Antibodies Against Henipa-Like Viruses in Brazilian Bats

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.

Corona- and Paramyxoviruses in Bats from Brazil: A Matter of Concern?

Chiroptera are one of the most diverse mammal orders. They are considered reservoirs of main human pathogens, where coronaviruses (CoVs) and paramyxoviruses (PMVs) may be highlighted. Moreover, the growing number of publications on CoVs and PMVs in wildlife reinforces the scientific community's interest in eco-vigilance, especially because of the emergence of important human pathogens such as the SARS-CoV-2 and Nipha viruses. Considering that Brazil presents continental dimensions, is biologically rich containing one of the most diverse continental biotas and presents a rich biodiversity of animals classified in the order Chiroptera, the mapping of CoV and PMV genetics related to human pathogens is important and the aim of the present work. CoVs can be classified into four genera: Alphacoronavirus, Betacoronavirus, Deltacoronavirus and Gammacoronavirus. Delta- and gammacoronaviruses infect mainly birds, while alpha- and betacoronaviruses contain important animal and human pathogens. Almost 60% of alpha- and betacoronaviruses are related to bats, which are considered natural hosts of these viral genera members. The studies on CoV presence in bats from Brazil have mainly assayed phyllostomid, molossid and vespertilionid bats in the South, Southeast and North territories. Despite Brazil not hosting rhinophilid or pteropodid bats, which are natural reservoirs of SARS-related CoVs and henipaviruses, respectively, CoVs and PMVs reported in Brazilian bats are genetically closely related to some human pathogens. Most works performed with Brazilian bats reported alpha-CoVs that were closely related to other bat-CoVs, despite a few reports of beta-CoVs grouped in the Merbecovirus and Embecovirus subgenera. The family Paramyxoviridae includes four subfamilies (Avulavirinae, Metaparamyxovirinae, Orthoparamyxovirinae and Rubulavirinae), and bats are significant drivers of PMV cross-species viral transmission. Additionally, the studies that have evaluated PMV presence in Brazilian bats have mainly found sequences classified in the Jeilongvirus and Morbillivirus genera that belong to the Orthoparamyxovirinae subfamily. Despite the increasing amount of research on Brazilian bats, studies analyzing these samples are still scarce. When surveying the representativeness of the CoVs and PMVs found and the available genomic sequences, it can be perceived that there may be gaps in the knowledge. The continuous monitoring of viral sequences that are closely related to human pathogens may be helpful in mapping and predicting future hotspots in the emergence of zoonotic agents.

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.

Detection of Serum Antibody Responses in Nipah Virus-Infected Pigs

Nipah virus (NiV) is an emerging, zoonotic paramyxovirus that is among the most pathogenic of viruses in humans. During the first reported outbreak of NiV in Malaysia and Singapore in the late 1990s, pigs served as an intermediate host, which enabled the transmission to humans. Although subsequent outbreaks in Asia only reported direct bat-to-human and human-to-human transmission, pigs are still considered a potential source for viral dissemination in the epidemiology of the disease. Thus, serological assays such as Enzyme-linked immunosorbent assay (ELISA) or virus neutralization test (VNT) represent powerful tools to characterize the serum antibody responses in NiV-infected pigs as well as to perform seroepidemiological surveillance studies on the potential circulation of NiV or NiV-related viruses among pig populations worldwide. This chapter describes both methods in detail. Furthermore, we discuss some of the major pitfalls and indicate how to avoid them.

First Genomic Evidence of a Henipa-like Virus in Brazil

The viral genus Henipavirus includes two highly virulent zoonotic viruses of serious public health concern. Hendra henipavirus and Nipah henipavirus outbreaks are restricted to Australia and Southeast Asia, respectively. The Henipavirus genus comprises mostly bat-borne viruses, but exceptions have already been described as novel viruses with rodents and shrews as reservoir animals. In the Americas, scarce evidence supports the circulation of these viruses. In this communication, we report a novel henipa-like virus from opossums (Marmosa demerarae) from a forest fragment area in the Peixe-Boi municipality, Brazil, after which the virus was named the Peixe-Boi virus (PBV). The application of next-generation sequencing and metagenomic approach led us to discover the original evidence of a henipa-like virus genome in Brazil and South America and the original description of a henipa-like virus in marsupial species. These findings emphasize the importance of further studies to characterize PBV and clarify its ecology, impact on public health, and its relationship with didelphid marsupials and henipaviruses.

Detection of novel paramyxoviruses in Chaerephon bat species in Nigeria and phylogenetics of paramyxoviruses co-evolution with bats in Africa

Bat paramyxoviruses (PmV) are a diverse group of viruses and include zoonotic viruses such as henipaviruses. Members of this group in other continents have been associated with severe respiratory and neurological infections in animals and humans. Furthermore, despite the richness of diverse bat species that can transmit this virus in African countries like Nigeria, there is very scanty information as to the presence and co-evolution of paramyxoviruses in bats. There is a need for continuous surveillance of zoonotic viruses and their biological reservoirs as this will help in the prevention and management of pathogens' spillovers. This study detected novel paramyxoviruses in Chaerephon nigeriae bat species found in Badagry, Lagos. Phylogenetic analyses of paramyxovirus sequences' co-evolution with frugivorous and insectivorous bats circulating in African countries were also performed using sequences of African origin available in the Database of Bat-Associated Viruses (DBatVir: http://www.mgc.ac.cn/DBatVir/). Oral swabs (n = 18) and blood samples (n = 32) were collected from C. nigeriae bats in Badagry, Lagos. The L gene of bat paramyxovirus was detected in all oral swabs using PCR techniques. Six of the amplicons were successfully sequenced. Estimated phylogenies placed the sequences in close relationship with those isolated from insectivorous bats. Phylogenetic analyses of previously sequenced isolates in the African region showed the likelihood of different co-evolution mechanisms of paramyxoviruses with frugivorous bats compared with insectivorous bats. This may be due to codon usage bias of the L gene. Spatial distribution of paramyxoviruses in African countries showed limited ongoing surveillance of this virus in the continent, especially in southern and northern countries. Extensive surveillance of paramyxoviruses with possible zoonotic potentials among bat species in the continent is recommended. This will provide further insights into co-evolution as well as prevent possible spillover into the human population.

Antivirals targeting paramyxovirus membrane fusion

The Paramyxoviridae family includes enveloped single-stranded negative-sense RNA viruses such as measles, mumps, human parainfluenza, canine distemper, Hendra, and Nipah viruses, which cause a tremendous global health burden. The ability of paramyxoviral glycoproteins to merge viral and host membranes allows entry of the viral genome into host cells, as well as cell-cell fusion, an important contributor to disease progression. Recent molecular and structural advances in our understanding of the paramyxovirus membrane fusion machinery gave rise to various therapeutic approaches aiming at inhibiting viral infection, spread, and cytopathic effects. These therapeutic approaches include peptide mimics, antibodies, and small molecule inhibitors with various levels of success at inhibiting viral entry, increasing the potential of effective antiviral therapeutic development.

Surveying the Vampire Bat (Desmodus rotundus) Serum Proteome: A Resource for Identifying Immunological Proteins and Detecting Pathogens

Bats are increasingly studied as model systems for longevity and as natural hosts for some virulent viruses. Yet the ability to characterize immune mechanisms of viral tolerance and to quantify infection dynamics in wild bats is often limited by small sample volumes and few species-specific reagents. Here, we demonstrate how proteomics can overcome these limitations by using data-independent acquisition-based shotgun proteomics to survey the serum proteome of 17 vampire bats (Desmodus rotundus) from Belize. Using just 2 μL of sample and relatively short separations of undepleted serum digests, we identified 361 proteins across 5 orders of magnitude. Levels of immunological proteins in vampire bat serum were then compared to human plasma via published databases. Of particular interest were antiviral and antibacterial components, circulating 20S proteasome complex and proteins involved in redox activity. Lastly, we used known virus proteomes to putatively identify Rh186 from Macacine herpesvirus 3 and ORF1a from Middle East respiratory syndrome-related coronavirus, indicating that mass spectrometry-based techniques show promise for pathogen detection. Overall, these results can be used to design targeted mass-spectrometry assays to quantify immunological markers and detect pathogens. More broadly, our findings also highlight the application of proteomics in advancing wildlife immunology and pathogen surveillance.

High Pathogenicity of Nipah Virus from Pteropus lylei Fruit Bats, Cambodia

We conducted an in-depth characterization of the Nipah virus (NiV) isolate previously obtained from a Pteropus lylei bat in Cambodia in 2003 (CSUR381). We performed full-genome sequencing and phylogenetic analyses and confirmed CSUR381 is part of the NiV-Malaysia genotype. In vitro studies revealed similar cell permissiveness and replication of CSUR381 (compared with 2 other NiV isolates) in both bat and human cell lines. Sequence alignments indicated conservation of the ephrin-B2 and ephrin-B3 receptor binding sites, the glycosylation site on the G attachment protein, as well as the editing site in phosphoprotein, suggesting production of nonstructural proteins V and W, known to counteract the host innate immunity. In the hamster animal model, CSUR381 induced lethal infections. Altogether, these data suggest that the Cambodia bat-derived NiV isolate has high pathogenic potential and, thus, provide insight for further studies and better risk assessment for future NiV outbreaks in Southeast Asia.

Serological Evidence for Henipa-like and Filo-like Viruses in Trinidad Bats

Bat-borne zoonotic pathogens belonging to the family Paramxyoviridae, including Nipah and Hendra viruses, and the family Filoviridae, including Ebola and Marburg viruses, can cause severe disease and high mortality rates on spillover into human populations. Surveillance efforts for henipaviruses and filoviruses have been largely restricted to the Old World; however, recent studies suggest a potentially broader distribution for henipaviruses and filoviruses than previously recognized. In the current study, we screened for henipaviruses and filoviruses in New World bats collected across 4 locations in Trinidad near the coast of Venezuela. Bat tissue samples were screened using previously established reverse-transcription polymerase chain reaction assays. Serum were screened using a multiplex immunoassay to detect antibodies reactive with the envelope glycoprotein of viruses in the genus Henipavirus and the family Filoviridae. Serum samples were also screened by means of enzyme-linked immunosorbent assay for antibodies reactive with Nipah G and F glycoproteins. Of 84 serum samples, 28 were reactive with ≥1 henipavirus glycoprotein by ≥1 serological method, and 6 serum samples were reactive against ≥1 filovirus glycoproteins. These data provide evidence of potential circulation of viruses related to the henipaviruses and filoviruses in New World bats.

A Novel Field-Deployable Method for Sequencing and Analyses of Henipavirus Genomes From Complex Samples on the MinION Platform

Viruses in the genus Henipavirus encompass 2 highly pathogenic emerging zoonotic pathogens, Hendra virus (HeV) and Nipah virus (NiV). Despite the impact on human health, there is currently limited full-genome sequence information available for henipaviruses. This lack of full-length genomes hampers our ability to understand the molecular drivers of henipavirus emergence. Furthermore, rapidly deployable viral genome sequencing can be an integral part of outbreak response and epidemiological investigations to study transmission chains. In this study, we describe the development of a reverse-transcription, long-range polymerase chain reaction (LRPCR) assay for efficient genome amplification of NiV, HeV, and a related non-pathogenic henipavirus, Cedar virus (CedPV). We then demonstrated the utility of our method by amplifying partial viral genomes from 6 HeV-infected tissue samples from Syrian hamsters and 4 tissue samples from a NiV-infected African green monkey with viral loads as low as 52 genome copies/mg. We subsequently sequenced the amplified genomes on the portable Oxford Nanopore MinION platform and analyzed the data using a newly developed field-deployable bioinformatic pipeline. Our LRPCR assay allows amplification and sequencing of 2 or 4 amplicons in semi-nested reactions. Coupled with an easy-to-use bioinformatics pipeline, this method is particularly useful in the field during outbreaks in resource-poor environments.

Differential Features of Fusion Activation within the Paramyxoviridae

Paramyxovirus (PMV) entry requires the coordinated action of two envelope glycoproteins, the receptor binding protein (RBP) and fusion protein (F). The sequence of events that occurs during the PMV entry process is tightly regulated. This regulation ensures entry will only initiate when the virion is in the vicinity of a target cell membrane. Here, we review recent structural and mechanistic studies to delineate the entry features that are shared and distinct amongst the Paramyxoviridae. In general, we observe overarching distinctions between the protein-using RBPs and the sialic acid- (SA-) using RBPs, including how their stalk domains differentially trigger F. Moreover, through sequence comparisons, we identify greater structural and functional conservation amongst the PMV fusion proteins, as compared to the RBPs. When examining the relative contributions to sequence conservation of the globular head versus stalk domains of the RBP, we observe that, for the protein-using PMVs, the stalk domains exhibit higher conservation and find the opposite trend is true for SA-using PMVs. A better understanding of conserved and distinct features that govern the entry of protein-using versus SA-using PMVs will inform the rational design of broader spectrum therapeutics that impede this process.

A key region of molecular specificity orchestrates unique ephrin-B1 utilization by Cedar virus

The emergent zoonotic henipaviruses, Hendra, and Nipah are responsible for frequent and fatal disease outbreaks in domestic animals and humans. Specificity of henipavirus attachment glycoproteins (G) for highly species-conserved ephrin ligands underpins their broad host range and is associated with systemic and neurological disease pathologies. Here, we demonstrate that Cedar virus (CedV)-a related henipavirus that is ostensibly nonpathogenic-possesses an idiosyncratic entry receptor repertoire that includes the common henipaviral receptor, ephrin-B2, but, distinct from pathogenic henipaviruses, does not include ephrin-B3. Uniquely among known henipaviruses, CedV can use ephrin-B1 for cellular entry. Structural analyses of CedV-G reveal a key region of molecular specificity that directs ephrin-B1 utilization, while preserving a universal mode of ephrin-B2 recognition. The structural and functional insights presented uncover diversity within the known henipavirus receptor repertoire and suggest that only modest structural changes may be required to modulate receptor specificities within this group of lethal human pathogens.

Prioritizing surveillance of Nipah virus in India

The 2018 outbreak of Nipah virus in Kerala, India, highlights the need for global surveillance of henipaviruses in bats, which are the reservoir hosts for this and other viruses. Nipah virus, an emerging paramyxovirus in the genus Henipavirus, causes severe disease and stuttering chains of transmission in humans and is considered a potential pandemic threat. In May 2018, an outbreak of Nipah virus began in Kerala, > 1800 km from the sites of previous outbreaks in eastern India in 2001 and 2007. Twenty-three people were infected and 21 people died (16 deaths and 18 cases were laboratory confirmed). Initial surveillance focused on insectivorous bats (Megaderma spasma), whereas follow-up surveys within Kerala found evidence of Nipah virus in fruit bats (Pteropus medius). P. medius is the confirmed host in Bangladesh and is now a confirmed host in India. However, other bat species may also serve as reservoir hosts of henipaviruses. To inform surveillance of Nipah virus in bats, we reviewed and analyzed the published records of Nipah virus surveillance globally. We applied a trait-based machine learning approach to a subset of species that occur in Asia, Australia, and Oceana. In addition to seven species in Kerala that were previously identified as Nipah virus seropositive, we identified at least four bat species that, on the basis of trait similarity with known Nipah virus-seropositive species, have a relatively high likelihood of exposure to Nipah or Nipah-like viruses in India. These machine-learning approaches provide the first step in the sequence of studies required to assess the risk of Nipah virus spillover in India. Nipah virus surveillance not only within Kerala but also elsewhere in India would benefit from a research pipeline that included surveys of known and predicted reservoirs for serological evidence of past infection with Nipah virus (or cross reacting henipaviruses). Serosurveys should then be followed by longitudinal spatial and temporal studies to detect shedding and isolate virus from species with evidence of infection. Ecological studies will then be required to understand the dynamics governing prevalence and shedding in bats and the contacts that could pose a risk to public health.

Comparative analysis of serologic cross-reactivity using convalescent sera from filovirus-experimentally infected fruit bats

With the exception of Reston and Bombali viruses, the marburgviruses and ebolaviruses (family Filoviridae) cause outbreaks of viral hemorrhagic fever in sub-Saharan Africa. The Egyptian rousette bat (ERB) is a natural reservoir host for the marburgviruses and evidence suggests that bats are also natural reservoirs for the ebolaviruses. Although the search for the natural reservoirs of the ebolaviruses has largely involved serosurveillance of the bat population, there are no validated serological assays to screen bat sera for ebolavirus-specific IgG antibodies. Here, we generate filovirus-specific antisera by prime-boost immunization of groups of captive ERBs with all seven known culturable filoviruses. After validating a system of filovirus-specific indirect ELISAs utilizing infectious-based virus antigens for detection of virus-specific IgG antibodies from bat sera, we assess the level of serological cross-reactivity between the virus-specific antisera and heterologous filovirus antigens. This data is then used to generate a filovirus antibody fingerprint that can predict which of the filovirus species in the system is most antigenically similar to the species responsible for past infection. Our filovirus IgG indirect ELISA system will be a critical tool for identifying bat species with high ebolavirus seroprevalence rates to target for longitudinal studies aimed at establishing natural reservoir host-ebolavirus relationships.

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.

Indirect ELISA based on Hendra and Nipah virus proteins for the detection of henipavirus specific antibodies in pigs

Hendra virus (HeV) and Nipah virus (NiV) belong to the genus Henipavirus in the family Paramyxoviridae. Henipavirus infections were first reported in the 1990’s causing severe and often fatal outbreaks in domestic animals and humans in Southeast Asia and Australia. NiV infections were observed in humans in Bangladesh, India and in the first outbreak in Malaysia, where pigs were also infected. HeV infections occurred in horses in the North-Eastern regions of Australia, with singular transmission events to humans. Bats of the genus Pteropus have been identified as the reservoir hosts for henipaviruses. Molecular and serological indications for the presence of henipa-like viruses in African fruit bats, pigs and humans have been published recently. In our study, truncated forms of HeV and NiV attachment (G) proteins as well as the full-length NiV nucleocapsid (N) protein were expressed using different expression systems. Based on these recombinant proteins, Enzyme-linked Immunosorbent Assays (ELISA) were developed for the detection of HeV or NiV specific antibodies in porcine serum samples. We used the NiV N ELISA for initial serum screening considering the general reactivity against henipaviruses. The G protein based ELISAs enabled the differentiation between HeV and NiV infections, since as expected, the sera displayed higher reactivity with the respective homologous antigens. In the future, these assays will present valuable tools for serosurveillance of swine and possibly other livestock or wildlife species in affected areas. Such studies will help assessing the potential risk for human and animal health worldwide by elucidating the distribution of henipaviruses.