Design and validation of a novel multi-epitopes vaccine against hantavirus

Hantavirus is a member of the order Bunyavirales and an emerging global pathogen. Hantavirus infections have affected millions of people globally based on available epidemiological data and research studies. Hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) are the two main human diseases associated with hantavirus infections. Hence, efforts are required to develop a potent vaccine against the pathogen. The only vaccine that is in use for hantavirus is an inactivated virus vaccine, "Hantavax", but it failed to produce neutralizing antibodies. Vaccine development is of much importance in dealing with the surge of hantavirus globally. In this study, hantavirus five proteins (N protein, G1 and G2, L protein, and non-structural proteins) were used in NetCTL 1.2 program to predict T-cell epitopes. To predict major histocompatibility complex (MHC) binding alleles, an immune epitope database (IEDB) was used. All predicted epitopes were then investigated for different immunoinformatics analyses such as antigenicity and toxicity analyses. The good water-soluble, non-toxic, probable antigenic, and DRB*0101 binder was selected. A multi-epitopes-based vaccine designing was then done where linkers were used to connect the shortlisted epitopes. In addition, an adjuvant molecule was supplementary to the multi-epitopes peptide to improve the vaccine's immunogenic potential. The final vaccine construct's three-dimensional structure was modeled by ab initio method. The vaccine molecule was then evaluated for its binding potential with TLR-3 immune receptor, which is key for its recognition and processing by the host immune system. Docking studies were performed using HADDOCK software. The best-docked complex was selected and visualized for intermolecular binding and interactions using UCSF Chimera 1.16 software. The findings revealed that the designed vaccine might be a potential vaccine against hantavirus and can be used in experimental animal model testings.Communicated by Ramaswamy H. Sarma.

Pathogenicity of novel hantavirus isolate and antigenicity and immunogenicity of novel strain-based inactivated vaccine

BACKGROUND

Hantaan virus (HTNV, Orthohantavirus hantanensae species, Hantaviridae family) is the main etiological agent responsible for hemorrhagic fever with renal syndrome (HFRS). The novel HTNV may pose a potential danger to the control and prevention of HFRS in China, which highlights the importance of vaccine development in public health management. In previous studies, our laboratory discovered and successfully isolated a new HTNV strain, HV004 strain, from Apodemus agrarius captured in an epidemic area in Hubei, China.

METHODS

An initial biological and pathogenicity characterization of HTNV 76-118 (standard train), HV114 strain (a clinical isolate from Hubei province in 1986), and the novel isolate HV004 strain from the epidemic areas of Hubei province were performed in susceptible cells and in vivo. An experimental HV004 strain inactivated vaccine was prepared, and its corresponding immunogenicity was analyzed in BALB/c mice.

RESULTS

HV004 strain had a similar but higher pathogenicity than HTNV 76-118 and HV114 in suckling mice. A subcutaneous vaccination (s.c.) with the inactivated HTNV vaccine adjuvanted with aluminum, followed by a challenge intraperitoneally with 106 FFU/ml HTNV, afforded full protection against an HTNV challenge. All immunized mice in every group elicited serum neutralizing antibodies with increasing dosages, which may protect mice from HTNV infection. A dose-dependent stimulation index of splenocytes was also observed in immunized mice. The percentage of IFN-γ-producing CD3+CD8+ T cells was significantly higher in the spleens of immunized mice than in those of control mice.

CONCLUSIONS

These findings suggest that the inactivated HTNV vaccine may stimulate mice to produce high levels of antibodies with neutralization activity and elicit specific anti-HTNV humoral and cellular immune responses in BALB/c mice against the prevalent strain of HTNV in south central China.

Antigenic mapping and functional characterization of human New World hantavirus neutralizing antibodies

Hantaviruses are high-priority emerging pathogens carried by rodents and transmitted to humans by aerosolized excreta or, in rare cases, person-to-person contact. While infections in humans are relatively rare, mortality rates range from 1 to 40% depending on the hantavirus species. There are currently no FDA-approved vaccines or therapeutics for hantaviruses, and the only treatment for infection is supportive care for respiratory or kidney failure. Additionally, the human humoral immune response to hantavirus infection is incompletely understood, especially the location of major antigenic sites on the viral glycoproteins and conserved neutralizing epitopes. Here, we report antigenic mapping and functional characterization for four neutralizing hantavirus antibodies. The broadly neutralizing antibody SNV-53 targets an interface between Gn/Gc, neutralizes through fusion inhibition and cross-protects against the Old World hantavirus species Hantaan virus when administered pre- or post-exposure. Another broad antibody, SNV-24, also neutralizes through fusion inhibition but targets domain I of Gc and demonstrates weak neutralizing activity to authentic hantaviruses. ANDV-specific, neutralizing antibodies (ANDV-5 and ANDV-34) neutralize through attachment blocking and protect against hantavirus cardiopulmonary syndrome (HCPS) in animals but target two different antigenic faces on the head domain of Gn. Determining the antigenic sites for neutralizing antibodies will contribute to further therapeutic development for hantavirus-related diseases and inform the design of new broadly protective hantavirus vaccines.

Neutralizing Monoclonal Antibodies against the Gn and the Gc of the Andes Virus Glycoprotein Spike Complex Protect from Virus Challenge in a Preclinical Hamster Model

Hantaviruses are the etiological agent of hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). The latter is associated with case fatality rates ranging from 30% to 50%. HCPS cases are rare, with approximately 300 recorded annually in the Americas. Recently, an HCPS outbreak of unprecedented size has been occurring in and around Epuyén, in the southwestern Argentinian state of Chubut. Since November of 2018, at least 29 cases have been laboratory confirmed, and human-to-human transmission is suspected. Despite posing a significant threat to public health, no treatment or vaccine is available for hantaviral disease. Here, we describe an effort to identify, characterize, and develop neutralizing and protective antibodies against the glycoprotein complex (Gn and Gc) of Andes virus (ANDV), the causative agent of the Epuyén outbreak. Using murine hybridoma technology, we generated 19 distinct monoclonal antibodies (MAbs) against ANDV GnGc. When tested for neutralization against a recombinant vesicular stomatitis virus expressing the Andes glycoprotein (GP) (VSV-ANDV), 12 MAbs showed potent neutralization and 8 showed activity in an antibody-dependent cellular cytotoxicity reporter assay. Escape mutant analysis revealed that neutralizing MAbs targeted both the Gn and the Gc. Four MAbs that bound different epitopes were selected for preclinical studies and were found to be 100% protective against lethality in a Syrian hamster model of ANDV infection. These data suggest the existence of a wide array of neutralizing antibody epitopes on hantavirus GnGc with unique properties and mechanisms of action.IMPORTANCE Infections with New World hantaviruses are associated with high case fatality rates, and no specific vaccine or treatment options exist. Furthermore, the biology of the hantaviral GnGc complex, its antigenicity, and its fusion machinery are poorly understood. Protective monoclonal antibodies against GnGc have the potential to be developed into therapeutics against hantaviral disease and are also great tools to elucidate the biology of the glycoprotein complex.

Sociocultural determinants of adoption of preventive practices for hantavirus: A knowledge, attitudes, and practices survey in Tonosí, Panama

Introduction

Hantaviruses are a group of single-stranded RNA viruses carried by small rodent reservoirs, transmitted to humans through inhalation of aerosolized particles of rodent feces, urine, or saliva. In Panama, the Choclo orthohantavirus has been associated with Hantavirus Pulmonary Syndrome (n = 54) and Hantavirus Fever (n = 53). In 2018, there were 107 cases of hantavirus diseases, the majority in the Tonosí district, and 4 deaths. As there is no vaccine or treatment for hantavirus, proper prevention measures by community members is key to stopping outbreaks.

Methodology and principal findings

We investigated hantavirus knowledge, attitudes, and practices in one corregimiento of Tonosí, Panama to determine what factors influence uptake of prevention practices and high level of knowledge. We conducted a cross-sectional survey with 124 residents covering hantavirus knowledge, attitudes based in the Health Belief Model (perceived severity, perceived susceptibility, perceived obstacles, perceived benefits, and cues to action) and prevention practices. There was an overall high level of knowledge (median score: 4/6), though 20% did not know the route of transmission. The mean number of reported practices performed per person was 8.4 (range: 4–12). Most people had heard of hantavirus through other community members. In linear regression, lower perceived obstacles predicted higher preventive practice score. Reported obstacles to preventive practices included physical restrictions, such as age and health state. In ordinal logistic regression, higher education level and knowing more people who had previously been sick with hantavirus contributed to higher knowledge score.

Conclusions

Future interventions should focus on removing barriers to performing preventive practices. As most people learned of hantavirus through community members, interventions should be community-based and involve those who have experienced the disease. Any future education materials should address confusions about route of transmission and be targeted at those with a lower education level.

Hantavirus is a pathogen spread by small rodents in many regions of the world. In Panama, infection with hantavirus can lead to Hantavirus Fever or Hantavirus Pulmonary Syndrome. In 2018, there were 107 cases of hantavirus infection in Panama, the majority in the Tonosí District, and 4 deaths. Currently, there is no treatment, cure, or vaccine for hantaviruses. It is important that communities carry out the recommended prevention measures. In this study, we investigated what influences people to carry out the proper prevention measures and what influences people’s knowledge of hantavirus in order to design interventions in highly affected communities. We found that barriers such as physical restrictions limit people’s ability to perform the measures. Additionally, we found that those with higher education and those that knew more people who had been sick with hantavirus were more likely to have higher knowledge of the disease. We recommend that future interventions are community-based and focus on removing obstacles to performing the recommended prevention practices and involve those who have been affected by the disease to spread information.

Spatiotemporal Dynamics of Hantavirus Cardiopulmonary Syndrome Transmission Risk in Brazil

BACKGROUND

Hantavirus disease in humans is rare but frequently lethal in the Neotropics. Several abundant and widely distributed Sigmodontinae rodents are the primary hosts of Orthohantavirus and, in combination with other factors, these rodents can shape hantavirus disease. Here, we assessed the influence of host diversity, climate, social vulnerability and land use change on the risk of hantavirus disease in Brazil over 24 years.

METHODS

Landscape variables (native forest, forestry, sugarcane, maize and pasture), climate (temperature and precipitation), and host biodiversity (derived through niche models) were used in spatiotemporal models, using the 5570 Brazilian municipalities as units of analysis.

RESULTS

Amounts of native forest and sugarcane, combined with temperature, were the most important factors influencing the increase of disease risk. Population at risk (rural workers) and rodent host diversity also had a positive effect on disease risk.

CONCLUSIONS

Land use change-especially the conversion of native areas to sugarcane fields-can have a significant impact on hantavirus disease risk, likely by promoting the interaction between the people and the infected rodents. Our results demonstrate the importance of understanding the interactions between landscape change, rodent diversity, and hantavirus disease incidence, and suggest that land use policy should consider disease risk. Meanwhile, our risk map can be used to help allocate preventive measures to avoid disease.

The ecological dynamics of hantavirus diseases: From environmental variability to disease prevention largely based on data from China

Hantaviruses can cause hantavirus pulmonary syndrome (HPS) in the Americas and hemorrhagic fever with renal syndrome (HFRS) in Eurasia. In recent decades, repeated outbreaks of hantavirus disease have led to public concern and have created a global public health burden. Hantavirus spillover from natural hosts into human populations could be considered an ecological process, in which environmental forces, behavioral determinants of exposure, and dynamics at the human–animal interface affect human susceptibility and the epidemiology of the disease. In this review, we summarize the progress made in understanding hantavirus epidemiology and rodent reservoir population biology. We mainly focus on three species of rodent hosts with longitudinal studies of sufficient scale: the striped field mouse (Apodemus agrarius, the main reservoir host for Hantaan virus [HTNV], which causes HFRS) in Asia, the deer mouse (Peromyscus maniculatus, the main reservoir host for Sin Nombre virus [SNV], which causes HPS) in North America, and the bank vole (Myodes glareolus, the main reservoir host for Puumala virus [PUUV], which causes HFRS) in Europe. Moreover, we discuss the influence of ecological factors on human hantavirus disease outbreaks and provide an overview of research perspectives.

Incorporation of CD40 ligand or granulocyte-macrophage colony stimulating factor into Hantaan virus (HTNV) virus-like particles significantly enhances the long-term immunity potency against HTNV infection

PURPOSE

Hantavirus infections cause severe haemorrhagic fever with renal syndrome (HFRS) in humans and are associated with high fatality rates. In 2017, numerous outbreaks were reported in China and Germany. This represents a significant public-healthcare issue with no effective HFRS vaccines that offer a long-term immune response. In this study, we investigated the long-term humoral and cellular immune responses and protective immunity of Hantaan virus (HTNV) granulocyte-macrophage colony stimulating factor (GM-CSF) and CD40 ligand (CD40L) virus-like particles (VLPs) in mice.

METHODOLOGY

GM-CSF and CD40L VLPs were constructed via co-transfection of pCI-S and pCI-M-CD40L, and pCI-S and pCI-M-GM-CSF, into dihydrofolatereductase (dhfr)-deficient Chinese hamster ovary cells, respectively. Mice were immunized with HTNV VLPs 2 weeks apart. The animals were challenged 6 months after immunization. Specific and neutralizing antibodies were assessed by ELISA; IFN-γ was measured by enzyme-linked immunospot (ELISpot) assay and effectiveness by cytotoxic T lymphocyte (CTL) cytotoxicity assays. Nucleic acid loads of HTNV were tested by quantitative real-time PCR and viral antigen was detected via indirect ELISA. Pathological alterations were detected via haematoxylin-eosin staining.

RESULTS

GM-CSF and CD40L VLPs provided stable, long-term protection with a high titre of neutralizing antibody in mice 6 months after immunization. Furthermore, VLPs increased HTNV-specific cellular immune responses via higher expression of IFN-γ and CTL responses. HTNV challenge assay results showed long-term protection against HFRS. No significant pathological alteration was observed in the organs of mice after immunization.

CONCLUSION

This is, to the best of our knowledge, the first report demonstrating the long-term potency of HTNV VLP vaccines against HTNV infection and offers new insights into HTNV vaccine development.

Two recombinant human monoclonal antibodies that protect against lethal Andes hantavirus infection in vivo

Andes hantavirus (ANDV) is an etiologic agent of hantavirus cardiopulmonary syndrome (HCPS), a severe disease characterized by fever, headache, and gastrointestinal symptoms that may progress to hypotension, pulmonary failure, and cardiac shock that results in a 25 to 40% case-fatality rate. Currently, there is no specific treatment or vaccine; however, several studies have shown that the generation of neutralizing antibody (Ab) responses strongly correlates with survival from HCPS in humans. In this study, we screened 27 ANDV convalescent HCPS patient sera for their capacity to bind and neutralize ANDV in vitro. One patient who showed high neutralizing titer was selected to isolate ANDV-glycoprotein (GP) Abs. ANDV-GP-specific memory B cells were single cell sorted, and recombinant immunoglobulin G antibodies were cloned and produced. Two monoclonal Abs (mAbs), JL16 and MIB22, potently recognized ANDV-GPs and neutralized ANDV. We examined the post-exposure efficacy of these two mAbs as a monotherapy or in combination therapy in a Syrian hamster model of ANDV-induced HCPS, and both mAbs protected 100% of animals from a lethal challenge dose. These data suggest that monotherapy with mAb JL16 or MIB22, or a cocktail of both, could be an effective post-exposure treatment for patients infected with ANDV-induced HCPS.

Hantavirus Gc induces long-term immune protection via LAMP-targeting DNA vaccine strategy

Hemorrhagic fever with renal syndrome (HFRS) occurs widely throughout Eurasia. Unfortunately, there is no effective treatment, and prophylaxis remains the best option against the major pathogenic agent, hantaan virus (HTNV), which is an Old World hantavirus. However, the absence of cellular immune responses and immunological memory hampers acceptance of the current inactivated HFRS vaccine. Previous studies revealed that a lysosome-associated membrane protein 1 (LAMP1)-targeting strategy involving a DNA vaccine based on the HTNV glycoprotein Gn successfully conferred long-term immunity, and indicated that further research on Gc, another HTNV antigen, was warranted. Plasmids encoding Gc and lysosome-targeted Gc, designated pVAX-Gc and pVAX-LAMP/Gc, respectively, were constructed. Proteins of interest were identified by fluorescence microscopy following cell line transfection. Five groups of 20 female BALB/c mice were subjected to the following inoculations: inactivated HTNV vaccine, pVAX-LAMP/Gc, pVAX-Gc, and, as the negative controls, pVAX-LAMP or the blank vector pVAX1. Humoral and cellular immunity were assessed by enzyme-linked immunosorbent assays (ELISAs) and 15-mer peptide enzyme-linked immunospot (ELISpot) epitope mapping assays. Repeated immunization with pVAX-LAMP/Gc enhanced adaptive immune responses, as demonstrated by the specific and neutralizing antibody titers and increased IFN-γ production. The inactivated vaccine induced a comparable humoral reaction, but the negative controls only elicited insignificant responses. Using a mouse model of HTNV challenge, the in vivo protection conferred by the inactivated vaccine and Gc-based constructs (with/without LAMP recombination) was confirmed. Evidence of pan-epitope reactions highlighted the long-term cellular response to the LAMP-targeting strategy, and histological observations indicated the safety of the LAMP-targeting vaccines. The long-term protective immune responses induced by pVAX-LAMP/Gc may be due to the advantage afforded by lysosomal targeting after exogenous antigen processing initiation and major histocompatibility complex (MHC) class II antigen presentation trafficking. MHC II-restricted antigen recognition effectively primes HTNV-specific CD4+ T-cells, leading to the promotion of significant immune responses and immunological memory. An epitope-spreading phenomenon was observed, which mirrors the previous result from the Gn study, in which the dominant IFN-γ-responsive hot-spot epitopes were shared between HLA-II and H2d. Importantly, the pan-epitope reaction to Gc indicated that Gc should be with potential for use in further hantavirus DNA vaccine investigations.

Antiviral therapy and prevention against hantavirus infections

Hantaviruses are emerging zoonoses hosted by small mammals. In humans, they cause two diseases. Hemorrhagic fever with renal syndrome is mainly caused by Dobrava-Belgrade virus, Puumala virus, Seoul virus and Hantaan virus in Asia and Europe. On the other hand, the most important causes of hantavirus cardiopulmonary syndrome are Sin Nombre virus and Andes virus in Americas. Ribavirin yet remains the only licensed drug against the hantavirus infections, but its sufficient antiviral activity remains an issue under discussion. There are still no available vaccines against hantaviruses except of some inactivated virus vaccines licensed only in East-Asian countries. Some of the vaccines are under development in pre-clinical stages. The review discuses about specific compounds with approved antiviral activity against hantaviruses. Other approaches such as development of vaccines, are compiled as well.

Recombinant DNA vaccine of Hantavirus Gn and LAMP1 induced long-term immune protection in mice

BACKGROUND

Prophylaxis is widely adopted the best choice against Hemorrhagic fever with renal syndrome (HFRS) caused by Hantavirus. However, loss of memory immune response maintenance remains as major shortcoming in current HFRS vaccine. A recombinant DNA vaccine, pVAX-LAMP/Gn was previously proved efficient, requiring long-term evaluations.

METHODS & RESULTS

Immune responses of Balb/c mice were assessed by specific and neutralizing antibodies, interferon-γ ELISpot assay, and cytotoxic T-lymphocyte cytotoxicity assay. HTNV-challenge assay identified long-term protection. Safety was confirmed by histological and behavioral analysis. Epitope-spreading phenomenon was noted, revealing two sets of dominant T-cell epitopes cross-species.

CONCLUSION

pVAX-LAMP/Gn established memory responses within a long-term protection. Lysosome-targeted strategy showed promise on Gn-based DNA vaccine and further investigations are warranted in other immunogenic Hantaviral antigens.

[THE PRESENT STATE OF EPIZOOTOLOGICAL MONITORING OF THE NATURAL FOCI OF INFECTIONS IN THE RUSSIAN FEDERATION]

The facilities of the Russian Federal Service for Supervision of Consumer Rights Protection and Human Welfare play a leading role in epizootological monitoring. The specialists (zoologists and entomologists) of Hygiene and Epidemiology Centers do basic work in the subjects of the Russian Federation. The data obtained in the participation of different ministries and departments are used to analyze the results of monitoring. The latter is one of the important steps in the management of the epidemic, process in natural focal infections. In recent years, there has been an unjustified reduction in the volume of studies in the natural foci. This negatively affects the reliability of estimates and predictions of the epidemic activity of the natural foci of infections. Ensuring the national, security of the Russian Federation, epidemiological surveillance, and control of its natural foci requires staffing and appropriate professional training in the zoological and entomological subdivisions of the Russian Federal Service for Supervision of Consumer Rights Protection and Human Welfare.

Construction and evaluation of DNA vaccine encoding Hantavirus glycoprotein N-terminal fused with lysosome-associated membrane protein

BACKGROUND

Hantaviral diseases can have a high case fatality rate within the absence of broadly effective antiviral treatments or vaccines. We developed a DNA vaccine targeting the Hantavirus glycoprotein N-terminal (Gn) to major histocompatibility complex class II compartment by fusing the antigen with lysosome-associated membrane protein 1 (LAMP1), which altered antigen presenting pathway and activated the CD4+ T cells.

METHODS

The segments of Gn and LAMP1 were cloned into vector pVAX1, and recombinant plasmid was constructed by inserting Gn sequence into LAMP1, between luminal and the transmembrane/cytoplasmic domains. Subsequently, the protein expression was identified through immunoprecipitation, western blot and Immunofluorescent assay. Adaptive immune responses were assessed by the presence of specific and neutralizing antibodies, interferon (ELISpot results, and cytotoxic T-lymphocyte (CTL) cytotoxicity. Epitope mapping was performed to study the T-cell epitopes. Protective immunity in vivo was evaluated using a novel HTNV-challenging model, and safety evaluation was based on histological and behavioral observations.

RESULTS

Native or LAMP1 targeting HTNV Gn was successfully identified. Humoral immune responses were enhanced, featuring with satisfying titers of specific and neutralizing antibody production. The boosted activities of IFN-γ and CTL cytotoxicity witnessed enhanced cellular immune responses. Effective protection against HTNV in vivo was conferred in all three vaccine groups by the challenge model. Safety was confirmed and one dominant T-cell epitope screened from immunized mice overlapped the specific T-cell hot spot in HFRS patients.

CONCLUSION

LAMP1 targeting strategy successfully enhanced the efficacy of HTNV Gn-based vaccine, which is highly immunogenic and safe, showing promise for immunoprophylaxis against HFRS. Further investigations are warranted in the future.

Hantavirus infections among overnight visitors to Yosemite National Park, California, USA, 2012

TOC summary: A rare hantavirus outbreak reaffirms the need for control of deer mice and public awareness of the risks posed by contact with them.

In summer 2012, an outbreak of hantavirus infections occurred among overnight visitors to Yosemite National Park in California, USA. An investigation encompassing clinical, epidemiologic, laboratory, and environmental factors identified 10 cases among residents of 3 states. Eight case-patients experienced hantavirus pulmonary syndrome, of whom 5 required intensive care with ventilatory support and 3 died. Staying overnight in a signature tent cabin (9 case-patients) was significantly associated with becoming infected with hantavirus (p<0.001). Rodent nests and tunnels were observed in the foam insulation of the cabin walls. Rodent trapping in the implicated area resulted in high trap success rate (51%), and antibodies reactive to Sin Nombre virus were detected in 10 (14%) of 73 captured deer mice. All signature tent cabins were closed and subsequently dismantled. Continuous public awareness and rodent control and exclusion are key measures in minimizing the risk for hantavirus infection in areas inhabited by deer mice.

Rodent-borne infectious disease outbreaks after flooding disasters: Epidemiology, management, and prevention

OBJECTIVE

To alert clinicians to the climatic conditions that can precipitate outbreaks of the rodent-borne infectious diseases most often associated with flooding disasters, leptospirosis (LS), and the Hantavirus-caused diseases, hemorrhagic fever with renal syndrome (HFRS) and Hantavirus pulmonary syndrome (HPS); to describe the epidemiology and presenting clinical manifestations and outcomes of these rodent-borne infectious diseases; and to recommend both prophylactic therapies and effective control and prevention strategies for rodent-borne infectious diseases.

DESIGN

Internet search engines, including Google®, Google Scholar®, Pub Med, Medline, and Ovid, were queried with the key words as search terms to examine the latest scientific articles on rodent-borne infectious disease outbreaks in the United States and worldwide to describe the epidemiology and presenting clinical manifestations and outcomes of LS and Hantavirus outbreaks.

SETTING

Not applicable.

PARTICIPANTS

Not applicable.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Rodent-borne infectious disease outbreaks following heavy rainfall and flooding disasters.

RESULTS

Heavy rainfall encourages excessive wild grass seed production that supports increased outdoor rodent population densities; and flooding forces rodents from their burrows near water sources into the built environment and closer to humans.

CONCLUSIONS

Healthcare providers should maintain high levels of suspicion for LS in patients developing febrile illnesses after contaminated freshwater exposures following heavy rainfall, flooding, and even freshwater recreational events; and for Hantavirus-caused infectious diseases in patients with hemorrhagic fevers that progress rapidly to respiratory or renal failure following rodent exposures.

In vitro and in vivo activity of ribavirin against Andes virus infection

Pathogenic hantaviruses are a closely related group of rodent-borne viruses which are responsible for two distinct diseases in humans, hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome (HPS, otherwise known as hantavirus cardiopulmonary syndrome, HCPS). The antiviral effect of ribavirin against Old World hantaviruses, most notably Hantaan virus, is well documented; however, only a few studies have addressed its inhibitory effect on New World hantaviruses. In the present study, we demonstrate that ribavirin is highly active against Andes virus (ANDV), an important etiological agent of HPS, both in vitro and in vivo using a lethal hamster model of HPS. Treatment of ANDV infected Vero E6 cells with ribavirin resulted in dose-dependent reductions in viral RNA and protein as well as virus yields with a half maximal inhibitory concentration between 5 and 12.5 µg ml⁻¹. In hamsters, treatment with as little as 5 mg kg⁻¹ day⁻¹ was 100% effective at preventing lethal HPS disease when therapy was administered by intraperitoneal injection from day 1 through day 10 post-infection. Significant reductions were observed in ANDV RNA and antigen positive cells in lung and liver tissues. Ribavirin remained completely protective when administered by intraperitoneal injections up to three days post-infection. In addition, we show that daily oral ribavirin therapy initiated 1 day post-infection and continuing for ten days is also protective against lethal ANDV disease, even at doses of 5 mg kg⁻¹ day⁻¹. Our results suggest ribavirin treatment is beneficial for postexposure prophylaxis against HPS-causing hantaviruses and should be considered in scenarios where exposure to the virus is probable. The similarities between the results obtained in this study and those from previous clinical evaluations of ribavirin against HPS, further validate the hamster model of lethal HPS and demonstrate its usefulness in screening antiviral agents against this disease.

[Hantavirus infections]

Hantaviruses are enveloped single-stranded ribonucleic acid (RNA) viruses that belong to the family Bunyaviridae. They are widely distributed and maintained in populations of specific insectivores or rodent host species (mice or rats). In their natural host, hantaviruses develop persistent and asymptomatic infections with lifelong virus shedding in excreta. Transmission to humans occurs via direct contact with faeces, urine and saliva of infected rodents, in particular by inhaling virus contaminated aerosol. There are a variety of virus types that occur in different geographic areas, dependent on the natural distribution of the host. Unlike asymptomatic infection in rodents, several types of hantaviruses cause acute febrile diseases in humans, known as haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). In Germany, human hantavirus infections frequently represent as nephropathia epidemica (NE), a generally mild HFRS form with influenza-like symptoms such as fever, myalgia, headache and gastrointestinal disorders. Kidney failure, a characteristic sign of hantavirus infections, is also common. German NE cases are primarily caused by Puumala viruses (PUUV) which naturally persist in the bank vole, a mouse species that is widely distributed in the whole area of Germany. During 2005 and 2007, in several regions of Southern and Western Germany there was an unexpected increase in PUUV-associated NE cases. Currently, 1687 symptomatic hantavirus infections have been reported until the end of 2007, which is the highest number of hantavirus diseases in Germany since the introduction of the German infection protective law (Deutsches Infektionsschutzgesetz) in 2001. Treatment of hantavirus infections is mainly supportive and involves intensive medical care. A specific antiviral therapy with ribavirin has been shown to be successful for treatment of HFRS patients in the early stage of disease. In Germany, there is no licensed vaccine applicable for the prevention of hantavirus diseases. Anti-infectious measures are, therefore, regarded to be the most effective strategy to prevent illnesses due to these emerging RNA viruses.

[Detection of a new natural virus focus Dobrava in the Astrakhan Region]

A natural focus of Dobrava hantavirus was first revealed in an arid zone of the Astrakhan Region, by using molecular genetic methods. A polymerase chain reaction was employed to examine 389 lung tissue suspension samples taken from 9 species. Hantavirus RNA was found in 35 samples from 22 field mice (Apodemus agrarius), 8 tamarisk gerbils (Meriones temariscinus), 4 common voles (Microtus arvalis), and 1 house mouse (Mus musculus). Sequencing determined the taxonomic affiliation of 18 new isolates to the Dobrava species and 1 isolate to the Puumala species although the new Dobrava isolated greatly differed from all known strains of this virus in the nucleotide sequence of the genomic M and S segments. Hantavirus-infected rodents were found in 3 of 4 districts of the Astrakhan Region, located in the steppe and semidesert zones and at the intrazonal stations of the Volga-Akhtuba flood-lands. The high (up to 12%) hantavirus infection rates were ascertained in a tamarisk gerbil, the typical inhabitant of desert and semidesert ecosystems.

Occupational risk of exposure to rodent-borne hantavirus at US forest service facilities in California

Hantavirus cardiopulmonary syndrome (HCPS) is a frequently fatal viral disease transmitted through rodent secretions and excretions. Working around deer mice can increase risk of infection. This study assessed potential risk of HCPS at facilities occupied by the US Forest Service (USFS) in California. In 2004-2005, 18 USFS facilities in eight National Forests in California were evaluated for evidence of rodent infestation and circulation of hantavirus. Structural deficiencies and evidence of rodent infestation were observed at 18 facilities. Serum antibodies to hantavirus were detected in 50 of 255 deer mice collected from 15 facilities. Seroprevalence was higher at elevations > 1,600 m (22%). Employees at 14 facilities had received training in rodent-borne disease prevention. Risk of HCPS among USFS employees should motivate inclusion of disease prevention information into employee safety training.

[Epidemiology and laboratories: the missing link on the plans to study and prevent infectious diseases in Chile]

Viral meningitis, hantavirus and Vibrio parahaemolyticus infections are used as examples to demonstrate that important shortcomings and limitations exist in Chile to study the epidemiology of infectious diseases with modern methods. The lack of a national network of well-connected local and national microbiology laboratories is one of these important shortcomings. The author summarizes the evolution of the systems and institutions that deal with the infectious diseases in the world and in Chile.

Effect of predators of juvenile rodents on the spread of the hantavirus epidemic

Effects of predators of juvenile mice on the spread of the Hantavirus are analyzed in the context of a recently proposed model. Two critical values of the predation probability are identified. When the smaller of them is exceeded, the hantavirus infection vanishes without extinguishing the mice population. When the larger is exceeded, the entire mice population vanishes. These results suggest the possibility of control of the spread of the epidemic by introducing predators in areas of mice colonies in a suitable way so that such control does not kill all the mice but lowers the epidemic spread.

Puumala and Tula hantaviruses in France

The first genome sequences of Tula (TULV) and Puumala (PUUV) hantaviruses undoubtedly originated from France were recovered from tissue samples of European common voles and bank voles captured in Jura region. Genetic analysis of S and M segments of French PUUV strain revealed its highest similarity to strains from neighboring Belgium and Germany and also from Slovakia. On phylogenetic trees, French PUUV strain was placed within the central European lineage formed by strains from these three countries. Both of our French TULV strains clustered together and formed a distinct, well-supported genetic lineage.

Cross-reactive immune responses in mice after genetic vaccination with cDNA encoding hantavirus nucleocapsid proteins

Hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) in about 150,000 individuals in Eurasia, and several hundred cases of hantavirus pulmonary syndrome (HPS) on the American continent annually. There is consequently a need for rapid diagnostics and effective prevention of hantaviral infections. In this study we have performed DNA-vaccination of mice with full-length genes encoding the immunogenic nucleocapsid protein (NP) of Puumala (PUUV), Seoul (SEOV) and Sin Nombre virus (SNV). The antibody reactivity towards the NPs, and deleted or truncated variants thereof, were studied to localise and investigate the major polyclonal B-cell epitopes. Our findings clearly show that the antibody reactivity in each immunised mouse is unique, not only in a quantitative respect (titers) but also in cross-reactivity and most likely also in the epitope specificity. Our experimental data in combination with B-cell prediction software indicate that strong homologous virus species specific and cross-reactive epitopes are located around amino acid residue 40 in the nucleocapsid proteins.

Regulation of rodent-borne viruses in the natural host: implications for human disease

Prevalence and transmission rates of rodent-borne viruses within host populations vary in time and space and among host-virus systems. Improving our understanding of the causes of these variations will lead to a better understanding of changes in disease risk to humans. The regulators of prevalence and transmission can be categorized into five major classes: (1) Environmental regulators such as weather and food supply affect transmission rates through their effect on reproductive success and population densities. (2) Anthropogenic factors, such as disturbance, may lead to ecosystem simplification and decreased diversity. These changes favor opportunistic species, which may serve as reservoirs for zoonotic viruses. (3) Genetic factors influence susceptibility of mice to infection or capacity for chronic shedding and may be related to population cycling. (4) Behavioral factors, such as fighting, increase risk of transmission of some viruses and result in different patterns of infection between male and female mice. Communal nesting may result in overwinter transmission in colder climates. (5) Physiologic factors control host response to infection and length of time the host remains infectious. Risk prediction is difficult because these regulators are numerous and often interact, and the relative importance of each varies according to the host species, season, year, and geographic location.

Are humans infected by Hantaviruses in Australia?

Hantavirus antibody-positive rodents have been found across Australia although, to date, there are no reports of infections in humans. This could be due to misdiagnosis clinically and/or inadequate laboratory technique/skills. There are close trading ties between Australia and Asian countries as well as our geographical neighbours where both human and rodent infections are found, so importation is a continuing threat. We consider that further sero-epidemiological surveys are warranted among rodents (especially those captured from ports in Australia), in patients from renal and respiratory wards of hospitals, and in residents and employees close to harbours using more specific and sensitive laboratory techniques than have been available in the past.

A pseudotype vesicular stomatitis virus containing Hantaan virus envelope glycoproteins G1 and G2 as an alternative to hantavirus vaccine in mice

We examined whether a vesicular stomatitis virus (VSV) pseudotype bearing the hantavirus envelope glycoproteins (GPs) G1 and G2 (VSVdeltaG*HTN) could be used as a safe and effective alternative to native hantavirus. Mice were immunized with purified particles of VSVdeltaG*HTN. After the second immunization, all mice produced anti-GP antibody as detected in ELISA and a neutralization test. After the third immunization, the mice were challenged with Hantaan virus. Neither anti-NP antibody production nor Hantaan virus-specific CD8 T-cell reactions were detected in these mice. The present study demonstrated the potential of using a pseudotype VSV system as a tool for developing a hantavirus vaccine.

[The epizootological and virological characteristics of a natural hantavirus infection focus in the subtropic zone of the Krasnodarsk Territory]

A natural focus of hantavirus infection was detected and examined during the studies conducted in 2000-2002 around the Sochi (the western spurs of the Great Caucasus Ridge, which descended to the Black Sea (the Krasnodar Territory of Russia). At least 4 rodent species, such as Microtus majori, A. (S.) ponticus, A. agrarius, A. (S.) ciscaucasicus, were shown to participate in the circulation of hantaviruses. A comparative analysis of the nucleotide sequences of genomic S- and M-segments of hantaviruses has provided evidence that 13 viral RNA isolates from the A. (S.) ciscaucasicus belong to the Dobrava/Belgrade virus clade; however the RNA isolate from the Microtus majori belong to the Tula virus clade.

Vaccination of C57/BL6 mice with Dobrava hantavirus nucleocapsid protein in Freund's adjuvant induced partial protection against challenge

Dobrava hantavirus (DOBV) causes a severe form of hemorrhagic fever with renal syndrome (HFRS) for which there is no therapy or vaccine available. We compared the immunogenicity and protective efficacy of recombinant DOBV nucleocapsid protein (rDOBV N) given with Alum or Freund's as adjuvant, or PBS, in C57/BL6 mice. All mice given Alum or Freund's seroconverted as did 6/8 mice given rDOBV N with PBS. Reciprocal geometric mean total IgG-titers were 5380, 18,100, and 800, respectively, while the mean IgG1/IgG2a ratios were 17.5, 9.25, and 12, respectively. Furthermore, ELIspot assays showed higher levels of IL-4 producing peripheral blood mononuclear cells (PBMCs) in the group given Alum as compared to the other groups. Interestingly, only mice receiving rDOBV N with Freund's adjuvant were protected from challenge (75% protected), indicating that the strong Th2-type of immune response induced by Alum against rDOBV N did not induce protection in mice.

New Ecological Aspects of Hantavirus Infection: A Change of A Paradigm and a Challenge of Prevention- A Review

In the last decades a significant number of so far unknown or underestimated pathogens have emerged as fundamental health hazards of the human population despite intensive research and exceptional efforts of modern medicine to embank and eradicate infectious diseases. Almost all incidents caused by such emerging pathogens could be ascribed to agents that are zoonotic or expanded their host range and crossed species barriers. Many different factors influence the status of a pathogen to remain unnoticed or evolves into a worldwide threat. The ability of an infectious agent to adapt to changing environmental conditions and variations in human behavior, population development, nutrition, education, social, and health status are relevant factors affecting the correlation between pathogen and host. Hantaviruses belong to the emerging pathogens having gained more and more attention in the last decades. These viruses are members of the family Bunyaviridae and are grouped into a separate genus known as Hantavirus. The serotypes Hantaan (HTN), Seoul (SEO), Puumala (PUU), and Dobrava (DOB) virus predominantly cause hemorrhagic fever with renal syndrome (HFRS), a disease characterized by renal failure, hemorrhages, and shock. In the recent past, many hantavirus isolates have been identified and classified in hitherto unaffected geographic regions in the New World (North, Middle, and South America) with characteristic features affecting the lungs of infected individuals and causing an acute pulmonary syndrome. Hantavirus outbreaks in the United States of America at the beginning of the 10th decade of the last century fundamentally changed our knowledge about the appearance of the hantavirus specific clinical picture, mortality, origin, and transmission route in human beings. The hantavirus pulmonary syndrome (HPS) was first recognized in 1993 in the Four Corners Region of the United States and had a lethality of more than 50%. Although the causative virus was first termed in connection with the geographic name of its outbreak region the analysis of the individual viruses indicate that the causing virus of HPS was a genetically distinct hantavirus and consequently termed as Sin Nombre virus. Hantaviruses are distributed worldwide and are assumed to share a long time period of co-evolution with specific rodent species as their natural reservoir. The degree of relatedness between virus serotypes normally coincides with the relatedness between their respective hosts. There are no known diseases that are associated with hantavirus infections in rodents underlining the amicable relationship between virus and host developed by mutual interaction in hundreds of thousands of years. Although rodents are the major reservoir, antibodies against hantaviruses are also present in domestic and wild animals like cats, dogs, pigs, cattle, and deer. Domestic animals and rodents live jointly in a similar habitat. Therefore the transmission of hantaviruses from rodents to domestic animals seems to be possible, if the target organs, tissues, and cell parenchyma of the co-habitat domestic animals possess adequate virus receptors and are suitable for hantavirus entry and replication. The most likely incidental infection of species other than rodents as for example humans turns hantaviruses from harmless to life-threatening pathogenic agents focusing the attention on this virus group, their ecology and evolution in order to prevent the human population from a serious health risk. Much more studies on the influence of non-natural hosts on the ecology of hantaviruses are needed to understand the directions that the hantavirus evolution could pursue. At least, domestic animals that share their environmental habitat with rodents and humans particularly in areas known as high endemic hantavirus regions have to be copiously screened. Each transfer of hantaviruses from their original natural hosts to other often incidental hosts is accompanied by a change of ecology, a change of environment, a modulation of numerous factors probably influencing the pathogenicity and virulence of the virus. The new environment exerts a modified evolutionary pressure on the virus forcing it to adapt and probably to adopt a form that is much more dangerous for other host species compared to the original one.

Soochong virus: An antigenically and genetically distinct hantavirus isolated fromApodemus peninsulae in Korea

Hantaan (HTN) virus, the etiologic agent of clinically severe hemorrhagic fever with renal syndrome (HFRS), was first isolated in 1976 from lung tissue of a striped-field mouse (Apodemus agrarius) captured in Songnae-ri, Gyeonggi Province, Republic of Korea. Found primarily in mountainous areas, the Korean field mouse (A. peninsulae) is the second-most dominant field rodent species found throughout Korea. A new hantavirus, designated Soochong (SOO), was isolated in Vero E6 cells from four A. peninsulae captured in August 1997 at Mt. Gyebang in Hongcheon-gun, Mt. Gachil, Inje-gun, Gangwon Province, and in September 1998 at Mt. Deogyu, Muju-gun, Jeollabuk Province. The entire S, M, and L genomic segments of SOO virus, amplified by RT-PCR from lung tissues of seropositive A. peninsulae and from virus-infected Vero E6 cells, diverged from HTN virus (strain 76-118) by 15.6%, 22.8%, and 21.7% at the nucleotide level and 3.5%, 9.5%, and 4.6% at the amino acid level, respectively. Phylogenetic analyses of the nucleotide and deduced amino acid sequences, using the maximum parsimony and neighbor-joining methods, indicated that SOO virus was distinct from A. agrarius-borne HTN virus. SOO virus shared a common ancestry with Amur virus from Far East Russia, as well as with H5 and B78 hantaviruses, previously isolated from HFRS patients in China. Cross-focus-reduction neutralizating antibody tests showed that SOO virus, which is the first hantavirus isolated in cell culture from A. peninsulae, could be classified as a new hantavirus serotype.

Hantaviruses: Immunology, Treatment, and Prevention

Hantaviruses are rodent-borne bunyaviruses that are associated with two main clinical diseases in humans: hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. It has been suggested that host-related immune mechanisms rather than direct viral cytopathology may be responsible for the principal abnormality (vascular dysfunction) in these syndromes. This review summarizes the current knowledge on hantaviral host immune responses, immune abnormalities, laboratory diagnosis, and antiviral therapy as well as the current approaches in vaccine development.

An amino-terminal segment of hantavirus nucleocapsid protein presented on hepatitis B virus core particles induces a strong and highly cross-reactive antibody response in mice

Previously, we have demonstrated that hepatitis B virus (HBV) core particles tolerate the insertion of the amino-terminal 120 amino acids (aa) of the Puumala hantavirus nucleocapsid (N) protein. Here, we demonstrate that the insertion of 120 amino-terminal aa of N proteins from highly virulent Dobrava and Hantaan hantaviruses allows the formation of chimeric core particles. These particles expose the inserted foreign protein segments, at least in part, on their surface. Analysis by electron cryomicroscopy of chimeric particles harbouring the Puumala virus (PUUV) N segment revealed 90% T = 3 and 10% T = 4 shells. A map computed from T = 3 shells shows additional density splaying out from the tips of the spikes producing the effect of an extra shell of density at an outer radius compared with wild-type shells. The inserted Puumala virus N protein segment is flexibly linked to the core spikes and only partially icosahedrally ordered. Immunisation of mice of two different haplotypes (BALB/c and C57BL/6) with chimeric core particles induces a high-titered and highly cross-reactive N-specific antibody response in both mice strains.

Yeast-Expressed Hantavirus Dobrava Nucleocapsid Protein Induces a Strong, Long-Lasting, and Highly Cross-Reactive Immune Response in Mice

In Europe, Dobrava virus (DOBV) carried by the yellow-necked field mouse Apodemus flavicollis is one of the hantaviruses that can cause severe hemorrhagic fever with renal syndrome in humans. For several hantaviruses, the nucleocapsid (N) protein has proven to be very immunogenic in humans and rodents and even can protect rodents against a virus challenge. To investigate the immunogenicity of DOBV N protein, BALB/c and C57BL/6 mice were immunized three times with a DOBV recombinant N (rN) protein expressed in yeast Saccharomyces cerevisiae together with complete Freund's, with incomplete Freund's, and without adjuvant, respectively. Mice of both strains elicited N-specific antibodies with end-point titers being as high as 1:1,000,000 in C57BL/6 mice. The antibodies induced by DOBV rN protein were highly cross-reactive to the rN proteins of hantaviruses Puumala and Hantaan. In both mice strains, DOBV rN protein induced N-specific antibodies of all IgG subclasses (IgG1, IgG2a, IgG2b, and IgG3), suggesting a mixed Th1/Th2 immune response. Taken together, yeast-expressed DOBV rN protein represents a promising vaccine candidate.

Experimental evaluation of rodent exclusion methods to reduce hantavirus transmission to residents in a Native American community in New Mexico

We conducted a pilot study to evaluate the efficacy of rodent proofing continuously occupied homes as a method for lowering the risk for hantavirus pulmonary syndrome (HPS) among residents of a Native American community in northwestern New Mexico. Rodent proofing of dwellings was paired with culturally appropriate health education. Seventy homes were randomly assigned to treatment or control categories. Treatment homes were rodent-proofed by sealing openings around foundations, doors, roofs, and pipes and repairing screens and windows. Repairs to each dwelling were limited to $500 US. After repairs were completed, 15-20 snap traps were placed in each treatment and control home and checked approximately every 2 days for an average of 3-4 weeks. During 23,373 trap nights, one house mouse (Mus musculus) was captured in one treatment home, and 20 mice (16 deer mice, Peromyscus maniculatus, two Pinyon mice, Peromyscus truei, and two unidentified mice) were captured in five control homes (one house had 14 captures, two had two captures, and two had one capture). Trap success was 0.01% in treatment homes and 0.15% in controls. Intensity of infestation (mean number of mice captured per infested home) was 1 in treatment homes and 4 in controls. Observations of evidence of infestation (feces, nesting material, gnaw marks, or reports of infestation by occupant) per 100 days of observation were 1.2 in treatment homes and 3.1 in controls. Statistical power of the experiment was limited because it coincided with a period of low rodent abundance (August-November 2000). Nevertheless, these results suggest that inexpensive rodent proofing of occupied rural homes can decrease the frequency and intensity of rodent intrusion, thereby reducing the risk of HPS among rural residents in the southwestern United States.

Emerging viruses: the case 'hantavirus'

This review briefly summarises the recent knowledge about hantavirus infections and raises particular problems in hantavirus research that need further investigation. The following questions are addressed: (i) are hantaviruses distributed worldwide and what leads to new outbreaks, (ii) what is known about hantavirus evolution, (iii) how can hantavirus species be defined, (iv) what are the determinants of hantavirus pathogenesis in humans, and (v) what problems are associated with the development of new vaccines and antiviral therapeutics.

[New data for the public health importance of hantaviruses in Hungary]

INTRODUCTION

The authors present recent results in the Hungarian hantavirus ecology and epidemiology. Most of the research was done between 1992-2000.

AIM

To determine the presence and geographic distribution of hantaviruses and to get more detailed information of human and small-mammal infection with these viruses in Hungary.

METHODS

For diagnostic purposes (patients' sera), serosurvey of healthy persons and serological investigations of small mammals, the following tests were used: indirect fluorescent antibody, high density particle agglutination and enzyme-linked immunosorbent assay (ELISA). Virus isolation, antigen-, and nucleic acid detection were conducted for ecological investigations.

RESULTS

235 of 831 patients proved to be seropositive. 2257 sera of age matched Hungarian citizens above 20 years were tested in 2000. The average seropositivity proved to be about 10% using two different methods. Sera of 1512 individuals of nearly 20 different mammalian species were tested. Serological results revealed the prevalence of antibodies to human pathogen hantaviruses among rodents of about 7.25 percent. Molecular analysis of viral nucleic acid isolates from organs of four rodents proved directly the presence of viruses belonging to Puumala and Dobrava/Belgrade species in Hungary. Sequences corresponding to the Dobrava/Belgrade type viruses were found in two different rodent species. This suggests the existence of two hosts with different living preferences.

CONCLUSIONS

At least two different human pathogen hantaviruses are circulating in Hungary. It has to be considered, that viruses belonging to the Dobrava/Belgrade species could emerge not only in the forested areas, but in the agricultural areas as well. Commercially available kits are not perfectly suitable for the detection of antibodies rised to domestic hantaviruses. It is necessary to built an appropriate laboratory for the hantavirus research in Hungary.

Vaccines against hantaviruses

Rodent-borne hantaviruses are etiologic agents for hemorrhagic fever with renal syndrome and hantavirus cardiopulmonary syndrome in the Old World and New World, respectively. These often severe diseases are relatively uncommon in most parts of the world and are sufficiently genetically variable that widely cross-protective vaccines will probably need to be polyvalent. The current status of hantavirus vaccines shall be reviewed and both conventional and speculative new vaccine technologies that may evolve within the field shall be considered.

[Efficacy of amixine in experimental hantavirus infection]

The experimental studies conducted on 2-week suckling mice infected with Hantaan virus, Strain 76-118) treated with oral and subcutaneous amoxine showed its prophylactic, therapeutical-and-prophylactic, and therapeutical efficiencies. Oral amoxine exhibited the highest efficiency when used in a dose of 10 mg/kg-1 96 hours before infection and throughout the incubation period. The protective efficiency was 61%. Subcutaneously, the agent was effective when three schemes for injection in a dose of 1 mg/kg-1. Its maximum effect was observed when amoxine was given by the therapeutical-and-prophylactic scheme. The death protection rate was 65%. The agent is effective in suppressing the reproduction of Hantaan virus in the brain tissue.

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.

Genetic vaccines protect against Sin Nombre hantavirus challenge in the deer mouse (Peromyscus maniculatus)

We used a deer mouse (Peromyscus maniculatus) infection model to test the protective efficacy of genetic vaccine candidates for Sin Nombre (SN) virus that were known to provoke immunological responses in BALB/c mice (Bharadwaj et al., Vaccine 17, 2836-2843, 1999 ). Protective epitopes were localized in each of four overlapping cDNA fragments that encoded portions of the SN virus G1 glycoprotein antigen; the nucleocapsid gene also was protective. The protective efficacy of glycoprotein gene fragments correlated with splenocyte proliferation in the presence of cognate antigen, but none induced neutralizing antibodies. Genetic vaccines against SN virus can protect outbred deer mice from infection even in the absence of a neutralizing antibody response.

DNA vaccination of mice with a plasmid encoding Puumala hantavirus nucleocapsid protein mimics the B-cell response induced by virus infection

Inoculation of naked DNA has been applied for the development of prophylactic and therapeutic vaccines against different viral infections. To study the humoral immune response induced by DNA vaccination we cloned the entire nucleocapsid protein-encoding sequence of the Puumala hantavirus strain Vranica/Hällnäs into the CMV promoter-driven expression unit of the plasmid pcDNA3, generating pcDNA3-VR1. A single dose injection of 50 microg of plasmid DNA into each M. tibialis anterior of BALB/c mice induced a high-titered antibody response against the nucleocapsid protein as documented 6 and 11 weeks after immunisation. PEPSCAN analysis of a serum pool of the pcDNA3-VR1-vaccinated animals revealed antibodies reacting with epitopes covering the whole nucleocapsid protein. The epitope-specificity of the immune response induced by DNA vaccination seems to reflect the antibody response in experimentally virus-infected bank voles (the natural host of the Puumala virus) and humans. The data suggest that DNA vaccination could be used for the identification of highly immunogenic epitopes in viral proteins.

Hantavirus infections and their prevention

Hantaviruses are rodent-borne bunyaviruses which cause haemorrhagic fever with renal syndrome and Hantavirus pulmonary syndrome in humans. This review covers the host interactions of the viruses, including the rodent reservoirs, the clinical outcome of human infections as well as the pathogenesis and laboratory diagnosis of infections. The current stage in prophylaxis and therapy of hantaviral diseases is described and different approaches in vaccine development are discussed.

Puumala (PUU) hantavirus strain differences and insertion positions in the hepatitis B virus core antigen influence B-cell immunogenicity and protective potential of core-derived particles

Hepatitis B virus (HBV) core-derived chimeric particles carrying a Puumala (PUU) hantavirus (strain Vranica/Hällnäs) nucleocapsid (N) protein sequence (aa 1-45), alternatively inserted at three distinct positions (N-, C-terminus, or the internal region), and mosaic particles consisting of HBV core as well as core/PUU (Vranica/Hällnäs) N (aa 1-45) readthrough protein were generated. Chimeric particles carrying the insert at the N-terminus or the internal region of core induced some protective immune response in bank voles (Clethrionomys glareolus) against a subsequent PUU virus (strain Kazan) challenge; 40-50% of the animals showed markers of protection. In contrast, internal insertion of PUU strain CG18-20 N (aa 1-45) into the HBV core caused a highly protective immune response in the bank vole model. Immunizations with particles carrying aa 75-119 of PUU (CG18-20) N at the C-terminus of core verified the presence of a second, minor protective region in the N protein. A strong PUU N-specific antibody response was detected not only in bank voles immunized with chimeric particles containing internal and N-terminal fusions of PUU N protein but also in animals immunized with the corresponding mosaic particles. Except for the exclusive occurrence of antibodies directed against aa 231-240 of N in non-protected animals post virus challenge, there was no additional obvious difference in the epitope-specificity of N-specific antibodies from immunized animals prior and post virus challenge.

[Epidemiologic problems in hantavirus infections]

The objective of the submitted paper was to present some information pertaining to epidemiological problems of hantavirus infection. In the Czech Republic the prevalence of these infections is not alarming but in the world cases of haemorrhagic fever with renal syndrome (HFRS) as well as hantavirus pulmonary syndrome (HPS) are reported. On the territory of the Czech Republic there are foci of hantaviruses and in conjunction with summer tourism or working activities abroad the import of this infection cannot be ruled out. With regard to the serious character of some forms of the disease it is essential to follow up this problem systematically.