Pathogenic Differences between Nipah Virus Bangladesh and Malaysia Strains in Primates: Implications for Antibody Therapy

Monoclonal antibody therapy demonstrates increased virulence of a lineage VII strain of Lassa virus in nonhuman primates

Lassa virus (LASV) is a World Health Organization (WHO) priority pathogen that causes high morbidity and mortality. Recently, we showed that a combination of three broadly neutralizing human monoclonal antibodies known as Arevirumab-3 (8.9F, 12.1F, 37.2D) based on the lineage IV Josiah strain protected 100% of cynomolgus macaques against heterologous challenge with lineage II and III strains of LASV when therapy was initiated beginning at day 8 after challenge. LASV strains from Benin and Togo represent a new lineage VII that are more genetically diverse from lineage IV than strains from lineages II and III. Here, we tested the ability of Arevirumab-3 to protect macaques against a LASV lineage VII Togo isolate when treatment was administered beginning 8 days after exposure. Unexpectedly, only 40% of treated animals survived challenge. In a subsequent study we showed that Arevirumab-3 protected 100% of macaques from lethal challenge when treatment was initiated 7 days after LASV Togo exposure. Based on our transcriptomics data, successful Arevirumab-3 treatment correlated with diminished neutrophil signatures and the predicted development of T cell responses. As the in vitro antiviral activity of Arevirumab-3 against LASV Togo was equivalent to lineage II and III strains, the reduced protection in macaques against Togo likely reflects the faster disease course of LASV Togo in macaques than other strains. This data causes concern regarding the ability of heterologous vaccines and treatments to provide cross protection against lineage VII LASV isolates.

Predicting the changes in neutralizing antibody interaction with G protein derived from Bangladesh isolates of Nipah virus: molecular dynamics based approach

The infectious Nipah virus (NiV) is categorized into NiV-M (Malaysia) and NiV-B (Bangladesh) groups based on its genome comparison, pathogenicity, and mortality rate. The development of therapeutic molecules has used NiV-M-derived data in multiple studies than NiV-B. In continuation with this, the protein level investigation is also less explored to understand the interaction with therapeutic neutralizing antibodies for NiV-B. So, this study focuses on understanding the impact of NiV-B-specific mutations on the interaction of therapeutic neutralizing antibodies with the G protein. The population-based comparative analysis of NiV-B G protein sequences with NiV-M sequence identified twenty-six mutations. These predominantly polar mutations were then used to model the mutant protein (G_MT). In a comparative study, the G protein G_MT and reference protein G_WT (Malaysian origin) were subjected to a protein docking with neutralizing human monoclonal antibody HENV26. The binding affinity and the free binding energy of the glycoprotein in complex with G-WT and G_MT were calculated using PRODIGY and MM/PBSA tools respectively. Based on the PRODIGY report, G-WT showed stronger binding (-13.8 kcal/mol) compared to that of the G_MT (-9.0 kcal/mol) with the HENV26 antibody. The stability of the complexes was evaluated using MM/PBSA which showed higher binding energy with HENV26 for G_WT (-75.11 kcal/mol) in contrast to G_MT (-41.66 kcal/mol). The results indicate that the mutant G protein has a reduced ability to bind to neutralizing antibodies, resulting in a decreased effectiveness against strains carrying these mutations.Communicated by Ramaswamy H. Sarma.

Nipah virus: epidemiology, pathogenesis, treatment, and prevention

Nipah virus (NiV) is a zoonotic paramyxovirus that has recently emerged as a crucial public health issue. It can elicit severe encephalitis and respiratory diseases in animals and humans, leading to fatal outcomes, exhibiting a wide range of host species tropism, and directly transmitting from animals to humans or through an intermediate host. Human-to-human transmission associated with recurrent NiV outbreaks is a potential global health threat. Currently, the lack of effective therapeutics or licensed vaccines for NiV necessitates the primary utilization of supportive care. In this review, we summarize current knowledge of the various aspects of the NiV, including therapeutics, vaccines, and its biological characteristics, epidemiology, pathogenesis, and clinical features. The objective is to provide valuable information from scientific and clinical research and facilitate the formulation of strategies for preventing and controlling the NiV.

Emerging and reemerging infectious diseases: global trends and new strategies for their prevention and control

To adequately prepare for potential hazards caused by emerging and reemerging infectious diseases, the WHO has issued a list of high-priority pathogens that are likely to cause future outbreaks and for which research and development (R&D) efforts are dedicated, known as paramount R&D blueprints. Within R&D efforts, the goal is to obtain effective prophylactic and therapeutic approaches, which depends on a comprehensive knowledge of the etiology, epidemiology, and pathogenesis of these diseases. In this process, the accessibility of animal models is a priority bottleneck because it plays a key role in bridging the gap between in-depth understanding and control efforts for infectious diseases. Here, we reviewed preclinical animal models for high priority disease in terms of their ability to simulate human infections, including both natural susceptibility models, artificially engineered models, and surrogate models. In addition, we have thoroughly reviewed the current landscape of vaccines, antibodies, and small molecule drugs, particularly hopeful candidates in the advanced stages of these infectious diseases. More importantly, focusing on global trends and novel technologies, several aspects of the prevention and control of infectious disease were discussed in detail, including but not limited to gaps in currently available animal models and medical responses, better immune correlates of protection established in animal models and humans, further understanding of disease mechanisms, and the role of artificial intelligence in guiding or supplementing the development of animal models, vaccines, and drugs. Overall, this review described pioneering approaches and sophisticated techniques involved in the study of the epidemiology, pathogenesis, prevention, and clinical theatment of WHO high-priority pathogens and proposed potential directions. Technological advances in these aspects would consolidate the line of defense, thus ensuring a timely response to WHO high priority pathogens.

Immunogenicity and Neutralization of Recombinant Vaccine Candidates Expressing F and G Glycoproteins against Nipah Virus

Nipah virus (NiV), of the Paramyxoviridae family, causes highly fatal infections in humans and is associated with severe neurological and respiratory diseases. Currently, no commercial vaccine is available for human use. Here, eight structure-based mammalian-expressed recombinant proteins harboring the NiV surface proteins, fusion glycoprotein (F), and the major attachment glycoprotein (G) were produced. Specifically, prefusion NiV-F and/or NiV-G glycoproteins expressed in monomeric, multimeric (trimeric F and tetra G), or chimeric forms were evaluated for their properties as sub-unit vaccine candidates. The antigenicity of the recombinant NiV glycoproteins was evaluated in intramuscularly immunized mice, and the antibodies in serum were assessed. Predictably, all homologous immunizations exhibited immunogenicity, and neutralizing antibodies to VSV-luciferase-based pseudovirus expressing NiV-GF glycoproteins were found in all groups. Comparatively, neutralizing antibodies were highest in vaccines designed in their multimeric structures and administered as bivalent (GMYtet + GBDtet) and trivalent (Ftri + GMYtet + GBDtet). Additionally, while all adjuvants were able to elicit an immunogenic response in vaccinated groups, bivalent (GMYtet + GBDtet) and trivalent (Ftri + GMYtet + GBDtet) induced more potent neutralizing antibodies when administered with oil-in-water nano-emulsion adjuvant, AddaS03. For all experiments, the bivalent GMYtet + GBDtet was the most immunogenic vaccine candidate. Results from this study highlight the potential use of these mammalian-expressed recombinant NiV as vaccine candidates, deserving further exploration.

Antiviral Activity, Pharmacoinformatics, Molecular Docking, and Dynamics Studies of Azadirachta indica Against Nipah Virus by Targeting Envelope Glycoprotein: Emerging Strategies for Developing Antiviral Treatment

The Nipah virus (NiV) belongs to the Henipavirus genus is a serious public health concern causing numerous outbreaks with higher fatality rate. Unfortunately, there is no effective medication available for NiV. To investigate possible inhibitors of NiV infection, we used in silico techniques to discover treatment candidates in this work. As there are not any approved treatments for NiV infection, the NiV-enveloped attachment glycoprotein was set as target for our study, which is responsible for binding to and entering host cells. Our in silico drug design approach included molecular docking, post-docking molecular mechanism generalised born surface area (MM-GBSA), absorption, distribution, metabolism, excretion/toxicity (ADME/T), and molecular dynamics (MD) simulations. We retrieved 418 phytochemicals associated with the neem plant (Azadirachta indica) from the IMPPAT database, and molecular docking was used to ascertain the compounds' binding strength. The top 3 phytochemicals with binding affinities of -7.118, -7.074, and -6.894 kcal/mol for CIDs 5280343, 9064, and 5280863, respectively, were selected for additional study based on molecular docking. The post-docking MM-GBSA of those 3 compounds was -47.56, -47.3, and -43.15 kcal/mol, respectively. As evidence of their efficacy and safety, all the chosen drugs had favorable toxicological and pharmacokinetic (Pk) qualities. We also performed MD simulations to confirm the stability of the ligand-protein complex structures and determine whether the selected compounds are stable at the protein binding site. All 3 phytochemicals, Quercetin (CID: 5280343), Cianidanol (CID: 9064), and Kaempferol (CID: 5280863), appeared to have outstanding binding stability to the target protein than control ribavirin, according to the molecular docking, MM-GBSA, and MD simulation outcomes. Overall, this work offers a viable approach to developing novel medications for treating NiV infection.

A systematic review on Nipah virus: global molecular epidemiology and medical countermeasures development

Nipah virus (NiV) is an emerging pathogen that causes encephalitis and a high mortality rate in infected subjects. This systematic review aimed to comprehensively analyze the global epidemiology and research advancements of NiV to identify the key knowledge gaps in the literature. Articles searched using literature databases, namely PubMed, Scopus, Web of Science, and Science Direct yielded 5,596 articles. After article screening, 97 articles were included in this systematic review, comprising 41 epidemiological studies and 56 research developments on NiV. The majority of the NiV epidemiological studies were conducted in Bangladesh, reflecting the country's significant burden of NiV outbreaks. The initial NiV outbreak was identified in Malaysia in 1998, with subsequent outbreaks reported in Bangladesh, India, and the Philippines. Transmission routes vary by country, primarily through pigs in Malaysia, consumption of date palm juice in Bangladesh, and human-to-human in India. However, the availability of NiV genome sequences remains limited, particularly from Malaysia and India. Mortality rates also vary according to the country, exceeding 70% in Bangladesh, India, and the Philippines, and less than 40% in Malaysia. Understanding these differences in mortality rate among countries is crucial for informing NiV epidemiology and enhancing outbreak prevention and management strategies. In terms of research developments, the majority of studies focused on vaccine development, followed by phylogenetic analysis and antiviral research. While many vaccines and antivirals have demonstrated complete protection in animal models, only two vaccines have progressed to clinical trials. Phylogenetic analyses have revealed distinct clades between NiV Malaysia, NiV Bangladesh, and NiV India, with proposals to classify NiV India as a separate strain from NiV Bangladesh. Taken together, comprehensive OneHealth approaches integrating disease surveillance and research are imperative for future NiV studies. Expanding the dataset of NiV genome sequences, particularly from Malaysia, Bangladesh, and India will be pivotal. These research efforts are essential for advancing our understanding of NiV pathogenicity and for developing robust diagnostic assays, vaccines and therapeutics necessary for effective preparedness and response to future NiV outbreaks.

A Comparative Experimental and Computational Study on the Nature of the Pangolin-CoV and COVID-19 Omicron

The relationship between pangolin-CoV and SARS-CoV-2 has been a subject of debate. Further evidence of a special relationship between the two viruses can be found by the fact that all known COVID-19 viruses have an abnormally hard outer shell (low M disorder, i.e., low content of intrinsically disordered residues in the membrane (M) protein) that so far has been found in CoVs associated with burrowing animals, such as rabbits and pangolins, in which transmission involves virus remaining in buried feces for a long time. While a hard outer shell is necessary for viral survival, a harder inner shell could also help. For this reason, the N disorder range of pangolin-CoVs, not bat-CoVs, more closely matches that of SARS-CoV-2, especially when Omicron is included. The low N disorder (i.e., low content of intrinsically disordered residues in the nucleocapsid (N) protein), first observed in pangolin-CoV-2017 and later in Omicron, is associated with attenuation according to the Shell-Disorder Model. Our experimental study revealed that pangolin-CoV-2017 and SARS-CoV-2 Omicron (XBB.1.16 subvariant) show similar attenuations with respect to viral growth and plaque formation. Subtle differences have been observed that are consistent with disorder-centric computational analysis.

Nipah virus disease: what can we do to improve patient care?

The year 2023 marked the 25th anniversary of the first detected outbreak of Nipah virus disease. Despite Nipah virus being a priority pathogen in the WHO Research and Development blueprint, the disease it causes still carries high mortality, unchanged since the first reported outbreaks. Although candidate vaccines for Nipah virus disease exist, developing new therapeutics has been underinvested. Nipah virus disease illustrates the typical market failure of medicine development for a high-consequence pathogen. The unpredictability of outbreaks and low number of infections affecting populations in low-income countries does not make an attractive business case for developing treatments for Nipah virus disease-a situation compounded by methodological challenges in clinical trial design. Nipah virus therapeutics development is not motivated by commercial interest. Therefore, we propose a regionally led, patient-centred, and public health-centred, end-to-end framework that articulates a public health vision and a roadmap for research, development, manufacturing, and access towards the goal of improving patient outcomes. This framework includes co-creating a regulatory-compliant, clinically meaningful, and context-specific clinical development plan and establishing quality standards in clinical care and research capabilities at sites where the disease occurs. The success of this approach will be measured by the availability and accessibility of improved Nipah virus treatments in affected communities and reduced mortality.

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.

A highly effective ferritin-based divalent nanoparticle vaccine shields Syrian hamsters against lethal Nipah virus

The Nipah virus (NiV), a highly deadly bat-borne paramyxovirus, poses a substantial threat due to recurrent outbreaks in specific regions, causing severe respiratory and neurological diseases with high morbidity. Two distinct strains, NiV-Malaysia (NiV-M) and NiV-Bangladesh (NiV-B), contribute to outbreaks in different geographical areas. Currently, there are no commercially licensed vaccines or drugs available for prevention or treatment. In response to this urgent need for protection against NiV and related henipaviruses infections, we developed a novel homotypic virus-like nanoparticle (VLP) vaccine co-displaying NiV attachment glycoproteins (G) from both strains, utilizing the self-assembling properties of ferritin protein. In comparison to the NiV G subunit vaccine, our nanoparticle vaccine elicited significantly higher levels of neutralizing antibodies and provided complete protection against a lethal challenge with NiV infection in Syrian hamsters. Remarkably, the nanoparticle vaccine stimulated the production of antibodies that exhibited superior cross-reactivity to homologous or heterologous henipavirus. These findings underscore the potential utility of ferritin-based nanoparticle vaccines in providing both broad-spectrum and long-term protection against NiV and emerging zoonotic henipaviruses challenges.

Potent human neutralizing antibodies against Nipah virus derived from two ancestral antibody heavy chains

Nipah virus (NiV) is a World Health Organization priority pathogen and there are currently no approved drugs for clinical immunotherapy. Through the use of a naïve human phage-displayed Fab library, two neutralizing antibodies (NiV41 and NiV42) targeting the NiV receptor binding protein (RBP) were identified. Following affinity maturation, antibodies derived from NiV41 display cross-reactivity against both NiV and Hendra virus (HeV), whereas the antibody based on NiV42 is only specific to NiV. Results of immunogenetic analysis reveal a correlation between the maturation of antibodies and their antiviral activity. In vivo testing of NiV41 and its mature form (41-6) show protective efficacy against a lethal NiV challenge in hamsters. Furthermore, a 2.88 Å Cryo-EM structure of the tetrameric RBP and antibody complex demonstrates that 41-6 blocks the receptor binding interface. These findings can be beneficial for the development of antiviral drugs and the design of vaccines with broad spectrum against henipaviruses.

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.

Evaluation of the interaction between potent small molecules against the Nipah virus Glycoprotein in Malaysia and Bangladesh strains, accompanied by the human Ephrin-B2 and Ephrin-B3 receptors; a simulation approach

Malaysia reported the first human case of Nipah virus (NiV) in late September 1998 with encephalitis and respiratory symptoms. As a result of viral genomic mutations, two main strains (NiV-Malaysia and NiV-Bangladesh) have spread around the world. There are no licensed molecular therapeutics available for this biosafety level 4 pathogen. NiV attachment glycoprotein plays a critical role in viral transmission through its human receptors (Ephrin-B2 and Ephrin-B3), so identifying small molecules that can be repurposed to inhibit them is crucial to developing anti-NiV drugs. Consequently, in this study annealing simulations, pharmacophore modeling, molecular docking, and molecular dynamics were used to evaluate seven potential drugs (Pemirolast, Nitrofurantoin, Isoniazid Pyruvate, Eriodictyol, Cepharanthine, Ergoloid, and Hypericin) against NiV-G, Ephrin-B2, and Ephrin-B3 receptors. Based on the annealing analysis, Pemirolast for efnb2 protein and Isoniazid Pyruvate for efnb3 receptor were repurposed as the most promising small molecule candidates. Furthermore, Hypericin and Cepharanthine, with notable interaction values, are the top Glycoprotein inhibitors in Malaysia and Bangladesh strains, respectively. In addition, docking calculations revealed that their binding affinity scores are related to efnb2-pem (- 7.1 kcal/mol), efnb3-iso (- 5.8 kcal/mol), gm-hyp (- 9.6 kcal/mol), gb-ceph (- 9.2 kcal/mol). Finally, our computational research minimizes the time-consuming aspects and provides options for dealing with any new variants of Nipah virus that might emerge in the future.

Potential for Person-to-Person Transmission of Henipaviruses: A Systematic Review of the Literature

Nipah virus Bangladesh (NiVB) is a bat-borne zoonosis transmitted between people through the respiratory route. The risk posed by related henipaviruses, including Hendra virus (HeV) and Nipah virus Malaysia (NiVM), is less clear. We conducted a broad search of the literature encompassing both human infections and animal models to synthesize evidence about potential for person-to-person spread. More than 600 human infections have been reported in the literature, but information on viral shedding was only available for 40 case-patients. There is substantial evidence demonstrating person-to-person transmission of NiVB, and some evidence for NiVM. Less direct evidence is available about the risk for person-to-person transmission of HeV, but animals infected with HeV shed more virus in the respiratory tract than those infected with NiVM, suggesting potential for transmission. As the group of known henipaviruses continues to grow, shared protocols for conducting and reporting from human investigations and animal experiments are urgently needed.

A comparative genomic approach to decipher the mutations associated with Nipah viral human isolates from southeast Asia

Background and Objectives

Multiple outbreaks over two decades and a high mortality rate have emphasized the Nipah virus (NiV) as a priority research area. The study focuses on identifying the mutational landscape in sequences from NiV human isolates from different geographical regions.

Materials and Methods

Thirty-seven NiV genomes of human samples from Malaysia, Bangladesh, and India were subjected to phylogeny and metagenomic analysis to decipher the genome variability using MEGA11 software and the meta-CATS web server. Using the Single-Likelihood Ancestor Counting method, the synonymous and nonsynonymous mutations among NiV genes were identified. Further, the nonsynonymous variations were used to identify mutations in all the NiV proteins.

Results

The NiV isolates were categorized into NiV-M, NiV-B, and NiV-I clades based on phylogenetic analysis. Metagenomic analysis revealed 1636 variations in the noncoding and coding regions of the genomes of the three clades of NiV. Further analysis of nonsynonymous mutations showed the phosphoprotein to be highly mutating, whereas the matrix protein was stable.

Conclusion

Deciphering the mutation pattern using a comparative genomics approach for human isolates provided valuable insight into the stability of NiV proteins which can be further used for understanding variations in host-pathogen interaction and developing effective therapeutic measures.

Vaccines based on the fusion protein consensus sequence protect Syrian hamsters from Nipah virus infection

Nipah virus (NiV), a bat-borne paramyxovirus, results in neurological and respiratory diseases with high mortality in humans and animals. Developing vaccines is crucial for fighting these diseases. Previously, only a few studies focused on the fusion (F) protein alone as the immunogen. Numerous NiV strains have been identified, including 2 representative strains from Malaysia (NiV-M) and Bangladesh (NiV-B), which differ significantly from each other. In this study, an F protein sequence with the potential to prevent different NiV strain infections was designed by bioinformatics analysis after an in-depth study of NiV sequences in GenBank. Then, a chimpanzee adenoviral vector vaccine and a DNA vaccine were developed. High levels of immune responses were detected after AdC68-F, pVAX1-F, and a prime-boost strategy (pVAX1-F/AdC68-F) in mice. After high titers of humoral responses were induced, the hamsters were challenged by the lethal NiV-M and NiV-B strains separately. The vaccinated hamsters did not show any clinical signs and survived 21 days after infection with either strain of NiV, and no virus was detected in different tissues. These results indicate that the vaccines provided complete protection against representative strains of NiV infection and have the potential to be developed as a broad-spectrum vaccine for human use.

Genomic characterization, transcriptome analysis, and pathogenicity of the Nipah virus (Indian isolate)

Nipah virus (NiV) is a high-risk pathogen which can cause fatal infections in humans. The Indian isolate from the 2018 outbreak in the Kerala state of India showed ~ 4% nucleotide and amino acid difference in comparison to the Bangladesh strains of NiV and the substitutions observed were mostly not present in the region of any functional significance except for the phosphoprotein gene. The differential expression of viral genes was observed following infection in Vero (ATCC® CCL-81™) and BHK-21 cells. Intraperitoneal infection in the 10-12-week-old, Syrian hamster model induced dose dependant multisystemic disease characterized by prominent vascular lesions in lungs, brain, kidney and extra vascular lesions in brain and lungs. Congestion, haemorrhages, inflammatory cell infiltration, thrombosis and rarely endothelial syncitial cell formation were seen in the blood vessels. Intranasal infection resulted in respiratory tract infection characterised by pneumonia. The model showed disease characteristics resembling the human NiV infection except that of myocarditis similar to that reported by NiV-Malaysia and NiV-Bangladesh isolates in hamster model. The variation observed in the genome of the Indian isolate at the amino acid levels should be explored further for any functional significance.

In silico prediction of interaction between Nipah virus attachment glycoprotein and host cell receptors Ephrin-B2 and Ephrin-B3 in domestic and peridomestic mammals

Nipah virus (NiV) is a lethal bat-borne zoonotic virus that causes mild to acute respiratory distress and neurological manifestations in humans with a high mortality rate. NiV transmission to humans occurs via consumption of bat-contaminated fruit and date palm sap (DPS), or through direct contact with infected individuals and livestock. Since NiV outbreaks were first reported in pigs from Malaysia and Singapore, non-neutralizing antibodies against NiV attachment Glycoprotein (G) have also been detected in a few domestic mammals. NiV infection is initiated after NiV G binds to the host cell receptors Ephrin-B2 and Ephrin-B3. In this study, we assessed the degree of NiV host tropism in domestic and peridomestic mammals commonly found in Bangladesh that may be crucial in the transmission of NiV by serving as intermediate hosts. We carried out a protein-protein docking analysis of NiV G complexes (n = 52) with Ephrin-B2 and B3 of 13 domestic and peridomestic species using bioinformatics tools. Protein models were generated by homology modelling and the structures were validated for model quality. The different protein-protein complexes in this study were stable, and their binding affinity (ΔG) scores ranged between -8.0 to -19.1 kcal/mol. NiV Bangladesh (NiV-B) strain displayed stronger binding to Ephrin receptors, especially with Ephrin-B3 than the NiV Malaysia (NiV-M) strain, correlating with the observed higher pathogenicity of NiV-B strains. From the docking result, we found that Ephrin receptors of domestic rat (R. norvegicus) had a higher binding affinity for NiV G, suggesting greater susceptibility to NiV infections compared to other study species. Investigations for NiV exposure to domestic/peridomestic animals will help us knowing more the possible role of rats and other animals as intermediate hosts of NiV and would improve future NiV outbreak control and prevention in humans and domestic animals.

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.

Both chimpanzee adenovirus-vectored and DNA vaccines induced long-term immunity against Nipah virus infection

Nipah virus (NiV) is a highly lethal zoonotic paramyxovirus that poses a severe threat to humans due to its high morbidity and the lack of viable countermeasures. Vaccines are the most crucial defense against NiV infections. Here, a recombinant chimpanzee adenovirus-based vaccine (AdC68-G) and a DNA vaccine (DNA-G) were developed by expressing the codon-optimized full-length glycoprotein (G) of NiV. Strong and sustained neutralizing antibody production, accompanied by an effective T-cell response, was induced in BALB/c mice by intranasal or intramuscular administration of one or two doses of AdC68-G, as well as by priming with DNA-G and boosting with intramuscularly administered AdC68-G. Importantly, the neutralizing antibody titers were maintained for up to 68 weeks in the mice that received intramuscularly administered AdC68-G and the prime DNA-G/boost AdC68-G regimen, without a significant decline. Additionally, Syrian golden hamsters immunized with AdC68-G and DNA-G via homologous or heterologous prime/boost immunization were completely protected against a lethal NiV virus challenge, without any apparent weight loss, clinical signs, or pathological tissue damage. There was a significant reduction in but not a complete absence of the viral load and number of infectious particles in the lungs and spleen tissue following NiV challenge. These findings suggest that the AdC68-G and DNA-G vaccines against NiV infection are promising candidates for further development.

A Survey of Henipavirus Tropism-Our Current Understanding from a Species/Organ and Cellular Level

Henipaviruses are single-stranded RNA viruses that have been shown to be virulent in several species, including humans, pigs, horses, and rodents. Isolated nearly 30 years ago, these viruses have been shown to be of particular concern to public health, as at least two members (Nipah and Hendra viruses) are highly virulent, as well as zoonotic, and are thus classified as BSL4 pathogens. Although only 5 members of this genus have been isolated and characterized, metagenomics analysis using animal fluids and tissues has demonstrated the existence of other novel henipaviruses, suggesting a far greater degree of phylogenetic diversity than is currently known. Using a variety of molecular biology techniques, it has been shown that these viruses exhibit varying degrees of tropism on a species, organ/tissue, and cellular level. This review will attempt to provide a general overview of our current understanding of henipaviruses, with a particular emphasis on viral tropism.

Animal Models for Henipavirus Research

Hendra virus (HeV) and Nipah virus (NiV) are zoonotic paramyxoviruses in the genus Henipavirus (HNV) that emerged nearly thirty years ago. Outbreaks of HeV and NiV have led to severe respiratory disease and encephalitis in humans and animals characterized by a high mortality rate. Despite the grave threat HNVs pose to public health and global biosecurity, no approved medical countermeasures for human use currently exist against HeV or NiV. To develop candidate vaccines and therapeutics and advance the field's understanding of HNV pathogenesis, animal models of HeV and NiV have been instrumental and remain indispensable. Various species, including rodents, ferrets, and nonhuman primates (NHPs), have been employed for HNV investigations. Among these, NHPs have demonstrated the closest resemblance to human HNV disease, although other animal models replicate some key disease features. Here, we provide a comprehensive review of the currently available animal models (mice, hamsters, guinea pigs, ferrets, cats, dogs, nonhuman primates, horses, and swine) to support HNV research. We also discuss the strengths and limitations of each model for conducting pathogenesis and transmission studies on HeV and NiV and for the evaluation of medical countermeasures.

Immunological correlates of protection afforded by PHV02 live, attenuated recombinant vesicular stomatitis virus vector vaccine against Nipah virus disease

Introduction

Immune correlates of protection afforded by PHV02, a recombinant vesicular stomatitis (rVSV) vector vaccine against Nipah virus (NiV) disease, were investigated in the African green monkey (AGM) model. Neutralizing antibody to NiV has been proposed as the principal mediator of protection against future NiV infection.

Methods

Two approaches were used to determine the correlation between neutralizing antibody levels and outcomes following a severe (1,000 median lethal doses) intranasal/intratracheal (IN/IT) challenge with NiV (Bangladesh): (1) reduction in vaccine dose given 28 days before challenge and (2) challenge during the early phase of the antibody response to the vaccine.

Results

Reduction in vaccine dose to very low levels led to primary vaccine failure rather than a sub-protective level of antibody. All AGMs vaccinated with the nominal clinical dose (2 × 107 pfu) at 21, 14, or 7 days before challenge survived. AGMs vaccinated at 21 days before challenge had neutralizing antibodies (geometric mean titer, 71.3). AGMs vaccinated at 7 or 14 days before challenge had either undetectable or low neutralizing antibody titers pre-challenge but had a rapid rise in titers after challenge that abrogated the NiV infection. A simple logistic regression model of the combined studies was used, in which the sole explanatory variable was pre-challenge neutralizing antibody titers. For a pre-challenge titer of 1:5, the predicted survival probability is 100%. The majority of animals with pre-challenge neutralizing titer of ≥1:20 were protected against pulmonary infiltrates on thoracic radiograms, and a majority of those with titers ≥1:40 were protected against clinical signs of illness and against a ≥fourfold antibody increase following challenge (indicating sterile immunity). Controls receiving rVSV-Ebola vaccine rapidly succumbed to NiV challenge, eliminating the innate immunity stimulated by the rVSV vector as a contributor to survival in monkeys challenged as early as 7 days after vaccination.

Discussion and conclusion

It was concluded that PHV02 vaccine elicited a rapid onset of protection and that any detectable level of neutralizing antibody was a functional immune correlate of survival.

Computer-assisted identification of potential quinolone derivatives targeting Nipah virus glycoprotein attachment with human cell surface receptor ephrin-B2: Multistep virtual screening

Nipah Virus (NiV) is a single-stranded, negative-sense, highly lethal RNA virus. Even though NiV has close to 70-80% of mortality in India and Bangladesh, still there is no available US FDA-approved drug or vaccine. NiV attachment glycoprotein (NiV-G) is critical for NiV to invade the human cell where ephrinB2 which is a crucial membrane-bound ligand that acts as a target of NiV. Most of the research has been performed targeting NiV or human ephrin-B to date. Quinolone derivatives are proven scaffolds for many approved drugs used to treat various bacterial, viral respiratory tract, and urinary tract infections, and rheumatologic disorders such as systemic lupus erythematosus, rheumatoid arthritis. Therefore, we have tried to find potential drug molecules employing quinolone scaffold-based derivatives from PubChem targeting both NiV-G and ephrin-B2 protein. A total of 1500+ quinolone derivatives were obtained from PubChem which were screened based on Drug Likeness followed by being subjected to XP docking employing Schrödinger software. The top ten best molecules were then chosen for their absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiling based on the docking score ranking. Further, the top five molecules were selected for 200ns molecular dynamics (MD) simulation study with Desmond module followed by MM-GBSA study by Prime module of Schrödinger. The exhaustive analysis leads us to the top three probable lead drug molecules for NiV are PubChem CID 23646770, an analog of PubChem CID 67726448, and PubChem CID 10613168 which have predicted Ki values of 0.480 μm, 0.785 μm, and 0.380 μm, respectively. These proposed molecules can be the future drugs targeting NiV-G and human ephrin-B2 which requires further in vivo validation.

Nipah Virus Bangladesh Infection Elicits Organ-Specific Innate and Inflammatory Responses in the Marmoset Model

The common marmoset (Callithrix jacchus) is increasingly recognized as an ideal nonhuman primate (NHP) at high biocontainment due to its smaller size and relative ease of handling. Here, we evaluated the susceptibility and pathogenesis of Nipah virus Bangladesh strain (NiVB) infection in marmosets at biosafety level 4. Infection via the intranasal and intratracheal route resulted in fatal disease in all 4 infected marmosets. Three developed pulmonary edema and hemorrhage as well as multifocal hemorrhagic lymphadenopathy, while 1 recapitulated neurologic clinical manifestations and cardiomyopathy on gross pathology. Organ-specific innate and inflammatory responses were characterized by RNA sequencing in 6 different tissues from infected and control marmosets. Notably, a unique transcriptome was revealed in the brainstem of the marmoset exhibiting neurological signs. Our results provide a more comprehensive understanding of NiV pathogenesis in an accessible and novel NHP model, closely reflecting clinical disease as observed in NiV patients.

Possible high risk of transmission of the Nipah virus in South and South East Asia: a review

Nipah virus (NiV) is a zoonotic, single-stranded RNA virus from the family Paramyxoviridae, genus Henipavirus. NiV is a biosafety-level-4 pathogen that is mostly spread by Pteropus species, which serve as its natural reservoir host. NiV is one of the major public health challenges in South and South East Asia. However, few molecular studies have been conducted to characterise NiV in a specific region. The main objective of this review is to understand the epidemiology, pathogenesis, molecular surveillance, transmission dynamics, genetic diversity, reservoir host, clinical characteristics, and phylogenetics of NiV. South and South East Asian nations have experienced NiV outbreaks. Phylogenetic analysis confirmed that two primary clades of NiV are in circulation. In humans, NiV causes severe respiratory illness and/or deadly encephalitis. NiV is mainly diagnosed by ELISA along with PCR. Therefore, we recommend that the governments of the region support the One Health approach to reducing the risk of zoonotic disease transmission in their respective countries.

Late remdesivir treatment initiation partially protects African green monkeys from lethal Nipah virus infection

Remdesivir is a nucleotide prodrug with preclinical efficacy against lethal Nipah virus infection in African green monkeys when administered 1 day post inoculation (dpi) (Lo et al., 2019). Here, we determined whether remdesivir treatment was still effective when treatment administration initiation was delayed until 3 dpi. Three groups of six African green monkeys were inoculated with a lethal dose of Nipah virus, genotype Bangladesh. On 3 dpi, one group received a loading dose of 10 mg/kg remdesivir followed by daily dosing with 5 mg/kg for 11 days, one group received 10 mg/kg on 12 consecutive days, and the remaining group received an equivalent volume of vehicle solution. Remdesivir treatment initiation on 3 dpi provided partial protection from severe Nipah virus disease that was dose dependent, with 67% of animals in the high dose group surviving the challenge. However, remdesivir treatment did not prevent clinical disease, and surviving animals showed histologic lesions in the brain. Thus, early administration seems critical for effective remdesivir treatment during Nipah virus infection.

Art of the Kill: Designing and Testing Viral Inactivation Procedures for Highly Pathogenic Negative Sense RNA Viruses

The study of highly pathogenic viruses handled under BSL-4 conditions and classified as Select Agents frequently involves the transfer of inactivated materials to lower containment levels for downstream analyses. Adhering to Select Agent and BSL-4 safety regulations requires validation or verification of the inactivation procedures, which comes with an array of challenges for each method. This includes the use of cytotoxic reagents for chemical inactivation and defining the precise inactivation parameters for physical inactivation. Here, we provide a workflow for various inactivation methods using Ebola, Nipah, and Lassa viruses as our examples. We choose three distinct inactivation methods (TRIzol/TRIzol LS, aldehyde fixation using different fixatives, and heat) to highlight the challenges of each method and provide possible solutions. We show that, whereas published chemical inactivation methods are highly reliable, the parameters for heat inactivation must be clearly defined to ensure complete inactivation. In addition to the inactivation data, we also provide examples and templates for the documentation required for approval and use of inactivation SOPs, including an inactivation report, the procedure sections of developed SOPs, and an electronic inactivation certificate that accompanies inactivated samples. The provided information can be used as a roadmap for similar studies at high and maximum containment laboratories.

A Recombinant Chimeric Cedar Virus-Based Surrogate Neutralization Assay Platform for Pathogenic Henipaviruses

The henipaviruses, Nipah virus (NiV), and Hendra virus (HeV) can cause fatal diseases in humans and animals, whereas Cedar virus is a nonpathogenic henipavirus. Here, using a recombinant Cedar virus (rCedV) reverse genetics platform, the fusion (F) and attachment (G) glycoprotein genes of rCedV were replaced with those of NiV-Bangladesh (NiV-B) or HeV, generating replication-competent chimeric viruses (rCedV-NiV-B and rCedV-HeV), both with and without green fluorescent protein (GFP) or luciferase protein genes. The rCedV chimeras induced a Type I interferon response and utilized only ephrin-B2 and ephrin-B3 as entry receptors compared to rCedV. The neutralizing potencies of well-characterized cross-reactive NiV/HeV F and G specific monoclonal antibodies against rCedV-NiV-B-GFP and rCedV-HeV-GFP highly correlated with measurements obtained using authentic NiV-B and HeV when tested in parallel by plaque reduction neutralization tests (PRNT). A rapid, high-throughput, and quantitative fluorescence reduction neutralization test (FRNT) using the GFP-encoding chimeras was established, and monoclonal antibody neutralization data derived by FRNT highly correlated with data derived by PRNT. The FRNT assay could also measure serum neutralization titers from henipavirus G glycoprotein immunized animals. These rCedV chimeras are an authentic henipavirus-based surrogate neutralization assay that is rapid, cost-effective, and can be utilized outside high containment.

Establishment of an Inactivation Method for Ebola Virus and SARS-CoV-2 Suitable for Downstream Sequencing of Low Cell Numbers

Technologies that facilitate the bulk sequencing of small numbers of cells as well as single-cell RNA sequencing (scRNA-seq) have aided greatly in the study of viruses as these analyses can be used to differentiate responses from infected versus bystander cells in complex systems, including in organoid or animal studies. While protocols for these analyses are typically developed with biosafety level 2 (BSL-2) considerations in mind, such analyses are equally useful for the study of viruses that require higher biosafety containment levels. Many of these workstreams, however, are not directly compatible with the more stringent biosafety regulations of BSL-3 and BSL-4 laboratories ensuring virus inactivation and must therefore be modified. Here we show that TCL buffer (Qiagen), which was developed for bulk sequencing of small numbers of cells and also facilitates scRNA-seq, inactivates both Ebola virus (EBOV) and SARS-CoV-2, BSL-4 and BSL-3 viruses, respectively. We show that additional heat treatment, necessary for the more stringent biosafety concerns for BSL-4-derived samples, was additionally sufficient to inactivate EBOV-containing samples. Critically, this heat treatment had minimal effects on extracted RNA quality and downstream sequencing results.

Recombinant vesicular stomatitis virus-vectored vaccine induces long-lasting immunity against Nipah virus disease

The emergence of the novel henipavirus, Langya virus, received global attention after the virus sickened over three dozen people in China. There is heightened concern that henipaviruses, as respiratory pathogens, could spark another pandemic, most notably the deadly Nipah virus (NiV). NiV causes near-annual outbreaks in Bangladesh and India and induces a highly fatal respiratory disease and encephalitis in humans. No licensed countermeasures against this pathogen exist. An ideal NiV vaccine would confer both fast-acting and long-lived protection. Recently, we reported the generation of a recombinant vesicular stomatitis virus-based (rVSV-based) vaccine expressing the NiV glycoprotein (rVSV-ΔG-NiVBG) that protected 100% of nonhuman primates from NiV-associated lethality within a week. Here, to evaluate the durability of rVSV-ΔG-NiVBG, we vaccinated African green monkeys (AGMs) one year before challenge with an uniformly lethal dose of NiV. The rVSV-ΔG-NiVBG vaccine induced stable and robust humoral responses, whereas cellular responses were modest. All immunized AGMs (whether receiving a single dose or prime-boosted) survived with no detectable clinical signs or NiV replication. Transcriptomic analyses indicated that adaptive immune signatures correlated with vaccine-mediated protection. While vaccines for certain respiratory infections (e.g., COVID-19) have yet to provide durable protection, our results suggest that rVSV-ΔG-NiVBG elicits long-lasting immunity.

Nonhuman Primate Models for Nipah and Hendra Virus Countermeasure Evaluation

Hendra and Nipah viruses are henipaviruses that have caused lethal human disease in Australia and Malaysia, Bangladesh, India, and the Philippines, respectively. These viruses are considered Category C pathogens by the US Centers for Disease Control. Nipah virus was recently placed on the World Health Organization Research and Development Blueprint Roadmaps for vaccine and therapeutic development. Given the infrequent and unpredictable nature of henipavirus outbreaks licensure of vaccines and therapeutics will likely require an animal model to demonstrate protective efficacy against henipavirus disease. Studies have shown that nonhuman primates are the most accurate model of human henipavirus disease and would be an important component of any application for licensure of a vaccine or antiviral drug under the US FDA Animal Rule. Nonhuman primate model selection and dosing are discussed regarding vaccine and therapeutic studies against henipaviruses.

Distinct VSV-based Nipah virus vaccines expressing either glycoprotein G or fusion protein F provide homologous and heterologous protection in a nonhuman primate model

BACKGROUND

Nipah virus (NiV) causes recurrent outbreaks of lethal respiratory and neurological disease in Southeast Asia. The World Health Organization considers the development of an effective vaccine against NiV a priority.

METHODS

We produced two NiV vaccine candidates using the licensed VSV-EBOV vaccine as a backbone and tested its efficacy against lethal homologous and heterologous NiV challenge with Nipah virus Bangladesh and Nipah virus Malaysia, respectively, in the African green monkey model.

FINDINGS

The VSV-EBOV vaccine expressing NiV glycoprotein G (VSV-NiVG) induced high neutralising antibody titers and afforded complete protection from homologous and heterologous challenge. The VSV-EBOV vaccine expressing NiV fusion protein F (VSV-NiVF) induced a lower humoral response and afforded complete homologous protection, but only partial heterologous protection. Both vaccines reduced virus shedding from the upper respiratory tract, and virus replication in the lungs and central nervous system. None of the protected animals vaccinated with VSV-NiVG or VSV-NiVF showed histological lesions in the CNS, but one VSV-NiVF-vaccinated animal that was not protected developed severe meningoencephalitis.

INTERPRETATION

The VSV-NiVG vaccine offers broad protection against NiV disease.

FUNDING

This study was supported by the Intramural Research Program, NIAID, NIH.

Overview of Experimental Vaccines and Antiviral Therapeutics for Henipavirus Infection

Hendra virus (HeV) and Nipah virus (NiV) are highly pathogenic paramyxoviruses, which have emerged in recent decades and cause sporadic outbreaks of respiratory and encephalitic disease in Australia and Southeast Asia, respectively. Over two billion people currently live in regions potentially at risk due to the wide range of the Pteropus fruit bat reservoir, yet there are no approved vaccines or therapeutics to protect against or treat henipavirus disease. In recent years, significant progress has been made toward developing various experimental vaccine platforms and therapeutics. Here, we describe these advances for both human and livestock vaccine candidates and discuss the numerous preclinical studies and the few that have progressed to human phase 1 clinical trial and the one approved veterinary vaccine.

Immune correlates of protection for SARS-CoV-2, Ebola and Nipah virus infection

Correlates of protection (CoP) are biological parameters that predict a certain level of protection against an infectious disease. Well-established correlates of protection facilitate the development and licensing of vaccines by assessing protective efficacy without the need to expose clinical trial participants to the infectious agent against which the vaccine aims to protect. Despite the fact that viruses have many features in common, correlates of protection can vary considerably amongst the same virus family and even amongst a same virus depending on the infection phase that is under consideration. Moreover, the complex interplay between the various immune cell populations that interact during infection and the high degree of genetic variation of certain pathogens, renders the identification of immune correlates of protection difficult. Some emerging and re-emerging viruses of high consequence for public health such as SARS-CoV-2, Nipah virus (NiV) and Ebola virus (EBOV) are especially challenging with regards to the identification of CoP since these pathogens have been shown to dysregulate the immune response during infection. Whereas, virus neutralising antibodies and polyfunctional T-cell responses have been shown to correlate with certain levels of protection against SARS-CoV-2, EBOV and NiV, other effector mechanisms of immunity play important roles in shaping the immune response against these pathogens, which in turn might serve as alternative correlates of protection. This review describes the different components of the adaptive and innate immune system that are activated during SARS-CoV-2, EBOV and NiV infections and that may contribute to protection and virus clearance. Overall, we highlight the immune signatures that are associated with protection against these pathogens in humans and could be used as CoP.

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.

A Study on the Nature of SARS-CoV-2 Using the Shell Disorder Models: Reproducibility, Evolution, Spread, and Attenuation

The basic tenets of the shell disorder model (SDM) as applied to COVID-19 are that the harder outer shell of the virus shell (lower PID—percentage of intrinsic disorder—of the membrane protein M, PID_M) and higher flexibility of the inner shell (higher PID of the nucleocapsid protein N, PID_N) are correlated with the contagiousness and virulence, respectively. M protects the virion from the anti-microbial enzymes in the saliva and mucus. N disorder is associated with the rapid replication of the virus. SDM predictions are supported by two experimental observations. The first observation demonstrated lesser and greater presence of the Omicron particles in the lungs and bronchial tissues, respectively, as there is a greater level of mucus in the bronchi. The other observation revealed that there are lower viral loads in 2017-pangolin-CoV, which is predicted to have similarly low PID_N as Omicron. The abnormally hard M, which is very rarely seen in coronaviruses, arose from the fecal–oral behaviors of pangolins via exposure to buried feces. Pangolins provide an environment for coronavirus (CoV) attenuation, which is seen in Omicron. Phylogenetic study using M shows that COVID-19-related bat-CoVs from Laos and Omicron are clustered in close proximity to pangolin-CoVs, which suggests the recurrence of interspecies transmissions. Hard M may have implications for long COVID-19, with immune systems having difficulty degrading viral proteins/particles.

Evaluation and comparison of three virucidal agents on inactivation of Nipah virus

Modern human activity is profoundly changing our relationship with microorganisms with the startling rise in the rate of emerging infectious diseases. Nipah virus together with Ebola virus and SARS-CoV-2 are prominent examples. Since COVID-19 and the West African Ebola virus disease outbreak, different chemical disinfectants have been developed for preventing the direct spread of viruses and their efficacy has also been evaluated. However, there are currently no published efficacy studies for the chemical disinfection of Nipah virus. In this study, the virucidal efficacy of three disinfectants (Micro-Chem Plus detergent disinfectant cleaner, FWD and Medical EtOH) against Nipah virus was evaluated in quantitative suspension tests including. Our results showed that the > 4 log reduction achieved for all products in inactivating Nipah virus in 15 s. Even, 19% ethanol was able to inactivate Nipah virus when applied for at least 8 min contact time. Comparative analysis displayed virucidal efficacy of each of the evaluated disinfectants against SARS-CoV-2, Ebola virus and Nipah virus, with only minor differences in working concentrations and contact times required for complete inactivation. We expect that our study can assist in decontamination in healthcare settings and high level biosafety laboratories and can be beneficial to control for emerging enveloped viruses.

Nipah Virus Detection at Bat Roosts after Spillover Events, Bangladesh, 2012-2019

Knowledge of the dynamics and genetic diversity of Nipah virus circulating in bats and at the human-animal interface is limited by current sampling efforts, which produce few detections of viral RNA. We report a series of investigations at Pteropus medius bat roosts identified near the locations of human Nipah cases in Bangladesh during 2012–2019. Pooled bat urine was collected from 23 roosts; 7 roosts (30%) had >1 sample in which Nipah RNA was detected from the first visit. In subsequent visits to these 7 roosts, RNA was detected in bat urine up to 52 days after the presumed exposure of the human case-patient, although the probability of detection declined rapidly with time. These results suggest that rapidly deployed investigations of Nipah virus shedding from bat roosts near human cases could increase the success of viral sequencing compared with background surveillance and could enhance understanding of Nipah virus ecology and evolution.

The Immunobiology of Nipah Virus

Nipah virus (NiV) is a highly lethal zoonotic paramyxovirus that emerged in Malaysia in 1998. It is a human pathogen capable of causing severe respiratory infection and encephalitis. The natural reservoir of NiV, Pteropus fruit bats, remains a continuous virus source for future outbreaks, although infection in the bats is largely asymptomatic. NiV provokes serious disease in various mammalian species. In the recent human NiV outbreaks in Bangladesh and India, both bats-to-human and human-to-human transmissions have been observed. NiV has been demonstrated to interfere with the innate immune response via interferon type I signaling, promoting viral dissemination and preventing antiviral response. Studies of humoral immunity in infected NiV patients and animal models have shown that NiV-specific antibodies were produced upon infection and were protective. Studies on cellular immunity response to NiV infection in human and animal models also found that the adaptive immune response, specifically CD4+ and CD8+ T cells, was stimulated upon NiV infection. The experimental vaccines and therapeutic strategies developed have provided insights into the immunological requirements for the development of successful medical countermeasures against NiV. This review summarizes the current understanding of NiV pathogenesis and innate and adaptive immune responses induced upon infection.

Henipavirus Immune Evasion and Pathogenesis Mechanisms: Lessons Learnt from Natural Infection and Animal Models

Nipah henipavirus (NiV) and Hendra henipavirus (HeV) are zoonotic emerging paramyxoviruses causing severe disease outbreaks in humans and livestock, mostly in Australia, India, Malaysia, Singapore and Bangladesh. Both are bat-borne viruses and in humans, their mortality rates can reach 60% in the case of HeV and 92% for NiV, thus being two of the deadliest viruses known for humans. Several factors, including a large cellular tropism and a wide zoonotic potential, con-tribute to their high pathogenicity. This review provides an overview of HeV and NiV pathogenicity mechanisms and provides a summary of their interactions with the immune systems of their different host species, including their natural hosts bats, spillover-hosts pigs, horses, and humans, as well as in experimental animal models. A better understanding of the interactions between henipaviruses and their hosts could facilitate the development of new therapeutic strategies and vaccine measures against these re-emerging viruses.

Computational, Experimental, and Clinical Evidence of a Specific but Peculiar Evolutionary Nature of (COVID-19) SARS-CoV-2

The shell disorder models have predicted that SARS-CoV-2 is of a specific but peculiar evolutionary nature. All coronaviruses (CoVs) closely related to SARS-CoV-2 have been found to have the hardest outer shells (M protein) among CoVs. This hard shell (low M percentage of intrinsic disorder (PID)) is associated with burrowing animals, for example, pangolins, and is believed to be responsible for the high contagiousness of SARS-CoV-2 because it will be more resistant to antimicrobial enzymes found in saliva/mucus. Incoming clinical and experimental data do support this along with a prediction based on another aspect of the shell (N, inner shell) disorder models that SARS-CoV-1 is more virulent than SARS-CoV-2 because SARS-CoV-2 produces fewer virus copies in vital organs even if large amounts of infections particles are shed orally and nasally. A phylogenetic study using M reveals a closer relationship of SARS-CoV to pangolin-CoVs than the bat-RaTG13 found in Yunnan, China. Previous studies may have been confused by recombinations that were poorly handled. The shell disorder models suggest that a pangolin-CoV strain may have entered the human population in 2017 or before as an attenuated virus, which could explain why SARS-CoV is found to be highly adapted to humans.

A recombinant VSV-vectored vaccine rapidly protects nonhuman primates against lethal Nipah virus disease

Concern has increased about the pandemic potential of Nipah virus (NiV). Similar to SARS-CoV-2, NiV is an RNA virus that is transmitted by respiratory droplets. There are currently no NiV vaccines licensed for human use. While several preventive vaccines have shown promise in protecting animals against lethal NiV disease, most studies have assessed protection 1 mo after vaccination. However, in order to contain and control outbreaks, vaccines that can rapidly confer protection in days rather than months are needed. Here, we show that a recombinant vesicular stomatitis virus vector expressing the NiV glycoprotein can completely protect monkeys vaccinated 7 d prior to NiV exposure and 67% of animals vaccinated 3 d before NiV challenge.

Nipah virus (NiV) is an emerging highly lethal zoonotic disease that, like SARS-CoV-2, can be transmitted via respiratory droplets. Single-injection vaccines that rapidly control NiV outbreaks are needed. To assess the ability of a vaccine to induce fast-acting protection, we immunized African green monkeys with a recombinant vesicular stomatitis virus (VSV) expressing the Bangladesh strain glycoprotein (NiV_BG) of NiV (rVSV-ΔG-NiV_BG). Monkeys were challenged 3 or 7 d later with a lethal dose of NiV_B. All monkeys vaccinated with rVSV-ΔG-NiV_BG 7 d prior to NiV_B exposure were protected from lethal disease, while 67% of animals vaccinated 3 d before NiV_B challenge survived. Vaccine protection correlated with natural killer cell and cytotoxic T cell transcriptional signatures, whereas lethality was linked to sustained interferon signaling. NiV G-specific antibodies in vaccinated survivors corroborated additional transcriptomic findings, supporting activation of humoral immunity. This study demonstrates that rVSV-based vaccines may have utility in rapidly protecting humans against NiV infection.

Detailed analysis of the pathologic hallmarks of Nipah virus (Malaysia) disease in the African green monkey infected by the intratracheal route

Disease associated with Nipah virus infection causes a devastating and often fatal spectrum of syndromes predominated by both respiratory and neurologic conditions. Additionally, neurologic sequelae may manifest months to years later after virus exposure or apparent recovery. In the two decades since this disease emerged, much work has been completed in an attempt to understand the pathogenesis and facilitate development of medical countermeasures. Here we provide detailed organ system-specific pathologic findings following exposure of four African green monkeys to 2.41×105 pfu of the Malaysian strain of Nipah virus. Our results further substantiate the African green monkey as a model of human Nipah virus disease, by demonstrating both the respiratory and neurologic components of disease. Additionally, we demonstrate that a chronic phase of disease exists in this model, that may provide an important opportunity to study the enigmatic late onset and relapse encephalitis as it is described in human disease.

Nipah Virus V Protein Binding Alters MDA5 Helicase Folding Dynamics

Nipah virus (NiV) is an emerging and deadly zoonotic paramyxovirus that is responsible for periodic epidemics of acute respiratory illness and encephalitis in humans. Previous studies have shown that the NiV V protein antagonizes host antiviral immunity, but the molecular mechanism is incompletely understood. To address this gap, we biochemically characterized NiV V binding to the host pattern recognition receptor MDA5. We find that the C-terminal domain of NiV V (VCTD) is sufficient to bind the MDA5SF2 domain when recombinantly co-expressed in bacteria. Analysis by hydrogen-deuterium exchange mass spectrometry (HDX-MS) studies revealed that NiV VCTD is conformationally dynamic, and binding to MDA5 reduces the dynamics of VCTD. Our results also suggest that the β-sheet region in between the MDA5 Hel1, Hel2, and Hel2i domains exhibits rapid HDX. Upon VCTD binding, these β-sheet and adjacent residues show significant protection. Collectively, our findings suggest that NiV V binding disrupts the helicase fold and dynamics of MDA5 to antagonize host antiviral immunity.

Chimeric Fusion (F) and Attachment (G) Glycoprotein Antigen Delivery by mRNA as a Candidate Nipah Vaccine

Nipah virus (NiV) represents a significant pandemic threat with zoonotic transmission from bats-to-humans with almost annual regional outbreaks characterized by documented human-to-human transmission and high fatality rates. Currently, no vaccine against NiV has been approved. Structure-based design and protein engineering principles were applied to stabilize the fusion (F) protein in its prefusion trimeric conformation (pre-F) to improve expression and increase immunogenicity. We covalently linked the stabilized pre-F through trimerization domains at the C-terminus to three attachment protein (G) monomers, forming a chimeric design. These studies detailed here focus on mRNA delivery of NiV immunogens in mice, assessment of mRNA immunogen-specific design elements and their effects on humoral and cellular immunogenicity. The pre-F/G chimera elicited a strong neutralizing antibody response and a superior NiV-specific Tfh and other effector T cell response compared to G alone across both the mRNA and protein platforms. These findings enabled final candidate selection of pre-F/G Fd for clinical development.

Recent advances in combating Nipah virus

Over the past 20 years, Nipah virus (NiV) has emerged as a significant, highly pathogenic bat-borne paramyxovirus causing severe respiratory disease and encephalitis in humans, and human-to-human transmission has been demonstrated in multiple outbreaks. In addition to causing serious illness in humans, NiV is a zoonotic pathogen capable of infecting a wide range of other mammalian species, including pigs and horses. While NiV has caused less than 700 human cases since its discovery in 1998/1999, the involvement of intermediate agricultural hosts can result in significant economic consequences. Owing to the severity of disease, capacity for human-to-human transmission, zoonotic potential, and lack of available approved therapeutic treatment options, NiV has been listed by the World Health Organization in their Blueprint list of priority pathogens as one of the eight most dangerous pathogens to monitor and prepare countermeasures to prevent a pandemic. Here, we discuss progress towards the development of therapeutic measures for the treatment of NiV infection and disease.