First Genomic Evidence of a Henipa-like Virus in Brazil

Potent Cross-neutralizing Antibodies Reveal Vulnerabilities of Henipavirus Fusion Glycoprotein

Hendra and Nipah viruses (HNVs), zoonotic paramyxoviruses with >50% case fatality rates, cause fatal encephalitis and respiratory disease, yet lack approved therapies. Here, nine rhesus-derived monoclonal antibodies (mAbs) targeting the fusion glycoprotein (F) prefusion conformation are developed. Four mAbs exhibit first-rate cross-neutralization against HNVs, with two showing synergistic potency when combined with attachment glycoprotein (G)-specific mAbs. Single-dose administration of mAbs confers robust protection against lethal Nipah virus challenge in hamsters. Structural insights reveal that 8 of the 9 potent mAbs adopt a human IGHV4-59-like framework with protruding CDRH3 loops, forming pushpin-shaped paratopes that stabilize the prefusion F-trimer by occupying vulnerable interprotomer cavities. Systematic mutational profiling identifies 14 prefusion-locking residues within the F ectodomain, classified as i) structural linchpins governing fusogenicity or ii) immunodominant hotspots targeted by cross-neutralizing mAbs. This work delivers promising therapeutic candidates against HNVs and provides blueprints for the rational design of antibodies and vaccines targeting viral fusion machinery.

Henipaviruses: epidemiology, ecology, disease, and the development of vaccines and therapeutics

SUMMARYHenipaviruses were first identified 30 years ago and have since been associated with over 30 outbreaks of disease in humans. Highly pathogenic henipaviruses include Hendra virus (HeV) and Nipah virus (NiV), classified as biosafety level 4 pathogens. In addition, NiV has been listed as a priority pathogen by the World Health Organization (WHO), the Coalition for Epidemic Preparedness Innovations (CEPI), and the UK Vaccines Research and Development Network (UKVN). Here, we re-examine epidemiological, ecological, clinical, and pathobiological studies of HeV and NiV to provide a comprehensive guide of the current knowledge and application to identify and evaluate countermeasures. We also discuss therapeutic and vaccine development efforts. Furthermore, with case identification, prevention, and treatment in mind, we highlight limitations in research and recognize gaps necessitating additional studies.

Genetic Diversity and Geographic Spread of Henipaviruses

Henipaviruses, such as Hendra and Nipah viruses, are major zoonotic pathogens that cause encephalitis and respiratory infections in humans and animals. The recent emergence of Langya virus in China highlights the need to understand henipavirus host diversity and geographic spread to prevent future outbreaks. Our analysis of the National Center for Biotechnology Information Virus and VIRION databases revealed ≈1,117 henipavirus sequences and 142 complete genomes. Bats (64.7%) and shrews (11.7%) dominated the host species record, and the genera Pteropus and Crocidura contained key henipavirus hosts in Asia, Australia, and Africa. Henipaviruses found in the Eidolon bat genus exhibited the highest within-host genetic distance. Phylogenetic analysis revealed batborne and rodent- or shrew-derived henipaviruses diverged ≈11,000 years ago and the first known lineage originating in Eidolon genus bats ≈9,900 years ago. Pathogenic henipaviruses diverged from their ancestors 2,800-1,200 years ago. Including atypical hosts and regions in future investigations is necessary to control future outbreaks.

Emerging and re-emerging viral infections of the central nervous system in Australasia and beyond

Viral infections of the central nervous system (CNS) have been emerging and re-emerging worldwide, and the Australasia region has not been spared. Enterovirus A71 and enterovirus D68, both human enteroviruses, are likely to replace the soon-to-be eradicated poliovirus to cause global outbreaks associated with neurological disease. Although prevalent elsewhere, the newly emergent orthoflavivirus, Japanese encephalitis virus (genotype IV), caused human infections in Australia in 2021, and almost certainly will continue to do so because of spillovers from the natural animal host-vector life cycle endemic in the country. Another orthoflavivirus, Murray Valley encephalitis virus, has re-emerged in Australia. The Hendra henipavirus together with Nipah henipavirus ​are listed as high-risk pathogens by the World Health Organization because both can cause lethal encephalitis. The former remains a health threat in Australasia because bats may still be able to spread the infection to unvaccinated Australian horses and other animals acting as intermediate hosts, and thence to humans. The global COVID-19 pandemic, caused by the emerging severe acute respiratory syndrome coronavirus-2, a virus transmitted from animals to humans that was first described and first arose in China, is associated with acute and long-lasting CNS pathology. Fortunately, the pathology and pathogenesis of these important neurotropic viruses are now better understood, leading to better management protocols and prevention strategies. Pathologists are in a unique position to contribute to the diagnosis and advancement in our knowledge of infectious diseases. This review summarises some of the current knowledge about a few important emerging and re-emerging CNS infections in Australasia and beyond.

Cross-protectivity of henipavirus soluble glycoprotein in an in vivo model of Nipah virus disease

Introduction

Nipah virus (NiV) is one of a group of highly pathogenic viruses classified within the Henipavirus genus. Since 2012 at least 11 new henipa-like viruses have been identified, including from new locations and reservoir hosts; the pathogenicity of these new viruses has yet to be determined, but two of them have been associated with morbidity, including fatalities.

Methods

The efficacy and cross-reactivity of two vaccine candidates derived from the soluble glycoproteins of both NiV and Hendra virus (HeV) was evaluated in our recently established hamster model.

Results

Both vaccine preparations resulted in strong humoral responses against NiV antigenic targets, demonstrating cross-reactive immunity. Efficacy was determined through challenge of hamsters with NiV Malaysian (NiV-M) strain. 100% of the hamsters survived a lethal challenge dose after prime/boost immunisation with glycoproteins derived from both NiV and HeV in the presence of adjuvant, with clinical signs and pathology being significantly reduced in immunised animals.

Discussion

This is first time the NiV and HeV soluble glycoproteins have been compared in the NiV-M hamster challenge model in the presence of Alhydrogel and AddaVax, providing evidence that glycoproteins from closely related henipavirus species can provide cross-protectivity against infection from alternate henipaviruses, supporting the potential of an effective pan-henipavirus vaccine for use in a frontline outbreak response.

Mapping the distribution of Nipah virus infections: a geospatial modelling analysis

BACKGROUND

Nipah virus is a zoonotic paramyxovirus responsible for disease outbreaks with high fatality rates in south and southeast Asia. However, knowledge of the potential geographical extent and risk patterns of the virus is poor. We aimed to establish an integrated spatiotemporal and phylogenetic database of Nipah virus infections in humans and animals across south and southeast Asia.

METHODS

In this geospatial modelling analysis, we developed an integrated database containing information on the distribution of Nipah virus infections in humans and animals from 1998 to 2021. We conducted phylodynamic analysis to examine the evolution and migration pathways of the virus and meta-analyses to estimate the adjusted case-fatality rate. We used two boosted regression tree models to identify the potential ecological drivers of Nipah virus occurrences in spillover events and endemic areas, and mapped potential risk areas for Nipah virus endemicity.

FINDINGS

749 people and eight bat species across nine countries were documented as being infected with Nipah virus. On the basis of 66 complete genomes of the virus, we identified two clades-the Bangladesh clade and the Malaysia clade-with the time of the most recent common ancestor estimated to be 1863. Adjusted case-fatality rates varied widely between countries and were higher for the Bangladesh clade than for the Malaysia clade. Multivariable meta-regression analysis revealed significant relationships between case-fatality rate estimates and viral clade (p=0·0021), source country (p=0·016), proportion of male patients (p=0·036), and travel time to health-care facilities (p=0·036). Temperature-related bioclimate variables and the probability of occurrence of Pteropus medius were important contributors to both the spillover and the endemic infection models.

INTERPRETATION

The suitable niches for Nipah virus are more extensive than previously reported. Future surveillance efforts should focus on high-risk areas informed by updated projections. Specifically, intensifying zoonotic surveillance efforts, enhancing laboratory testing capacity, and implementing public health education in projected high-risk areas where no human cases have been reported to date will be crucial. Additionally, strengthening wildlife surveillance and investigating potential modes of transmission in regions with documented human cases is needed.

FUNDING

The Key Research and Development Program of China.

Indiscriminate activities of different henipavirus polymerase complex proteins allow for efficient minigenome replication in hybrid systems

The henipaviruses, including Nipah virus (NiV) and Hendra virus (HeV), are biosafety level 4 (BSL-4) zoonotic pathogens that cause severe neurological and respiratory disease in humans. To study the replication machinery of these viruses, we developed robust minigenome systems that can be safely used in BSL-2 conditions. The nucleocapsid (N), phosphoprotein (P), and large protein (L) of henipaviruses are critical elements of their replication machinery and thus essential support components of the minigenome systems. Here, we tested the effects of diverse combinations of the replication support proteins on the replication capacity of the NiV and HeV minigenomes by exchanging the helper plasmids coding for these proteins among the two viruses. We demonstrate that all combinations including one or more heterologous proteins were capable of replicating both the NiV and HeV minigenomes. Sequence alignment showed identities of 92% for the N protein, 67% for P, and 87% for L. Notably, variations in amino acid residues were not concentrated in the N-P and P-L interacting regions implying that dissimilarities in amino acid composition among NiV and HeV polymerase complex proteins may not impact their interactions. The observed indiscriminate activity of NiV and HeV polymerase complex proteins is different from related viruses, which can support the replication of heterologous genomes only when the whole polymerase complex belongs to the same virus. This newly observed promiscuous property of the henipavirus polymerase complex proteins likely attributed to their conserved interaction regions could potentially be harnessed to develop universal anti-henipavirus antivirals.IMPORTANCEGiven the severity of disease induced by Hendra and Nipah viruses in humans and the continuous emergence of new henipaviruses as well as henipa-like viruses, it is necessary to conduct a more comprehensive investigation of the biology of henipaviruses and their interaction with the host. The replication of henipaviruses and the development of antiviral agents can be studied in systems that allow experiments to be performed under biosafety level 2 conditions. Here, we developed robust minigenome systems for the Nipah virus (NiV) and Hendra virus (HeV) that provide a convenient alternative for studying NiV and HeV replication. Using these systems, we demonstrate that any combination of the three polymerase complex proteins of NiV and HeV could effectively initiate the replication of both viral minigenomes, which suggests that the interaction regions of the polymerase complex proteins could be effective targets for universal and effective anti-henipavirus interventions.

Infection and transmission of henipavirus in animals

Henipavirus (HNV) is well known for two zoonotic viruses in the genus, Hendra virus (HeV) and Nipah virus (NiV), which pose serious threat to human and animal health. In August 2022, a third zoonotic virus in the genus Henipavirus, Langya virus (LayV), was discovered in China. The emergence of HeV, NiV, and LayV highlights the persistent threat of HNV to human and animal health. In addition to the above three HNVs, new species within this genus are still being discovered. Although they have not yet caused a pandemic in humans or livestock, they still have the risk of spillover as a potential threat to the health of humans and animals. It's important to understand the infection and transmission of different HNV in animals for the prevention and control of current or future HNV epidemics. Therefore, this review mainly summarizes the animal origin, animal infection and transmission of HNV that have been found worldwide, and further analyzes and summarizes the rules of infection and transmission, so as to provide a reference for relevant scientific researchers. Furthermore, it can provide a direction for epidemic prevention and control, and animal surveillance to reduce the risk of the global pandemic of HNV.

A potent Henipavirus cross-neutralizing antibody reveals a dynamic fusion-triggering pattern of the G-tetramer

The Hendra and Nipah viruses (HNVs) are highly pathogenic pathogens without approved interventions for human use. In addition, the interaction pattern between the attachment (G) and fusion (F) glycoproteins required for virus entry remains unclear. Here, we isolate a panel of Macaca-derived G-specific antibodies that cross-neutralize HNVs via multiple mechanisms. The most potent antibody, 1E5, confers adequate protection against the Nipah virus challenge in female hamsters. Crystallography demonstrates that 1E5 has a highly similar binding pattern to the receptor. In cryo-electron microscopy studies, the tendency of 1E5 to bind to the upper or lower heads results in two distinct quaternary structures of G. Furthermore, we identify the extended outer loop β1S2-β1S3 of G and two pockets on the apical region of fusion (F) glycoprotein as the essential sites for G-F interactions. This work highlights promising drug candidates against HNVs and contributes deeper insights into the viruses.

Structure and design of Langya virus glycoprotein antigens

Langya virus (LayV) is a recently discovered henipavirus (HNV), isolated from febrile patients in China. HNV entry into host cells is mediated by the attachment (G) and fusion (F) glycoproteins which are the main targets of neutralizing antibodies. We show here that the LayV F and G glycoproteins promote membrane fusion with human, mouse, and hamster target cells using a different, yet unknown, receptor than Nipah virus (NiV) and Hendra virus (HeV) and that NiV- and HeV-elicited monoclonal and polyclonal antibodies do not cross-react with LayV F and G. We determined cryoelectron microscopy structures of LayV F, in the prefusion and postfusion states, and of LayV G, revealing their conformational landscape and distinct antigenicity relative to NiV and HeV. We computationally designed stabilized LayV G constructs and demonstrate the generalizability of an HNV F prefusion-stabilization strategy. Our data will support the development of vaccines and therapeutics against LayV and closely related HNVs.

Therapeutic administration of a cross-reactive mAb targeting the fusion glycoprotein of Nipah virus protects nonhuman primates

No licensed vaccines or therapies exist for patients infected with Nipah virus (NiV), although an experimental human monoclonal antibody (mAb) cross-reactive to the NiV and Hendra virus (HeV) G glycoprotein, m102.4, has been tested in a phase 1 trial and has been provided under compassionate use for both HeV and NiV exposures. NiV is a highly pathogenic zoonotic paramyxovirus causing regular outbreaks in humans and animals in South and Southeast Asia. The mortality rate of NiV infection in humans ranges from 40% to more than 90%, making it a substantial public health concern. The NiV G glycoprotein mediates host cell attachment, and the F glycoprotein facilitates membrane fusion and infection. We hypothesized that a mAb against the prefusion conformation of the F glycoprotein may confer better protection than m102.4. To test this, two potent neutralizing mAbs against NiV F protein, hu1F5 and hu12B2, were compared in a hamster model. Hu1F5 provided superior protection to hu12B2 and was selected for comparison with m102.4 for the ability to protect African green monkeys (AGMs) from a stringent NiV challenge. AGMs were exposed intranasally to the Bangladesh strain of NiV and treated 5 days after exposure with either mAb (25 milligrams per kilogram). Whereas only one of six AGMs treated with m102.4 survived until the study end point, all six AGMs treated with hu1F5 were protected. Furthermore, a reduced 10 milligrams per kilogram dose of hu1F5 also provided complete protection against NiV challenge, supporting the upcoming clinical advancement of this mAb for postexposure prophylaxis and therapy.

Structure-guided mutagenesis of Henipavirus receptor-binding proteins reveals molecular determinants of receptor usage and antibody-binding epitopes

Nipah virus (NiV) is a highly lethal, zoonotic Henipavirus (HNV) that causes respiratory and neurological signs and symptoms in humans. Similar to other paramyxoviruses, HNVs mediate entry into host cells through the concerted actions of two surface glycoproteins: a receptor-binding protein (RBP) that mediates attachment and a fusion glycoprotein (F) that triggers fusion in an RBP-dependent manner. NiV uses ephrin-B2 (EFNB2) and ephrin-B3 (EFNB3) as entry receptors. Ghana virus (GhV), a novel HNV identified in a Ghanaian bat, uses EFNB2 but not EFNB3. In this study, we employ a structure-informed approach to identify receptor-interfacing residues and systematically introduce GhV-RBP residues into a NiV-RBP backbone to uncover the molecular determinants of EFNB3 usage. We reveal two regions that severely impair EFNB3 binding by NiV-RBP and EFNB3-mediated entry by NiV pseudotyped viral particles. Further analyses uncovered two-point mutations (NiVN557SGhV and NiVY581TGhV) pivotal for this phenotype. Moreover, we identify NiV interaction with Y120 of EFNB3 as important for the usage of this receptor. Beyond these EFNB3-related findings, we reveal two domains that restrict GhV binding of EFNB2, confirm the HNV-head as an immunodominant target for polyclonal and monoclonal antibodies, and describe putative epitopes for GhV- and NiV-specific monoclonal antibodies. Cumulatively, the work presented here generates useful reagents and tools that shed insight to residues important for NiV usage of EFNB3, reveal regions critical for GhV binding of EFNB2, and describe putative HNV antibody-binding epitopes.

IMPORTANCE

Hendra virus and Nipah virus (NiV) are lethal, zoonotic Henipaviruses (HNVs) that cause respiratory and neurological clinical features in humans. Since their initial outbreaks in the 1990s, several novel HNVs have been discovered worldwide, including Ghana virus. Additionally, there is serological evidence of zoonotic transmission, lending way to concerns about future outbreaks. HNV infection of cells is mediated by the receptor-binding protein (RBP) and the Fusion protein (F). The work presented here identifies NiV RBP amino acids important for the usage of ephrin-B3 (EFNB3), a receptor highly expressed in neurons and predicted to be important for neurological clinical features caused by NiV. This study also characterizes epitopes recognized by antibodies against divergent HNV RBPs. Together, this sheds insight to amino acids critical for HNV receptor usage and antibody binding, which is valuable for future studies investigating determinants of viral pathogenesis and developing antibody therapies.

Pathogenicity and virulence of henipaviruses

Paramyxoviruses are a family of single-stranded negative-sense RNA viruses, many of which are responsible for a range of respiratory and neurological diseases in humans and animals. Among the most notable are the henipaviruses, which include the deadly Nipah (NiV) and Hendra (HeV) viruses, the causative agents of outbreaks of severe disease and high case fatality rates in humans and animals. NiV and HeV are maintained in fruit bat reservoirs primarily in the family Pteropus and spillover into humans directly or by an intermediate amplifying host such as swine or horses. Recently, non-chiropteran associated Langya (LayV), Gamak (GAKV), and Mojiang (MojV) viruses have been discovered with confirmed or suspected ability to cause disease in humans or animals. These viruses are less genetically related to HeV and NiV yet share many features with their better-known counterparts. Recent advances in surveillance of wild animal reservoir viruses have revealed a high number of henipaviral genome sequences distributed across most continents, and mammalian orders previously unknown to harbour henipaviruses. In this review, we summarize the current knowledge on the range of pathogenesis observed for the henipaviruses as well as their replication cycle, epidemiology, genomics, and host responses. We focus on the most pathogenic viruses, including NiV, HeV, LayV, and GAKV, as well as the experimentally non-pathogenic CedV. We also highlight the emerging threats posed by these and potentially other closely related viruses.

Structure guided mutagenesis of Henipavirus Receptor Binding Proteins reveals molecular determinants of receptor usage and antibody binding epitopes

Nipah virus (NiV) is a highly lethal, zoonotic henipavirus (HNV) that causes respiratory and neurological signs and symptoms in humans. Similar to other paramyxoviruses, HNVs mediate entry into host cells through the concerted actions of two surface glycoproteins: a receptor binding protein (RBP) that mediates attachment and a fusion glycoprotein (F) that triggers fusion in an RBP-dependent manner. NiV uses ephrin-B2 (EFNB2) and ephrin-B3 (EFNB3) as entry receptors. Ghana virus (GhV), a novel HNV identified in a Ghanaian bat, use EFNB2 but not EFNB3. In this study, we employ a structure-informed approach to identify receptor interfacing residues and systematically introduce GhV-RBP residues into a NiV-RBP backbone to uncover the molecular determinants of EFNB3 usage. We reveal two regions that severely impair EFNB3 binding by NiV-RBP and EFNB3-mediated entry by NiV pseudotyped viral particles. Further analyses uncovered two point mutations (NiVN557SGhV and NiVY581TGhV) pivotal for this phenotype. Moreover, we identify NiV interaction with Y120 of EFNB3 as important for usage of this receptor. Beyond these EFNB3-related findings, we reveal two domains that restrict GhV binding of EFNB2, identify the HNV-head as an immunodominant target for polyclonal and monoclonal antibodies, and describe putative epitopes for GhV and NiV-specific monoclonal antibodies. Cumulatively, the work presented here generates useful reagents and tools that shed insight to residues important for NiV usage of EFNB3, reveals regions critical for GhV binding of EFNB2, and describes putative HNV antibody binding epitopes.

Structure and design of Langya virus glycoprotein antigens

Langya virus (LayV) is a recently discovered henipavirus (HNV), isolated from febrile patients in China. HNV entry into host cells is mediated by the attachment (G) and fusion (F) glycoproteins which are the main targets of neutralizing antibodies. We show here that the LayV F and G glycoproteins promote membrane fusion with human, mouse and hamster target cells using a different, yet unknown, receptor than NiV and HeV and that NiV- and HeV-elicited monoclonal and polyclonal antibodies do not cross-react with LayV F and G. We determined cryo-electron microscopy structures of LayV F, in the prefusion and postfusion states, and of LayV G, revealing previously unknown conformational landscapes and their distinct antigenicity relative to NiV and HeV. We computationally designed stabilized LayV G constructs and demonstrate the generalizability of an HNV F prefusion-stabilization strategy. Our data will support the development of vaccines and therapeutics against LayV and closely related HNVs.

Henipavirus zoonosis: outbreaks, animal hosts and potential new emergence

Hendra virus (HeV) and Nipah virus (NiV) are biosafety level 4 zoonotic pathogens causing severe and often fatal neurological and respiratory disease. These agents have been recognized by the World Health Organization as top priority pathogens expected to result in severe future outbreaks. HeV has caused sporadic infections in horses and a small number of human cases in Australia since 1994. The NiV Malaysia genotype (NiV-M) was responsible for the 1998-1999 epizootic outbreak in pigs with spillover to humans in Malaysia and Singapore. Since 2001, the NiV Bangladesh genotype (NiV-B) has been the predominant strain leading to outbreaks almost every year in Bangladesh and India, with hundreds of infections in humans. The natural reservoir hosts of HeV and NiV are fruit bats, which carry the viruses without clinical manifestation. The transmission pathways of henipaviruses from bats to humans remain poorly understood. Transmissions are often bridged by an intermediate animal host, which amplifies and spreads the viruses to humans. Horses and pigs are known intermediate hosts for the HeV outbreaks in Australia and NiV-M epidemic in Malaysia and Singapore, respectively. During the NiV-B outbreaks in Bangladesh, following initial spillover thought to be through the consumption of date palm sap, the spread of infection was largely human-to-human transmission. Spillover of NiV-B in recent outbreaks in India is less understood, with the primary route of transmission from bat reservoir to the initial human infection case(s) unknown and no intermediate host established. This review aims to provide a concise update on the epidemiology of henipaviruses covering their previous and current outbreaks with emphasis on the known and potential role of livestock as intermediate hosts in disease transmission. Also included is an up-to-date summary of newly emerging henipa-like viruses and animal hosts. In these contexts we discuss knowledge gaps and new challenges in the field and propose potential future directions.

Structures of Langya Virus Fusion Protein Ectodomain in Pre- and Postfusion Conformation

Langya virus (LayV) is a paramyxovirus in the Henipavirus genus, closely related to the deadly Nipah (NiV) and Hendra (HeV) viruses, that was identified in August 2022 through disease surveillance following animal exposure in eastern China. Paramyxoviruses present two glycoproteins on their surface, known as attachment and fusion proteins, that mediate entry into cells and constitute the primary antigenic targets for immune response. Here, we determine cryo-electron microscopy (cryo-EM) structures of the uncleaved LayV fusion protein (F) ectodomain in pre- and postfusion conformations. The LayV-F protein exhibits pre- and postfusion architectures that, despite being highly conserved across paramyxoviruses, show differences in their surface properties, in particular at the apex of the prefusion trimer, that may contribute to antigenic variability. While dramatic conformational changes were visualized between the pre- and postfusion forms of the LayV-F protein, several domains remained invariant, held together by highly conserved disulfides. The LayV-F fusion peptide (FP) is buried within a highly conserved, hydrophobic interprotomer pocket in the prefusion state and is notably less flexible than the rest of the protein, highlighting its "spring-loaded" state and suggesting that the mechanism of pre-to-post transition must involve perturbations to the pocket and release of the fusion peptide. Together, these results offer a structural basis for how the Langya virus fusion protein compares to its Henipavirus relatives and propose a mechanism for the initial step of pre- to postfusion conversion that may apply more broadly to paramyxoviruses. IMPORTANCE The Henipavirus genus is quickly expanding into new animal hosts and geographic locations. This study compares the structure and antigenicity of the Langya virus fusion protein to other henipaviruses, which have important vaccine and therapeutic development implications. Furthermore, the study proposes a new mechanism to explain the early steps of the fusion initiation process that can be more broadly applied to the Paramyxoviridae family.