Hendra Virus Infection Research Articles

PHYSIOLOGIC BIOMARKERS AND HENDRA VIRUS INFECTION IN AUSTRALIAN BLACK FLYING FOXES (PTEROPUS ALECTO).

Bats of the genus Pteropus (Pteropodidae), colloquially known as flying foxes, are recognized as the natural reservoir of Hendra virus, a zoonotic paramyxovirus responsible for mortality in horses and humans. Some previous studies have suggested that physiologic and ecologic factors promote Hendra virus infection in flying foxes, and by extension, spillover to horses and humans. However, the impact of Hendra virus infection on relevant physiologic biomarkers in flying foxes has not been measured. Over 12 mo in eastern Australia, we captured and sampled 446 individual black flying foxes ( Pteropus alecto ), a putative primary reservoir host species, and measured a suite of hematologic, plasma biochemistry, and urinary biomarkers. All mean hematologic and biochemical values in both Hendra virus-positive and virus-negative cohorts were within the published reference ranges for black flying foxes. We found no association between Hendra virus infection (as indicated by PCR detection of Hendra virus RNA) and biomarkers for nutritional stress, reproductive stress, or extreme metabolic demand. However, we identified associations between several other biomarkers and Hendra virus infection, which may partly elucidate the physiologic effects of Hendra virus infection in flying foxes. Our findings highlight the need for critical evaluation of putative risk factors for infection in flying foxes and provide insights for future epidemiologic studies of Hendra virus and related viruses in the Pteropus species.

Protection from Hendra virus infection with Canarypox recombinant vaccine.

Hendra virus (HeV) is an emerging zoonotic pathogen, which causes severe respiratory illness and encephalitis in humans and horses. Since its first appearance in 1994, spillovers of HeV from its natural reservoir fruit bats occur on almost an annual basis. The high mortality rate in both humans and horses and the wide-ranging reservoir distribution are making HeV a serious public health problem, especially for people exposed to sick horses. This study has aimed to develop an efficient low-cost HeV vaccine for horses based on Canarypox recombinant vector expressing HeV glycoproteins, attachment glycoprotein (G) and fusion protein (F). This vaccine was used to immunise hamsters and then challenged intraperitoneally with HeV 3 weeks later. The higher tested dose of the vaccine efficiently prevented oropharyngeal virus shedding and protected animals from clinical disease and virus-induced mortality. Vaccine induced generation of seroneutralising antibodies and prevented virus-induced histopathological changes and a production of viral RNA and antigens in animal tissues. Interestingly, some vaccinated animals, including those immunised at a lower dose, were protected in the absence of detectable specific antibodies, suggesting the induction of an efficient virus-specific cellular immunity. Finally, ponies immunised using the same vaccination protocol as hamsters developed strong seroneutralising titres against both HeV and closely related Nipah virus, indicating that this vaccine may have the ability to induce cross-protection against Henipavirus infection. These data suggest that Canarypox-based vectors encoding for HeV glycoproteins present very promising new vaccine candidate to prevent infection and shedding of the highly lethal HeV.

Hendra Virus Infection Dynamics in the Grey-Headed Flying Fox (Pteropus poliocephalus) at the Southern-Most Extent of Its Range: Further Evidence This Species Does Not Readily Transmit the Virus to Horses.

Hendra virus (HeV) is an important emergent virus in Australia known to infect horses and humans in certain regions of the east coast. Whilst pteropid bats (“flying foxes”) are considered the natural reservoir of HeV, which of the four mainland species is the principal reservoir has been a source of ongoing debate, particularly as shared roosting is common. To help resolve this, we sampled a colony consisting of just one of these species, the grey-headed flying fox, (Pteropus poliocephalus), at the southernmost extent of its range. Using the pooled urine sampling technique at approximately weekly intervals over a two year period, we determined the prevalence of HeV and related paramyxoviruses using a novel multiplex (Luminex) platform. Whilst all the pooled urine samples were negative for HeV nucleic acid, we successfully identified four other paramyxoviruses, including Cedar virus; a henipavirus closely related to HeV. Collection of serum from individually caught bats from the colony showed that antibodies to HeV, as estimated by a serological Luminex assay, were present in between 14.6% and 44.5% of animals. The wide range of the estimate reflects uncertainties in interpreting intermediate results. Interpreting the study in the context of HeV studies from states to the north, we add support for an arising consensus that it is the black flying fox and not the grey-headed flying fox that is the principal source of HeV in spillover events to horses.

Hendra virus and Nipah virus animal vaccines

Hendra virus (HeV) and Nipah virus (NiV) are zoonotic viruses that emerged in the mid to late 1990s causing disease outbreaks in livestock and people. HeV appeared in Queensland, Australia in 1994 causing a severe respiratory disease in horses along with a human case fatality. NiV emerged a few years later in Malaysia and Singapore in 1998–1999 causing a large outbreak of encephalitis with high mortality in people and also respiratory disease in pigs which served as amplifying hosts. The key pathological elements of HeV and NiV infection in several species of mammals, and also in people, are a severe systemic and often fatal neurologic and/or respiratory disease. In people, both HeV and NiV are also capable of causing relapsed encephalitis following recovery from an acute infection. The known reservoir hosts of HeV and NiV are several species of pteropid fruit bats. Spillovers of HeV into horses continue to occur in Australia and NiV has caused outbreaks in people in Bangladesh and India nearly annually since 2001, making HeV and NiV important transboundary biological threats. NiV in particular possesses several features that underscore its potential as a pandemic threat, including its ability to infect humans directly from natural reservoirs or indirectly from other susceptible animals, along with a capacity of limited human-to-human transmission. Several HeV and NiV animal challenge models have been developed which have facilitated an understanding of pathogenesis and allowed for the successful development of both active and passive immunization countermeasures.

In this issue – April 2016

In this issue – April 2016

Temporal Variation in Physiological Biomarkers in Black Flying-Foxes (Pteropus alecto), Australia.

Bats of the genus Pteropus (Pteropodidae) are recognised as the natural host of multiple emerging pathogenic viruses of animal and human health significance, including henipaviruses, lyssaviruses and ebolaviruses. Some studies have suggested that physiological and ecological factors may be associated with Hendra virus infection in flying-foxes in Australia; however, it is essential to understand the normal range and seasonal variability of physiological biomarkers before seeking physiological associations with infection status. We aimed to measure a suite of physiological biomarkers in P. alecto over time to identify any seasonal fluctuations and to examine possible associations with life-cycle and environmental stressors. We sampled 839 adult P. alecto in the Australian state of Queensland over a 12-month period. The adjusted population means of every assessed hematologic and biochemical parameter were within the reported reference range on every sampling occasion. However, within this range, we identified significant temporal variation in these parameters, in urinary parameters and body condition, which primarily reflected the normal annual life cycle. We found no evident effect of remarkable physiological demands or nutritional stress, and no indication of clinical disease driving any parameter values outside the normal species reference range. Our findings identify underlying temporal physiological changes at the population level that inform epidemiological studies and assessment of putative physiological risk factors driving Hendra virus infection in P. alecto. More broadly, the findings add to the knowledge of Pteropus populations in terms of their relative resistance and resilience to emerging infectious disease.

Expression, characterisation and antigenicity of a truncated Hendra virus attachment protein expressed in the protozoan host Leishmania tarentolae

Hendra virus (HeV) is an emerging zoonotic paramyxovirus within the genus Henipavirus that has caused severe morbidity and mortality in humans and horses in Australia since 1994. HeV infection of host cells is mediated by the membrane bound attachment (G) and fusion (F) glycoproteins, that are essential for receptor binding and fusion of viral and cellular membranes. The eukaryotic unicellular parasite Leishmania tarentolae has recently been established as a powerful tool to express recombinant proteins with mammalian-like glycosylation patterns, but only few viral proteins have been expressed in this system so far. Here, we describe the purification of a truncated, Strep-tag labelled and soluble version of the HeV attachment protein (sHeV G) expressed in stably transfected L. tarentolae cells. After Strep-tag purification the identity of sHeV G was confirmed by immunoblotting and mass spectrometry. The functional binding of sHeV G to the HeV cell entry receptor ephrin-B2 was confirmed in several binding assays. Generated polyclonal rabbit antiserum against sHeV G reacted with both HeV and Nipah virus (NiV) G proteins in immunofluorescence assay and efficiently neutralised NiV infection, thus further supporting the preserved antigenicity of the purified protein.

Intangible and Economic Impacts of Hendra Virus Prevention Strategies.

Hendra virus (HeV), a potentially fatal zoonotic disease spread by flying foxes, to date has always infected humans via a spillover event from equine HeV infection. In a theoretical case study, we compared the impacts of two different HeV prevention strategies - vaccination and flying fox roost removal - using a recently developed framework that considers different stakeholder group perspectives. The perspectives of the four selected stakeholder groups regarding intangibles were inferred from public discussions and coverage in the media. For all stakeholder groups, the option to vaccinate horses was found to add value to the economic results when the intangible impacts were included in the analysis, while the option for roost removal unanimously detracted from economic analysis value when the intangible impacts were included. Both the mean and median stakeholder-adjusted value ratios (2.25 and 2.12, respectively) for vaccination were inflated when intangible impacts were included, by value-adding to the results of a traditional economic analysis. In the roost removal strategy, these ratios (1.19 and 1.16, respectively) were deflated when intangible impacts were included. Results of this theoretical study suggest that the inclusion of intangible impacts promotes the value of a two-dose initial vaccination protocol using a subunit vaccination considered to offer complete protection for horses, as a strategy to control HeV, whereas roost removal becomes an even more costly strategy. Outcome of the analysis is particularly sensitive to the intangible value placed on human health. Further evaluation - via sociological methods - of values placed on intangibles by various stakeholder groups is warranted.

Routes of Hendra Virus Excretion in Naturally-Infected Flying-Foxes: Implications for Viral Transmission and Spillover Risk.

Pteropid bats or flying-foxes (Chiroptera: Pteropodidae) are the natural host of Hendra virus (HeV) which sporadically causes fatal disease in horses and humans in eastern Australia. While there is strong evidence that urine is an important infectious medium that likely drives bat to bat transmission and bat to horse transmission, there is uncertainty about the relative importance of alternative routes of excretion such as nasal and oral secretions, and faeces. Identifying the potential routes of HeV excretion in flying-foxes is important to effectively mitigate equine exposure risk at the bat-horse interface, and in determining transmission rates in host-pathogen models. The aim of this study was to identify the major routes of HeV excretion in naturally infected flying-foxes, and secondarily, to identify between-species variation in excretion prevalence. A total of 2840 flying-foxes from three of the four Australian mainland species (Pteropus alecto, P. poliocephalus and P. scapulatus) were captured and sampled at multiple roost locations in the eastern states of Queensland and New South Wales between 2012 and 2014. A range of biological samples (urine and serum, and urogenital, nasal, oral and rectal swabs) were collected from anaesthetized bats, and tested for HeV RNA using a qRT-PCR assay targeting the M gene. Forty-two P. alecto (n = 1410) had HeV RNA detected in at least one sample, and yielded a total of 78 positive samples, at an overall detection rate of 1.76% across all samples tested in this species (78/4436). The rate of detection, and the amount of viral RNA, was highest in urine samples (>serum, packed haemocytes >faecal >nasal >oral), identifying urine as the most plausible source of infection for flying-foxes and for horses. Detection in a urine sample was more efficient than detection in urogenital swabs, identifying the former as the preferred diagnostic sample. The detection of HeV RNA in serum is consistent with haematogenous spread, and with hypothesised latency and recrudesence in flying-foxes. There were no detections in P. poliocephalus (n = 1168 animals; n = 2958 samples) or P. scapulatus (n = 262 animals; n = 985 samples), suggesting (consistent with other recent studies) that these species are epidemiologically less important than P. alecto in HeV infection dynamics. The study is unprecedented in terms of the individual animal approach, the large sample size, and the use of a molecular assay to directly determine infection status. These features provide a high level of confidence in the veracity of our findings, and a sound basis from which to more precisely target equine risk mitigation strategies.

Natural Hendra Virus Infection in Flying-Foxes - Tissue Tropism and Risk Factors.

Hendra virus (HeV) is a lethal zoonotic agent that emerged in 1994 in Australia. Pteropid bats (flying-foxes) are the natural reservoir. To date, HeV has spilled over from flying-foxes to horses on 51 known occasions, and from infected horses to close-contact humans on seven occasions. We undertook screening of archived bat tissues for HeV by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Tissues were tested from 310 bats including 295 Pteropodiformes and 15 Vespertilioniformes. HeV was detected in 20 individual flying-foxes (6.4%) from various tissues including spleen, kidney, liver, lung, placenta and blood components. Detection was significantly higher in Pteropus Alecto and P. conspicillatus, identifying species as a risk factor for infection. Further, our findings indicate that HeV has a predilection for the spleen, suggesting this organ plays an important role in HeV infection. The lack of detections in the foetal tissues of HeV-positive females suggests that vertical transmission is not a regular mode of transmission in naturally infected flying-foxes, and that placental and foetal tissues are not a major source of infection for horses. A better understanding of HeV tissue tropism will strengthen management of the risk of spillover from flying-foxes to horses and ultimately humans.

Flying-Fox Roost Disturbance and Hendra Virus Spillover Risk

Bats of the genus Pteropus (flying-foxes) are the natural host of Hendra virus (HeV) which periodically causes fatal disease in horses and humans in Australia. The increased urban presence of flying-foxes often provokes negative community sentiments because of reduced social amenity and concerns of HeV exposure risk, and has resulted in calls for the dispersal of urban flying-fox roosts. However, it has been hypothesised that disturbance of urban roosts may result in a stress-mediated increase in HeV infection in flying-foxes, and an increased spillover risk. We sought to examine the impact of roost modification and dispersal on HeV infection dynamics and cortisol concentration dynamics in flying-foxes. The data were analysed in generalised linear mixed models using restricted maximum likelihood (REML). The difference in mean HeV prevalence in samples collected before (4.9%), during (4.7%) and after (3.4%) roost disturbance was small and non-significant (P = 0.440). Similarly, the difference in mean urine specific gravity-corrected urinary cortisol concentrations was small and non-significant (before = 22.71 ng/mL, during = 27.17, after = 18.39) (P= 0.550). We did find an underlying association between cortisol concentration and season, and cortisol concentration and region, suggesting that other (plausibly biological or environmental) variables play a role in cortisol concentration dynamics. The effect of roost disturbance on cortisol concentration approached statistical significance for region, suggesting that the relationship is not fixed, and plausibly reflecting the nature and timing of disturbance. We also found a small positive statistical association between HeV excretion status and urinary cortisol concentration. Finally, we found that the level of flying-fox distress associated with roost disturbance reflected the nature and timing of the activity, highlighting the need for a ‘best practice’ approach to dispersal or roost modification activities. The findings usefully inform public discussion and policy development in relation to Hendra virus and flying-fox management.

Transcriptome Profiling of the Virus-Induced Innate Immune Response in Pteropus vampyrus and Its Attenuation by Nipah Virus Interferon Antagonist Functions.

Bats are important reservoirs for several viruses, many of which cause lethal infections in humans but have reduced pathogenicity in bats. As the innate immune response is critical for controlling viruses, the nature of this response in bats and how it may differ from that in other mammals are of great interest. Using next-generation transcriptome sequencing (mRNA-seq), we profiled the transcriptional response of Pteropus vampyrus bat kidney (PVK) cells to Newcastle disease virus (NDV), an avian paramyxovirus known to elicit a strong innate immune response in mammalian cells. The Pteropus genus is a known reservoir of Nipah virus (NiV) and Hendra virus (HeV). Analysis of the 200 to 300 regulated genes showed that genes for interferon (IFN) and antiviral pathways are highly upregulated in NDV-infected PVK cells, including genes for beta IFN, RIG-I, MDA5, ISG15, and IRF1. NDV-infected cells also upregulated several genes not previously characterized to be antiviral, such as RND1, SERTAD1, CHAC1, and MORC3. In fact, we show that MORC3 is induced by both IFN and NDV infection in PVK cells but is not induced by either stimulus in human A549 cells. In contrast to NDV infection, HeV and NiV infection of PVK cells failed to induce these innate immune response genes. Likewise, an attenuated response was observed in PVK cells infected with recombinant NDVs expressing the NiV IFN antagonist proteins V and W. This study provides the first global profile of a robust virus-induced innate immune response in bats and indicates that henipavirus IFN antagonist mechanisms are likely active in bat cells. Bats are the reservoir host for many highly pathogenic human viruses, including henipaviruses, lyssaviruses, severe acute respiratory syndrome coronavirus, and filoviruses, and many other viruses have also been isolated from bats. Viral infections are reportedly asymptomatic or heavily attenuated in bat populations. Despite their ecological importance to viral maintenance, research into their immune system and mechanisms for viral control has only recently begun. Nipah virus and Hendra virus are two paramyxoviruses associated with high mortality rates in humans and whose reservoir is the Pteropus genus of bats. Greater knowledge of the innate immune response of P. vampyrus bats to viral infection may elucidate how bats serve as a reservoir for so many viruses.

Focus on: Hendra virus in Australia

Cases of Hendra virus infection in horses in Australia have been seen regularly since the virus was first isolated in 1994. Kristopher Hughes, associate professor of equine medicine at Charles...

Detailed morphological characterisation of Hendra virus infection of different cell types using super-resolution and conventional imaging.

BackgroundHendra virus (HeV) is a pleomorphic virus belonging to the Paramyxovirus family. Our long-term aim is to understand the process of assembly of HeV virions. As a first step, we sought to determine the most appropriate cell culture system with which to study this process, and then to use this model to define the morphology of the virus and identify the site of assembly by imaging key virus encoded proteins in infected cells.MethodsA range of primary cells and immortalised cell lines were infected with HeV, fixed at various time points post-infection, labelled for HeV proteins and imaged by confocal, super-resolution and transmission electron microscopy.ResultsSignificant differences were noted in viral protein distribution depending on the infected cell type. At 8 hpi HeV G protein was detected in the endoplasmic reticulum and M protein was seen predominantly in the nucleus in all cells tested. At 18 hpi, HeV-infected Vero cells showed M and G proteins throughout the cell and in transmission electron microscope (TEM) sections, in pleomorphic virus-like structures. In HeV infected MDBK, A549 and HeLa cells, HeV M protein was seen predominantly in the nucleus with G protein at the membrane. In HeV-infected primary bovine and porcine aortic endothelial cells and two bat-derived cell lines, HeV M protein was not seen at such high levels in the nucleus at any time point tested (8,12, 18, 24, 48 hpi) but was observed predominantly at the cell surface in a punctate pattern co-localised with G protein. These HeV M and G positive structures were confirmed as round HeV virions by TEM and super-resolution (SR) microscopy. SR imaging demonstrated for the first time sub-virion imaging of paramyxovirus proteins and the respective localisation of HeV G, M and N proteins within virions.ConclusionThese findings provide novel insights into the structure of HeV and show that for HeV imaging studies the choice of tissue culture cells may affect the experimental results. The results also indicate that HeV should be considered a predominantly round virus with a mean diameter of approximately 280 nm by TEM and 310 nm by SR imaging.

Rhabdovirus-based vaccine platforms against henipaviruses.

The emerging zoonotic pathogens Hendra virus (HeV) and Nipah virus (NiV) are in the genus Henipavirus in the family Paramyxoviridae. HeV and NiV infections can be highly fatal to humans and livestock. The goal of this study was to develop candidate vaccines against henipaviruses utilizing two well-established rhabdoviral vaccine vector platforms, recombinant rabies virus (RABV) and recombinant vesicular stomatitis virus (VSV), expressing either the codon-optimized or the wild-type (wt) HeV glycoprotein (G) gene. The RABV vector expressing the codon-optimized HeV G showed a 2- to 3-fold increase in incorporation compared to the RABV vector expressing wt HeV G. There was no significant difference in HeV G incorporation in the VSV vectors expressing either wt or codon-optimized HeV G. Mice inoculated intranasally with any of these live recombinant viruses showed no signs of disease, including weight loss, indicating that HeV G expression and incorporation did not increase the neurotropism of the vaccine vectors. To test the immunogenicity of the vaccine candidates, we immunized mice intramuscularly with either one dose of the live vaccines or 3 doses of 10 μg chemically inactivated viral particles. Increased codon-optimized HeV G incorporation into RABV virions resulted in higher antibody titers against HeV G compared to inactivated RABV virions expressing wt HeV G. The live VSV vectors induced more HeV G-specific antibodies as well as higher levels of HeV neutralizing antibodies than the RABV vectors. In the case of killed particles, HeV neutralizing serum titers were very similar between the two platforms. These results indicated that killed RABV with codon-optimized HeV G should be the vector of choice as a dual vaccine in areas where rabies is endemic. Scientists have been tracking two new viruses carried by the Pteropid fruit bats: Hendra virus (HeV) and Nipah virus (NiV). Both viruses can be fatal to humans and also pose a serious risk to domestic animals. A recent escalation in the frequency of outbreaks has increased the need for a vaccine that prevents HeV and NiV infections. In this study, we performed an extensive comparison of live and killed particles of two recombinant rhabdoviral vectors, rabies virus and vesicular stomatitis virus (VSV), expressing wild-type or codon-optimized HeV glycoprotein, with the goal of developing a candidate vaccine against HeV. Based on our data from the presented mouse immunogenicity studies, we conclude that a killed RABV vaccine would be highly effective against HeV infections and would make an excellent vaccine candidate in areas where both RABV and henipaviruses pose a threat to human health.

Hendra virus in Queensland, Australia, during the winter of 2011: Veterinarians on the path to better management strategies

Following the emergence of Hendra virus (HeV), private veterinarians have had to adopt additional infection control strategies to manage this zoonosis. Between 1994 and 2010, seven people became infected with HeV, four fatally. All infected people were at a higher risk of exposure from contact with horses as they were either veterinary personnel, assisting veterinarians, or working in the horse industry. The management of emerging zoonoses is best approached from a One Health perspective as it benefits biosecurity as well as a public health, including the health of those most at risk, in this case private veterinarians. In 2011 we conducted a cross-sectional study of private veterinarians registered in Queensland and providing veterinary services to horses. The aim of this study was to gauge if participants had adopted recommendations for improved infection control, including the use of personal protective equipment (PPE), and the development of HeV specific management strategies during the winter of 2011. A majority of participants worked in practices that had a formal HeV management plan, mostly based on the perusal of official guidelines and an HeV field kit. The use of PPE increased as the health status of an equine patient decreased, demonstrating that many participants evaluated the risk of exposure to HeV appropriately; while others remained at risk of HeV infection by not using the appropriate PPE even when attending a sick horse. This study took place after Biosecurity Queensland had sent a comprehensive package about HeV management to all private veterinarians working in Queensland. However, those who had previous HeV experience through the management of suspected cases or had attended a HeV specific professional education programme in the previous 12 months were more likely to use PPE than those who had not. This may indicate that for private veterinarians in Queensland personal experience and face-to-face professional education sessions may be more effective in the improvement of HeV management than passive education via information packages. The role of different education pathways in the sustainable adoption of veterinary infection control measures should be further investigated.

Flying-fox species density--a spatial risk factor for Hendra virus infection in horses in eastern Australia.

Hendra virus causes sporadic but typically fatal infection in horses and humans in eastern Australia. Fruit-bats of the genus Pteropus (commonly known as flying-foxes) are the natural host of the virus, and the putative source of infection in horses; infected horses are the source of human infection. Effective treatment is lacking in both horses and humans, and notwithstanding the recent availability of a vaccine for horses, exposure risk mitigation remains an important infection control strategy. This study sought to inform risk mitigation by identifying spatial and environmental risk factors for equine infection using multiple analytical approaches to investigate the relationship between plausible variables and reported Hendra virus infection in horses. Spatial autocorrelation (Global Moran’s I) showed significant clustering of equine cases at a distance of 40 km, a distance consistent with the foraging ‘footprint’ of a flying-fox roost, suggesting the latter as a biologically plausible basis for the clustering. Getis-Ord Gi* analysis identified multiple equine infection hot spots along the eastern Australia coast from far north Queensland to central New South Wales, with the largest extending for nearly 300 km from southern Queensland to northern New South Wales. Geographically weighted regression (GWR) showed the density of P. alecto and P. conspicillatus to have the strongest positive correlation with equine case locations, suggesting these species are more likely a source of infection of Hendra virus for horses than P. poliocephalus or P. scapulatus. The density of horses, climate variables and vegetation variables were not found to be a significant risk factors, but the residuals from the GWR suggest that additional unidentified risk factors exist at the property level. Further investigations and comparisons between case and control properties are needed to identify these local risk factors.

A Recombinant Hendra Virus G Glycoprotein Subunit Vaccine Protects Nonhuman Primates against Hendra Virus Challenge

Hendra virus (HeV) is a zoonotic emerging virus belonging to the family Paramyxoviridae. HeV causes severe and often fatal respiratory and/or neurologic disease in both animals and humans. Currently, there are no licensed vaccines or antiviral drugs approved for human use. A number of animal models have been developed for studying HeV infection, with the African green monkey (AGM) appearing to most faithfully reproduce the human disease. Here, we assessed the utility of a newly developed recombinant subunit vaccine based on the HeV attachment (G) glycoprotein in the AGM model. Four AGMs were vaccinated with two doses of the HeV vaccine (sGHeV) containing Alhydrogel, four AGMs received the sGHeV with Alhydrogel and CpG, and four control animals did not receive the sGHeV vaccine. Animals were challenged with a high dose of infectious HeV 21 days after the boost vaccination. None of the eight specifically vaccinated animals showed any evidence of clinical illness and survived the challenge. All four controls became severely ill with symptoms consistent with HeV infection, and three of the four animals succumbed 8 days after exposure. Success of the recombinant subunit vaccine in AGMs provides pivotal data in supporting its further preclinical development for potential human use. A Hendra virus attachment (G) glycoprotein subunit vaccine was tested in nonhuman primates to assess its ability to protect them from a lethal infection with Hendra virus. It was found that all vaccinated African green monkeys were completely protected against subsequent Hendra virus infection and disease. The success of this new subunit vaccine in nonhuman primates provides critical data in support of its further development for future human use.

The RNA-Dependent-RNA Polymerase, an Emerging Antiviral Drug Target for the Hendra Virus

Australia is facing a major national medical challenge with the emergence of the Hendra virus (HeV) as a medically and economically important pathogen of humans and animals. Clinical symptoms of human HeV infection can include fever, hypotension, dizziness, encephalitis, respiratory haemorrhage and edema. The window of opportunity for successful patient treatment remains unknown, but is likely to be very narrow. Currently, very few effective therapeutic options are available for the case management of severe HeV infections or the rapid silencing of local outbreaks. This underscores the need for more activity in the drug discovery arena to develop much needed therapeutics that specifically targets this deadly disease. The structural analysis of HeV is very much in its infancy, which leaves many gaps in our understanding of the biology of HeV and makes structure-guided drug design difficult. Structural studies of the viral RNAdependent- RNA polymerase (RdRp), which is the heart of the viral replication machinery, will set the stage for rational drug design and fill a major gap in our understanding of the HeV replication machinery. This review examines the current knowledge based on the multi-domain architecture of the Hendra RdRp and highlights which essential domain functions represent tangible targets for drug development against this deadly disease.

Characterization of African bat henipavirus GH-M74a glycoproteins

In recent years, novel henipavirus-related sequences have been identified in bats in Africa. To evaluate the potential of African bat henipaviruses to spread in non-bat mammalian cells, we compared the biological functions of the surface glycoproteins G and F of the prototype African henipavirus GH-M74a with those of the glycoproteins of Nipah virus (NiV), a well-characterized pathogenic member of the henipavirus genus. Glycoproteins are central determinants for virus tropism, as efficient binding of henipavirus G proteins to cellular ephrin receptors and functional expression of fusion-competent F proteins are indispensable prerequisites for virus entry and cell-to-cell spread. In this study, we analysed the ability of the GH-M74a G and F proteins to cause cell-to-cell fusion in mammalian cell types readily permissive to NiV or Hendra virus infections. Except for limited syncytium formation in a bat cell line derived from Hypsignathus monstrosus, HypNi/1.1 cells, we did not observe any fusion. The highly restricted fusion activity was predominantly due to the F protein. Whilst GH-M74a G protein was found to interact with the main henipavirus receptor ephrin-B2 and induced syncytia upon co-expression with heterotypic NiV F protein, GH-M74a F protein did not cause evident fusion in the presence of heterotypic NiV G protein. Pulse-chase and surface biotinylation analyses revealed delayed F cleavage kinetics with a reduced expression of cleaved and fusion-active GH-M74a F protein on the cell surface. Thus, the F protein of GH-M74a showed a functional defect that is most likely caused by impaired trafficking leading to less efficient proteolytic activation and surface expression.