Use of monoclonal antibodies against Hendra and Nipah viruses in an antigen capture ELISA

Current status of diagnostic assays for emerging zoonotic viruses: Nipah and Hendra

INTRODUCTION

Nipah and Hendra viruses belong to the Paramyxoviridae family, which pose a significant threat to human health, with sporadic outbreaks causing severe morbidity and mortality. Early symptoms include fever, cough, sore throat, and headache, which offer little in terms of differential diagnosis. There are no specific therapeutics and vaccines for these viruses.

AREAS COVERED

This review comprehensively covers a spectrum of diagnostic techniques for Nipah and Hendra virus infections, discussed in conjunction with appropriate type of samples during the progression of infection. Serological assays, reverse transcriptase Real-Time PCR assays, and isothermal amplification assays are discussed in detail, along with a listing of few commercially available detection kits. Patents protecting inventions in Nipah and Hendra virus detection are also covered.

EXPERT OPINION

Despite several outbreaks of Nipah and Hendra infections in the past decade, in-depth research into their pathogenesis, Point-of-Care diagnostics, specific therapies, and human vaccines is lacking. A prompt and accurate diagnosis is pivotal for efficient outbreak management, patient treatment, and the adoption of preventative measures. The emergence of rapid point-of-care tests holds promise in enhancing diagnostic capabilities in real-world settings. The patent landscape emphasizes the importance of innovation and collaboration within the legal and business realms.

Enzyme-Linked Immunosorbent Assay Using Henipavirus-Receptor EphrinB2 and Monoclonal Antibodies for Detecting Nipah and Hendra Viruses

The Nipah virus (NiV) and the Hendra virus (HeV) are highly pathogenic zoonotic diseases that can cause fatal infections in humans and animals. Early detection is critical for the control of NiV and HeV infections. We present the development of two antigen-detection ELISAs (AgELISAs) using the henipavirus-receptor EphrinB2 and monoclonal antibodies (mAbs) to detect NiV and HeV. The NiV AgELISA detected only NiV, whereas the NiV/HeV AgELISA detected both NiV and HeV. The diagnostic specificities of the NiV AgELISA and the NiV/HeV AgELISA were 100% and 97.8%, respectively. Both assays were specific for henipaviruses and showed no cross-reactivity with other viruses. The AgELISAs detected NiV antigen in experimental pig nasal wash samples taken at 4 days post-infection. With the combination of both AgELISAs, NiV can be differentiated from HeV. Complementing other henipavirus detection methods, these two newly developed AgELISAs can rapidly detect NiV and HeV in a large number of samples and are suitable for use in remote areas where other tests are not available.

Nipah Virus: An Overview of the Current Status of Diagnostics and Their Role in Preparedness in Endemic Countries

Nipah virus (NiV) is a paramyxovirus responsible for a high mortality rate zoonosis. As a result, it has been included in the list of Blueprint priority pathogens. Bats are the main reservoirs of the virus, and different clinical courses have been described in humans. The Bangladesh strain (NiV-B) is often associated with severe respiratory disease, whereas the Malaysian strain (NiV-M) is often associated with severe encephalitis. An early diagnosis of NiV infection is crucial to limit the outbreak and to provide appropriate care to the patient. Due to high specificity and sensitivity, qRT-PCR is currently considered to be the optimum method in acute NiV infection assessment. Nasal swabs, cerebrospinal fluid, urine, and blood are used for RT-PCR testing. N gene represents the main target used in molecular assays. Different sensitivities have been observed depending on the platform used: real-time PCR showed a sensitivity of about 103 equivalent copies/reaction, SYBRGREEN technology's sensitivity was about 20 equivalent copies/reaction, and in multiple pathogen card arrays, the lowest limit of detection (LOD) was estimated to be 54 equivalent copies/reaction. An international standard for NiV is yet to be established, making it difficult to compare the sensitivity of the different methods. Serological assays are for the most part used in seroprevalence studies owing to their lower sensitivity in acute infection. Due to the high epidemic and pandemic potential of this virus, the diagnosis of NiV should be included in a more global One Health approach to improve surveillance and preparedness for the benefit of public health. Some steps need to be conducted in the diagnostic field in order to become more efficient in epidemic management, such as development of point-of-care (PoC) assays for the rapid diagnosis of NiV.

Evaluation of three rapid low-resource molecular tests for Nipah virus

Accurate and timely diagnosis of Nipah virus (NiV) requires rapid, inexpensive, and robust diagnostic tests to control spread of disease. Current state of the art technologies are slow and require laboratory infrastructure that may not be available in all endemic settings. Here we report the development and comparison of three rapid NiV molecular diagnostic tests based on reverse transcription recombinase-based isothermal amplification coupled with lateral flow detection. These tests include a simple and fast one-step sample processing step that inactivates the BSL-4 pathogen, enabling safe testing without the need for multi-step RNA purification. The rapid NiV tests targeted the Nucleocapsid protein (N) gene with analytical sensitivity down to 1,000 copies/μL for synthetic NiV RNA and did not cross-react with RNA of other flaviviruses or Chikungunya virus, which can clinically present with similar febrile symptoms. Two tests detected 50,000-100,000 TCID₅₀/mL (100-200 RNA copies/reaction) of the two distinct strains of NiV, Bangladesh (NiV_B) and Malaysia (NiV_M), and took 30 min from sample to result, suggesting these tests are well suited for rapid diagnosis under resource-limited conditions due to rapidity, simplicity, and low equipment requirements. These Nipah tests represent a first step toward development of near-patient NiV diagnostics that are appropriately sensitive for first-line screening, sufficiently robust for a range of peripheral settings, with potential to be safely performed outside of biohazard containment facilities.

Anti-Nipah Virus Enzyme-Linked Immunosorbent Assays with Non-human Primate and Hamster Serum

Enzyme-linked Immunosorbent assays or ELISAs are a versatile method for detecting various immunological ligands of interest. As the name suggests, ELISAs rely on the interaction between a ligand and an antibody to produce results. In the study of infectious disease, ELISAs are commonly used to determine if a pathogen-specific immune response has occurred in a host organism. These assays can be performed in serosurveys as part of epidemiological investigations during, or following, an infectious disease outbreak. In the research environment, ELISAs are used to quantify the humoral immune response following infection or vaccination of a host organism. Data from these assays can be used to determine the type of immune response elicited (e.g. IgG1 vs IgG2) and the robustness of the response. Here, we describe ELISAs that were developed for the study of either hamsters or non-human primates vaccinated against Nipah virus infection, or infected with Nipah virus. The ELISAs described include assays for both IgG and IgM in the hamster and non-human primate models for Nipah virus-induced disease. An assay was also developed for the detection of IgA in bronchoalveolar lavage from non-human primates.

Nipah Virus Disease: Epidemiological, Clinical, Diagnostic and Legislative Aspects of This Unpredictable Emerging Zoonosis

Nipah virus (NiV) infection is a viral disease caused by a Henipavirus, belonging to the Paramyxoviridae family, responsible for a zoonosis. The course of the disease can be very serious and lead to death. NiV natural hosts are fruit bats (also known as megabats) belonging to the Pteropodidae family, especially those of the Pteropus genus. Natural infection in domestic animals has been described in farming pigs, horses, domestic and feral dogs and cats. Natural NiV transmission is possible intra-species (pig-to-pig, human-to-human) and inter-species (flying bat-to-human, pig-to-human, horse-to-human). The infection can be spread by humans or animals in different ways. It is peculiar how the viral transmission modes among different hosts also change depending on the geographical area for different reasons, including different breeding methods, eating habits and the recently identified genetic traits/molecular features of main virus proteins related to virulence. Outbreaks have been described in Malaysia, Singapore, Bangladesh, India and the Philippines with, in some cases, severe respiratory and neurological disease and high mortality in both humans and pigs. Diagnosis can be made using different methods including serological, molecular, virological and immunohistochemical methods. The cornerstones for control of the disease are biosecurity (via the correct management of reservoir and intermediate/amplifying hosts) and potential vaccines which are still under development. However, the evaluation of the potential influence of climate and anthropogenic changes on the NiV reservoir bats and their habitat as well as on disease spread and inter-specific infections is of great importance. Bats, as natural reservoirs of the virus, are responsible for the viral spread and, therefore, for the outbreaks of the disease in humans and animals. Due to the worldwide distribution of bats, potential new reports and spillovers are not to be dismissed in the future.

Nipah and Hendra Viruses: Deadly Zoonotic Paramyxoviruses with the Potential to Cause the Next Pandemic

Nipah and Hendra viruses are deadly zoonotic paramyxoviruses with a case fatality rate of upto 75%. The viruses belong to the genus henipavirus in the family Paramyxoviridae, a family of negative-sense single-stranded RNA viruses. The natural reservoirs of NiV and HeV are bats (flying foxes) in which the virus infection is asymptomatic. The intermediate hosts for NiV and HeV are swine and equine, respectively. In humans, NiV infections result in severe and often fatal respiratory and neurological manifestations. The Nipah virus was first identified in Malaysia and Singapore following an outbreak of encephalitis in pig farmers and subsequent outbreaks have been reported in Bangladesh and India almost every year. Due to its extreme pathogenicity, pandemic potential, and lack of established antiviral therapeutics and vaccines, research on henipaviruses is highly warranted so as to develop antivirals or vaccines that could aid in the prevention and control of future outbreaks.

Detection of Nipah and Hendra Viruses Using Recombinant Human Ephrin B2 Capture Virus in Immunoassays

Nipah virus (NiV) and Hendra virus (HeV) are classified as high-consequence zoonotic viruses characterized by high pathogenicity and high mortality in animals and humans. Rapid diagnosis is essential to containing the outbreak. In this study, the henipavirus receptor ephrin B2 was examined to determine whether it could be used as a universal ligand for henipavirus detection in immunoassays. Enzyme-linked immunosorbent assays (ELISAs) were developed using recombinant ephrin B2 as the capture ligand and two monoclonal antibodies (mAbs) as detection reagents. Using mAb F27NiV-34, which cross-reacts with NiV and HeV, we were able to detect NiV and HeV, while mAb F20NiV-65 was used to detect NiV. Therefore, using these two ELISAs, we were able to differentiate between NiV and HeV. Furthermore, we developed a rapid lateral flow strip test for NiV detection using ephrin B2 as the capture ligand combined with mAb F20NiV-65 as the detector. Taken together, our results show that the combination of ephrin B2 and a specific mAb provides an excellent pairing for NiV and HeV detection.

Griffithsin Inhibits Nipah Virus Entry and Fusion and Can Protect Syrian Golden Hamsters From Lethal Nipah Virus Challenge

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus that causes fatal encephalitis and respiratory disease in humans. There is currently no approved therapeutic for human use against NiV infection. Griffithsin (GRFT) is high-mannose oligosaccharide binding lectin that has shown in vivo broad-spectrum activity against viruses, including severe acute respiratory syndrome coronavirus, human immunodeficiency virus 1, hepatitis C virus, and Japanese encephalitis virus. In this study, we evaluated the in vitro antiviral activities of GRFT and its synthetic trimeric tandemer (3mG) against NiV and other viruses from 4 virus families. The 3mG had comparatively greater potency than GRFT against NiV due to its enhanced ability to block NiV glycoprotein-induced syncytia formation. Our initial in vivo prophylactic evaluation of an oxidation-resistant GRFT (Q-GRFT) showed significant protection against lethal NiV challenge in Syrian golden hamsters. Our results warrant further development of Q-GRFT and 3mG as potential NiV therapeutics.

Nipah virus: epidemiology, pathology, immunobiology and advances in diagnosis, vaccine designing and control strategies - a comprehensive review

Nipah (Nee-pa) viral disease is a zoonotic infection caused by Nipah virus (NiV), a paramyxovirus belonging to the genus Henipavirus of the family Paramyxoviridae. It is a biosafety level-4 pathogen, which is transmitted by specific types of fruit bats, mainly Pteropus spp. which are natural reservoir host. The disease was reported for the first time from the Kampung Sungai Nipah village of Malaysia in 1998. Human-to-human transmission also occurs. Outbreaks have been reported also from other countries in South and Southeast Asia. Phylogenetic analysis affirmed the circulation of two major clades of NiV as based on currently available complete N and G gene sequences. NiV isolates from Malaysia and Cambodia clustered together in NiV-MY clade, whereas isolates from Bangladesh and India clusterered within NiV-BD clade. NiV isolates from Thailand harboured mixed population of sequences. In humans, the virus is responsible for causing rapidly progressing severe illness which might be characterized by severe respiratory illness and/or deadly encephalitis. In pigs below six months of age, respiratory illness along with nervous symptoms may develop. Different types of enzyme-linked immunosorbent assays along with molecular methods based on polymerase chain reaction have been developed for diagnostic purposes. Due to the expensive nature of the antibody drugs, identification of broad-spectrum antivirals is essential along with focusing on small interfering RNAs (siRNAs). High pathogenicity of NiV in humans, and lack of vaccines or therapeutics to counter this disease have attracted attention of researchers worldwide for developing effective NiV vaccine and treatment regimens.

Advances in diagnostics, vaccines and therapeutics for Nipah virus

Nipah virus is an emerging zoonotic paramyxovirus that causes severe and often fatal respiratory and neurological disease in humans. The virus was first discovered after an outbreak of encephalitis in pig farmers in Malaysia and Singapore with subsequent outbreaks in Bangladesh or India occurring almost annually. Due to the highly pathogenic nature of NiV, its pandemic potential, and the lack of licensed vaccines or therapeutics, there is a requirement for research and development into highly sensitive and specific diagnostic tools as well as antivirals and vaccines to help prevent and control future outbreak situations.

Nipah virus: epidemiology, pathology, immunobiology and advances in diagnosis, vaccine designing and control strategies - a comprehensive review

Nipah (Nee-pa) viral disease is a zoonotic infection caused by Nipah virus (NiV), a paramyxovirus belonging to the genus Henipavirus of the family Paramyxoviridae. It is a biosafety level-4 pathogen, which is transmitted by specific types of fruit bats, mainly Pteropus spp. which are natural reservoir host. The disease was reported for the first time from the Kampung Sungai Nipah village of Malaysia in 1998. Human-to-human transmission also occurs. Outbreaks have been reported also from other countries in South and Southeast Asia. Phylogenetic analysis affirmed the circulation of two major clades of NiV as based on currently available complete N and G gene sequences. NiV isolates from Malaysia and Cambodia clustered together in NiV-MY clade, whereas isolates from Bangladesh and India clusterered within NiV-BD clade. NiV isolates from Thailand harboured mixed population of sequences. In humans, the virus is responsible for causing rapidly progressing severe illness which might be characterized by severe respiratory illness and/or deadly encephalitis. In pigs below six months of age, respiratory illness along with nervous symptoms may develop. Different types of enzyme-linked immunosorbent assays along with molecular methods based on polymerase chain reaction have been developed for diagnostic purposes. Due to the expensive nature of the antibody drugs, identification of broad-spectrum antivirals is essential along with focusing on small interfering RNAs (siRNAs). High pathogenicity of NiV in humans, and lack of vaccines or therapeutics to counter this disease have attracted attention of researchers worldwide for developing effective NiV vaccine and treatment regimens.

Diagnostics for Nipah virus: a zoonotic pathogen endemic to Southeast Asia

Nipah virus (NiV) is an emerging pathogen that, unlike other priority pathogens identified by WHO, is endemic to Southeast Asia. It is most commonly transmitted through exposure to saliva or excrement from the Pteropus fruit bat, or direct contact with intermediate animal hosts, such as pigs. NiV infection causes severe febrile encephalitic disease and/or respiratory disease; treatment options are limited to supportive care. A number of in-house diagnostic assays for NiV using serological and nucleic acid amplification techniques have been developed for NiV and are used in laboratory settings, including some early multiplex panels for differentiation of NiV infection from other febrile diseases. However, given the often rural and remote nature of NiV outbreak settings, there remains a need for rapid diagnostic tests that can be implemented at the point of care. Additionally, more reliable assays for surveillance of communities and livestock will be vital to achieving a better understanding of the ecology of the fruit bat host and transmission risk to other intermediate hosts, enabling implementation of a ‘One Health’ approach to outbreak prevention and the management of this zoonotic disease. An improved understanding of NiV viral diversity and infection kinetics or dynamics will be central to the development of new diagnostics, and access to clinical specimens must be improved to enable effective validation and external quality assessments. Target product profiles for NiV diagnostics should be refined to take into account these outstanding needs.

Viruses Associated With Foodborne Infections

Foodborne pathogens cause acute and chronic health outcomes of very different durations, severity and mortality, resulting in high costs and burdens to society. The issues of food safety and food poisoning are being increasingly emphasised, particularly in developed countries. Infection/contamination with many agents i.e., bacterial, parasitic and viral entities can result in foodborne illness. This article will focus mainly on viral agents of infection.

A range of different viruses can cause food poisoning/foodborne infection, and infection can result in a myriad of symptoms, ranging from mild, acute disease to chronic, debilitating disease and even death. Due to the inherent differences between bacteria and viruses, namely the fact that viruses do not replicate in food, while bacteria do, viruses are frequently difficult to detect. This is compounded by the fact that many of the viruses associated with enteric disease do not replicate in cell culture. These factors can lead to a lag between reporting, detection and analysis of foodborne viruses versus bacterial agents. Despite these constraints, it is now evident that there are both well-established and emerging viruses implicated in foodborne infections, and the role of molecular detection and characterisation is becoming increasingly important.

4'-Azidocytidine (R1479) inhibits henipaviruses and other paramyxoviruses with high potency

The henipaviruses Nipah virus and Hendra virus are highly pathogenic zoonotic paramyxoviruses which have caused fatal outbreaks of encephalitis and respiratory disease in humans. Despite the availability of a licensed equine Hendra virus vaccine and a neutralizing monoclonal antibody shown to be efficacious against henipavirus infections in non-human primates, there remains no approved therapeutics or vaccines for human use. To explore the possibility of developing small-molecule nucleoside inhibitors against henipaviruses, we evaluated the antiviral activity of 4'-azidocytidine (R1479), a drug previously identified to inhibit flaviviruses, against henipaviruses along with other representative members of the family Paramyxoviridae. We observed similar levels of R1479 antiviral activity across the family, regardless of virus genus. Our brief study expands the documented range of viruses susceptible to R1479, and provides the basis for future investigation and development of 4'-modified nucleoside analogs as potential broad-spectrum antiviral therapeutics across both positive and negative-sense RNA virus families.

GS-5734 and its parent nucleoside analog inhibit Filo-, Pneumo-, and Paramyxoviruses

GS-5734 is a monophosphate prodrug of an adenosine nucleoside analog that showed therapeutic efficacy in a non-human primate model of Ebola virus infection. It has been administered under compassionate use to two Ebola patients, both of whom survived, and is currently in Phase 2 clinical development for treatment of Ebola virus disease. Here we report the antiviral activities of GS-5734 and the parent nucleoside analog across multiple virus families, providing evidence to support new indications for this compound against human viruses of significant public health concern.

Development, characterization and application of monoclonal antibodies against Brazilian Dengue virus isolates

Dengue is the most prevalent human arboviral disease. The morbidity related to dengue infection supports the need for an early, quick and effective diagnostic test. Brazil is a hotspot for dengue, but no serological diagnostic test has been produced using Brazilian dengue virus isolates. This study aims to improve the development of immunodiagnostic methods for dengue virus (DENV) detection through the production and characterization of 22 monoclonal antibodies (mAbs) against Brazilian isolates of DENV-1, -2 and -3. The mAbs include IgG2bκ, IgG2aκ and IgG1κ isotypes, and most were raised against the envelope or the pre-membrane proteins of DENV. When the antibodies were tested against the four DENV serotypes, different reactivity patterns were identified: group-specific, subcomplex specific (DENV-1, -3 and -4 and DENV-2 and -3) and dengue serotype-specific (DENV-2 or -3). Additionally, some mAbs cross-reacted with yellow fever virus (YFV), West Nile virus (WNV) and Saint Louis encephalitis virus (SLEV). None of the mAbs recognized the alphavirus Venezuelan equine encephalitis virus (VEEV). Furthermore, mAbs D3 424/8G, D1 606/A12/B9 and D1 695/12C/2H were used to develop a capture enzyme-linked immunosorbent assay (ELISA) for anti-dengue IgM detection in sera from patients with acute dengue. To our knowledge, these are the first monoclonal antibodies raised against Brazilian DENV isolates, and they may be of special interest in the development of diagnostic assays, as well as for basic research.

Evaluation of luciferase and GFP-expressing Nipah viruses for rapid quantitative antiviral screening

Nipah virus (NiV) outbreaks have occurred in Malaysia, India, and Bangladesh, and the virus continues to cause annual outbreaks of fatal human encephalitis in Bangladesh due to spillover from its bat host reservoir. Due to its high pathogenicity, its potential use for bio/agro-terrorism, and to the current lack of approved therapeutics, NiV is designated as an overlap select agent requiring biosafety level-4 containment. Although the development of therapeutic monoclonal antibodies and soluble protein subunit vaccines have shown great promise, the paucity of effective antiviral drugs against NiV merits further exploration of compound libraries using rapid quantitative antiviral assays. As a proof-of-concept study, we evaluated the use of fluorescent and luminescent reporter NiVs for antiviral screening. We constructed and rescued NiVs expressing either Renilla luciferase or green fluorescent protein, and characterized their reporter signal kinetics in different cell types as well as in the presence of several inhibitors. The 50% effective concentrations (EC50s) derived for inhibitors against both reporter viruses are within range of EC50s derived from virus yield-based dose-response assays against wild-type NiV (within 1Log10), thus demonstrating that both reporter NiVs can serve as robust antiviral screening tools. Utilizing these live NiV-based reporter assays requires modest instrumentation, and circumvents the time and labor-intensive steps associated with cytopathic effect or viral antigen-based assays. These reporter NiVs will not only facilitate antiviral screening, but also the study of host cell components that influence the virus life cycle.

Nipah virus infection: current scenario

The emergence of Nipah virus (NiV) infection into the pig population and subsequently into the human population is believed to be due to changes in ecological conditions. In Malaysia, A major NiV outbreak occurred in pigs and humans from September 1998 to April 1999 that resulted in infection of 265 and death of 105 persons. About 1.1 million pigs had to be destroyed to control the outbreak. The disease was recorded in the form of a major outbreak in India in 2001 and then a small incidence in 2007, both the outbreaks in West Bengal only in humans without any involvement of pigs. There were series of human Nipah incidences in Bangladesh from 2001 till 2013 almost every year with mortality exceeding 70 %. The disease transmission from pigs acting as an intermediate host during Malaysian and Singapore outbreaks has changed in NIV outbreaks in India and Bangladesh, transmitting the disease directly from bats to human followed by human to human. The drinking of raw date palm sap contaminated with fruit bat urine or saliva containing NiV is the only known cause of outbreak of the disease in Bangladesh outbreaks. The virus is now known to exist in various fruit bats of Pteropus as well as bats of other genera in a wider belt from Asia to Africa.

Hendra virus: a one health tale of flying foxes, horses and humans

Hendra virus, a member of the family Paramyxoviridae, was first recognized following a devastating outbreak in Queensland, Australia, in 1994. The naturally acquired symptomatic infection, characterized by a rapidly progressive illness involving the respiratory system and/or CNS, has so far only been recognized in horses and humans. However, there is potential for other species to be infected, with significant consequences for animal and human health. Prevention of infection involves efforts to interrupt the bat-to-horse and horse-to-human transmission interfaces. Education and infection-control efforts remain the key to reducing risk of transmission, particularly as no effective antiviral treatment is currently available. The recent release of an equine Hendra G glycoprotein subunit vaccine is an exciting advance that offers the opportunity to curb the recent increase in equine transmission events occurring in endemic coastal regions of Australia and thereby reduce the risk of infection in humans.

Elucidation and clinical role of emerging viral respiratory tract infections in children

Acute respiratory viral infections (ARVI's) are the most common infectious disease in humans. With the appearance of molecular techniques the recovery of viruses has dramatically increased. Nowadays virologists can quickly discriminate virological families and related viruses from emerging viruses and consequently identify novel viruses. Many new respiratory viruses have been identified in children in the past 15 years. In this review we shortly discuss novel respiratory viruses and their pathogenic role in pediatric respiratory disease. Advantages and drawbacks of the technique and our current knowledge will be discussed. We will conclude this review with a general discussion on the future role of molecular diagnostic virology in the clinic.

Antigen capture ELISA system for henipaviruses using polyclonal antibodies obtained by DNA immunization

A novel antigen-capture sandwich ELISA system targeting the glycoproteins of the henipaviruses Nipah virus (NiV) and Hendra virus (HeV) was developed. Utilizing purified polyclonal antibodies derived from NiV glycoprotein-encoding DNA-immunized rabbits, we established a system that can detect the native antigenic structures of the henipavirus surface glycoproteins using simplified and inexpensive methods. The lowest detection limit against live viruses was achieved for NiV Bangladesh strain, 2.5 × 10(4) TCID(50). Considering the recent emergence of genetic variants of henipaviruses and the resultant problems that arise for PCR-based detection, this system could serve as an alternative rapid diagnostic and detection assay.

Diagnosis of henipavirus infection: current capabilities and future directions

Since the last major review on diagnosis of henipavirus infection about a decade ago, significant progress has been made in many different areas of test development, especially in the development of molecular tests using real-time PCR and many novel serological test platforms. In addition to provide an updated review of the current test capabilities, this review also identifies key future challenges in henipavirus diagnosis.

Emerging tropical diseases in Australia. Part 5. Hendra virus

Hendra virus (HeV) was first isolated in 1994, from a disease outbreak involving at least 21 horses and two humans in the Brisbane suburb of Hendra, Australia. The affected horses and humans all developed a severe but unidentified respiratory disease that resulted in the deaths of one of the human cases and the deaths or putting down of 14 of the horses. The virus, isolated by culture from a horse and the kidney of the fatal human case, was initially characterised as a new member of the genus Morbillivirus in the family Paramyxoviridae. Comparative sequence analysis of part of the matrix protein gene of the virus and the discovery that the virus had an exceptionally large genome subsequently led to HeV being assigned to a new genus, Henipavirus, along with Nipah virus (a newly emergent virus in pigs). The regular outbreaks of HeV-related disease that have occurred in Australia since 1994 have all been characterised by acute respiratory and neurological manifestations, with high levels of morbidity and mortality in the affected horses and humans. The modes of transmission of HeV remain largely unknown. Although fruit bats have been identified as natural hosts of the virus, direct bat-horse, bat-human or human-human transmission has not been reported. Human infection can occur via exposure to infectious urine, saliva or nasopharyngeal fluid from horses. The treatment options and efficacy are very limited and no vaccine exists. Reports on the outbreaks of HeV in Australia are collated in this review and the available data on the biology, transmission and detection of the pathogen are summarized and discussed.