-/- mice can develop clinical symptoms and pathological changes resembling patients with HFRS, suggesting a new model for studying the pathogenesis and testing of candidate vaccines and therapeutics.

HTNV infection of CD8+ T cells is associated with disease progression in HFRS patients

Hantaan viruses (HTNVs) are zoonotic pathogens transmitted mainly by rodents and capable of infecting humans. Increasing knowledge of the human response to HTNV infection can guide the development of new preventative vaccines and therapeutic strategies. Here, we show that HTNV can infect CD8+ T cells in vivo in patients diagnosed with hemorrhagic fever with renal syndrome (HFRS). Electron microscopy-mediated tracking of the life cycle and ultrastructure of HTNV-infected CD8+ T cells in vitro showed an association between notable increases in cytoplasmic multivesicular bodies and virus production. Notably, based on a clinical cohort of 280 patients, we found that circulating HTNV-infected CD8+ T cell numbers in blood were proportional to disease severity. These results demonstrate that viral infected CD8+ T cells may be used as an adjunct marker for monitoring HFRS disease progression and that modulating T cell functions may be explored for new treatment strategies.

The Glycoprotein and Nucleocapsid Protein of Hantaviruses Manipulate Autophagy Flux to Restrain Host Innate Immune Responses

Hantavirus infection, which causes severe zoonotic diseases with high mortality in humans, has become a global public health concern. Here, we demonstrate that Hantaan virus (HTNV), the prevalent prototype of the hantavirus in Asia, can restrain innate immune responses by manipulating host autophagy flux. HTNV induces complete mitophagy at the early stage of infection but incomplete autophagy at the late stage, and these responses involve the viral glycoprotein (Gn) and nucleocapsid protein (NP), respectively. Gn translocates to mitochondria and interacts with TUFM, recruiting LC3B and promoting mitophagy. Gn-induced mitophagy inhibits type I interferon (IFN) responses by degrading MAVS. Additionally, we found that NP competes with Gn for binding to LC3B, which inhibits Gn-mediated autophagosome formation, and interacts with SNAP29, which prevents autophagosome-lysosome fusion. Thus, NP disturbs the autophagic degradation of Gn. These findings highlight how hantaviruses repurpose host autophagy and evade innate immune responses for their life cycle and pathogenesis.

Recent Increase of Human Granulocytic Anaplasmosis and Co-Infection with Scrub Typhus or Korean Hemorrhagic Fever with Renal Syndrome in Korea

We report 17 patients with human granulocytic anaplasmosis between January 2015 and September 2018 at two tertiary university hospitals in Korea. Monthly incidence peaked in May and June. Among these patients, we identified three who were co-infected with scrub typhus, and one patient with hemorrhagic fever with renal syndrome.

The Long Noncoding RNA NEAT1 Exerts Antihantaviral Effects by Acting as Positive Feedback for RIG-I Signaling

Hantavirus infection, which causes zoonotic diseases with a high mortality rate in humans, has long been a global public health concern. Over the past decades, accumulating evidence suggests that long noncoding RNAs (lncRNAs) play key regulatory roles in innate immunity. However, the involvement of host lncRNAs in hantaviral control remains uncharacterized. In this study, we identified the lncRNA NEAT1 as a vital antiviral modulator. NEAT1 was dramatically upregulated after Hantaan virus (HTNV) infection, whereas its downregulation in vitro or in vivo delayed host innate immune responses and aggravated HTNV replication. Ectopic expression of NEAT1 enhanced beta interferon (IFN-β) production and suppressed HTNV infection. Further investigation suggested that NEAT1 served as positive feedback for RIG-I signaling. HTNV infection activated NEAT1 transcription through the RIG-I-IRF7 pathway, whereas NEAT1 removed the transcriptional inhibitory effects of the splicing factor proline- and glutamine-rich protein (SFPQ) by relocating SFPQ to paraspeckles, thus promoting the expression of RIG-I and DDX60. RIG-I and DDX60 had synergic effects on IFN production. Taken together, our findings demonstrate that NEAT1 modulates the innate immune response against HTNV infection, providing another layer of information about the role of lncRNAs in controlling viral infections.IMPORTANCE Hantaviruses have attracted worldwide attention as archetypal emerging pathogens. Recently, increasing evidence has highlighted long noncoding RNAs (lncRNAs) as key regulators of innate immunity; however, their roles in hantavirus infection remain unknown. In the present work, a new unexplored function of lncRNA NEAT1 in controlling HTNV replication was found. NEAT1 promoted interferon (IFN) responses by acting as positive feedback for RIG-I signaling. This lncRNA was induced by HTNV through the RIG-I-IRF7 pathway in a time- and dose-dependent manner and promoted HTNV-induced IFN production by facilitating RIG-I and DDX60 expression. Intriguingly, NEAT1 relocated SFPQ and formed paraspeckles after HTNV infection, which might reverse inhibitive effects of SFPQ on the transcription of RIG-I and DDX60. To the best of our knowledge, this is the first study to address the regulatory role of the lncRNA NEAT1 in host innate immunity after HTNV infection. In summary, our findings provide additional insights regarding the role of lncRNAs in controlling viral infections.

Effects of Different Doses of Nucleocapsid Protein from Hantaan Virus A9 Strain on Regulation of Interferon Signaling

Hantaan virus A9 strain (HTNV A9) is an etiologic agent of hemorrhagic fever with renal syndrome in China. The virulence of the pathogenic hantaviruses is determined by their ability to alter key signaling pathways of early interferon (IFN) induction within cells. The potential role of HTNV A9 structural proteins, such as nucleocapsid (N) and envelope glycoproteins (Gn and Gc), in regulating human's innate antiviral immune response has not yet been clarified. In this study, we investigated the effect of HTNV A9 N protein on the regulation of the IFN pathway. We found that A9 N protein can influence the host innate immune response by regulating the activation of IFNβ. The A9 N protein stimulates IFN response in low doses, whereas significantly inhibits IFNβ production at high doses. Furthermore, A9 N protein constitutively inhibits nuclear factor kappa B activation. A high dose of A9 N protein could inhibit either Poly IC-induced IFNβ or vesicular stomatitis virus-induced IFNβ and interferon-stimulated gene production. Our results indicate that HTNV A9 N protein helps virus establish successful infection by downregulating the IFN response and shed new light to the understanding of the interaction between the host innate immunity and virus during Hantaan virus infection.

Hantaan virus infection induces both Th1 and ThGranzyme B+ cell immune responses that associated with viral control and clinical outcome in humans

Hantaviruses infection causing severe emerging diseases with high mortality rates in humans has become public health concern globally. The potential roles of CD4(+)T cells in viral control have been extensively studied. However, the contribution of CD4(+)T cells to the host response against Hantaan virus (HTNV) infection remains unclear. Here, based on the T-cell epitopes mapped on HTNV glycoprotein, we studied the effects and characteristics of CD4(+)T-cell responses in determining the outcome of hemorrhagic fever with renal syndrome. A total of 79 novel 15-mer T-cell epitopes on the HTNV glycoprotein were identified, among which 20 peptides were dominant target epitopes. Importantly, we showed the presence of both effective Th1 responses with polyfunctional cytokine secretion and ThGranzyme B(+) cell responses with cytotoxic mediators production against HTNV infection. The HTNV glycoprotein-specific CD4(+)T-cell responses inversely correlated with the plasma HTNV RNA load in patients. Individuals with milder disease outcomes showed broader epitopes targeted and stronger CD4(+)T-cell responses against HTNV glycoproteins compared with more severe patients. The CD4(+)T cells characterized by broader antigenic repertoire, stronger polyfunctional responses, better expansion capacity and highly differentiated effector memory phenotype(CD27-CD28-CCR7-CD45RA-CD127(hi)) would elicit greater defense against HTNV infection and lead to much milder outcome of the disease. The host defense mediated by CD4(+)T cells may through the inducing antiviral condition of the host cells and cytotoxic effect of ThGranzyme B+ cells. Thus, these findings highlight the efforts of CD4(+)T-cell immunity to HTNV control and provide crucial information to better understand the immune defense against HTNV infection.

IL-33/ST2 correlates with severity of haemorrhagic fever with renal syndrome and regulates the inflammatory response in Hantaan virus-infected endothelial cells

BACKGROUND

Hantaan virus (HTNV) causes a severe lethal haemorrhagic fever with renal syndrome (HFRS) in humans. Despite a limited understanding of the pathogenesis of HFRS, the importance of the abundant production of pro-inflammatory cytokines has been widely recognized. Interleukin 33 (IL-33) has been demonstrated to play an important role in physiological and pathological immune responses. After binding to its receptor ST2L, IL-33 stimulates the Th2-type immune response and promotes cytokine production. Depending on the disease model, IL-33 either protects against infection or exacerbates inflammatory disease, but it is unknown how the IL-33/ST2 axis regulates the immune response during HTNV infection.

METHODOLOGY/PRINCIPAL FINDINGS

Blood samples were collected from 23 hospitalized patients and 28 healthy controls. The levels of IL-33 and soluble ST2 (sST2) in plasma were quantified by ELISA, and the relationship between IL-33, sST2 and the disease severity was analyzed. The role of IL-33/sST2 axis in the production of pro-inflammatory cytokines was studied on HTNV-infected endothelial cells. The results showed that the plasma IL-33 and sST2 were significantly higher in patients than in healthy controls. Spearman analysis showed that elevated IL-33 and sST2 levels were positively correlated with white blood cell count and viral load, while negatively correlated with platelet count. Furthermore, we found that IL-33 enhanced the production of pro-inflammatory cytokines in HTNV-infected endothelial cells through NF-κB pathway and that this process was inhibited by the recombinant sST2.

CONCLUSION/SIGNIFICANCE

Our results indicate that the IL-33 acts as an initiator of the "cytokine storm" during HTNV infection, while sST2 can inhibit this process. Our findings could provide a promising immunotherapeutic target for the disease control.

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.

Prevalence of antibodies against hantaviruses in serum and saliva of adults living or working on farms in Yorkshire, United Kingdom

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

Elevated plasma soluble Sema4D/CD100 levels are associated with disease severity in patients of hemorrhagic fever with renal syndrome

Background

Hantaan virus (HTNV) could cause a severe lethal hemorrhagic fever with renal syndrome (HFRS) in humans. Despite a limited understanding of the pathogenesis of HFRS, the importance of host-related immune responses in the pathogenesis of HFRS has been widely recognized. CD100/Sema4D has been demonstrated to play an important role in physiological and pathological immune responses, but the functional role of CD100 in infectious diseases has only been inadequately reported. The aim of this study was to investigate the pathological significance of CD100 in patients after HTNV infection.

Methodology/Principal Findings

Blood samples were collected from 99 hospitalized patients in Tangdu Hospital and 27 health controls. The level of soluble CD100 (sCD100) in plasma were quantified by ELISA and the relationship between sCD100 and the disease course or severity were analyzed. The expressions of membrane CD100 on various subpopulations of peripheral blood mononuclear cell (PBMC) were analyzed by flow cytometry. The results showed that sCD100 level in acute phase of HFRS was significantly higher in patients than that in healthy controls (P<0.0001) and the sCD100 level declined in convalescent phase. Multivariate model analysis showed that platelet count, white blood cell count, serum creatinine level and blood urea nitrogen level were associated with sCD100 levels and contributed independently to the elevated sCD100 levels. The expression of membrane CD100 on PBMCs decreased in the acute phase of HFRS patients compared with that of the normal controls and recovered in the convalescent phase.

Conclusions

We reported the elevated level of plasma sCD100 in HFRS patients and the elevated level might be a result from the shedding of membrane CD100 on PBMC. The elevated level of sCD100 was associated with disease severity, suggesting that sCD100 might be a cause or a consequence of progression of HFRS. The underlying mechanisms should be explored further.

Identification of a novel B-cell epitope of Hantaan virus glycoprotein recognized by neutralizing 3D8 monoclonal antibody

Hantaan virus (HTNV), a member of the family Bunyaviridae, is a major agent causing haemorrhagic fever with renal syndrome, a high-mortality-rate disease threatening approximately 150 000 people around the world yearly. The 3D8 mAb displays a neutralizing activity to HTNV infection. In this study, the B-cell epitopes of HTNV glycoproteins (GPs) were finely mapped by peptide scanning. A new B-cell epitope (882)GFLCPEFPGSFRKKC(896) of HTNV, which locates on Gc, has been screened out from a set of 15-mer synthesized peptides covering the full-length of HTNV-GPs. It has been shown by the alanine-scanning technique that (885)C, (893)R, (894)K, (895)K and (896)C are the key amino acids of the binding sites of the GPs. The implications of identifying a novel B-cell epitope for hantavirus immunology and vaccinology are discussed.

[Long term epidemiological effects of vaccination on hemorrhagical fever with renal syndrome (HFRS) in Shaanxi provincial HFRS epidemic areas]

OBJECTIVE

To evaluate the protective rate and the variation of HFRS-IgG on hemorrhagical fever with renal syndrome (HFRS) vaccine.

METHODS

Cluster, random sampling and cross-sectional study were used to assess the protective rate of HFRS vaccination. Level of HFRS-IgG was detected with ELISA in epidemic and non-epidemic areas of HFRS.

RESULTS

Curve equation was obtained as Yprotective rate=(0.863+0.283/Xvaccination term)×100% by protective rate with vaccination term. Protective rates showed a reducing trend, 90% after 7-8 years of vaccination, 88% after 10 years, and 94% on average. Absorbance (A) value of HFRS-IgG was 4 times higher in persons with vaccination than those without, in the epidemic area. Higher antibody level could be obtained after primary vaccination, but the level of antibody had a 50% reduction after 5-10 years of vaccination, and a 60% reduction after 10 years of vaccination.

CONCLUSION

HFRS antibody had a 50% reduction after 5-10 years of vaccination. The protective rate of HFRS vaccination had a 90% loss, after 7-8 years of vaccination. Booster dose was necessary after 7 years of vaccination.

RNA helicase retinoic acid-inducible gene I as a sensor of Hantaan virus replication

Hantaan virus (HTNV) causes severe human disease. The HTNV genome consists of three ssRNA segments of negative polarity that are complexed with viral nucleocapsid (N) protein. How the human innate immune system detects HTNV is unclear. RNA helicase retinoic acid-inducible gene I (RIG-I) does not sense genomic HTNV RNA. So far it has not been analysed whether pathogen-associated molecular patterns generated during the HTNV replication trigger RIG-I-mediated innate responses. Indeed, we found that knock-down of RIG-I in A549 cells, an alveolar epithelial cell line, increases HTNV replication and prevents induction of 2',5'-oligoadenylate synthetase, an interferon-stimulated gene. Moreover, overexpression of wild-type or constitutive active RIG-I in Huh7.5 cells lacking a functional RIG-I diminished HTNV virion production. Intriguingly, reporter assays revealed that in vitro-transcribed HTNV N RNA and expression of the HTNV N ORF triggers RIG-I signalling. This effect was completely blocked by the RNA-binding domain of vaccinia virus E3 protein, suggesting that dsRNA-like secondary structures of HTNV N RNA stimulate RIG-I. Finally, transfection of HTNV N RNA into A549 cells resulted in a 2 log-reduction of viral titres upon challenge with virus. Our study is the first demonstration that RIG-I mediates antiviral innate responses induced by HTNV N RNA during HTNV replication and interferes with HTNV growth.

[Construction and immunogenic study of recombinant adenovirus containing chimeric gene G2S0.7 and CTL epitopes of Hantaan virus]

AIM

To express G2 fragment of M segment and 0.7 kb fragment of S segment and several CTL epitopes of S segment in adenovirus expression system and investigate the immunological properties of hantaan virus chimeric gene.

METHODS

The recombinant adenovirus was constructed and the recombinant adenovirus was obtained after transfecting HEK293 cells. The titer of it was determined and the expressed product was detected by IFA and ELISA. Further, BALB/c mice were vaccinated by the recombinant adenovirus and the immune response was tested by ELISA, microcell-culture neutralizing experiment, T lymphocyte proliferation test (MTT assay) and cell-mediated cytotoxicity assay.

RESULTS

The recombinant adenovirus AG2S0.7CTL1, AG2S0.7CTL2 were constructed successfully and the titer of it was about 10¹⁰-10¹¹ pfu/mL. The expressed protein could be recognized by the hantaan virus NP-specific mAb and glycoprotein G2-specific mAb. The recombinant adenovirus containing CTL epitopes could elicit effectively the cellular immune response aimed to the NP and GP of hantaan virus in BALB/c mice.

CONCLUSION

The recombinant adenovirus containing CTL epitopes could induce the higher cellular immune response than the group that not containing CTL epitopes.

Alpha/beta interferon (IFN-alpha/beta)-independent induction of IFN-lambda1 (interleukin-29) in response to Hantaan virus infection

Type III interferons ([IFNs] IFN-lambda and interleukin-28 and -29 [IL-28/29]) are recently recognized cytokines with innate antiviral effects similar to those of type I IFNs (IFN-alpha/beta). Like IFN-alpha/beta, IFN-lambda-expression can be induced by viruses, and it is believed that type I and III IFNs are regulated in the same manner. Hantaviruses are weak IFN-alpha/beta inducers and have surprisingly been shown to activate IFN-alpha/beta-independent IFN-stimulated gene (ISG) expression. Here, we show that in Hantaan virus (HTNV)-infected human epithelial A549 cells, induction of IFN-lambda1 preceded induction of MxA and IFN-beta by 12 and 24 h, respectively, and IFN-alpha was not induced at all. Furthermore, induction of IFN-lambda1 and MxA was observed in HTNV-infected African green monkey epithelial Vero E6 cells, a cell line that cannot produce type I IFNs, clearly showing that HTNV can induce IFN-lambda1 and ISGs in the complete absence of IFN-alpha/beta. In HTNV-infected human fibroblast MRC-5 cells, which lack the IFN-lambda receptor, induction of MxA coincided in time with IFN-beta-induction. UV-inactivated HTNV did not induce any IFNs or MxA in any cell line, showing that activation of IFN-lambda1 is dependent on replicating virus. Induction of both IFN-beta and IFN-lambda1 in A549 cells after poly(I:C)-stimulation was strongly inhibited in HTNV-infected cells, suggesting that HTNV can inhibit signaling pathways used to simultaneously activate types I and III IFNs. In conclusion, we show that HTNV can cause type I IFN-independent IFN-lambda1 induction and IFN-lambda1-specific ISG induction. Importantly, the results suggest the existence of specific signaling pathways that induce IFN-lambda1 without simultaneous type I IFN induction during virus infection.

Reversible splenium lesion of the corpus callosum in hemorrhagic fever with renal failure syndrome

This is the first case of virus-associated encephalitis/encephalopathy in which the pathogen was Hantaan virus. A 53-yr-old man presented fever, renal failure and a hemorrhagic tendency and he was diagnosed with hemorrhagic fever with renal failure syndrome (HFRS). In the course of his illness, mild neurologic symptoms such as dizziness and confusion developed and magnetic resonance images revealed a reversible lesion in the splenium of the corpus callosum. This case suggests that HFRS patients with neurologic symptoms like dizziness and mental slowing should be considered to have structural brain lesions and to require brain imaging studies.

Production and characterization of a recombinant single-chain antibody against Hantaan virus envelop glycoprotein

Hantaan virus (HTNV) is the type of Hantavirus causing hemorrhagic fever with renal syndrome, for which no specific therapeutics are available so far. Cell type-specific internalizing antibodies can be used to deliver therapeutics intracellularly to target cell and thus, have potential application in anti-HTNV infection. To achieve intracellular delivery of therapeutics, it is necessary to obtain antibodies that demonstrate sufficient cell type-specific binding, internalizing, and desired cellular trafficking. Here, we describe the prokaryotic expression, affinity purification, and functional testing of a single-chain Fv antibody fragment (scFv) against HTNV envelop glycoprotein (GP), an HTNV-specific antigen normally located on the membranes of HTNV-infected cells. This HTNV GP-targeting antibody, scFv3G1, was produced in the cytoplasm of Escherichia coli cells as a soluble protein and was purified by immobilized metal affinity chromatography. The purified scFv possessed a high specific antigen-binding activity to HTNV GP and HTNV-infected Vero E6 cells and could be internalized into HTNV-infected cells probably through the clathrin-dependent endocytosis pathways similar to that observed with transferrin. Our results showed that the E. coli-produced scFv had potential applications in targeted and intracellular delivery of therapeutics against HTNV infections.

Ecology of Hantaan virus at Twin Bridges Training Area, Gyeonggi Province, Republic of Korea, 2005-2007

The Twin Bridges Training Area (TBTA) in the Republic of Korea consists of dirt roads, barren training areas, and forested hillsides adjacent to linear and broad expanses of tall grasses, herbaceous, and scrub vegetation. Of the six species of small mammals, the striped field mouse, Apodemus agrarius, was the most frequently captured (96.1%). Apodemus agrarius capture rates varied from 17.7 to 33.2% during three trapping periods. Gravid females were observed during November-December 2006 (8.4%) and March 2007 (5.1%). In 2005, the overall seroprevalence of Hantaan virus (HTNV) was high (34.4%) and lower during surveys in 2006 (14.2%) and 2007 (13.8%). Seroprevalence was directly correlated with weight increase of A. agrarius.

[Comparison on the difference of virulence between Hantaan virus and Seoul virus isolated both from Rattus norvegicus]

OBJECTIVE

Comparing the difference of virulence between the strain CGRn5310 (HTNV) and the strain HR54 (SEOV) isolated both from Rattus norvegicus.

METHODS

Suckling mice were used to compare the difference of virulence between the two strains. Hantavirus antigens were detected in brain and lung tissues collected from the infected mice.

RESULTS

Compared with the control group, all infected mice grew slowly. Furthermore, the mice inoculated intracerebrally with either CGRn5310 or HR45 appeared ruffled fur, and reduced activity, followed by neurological symptoms, such as paralyses and convulsions. The half lethal dose (LD(50)) of CGRn5310 strain was 10(-6.42), whereas the LD(50) of HR54 strain was 10(-4.51). Hantavirus antigens were identified in brain and lung tissues from the mice infected with the strain CGRn5310 and the strain HR54.

CONCLUSION

LD(50) of the strain CGRn5310 was significantly higher than that of the strain HR54. Our results suggested that the virulence of the spillover hantavirus might only slightly be influenced by the non-reservoir rodents.

Hantaan virus triggers TLR3-dependent innate immune responses

Immediately after viral infection, innate responses including expression of IFN-alpha/beta and IFN-stimulated genes (ISGs) are elicited ubiquitously by recruitment of specific pathogen recognition receptors. The velocity to induce IFN-alpha/beta and ISGs in response to an infection is often decisive for virulence. Interestingly, in primary endothelial cells ISGs are induced later by hantaviruses pathogenic to humans than those considered to be nonpathogenic or of low virulence. Here we demonstrate that pathogenic Hantaan (HTNV) and putatively nonpathogenic Prospect Hill hantavirus (PHV) differentially activate innate responses in the established cell lines A549 and HuH7. STAT1alpha phosphorylation was detectable 3 h after PHV inoculation but not within the first 2 days after HTNV inoculation. The velocity to induce the ISGs MxA and ISG15 correlated inversely with amounts of virus produced. Moreover, expression of the inflammatory chemokine CCL5 was also induced differentially. Both hantaviruses induced innate responses via TRAF3 (TNF receptor-associated factor 3), and TLR3 was required for HTNV-induced expression of MxA, but not for the MxA induction triggered by PHV. Infection of RIG-I-deficient HuH7.5 cells revealed that RIG-I (retinoic acid receptor I) was not necessary for induction of innate responses by PHV. Taken together, these data suggest that HTNV and PHV elicit different signaling cascades that converge via TRAF3. Early induction of antiviral responses might contribute to efficient elimination of PHV. Subsequent to clearance of the infection, innate responses most likely cease; vice versa, retarded induction of antiviral responses could lead to increased HTNV replication and dissemination, which might cause a prolonged inflammatory response and might contribute to the in vivo virulence.

[Application of flow microbeads assay in detection of specific antibodies and cytokines in serum from patients with hemorrhagic fever with renal syndrome]

AIM

To establish a flow microbeads assay (FMA) to examine the level of hemorrhagic fever with renal syndrome virus (HFRS V.) specific IgM, IgG and cytokines in HFRS patients.

METHODS

Serum samples from 28 cases of HFRS and 20 healthy controls were studied. Serum levels of anti-HFRS V. antibodies were qualified and inflammatory cytokines IL-6 and TNF-alpha were quantified by FMA. The results were compared with the results by ELISA.

RESULTS

FMA showed that the positivity rates for anti-HFRS V. IgM and IgG were 92.85% and 71.43%, respectively. None was detected positive in healthy control group. The serum level of IL-6 and TNF-alpha in HFRS group were (532.62+/-397.19) ng/L and (392.68+/-177.68)ng/L, respectively, which were significantly higher than that in healthy control group (38.77+/-20.32 ng/L and 15.91+/-6.91 ng/L, P<0.01). In contrast, ELISA showed that the positivity rates for anti-HFRS V. IgM and IgG were 71.43% and 50.00%, respectively. None was detected positive in healthy control group. The serum level of IL-6 and TNF-alpha in HFRS group were (256.46+/-102.51) ng/L ang (45.63+/-5.32) ng/L, respectively, which were significantly higher than that in healthy control group (53.80+/-19.21 ng/L and 5.81+/-3.58 ng/L, P<0.01).

CONCLUSION

A FMA method is established to monitor the immune response in HFRS patients, which has better sensitivity than ELISA, and thus provides a useful tool for study of HFRS.

[Application of Epstein-Barr virus-transformed B lymphoblastic cells in identification of CTL epitopes specific for Hantaan virus]

AIM

To establish Epstein-Barr virus (EBV)-transformed B lymphoblastic cell lines (B-LCL) to present peptides as antigen-presenting cells (APC) and stimulate short-cultured T cells secreting IFN-gamma, by which the T cell epitopes are identified.

METHODS

PBMCs from patients with hemorrhagic fever with renal syndrome (HFRS) were transformed using EBV from supernatant of B95-8 cells. ELISPOT assay was then employed to evaluate the IFN-gamma production of short-cultured G9L-specific CD8(+) T cells stimulated with peptide-pulsed autologous B-LCL cells.

RESULTS

B-LCL pulsed with G9L or G9L-nested V15R can stimulate G9L-specific CD8(+) T cells producing IFN-gamma, but not B-LCL pulsed with non-homologous I15P.

CONCLUSION

B-LCL can efficiently and specifically present peptides to peptide-specific T cells as non-professional APC.

Collective immunity of the population from endemic zones of hemorrhagic fever with renal syndrome in Kosovo

Hemorrhagic fever with renal syndrome (HFRS), also known as mice fever is an acute viral zoonosis and it appears in the natural focus after the human contact with Hantaan virus infected mice. The objective (purpose) of this study was to investigate the prevalence of specific antibodies in HFRS, in convalescent persons (collective immunity in endemic hearths). In this project we applied the epidemiological method of studying with retrospective-perspective, the serological method for determination and detecting antibodies from the persons of epidemical focus and statistical methods. The disease diagnosis is based on the epidemiological, clinical and serological records. The collected samples have been sent to referral laboratory in Medical Faculty-Institute of Microbiology Ljubljana for laboratory confirmation. From the results we came to conclusion that in the territory of Republic of Kosovo, the HFRS is still a serious health, economic and biological problem. The lethality rate from HFRS in 1986 was 15.4%, 1986-89 10.8%, from 1995-2006 8.70%. The lowest rates of morbidity, mortality and lethality of HFRS compared with the previous periods of time, prove collective immunity growth in Dukagjini valley. For collective immunity research and to conduct the persistence of antibodies for viral corresponding (relative) antigen, after the disease, the samples were collected in the time period of May-June 2008, with 203 persons that were tested with serological method IIF (Indirect immune fluorescence) from which 187 cases (92.1%) resulted sero-negative and 16 cases (7.9%) resulted sero-positive with HFRS. This proves the collective immunity increase for HFRS. From 13 recovered patients previously diagnosed with HFRS (1986-1989-1995), levels of antibodies were screened in 2008 with IIF. Out of 13 persons, positive antibodies were found in 10 cases, while 3 cases were negative for antibodies (HTN, PUU, and DOB). After 13, 19 and 22 years HTN, PUU and DOB antibodies persisted in level (1:16-1:512). Based on the gathered results, we came to conclusion that it is necessary to compile the National Strategy of Surveillance for the Kosovo Health System for a 5 year period, for avoiding this high risk disease.

[3 cases of hemorrhagic fever with renal syndrome morbidity]

Viral origin of hemorrhagic fever with renal syndrome (HFRS) is known since 40th years of last century. Also it is known that contamination of person is performed mainly by air pollution way. We observed a focus with 3 HFRS cases (with laboratory confirmation--antibodies to HFRS Hantavirus were found) in one family with one lethal outcome. Contamination of patients occurred by air pollution way during stocking vegetables contaminated with rodent's excrements. Lethal outcome was stipulated by incorrect diagnosis made by district doctor (nonmetering epidemiological anamnesis and HFRS territory endemicity and seasonal prevalence) which leaded to late hospitalization and absence of possibility to render all complex of treatment and reanimation in the hospital.

[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.

[Discovery, clinical and etiological characteristic of hemorrhagic fever with renal syndrome in the subtropical zone of Krasnodar region]

Twenty-six patients with hemorrhagic fever with renal syndrome (HFRS) were revealed as a result of serological examination of 582 patients with fever living around Sochi town. Etiologic role of Dobrava virus subtype as the cause of HFRS was assessed by immunofluorescent and ELISA assays, and neutralization test. The principal host of this virus and source of infection for humans is Caucasian forest mouse Apodemus ponticus. HFRS morbidity was sporadic and not dependent from patients' occupation and season. Comparative analysis of clinical and laboratory data from HFRS cases caused by DOB/Sochi and DOB/Lipetsk subspecies, as well as Puumala virus showed higher proportion of severe forms of disease in patients with HFRS from Sochi.

[Transformation of full-length gene of mouse/human chimeric antibody against Hantaan virus into Arabidopsis thaliana]

AIM

To construct the transgenic Arabidopsis thaliana containing full-length gene of mouse/human chimeric antibody(3G1MH) against Hantaan virus.

METHODS

The recombinant plasmid 3G1MH-pCAMBIA2301 was transformed into Agrobacterium tumefaciens GV3101 by TSS freeze-thaw method, and then the recombinant was transferred into wild Arabidopsis thaliana by vacuum-transgenic method. The regenerated transgenic plants were selected with kanamycin, and confirmed by PCR and Northern blot.

RESULTS

PCR result showed stable integration of the 3G1MH gene IN Arabidopsis thaliana genome in 7 stains of the transformed plants. Northern blot analyses confirmed the transcription of heavy and light chains in the transgenic plants.

CONCLUSION

The successful establishment of 3G1MH transgenic Arabidopsis thaliana plants pave the way for further research on expressing therapeutic antibody in transgenic plants.

Immunological properties of a fusion protein containing nucleocapsid protein and glycoprotein Gn of Hantaan virus

Escherichia coli and the baculovirus Bac-to-Bac system were used to express chimeric gene GnS0.7 consisting of glycoprotein Gn gene and the 0.7 kb fragment of S genome segment carrying nucleoprotein (N) gene of Hantaan virus (HTNV). The expressed fusion protein GnN0.7 was recognized by monoclonal antibodies (MAbs) to HTNV Gn glycoprotein and N protein, respectively. Its molecular mass as determined by Western blot analysis corresponded to the predicted value. The mice immunized with insect Spodoptera frugiperda (Sf9) cells transfected with recombinant baculovirus carrying GnS0.7 gene, produced serum antibodies with titer up to 3,200 as assayed by immunofluorescence. Moreover, immunized mice showed positive proliferation index for splenocytes stimulated with HTNV Gn and N, respectively. These results indicated that insect Sf9 cells infected with the recombinant baculovirus expressed a fully biologically active fusion protein that elicited not only humoral but also cellular immune response in mice. Hence, this protein may be used as a genetically engineered subunit HTNV vaccine representing efficacious and safe alternative to traditional vaccines.

Interferon-stimulated genes response in endothelial cells following Hantaan virus infection

The regulation mechanism of interferon (IFN) and IFN-stimulated genes is a very complex procedure and is dependent on cell types and virus species. We observed molecular changes related to anti-viral responses in endothelial cells during Hantaan virus (HTNV) infection. We found that there are two patterns of gene expression, the first pattern of gene expression being characterized by early induction and short action, as in that of type I IFNs,' and the other being characterized by delayed induction and long duration, as those of IRF-7, MxA, and TAP-1/2. Even though there are significant differences in their induction folds, we found that all of IFN-alpha/beta, IRF- 3/7, MxA, and TAP-1/2 mRNA expressions reached the peak when the viral replication was most active, which took place 3 days of post infection (d.p.i.). In addition, an interesting phenomenon was observed; only one gene was highly expressed in paired genes such as IFN-alpha/beta' (3/277-folds), IRF-3/7 (2.2/29.4-folds), and TAP- 1/2 (26.2/6.1-folds). Therefore, IFN-beta, IRF-7, and TAP-1 seem to be more important for the anti-viral response in HTNV infection. MxA was increased to 296-folds at 3 d.p.i. and kept continuing 207-folds until 7 d.p.i.. The above results indicate that IFN-beta works for an early anti-viral response, while IRF7, MxA, and TAP-1 work for prolonged anti-viral response in HTNV infection.

[Development and evaluation of a double antigen sandwich ELISA for the detection of total antibodies against hemorrhagic fever with renal syndrome virus]

OBJECTIVES

To develop and evaluate a method for detection of the total antibodies against hemorrhagic fever with renal syndrome (HFRS) virus with improved sensitivity and simplified operation procedure.

METHODS

The nucleic proteins of hantavirus were used as coating antigens as well as detection antigens labeled with horse radish peroxidase (HRP). The operation protocol was established, optimized and compared with indirect fluorescence assay (IFA).

RESULTS

The specificity of this method was 100 percent in the test of different human sera and 4-8 times more sensitive than IFA. And, it is simpler without requiring any change of the reagents, different sources of samples did not affect the results of the test.

CONCLUSION

This method is specific, sensitive and simple for detection of the total antibodies in sera against hantavirus, could be used for the screening of Hantavirus infection in human and host rodent animals.

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.

Analysis of the immune response of Hantaan virus nucleocapsid protein-specific CD8+ T cells in mice

The major histocompatibility complex (MHC) class-I restricted epitope of Hantaan virus nucleocapsid protein (N) was identified using overlapping peptides and BALB/c mice. Using the MHC tetramer derived from the epitope, we found that the level of N-specific CD8(+) T cells increased to approximately 20% of all antigen-specific CD8(+) T cells in a mouse model of transient infection. However, N-specific CD8(+) T cells were undetectable in a mouse model of persistent infection, both in the persistently infected phase and in the convalescent phase. Levels of CD8(+) T cells producing interferon-gamma were weak in both the acute and convalescent phases in the persistently infected model. These results indicate that hantavirus strongly suppresses the production of N-specific CD8(+) T cells throughout the course of infection in persistently infected mice. Moreover, N-specific CD8(+) T cells were not effective in recovering persistently infected mice, despite the existence of abundant N antigen in vivo.

Detection of Circulating Antigen with a MAb-Based Sandwich-ELISA and Its Comparison with Specific IgM Detection in Sera of Patients with Hemorrhagic Fever with Renal Syndrome

A monoclonal antibody (1H2) against nucleocapsid protein of Hantavirus was developed. A sandwich enzyme-linked immunosorbent assay (ELISA) with the monoclonal antibody (MAb) was established and evaluated for detecting circulating antigen (CAg) in serum of patients with hemorrhagic fever with renal syndrome (HFRS). Results were compared to that of an immunoglobulin M (IgM)-detecting ELISA. Of 143 patients with HFRS, 106 were positive for CAg of Hantavirus and 128 positive for specific IgM. Among the 15 HFRS patients in whom specific IgM was not detected, 10 were positive for CAg. Of 100 controls including 40 hepatitis B cases, 40 measles cases, and 20 healthy persons all were negative for both CAg and specific IgM. Detection of Hantavirus CAg with a MAb-based sandwich ELISA (MBS-ELISA) established in the present study adds a new diagnostic tool for HFRS, and it increases the diagnostic rate to conventional specific IgM detection, especially for patient in the early stage of HFRS.

[Late consequences of hemorrhagic fever with renal syndrome in a woman who had it during pregnancy]

The authors adduce a brief description of the features and outcomes of hemorrhagic fever with renal syndrome (HFRS) in 8 pregnant women. The results of the examination of a 54-year-old woman and her son, who suffered from a severe form of HERS 28 years ago during the 31st week of pregnancy, are presented in detail. Antibodies to Hantaan virus 1:32 were found; magnetic resonance tomography of the skull revealed sequelae of hypophysial hemorrhage with the formation of "partly empty ephippium". The antibodies were not found in the son; hydrocephalus, forehead cortex atrophy, and lateral ventricular asymmetry were revealed.

[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.

Genetic properties of medium (M) and small (S) genomic RNA segments of Seoul hantavirus isolated from Rattus norvegicus and antigenicity analysis of recombinant nucleocapsid protein

A novel isolate of Seoul (SEO) hantaviruses was detected and identified in Rattus norvegicus in Shandong Province, China and designated as JUN5-14. The partial M segment and the coding region of nucleocapsid protein (NP) in the S segment of JUN5-14 were PCR-amplified and sequenced. Nucleotide sequence analysis of the partial M segment (300 bp) revealed that JUN5-14 isolate was closely related to former SEO isolates in Shandong (97.3-99.0% homology) and non-Shandong SEO viruses (84.1-97.7% homology) but distantly related to other hantaviruses (61.5-75.1% homology). Consistent with the M segment, the coding region of the NP showed 87.5-97.8% and 97.9-99.8% identity with SEO viruses and 55.2-75.8% and 47.2-84.4% homology with other hantaviruses, at nucleotide and amino acid level, respectively. The virus isolate was identified as a member of the subtype 3 (S3) of SEO viruses by phylogenetic trees generated from the nucleotide sequences of the S and M segments. In order to develop a diagnostic assay for hantavirus infection in human, the full-length NP gene of JUN5-14 was expressed in BHK21 cells using the T7 RNA polymerase expression system. The NP expression was confirmed by indirect immunofluorescence assay (IFA) and Western blotting. The expressed NP protein was used as antigen to detect antibody response against NP in patients with hemorrhagic fever with renal syndrome (HFRS) in an IgG-IFA. Sixteen out of seventeen serum samples showed positive for the presence of anti-NP antibodies, indicating that the recombinant NP (rNP) protein of JUN5-14 was a good antigen for detecting hantavirus infection in human.

Truncated Recombinant Dobrava Hantavirus Nucleocapsid Proteins Induce Strong, Long-Lasting Immune Responses in Mice

We describe the cloning and expression of Dobrava hantavirus (DOBV) nucleocapsid proteins and a truncated form consisting of the first 118 N-terminal amino acids, and the capacity of these E. coli ICONE 200-expressed recombinant proteins (rNp) to induce a protective immune response against DOBV in mice. As an alternative carrier protein, the outer membrane protein A derived from Klebsiella pneumoniae (rP40) has been coupled to different rNp constructs. All recombinant proteins were found to be highly immunogenic after three immunizations of rNp. The immunizations resulted in the induction of a strong Np-specific IgG response with a predominance of IgG1 over IgG2b and IgG2a, suggesting a mixed Th1/Th2 cell involvement. A specific IgG3 response could not be detected. Mice immunized with recombinant DOBV rNp without rP40 showed lower nucleocapsid-specific antibody responses in comparison with the rP40-conjugated constructs, but all mice were found to be protected against DOBV challenge. Our results indicate that the rNp constructs coupled to rP40, represent promising vaccine candidates.

Hantaan/Andes virus DNA vaccine elicits a broadly cross-reactive neutralizing antibody response in nonhuman primates

At least four hantavirus species cause disease with prominent renal involvement-hemorrhagic fever with renal syndrome (HFRS); and several hantavirus strains cause disease with significant pulmonary involvement-hantavirus pulmonary syndrome (HPS). The most prevalent and lethal hantaviruses associated with HFRS and HPS are Hantaan virus (HTNV) and Andes virus (ANDV), respectively. Here, we constructed a DNA vaccine plasmid (pWRG/HA-M) that contains both the HTNV and ANDV M gene segments. Rhesus macaques vaccinated with pWRG/HA-M produced antibodies that bound the M gene products (i.e., G1 and G2 glycoproteins), and neutralized both HTNV and ANDV. Neutralizing antibody titers elicited by the dual-immunogen pWRG/HA-M, or single-immunogen plasmids expressing only the HTNV or ANDV glycoproteins, increased rapidly to high levels after a booster vaccination administered 1-2 years after the initial vaccination series. Memory responses elicited by this long-range boost exhibited an increased breadth of cross-neutralizing activity relative to the primary response. This is the first time that hantavirus M gene-based DNA vaccines have been shown to elicit a potent memory response, and to elicit antibody responses that neutralize viruses that cause both HFRS and HPS.

Characterization of truncated hantavirus nucleocapsid proteins and their application for serotyping

Hemorrhagic fever with renal syndrome (HFRS) is a fulminant infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. Hantaviruses associated with this belong to different serotypes: Hantaan (HTN), Seoul (SEO), Dobrava/Belgrade (DOB), and Puumala (PUU). The first two, HTN and SEO, are endemic in China. To investigate the epidemiology of HFRS and virus transmission in China, we constructed prokaryotic plasmids encoding truncated recombinant HTN and SEO nucleocapsid proteins (NPs), which lacked 154 amino acid (aa), 99 aa, or 49 aa in the N-terminal region, respectively. After expression, the truncated rNPs were tested as serotyping antigens, particularly for use in the enzyme-linked immunosorbent assay (ELISA). In addition, 68 acute and 52 convalescent sera were collected from HFRS patients from Harbin, Lantian, and Kaifeng regions in China in 2004, which had hantavirus specific antibodies by IFA. A neutralization test was used to differentiate these, which showed that 73 were due to HTN infection, 33 to SEO infection, and 14 undetermined. By ELISA, the truncated rNPs, that lacked 99 (rNP100) or 49 (rNP50) N-terminal amino acids of the NPs of HTN and SEO, were able to differentiate HTNV and SEOV-specific immune sera, but the rNP155 could not. Particularly, the ELISAs based on the rNP50s had a result comparable to PRNT. Thus, the rNP50 is recommended as efficient serotyping antigen for hantavirus infection diagnosis by ELISA.

Analysis of immune responses against nucleocapsid protein of the Hantaan virus elicited by virus infection or DNA vaccination

Even though neutralizing antibodies against the Hantaan virus (HTNV) has been proven to be critical against viral infections, the cellular immune responses to HTNV are also assumed to be important for viral clearance. In this report, we have examined the cellular and humoral immune responses against the HTNV nucleocapsid protein (NP) elicited by virus infection or DNA vaccination. To examine the cellular immune response against HTNV NP, we used H-2K(b) restricted T-cell epitopes of NP. The NP-specific CD8(+) T cell response was analyzed using a (51)Cr-release assay, intracellular cytokine staining assay, enzyme-linked immunospot assay and tetramer binding assay in C57BL/6 mice infected with HTNV. Using these methods, we found that HTNV infection elicited a strong NP-specific CD8(+) T cell response at eight days after infection. We also found that several different methods to check the NP-specific CD8(+) T cell response showed a very high correlation among analysis. In the case of DNA vaccination by plasmid encoding nucleocapsid gene, the NP-specific antibody response was elicited 2 approximately 4 weeks after immunization and maximized at 6 approximately 8 weeks. NP-specific CD8(+) T cell response reached its peak 3 weeks after immunization. In a challenge test with the recombinant vaccinia virus expressing NP (rVV-HTNV-N), the rVV-HTNV-N titers in DNA vaccinated mice were decreased about 100-fold compared to the negative control mice.

[Identification of HTNV-NP-specific T lymphocyte epitopes and analysis of the epitope-specific T cell response]

AIM

To identify the nucleocapsid protein of Hantaan virus (HTNV-NP)-specific T lymphocyte epitopes and analyze the epitope-specific T cell response during hemorrhagic fever with renal syndrome (HFRS).

METHODS

T lymphocyte epitopes and frequencies of epitope-specific T cells were determined by ELISPOT using PBMCs from HFRS patients stimulated by individual or mixture of overlapping 15-mer peptides spanning the amino acid sequence of HTNV-NP.

RESULTS

Out of 10 peptide mixtures, 8 elicited strong HTNV-NP-specific responses in 18 of 47 HFRS patients, and the T cell response was found at early stage of HFRS. Moreover, 17 HTNV-NP-specific T lymphocyte epitopes were identified in 11 patients, and most epitopes were clustered near the center of NP in linear structure. Among them, 14 T lymphocyte epitopes were described for the first time.

CONCLUSION

HTNV-NP-specific T cell response can be elicited at early stage of HFRS and T lymphocyte epitopes mainly located in the center of NP, suggesting that it may play an important role in immune protection during HTNV infection.

[Hemorrhagic fever with renal syndrome among servicemen in Primorskiĭ Region of Russia]

The data about the incidence of hemorrhagic fever with renal syndrome (HFRS) among the servicemen stationed in HFRS endemic territories at Primorye Region are presented. The authors have shown the epidemiological significance of outbreaks, group and sporadic cases of HFRS especially in servicemen aged 18-20. During the outbreaks the maximal HFRS incidence is registered during 2 weeks after the first case. 104 HFRS cases were registered in the servicemen. Among them 77.8 +/- 3.0% were at the age of 18-20; 7.4 +/- 2.9% of these cases were lethal.

[Expression and genetic immunization of hantaan virus G2 recombinant adenovirus]

AIM

To express hantaan virus(HTNV) envelope glycoprotein G(2) recombinant adenovirus(Adeno-G(2)) in vero E6 cells and explore its property of inducing immune response.

METHODS

Vero E6 cells were infected with the HTNV Adeno-G(2) (100 MOI). The expression of Adeno-G(2) in the infected Vero E6 cells was detected by IFA. BALB/c mice were immunized with HTNV Adeno-G(2), then the immune response to Adeno-G(2) was tested by ELISA, microcell-culture neutralizing experiment and lymphocyte proliferation test (MTT colorimetry).

RESULTS

IFA detection showed the expression of Adeno-G(2) in the infected Vero E6 cells. The titer of specific antibody was 1:40; The low-titer neutralization antibody was also detected. But the lymphocyte proliferation reaction was not notable.

CONCLUSION

The HTNV Adeno-G(2) can stimulate BALB/c mice to develop specific humoral immune response instead of specific cell-mediated immunity. This study provides the experimental basis for the development of gene engineering vaccine of HFRS.

Hanta hemorrhagic fever with renal syndrome: a case report and review

Hantavirus infection is seldom reported in Taiwan. The spectrum of clinical severity ranges from mild to severe and may cover Hantavirus pulmonary syndrome and hemorrhagic fever with renal syndrome (HFRS). We report a case of HFRS in a 24-year-old soldier presenting with fever, chills, abdominal pain and generalized myalgia. His clinical course progressed through febrile, hypotensive, oliguria and polyuria phases. Hantavirus infection was proven by serology at the second hospital week. The patient was successfully treated with supportive management. Clinicians should be alert to the possibility of HFRS when examining patients with symptoms of fever, renal function impairment, hemorrhagic tendency and with rural exposure in Taiwan.