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Viruses Sep 2021Syncytium formation, i.e., cell-cell fusion resulting in the formation of multinucleated cells, is a hallmark of infection by paramyxoviruses and other pathogenic... (Review)
Review
Syncytium formation, i.e., cell-cell fusion resulting in the formation of multinucleated cells, is a hallmark of infection by paramyxoviruses and other pathogenic viruses. This natural mechanism has historically been a diagnostic marker for paramyxovirus infection in vivo and is now widely used for the study of virus-induced membrane fusion in vitro. However, the role of syncytium formation in within-host dissemination and pathogenicity of viruses remains poorly understood. The diversity of henipaviruses and their wide host range and tissue tropism make them particularly appropriate models with which to characterize the drivers of syncytium formation and the implications for virus fitness and pathogenicity. Based on the henipavirus literature, we summarized current knowledge on the mechanisms driving syncytium formation, mostly acquired from in vitro studies, and on the in vivo distribution of syncytia. While these data suggest that syncytium formation widely occurs across henipaviruses, hosts, and tissues, we identified important data gaps that undermined our understanding of the role of syncytium formation in virus pathogenesis. Based on these observations, we propose solutions of varying complexity to fill these data gaps, from better practices in data archiving and publication for in vivo studies, to experimental approaches in vitro.
Topics: Giant Cells; HEK293 Cells; Henipavirus Infections; Host Specificity; Host-Pathogen Interactions; Humans; Membrane Fusion; Paramyxoviridae; Virus Attachment; Virus Internalization
PubMed: 34578336
DOI: 10.3390/v13091755 -
PLoS Pathogens Sep 2023The Pneumoviridae family of viruses includes human metapneumovirus (HMPV) and respiratory syncytial virus (RSV). The closely related Paramyxoviridae family includes...
Structure-based design of a single-chain triple-disulfide-stabilized fusion-glycoprotein trimer that elicits high-titer neutralizing responses against human metapneumovirus.
The Pneumoviridae family of viruses includes human metapneumovirus (HMPV) and respiratory syncytial virus (RSV). The closely related Paramyxoviridae family includes parainfluenza viruses (PIVs). These three viral pathogens cause acute respiratory tract infections with substantial disease burden in the young, the elderly, and the immune-compromised. While promising subunit vaccines are being developed with prefusion-stabilized forms of the fusion glycoproteins (Fs) of RSV and PIVs, for which neutralizing titers elicited by the prefusion (pre-F) conformation of F are much higher than for the postfusion (post-F) conformation, with HMPV, pre-F and post-F immunogens described thus far elicit similar neutralizing responses, and it has been unclear which conformation, pre-F or post-F, would be the most effective HMPV F-vaccine immunogen. Here, we investigate the impact of further stabilizing HMPV F in the pre-F state. We replaced the furin-cleavage site with a flexible linker, creating a single chain F that yielded increased amounts of pre-F stabilized trimers, enabling the generation and assessment of F trimers stabilized by multiple disulfide bonds. Introduced prolines could increase both expression yields and antigenic recognition by the pre-F specific antibody, MPE8. The cryo-EM structure of a triple disulfide-stabilized pre-F trimer with the variable region of antibody MPE8 at 3.25-Å resolution confirmed the formation of designed disulfides and provided structural details on the MPE8 interface. Immunogenicity assessments in naïve mice showed the triple disulfide-stabilized pre-F trimer could elicit high titer neutralization, >10-fold higher than elicited by post-F. Immunogenicity assessments in pre-exposed rhesus macaques showed the triple disulfide-stabilized pre-F could recall high neutralizing titers after a single immunization, with little discrimination in the recall response between pre-F and post-F immunogens. However, the triple disulfide-stabilized pre-F adsorbed HMPV-directed responses from commercially available pooled human immunoglobulin more fully than post-F. Collectively, these results suggest single-chain triple disulfide-stabilized pre-F trimers to be promising HMPV-vaccine antigens.
Topics: Aged; Humans; Animals; Mice; Metapneumovirus; Macaca mulatta; Antibodies; Respiratory Syncytial Virus, Human; Antigens, Viral; Disulfides; Glycoproteins; Parainfluenza Virus 1, Human
PubMed: 37738240
DOI: 10.1371/journal.ppat.1011584 -
Current Opinion in Immunology Aug 2022Viral proteins fold into a variety of structures as they perform their functions. Structure-based vaccine design aims to exploit knowledge of an antigen's architecture... (Review)
Review
Viral proteins fold into a variety of structures as they perform their functions. Structure-based vaccine design aims to exploit knowledge of an antigen's architecture to stabilize it in a vulnerable conformation. We summarize the general principles of structure-based vaccine design, with a focus on the major types of sequence modifications: proline, disulfide, cavity-filling, electrostatic and hydrogen-bond substitution, as well as domain deletion. We then review recent applications of these principles to vaccine-design efforts across five viral families: Coronaviridae, Orthomyxoviridae, Paramyxoviridae, Pneumoviridae, and Filoviridae. Outstanding challenges include continued application of proven design principles to pathogens of interest, as well as development of new strategies for those pathogens that resist traditional techniques.
Topics: Coronaviridae; Filoviridae; Humans; Orthomyxoviridae; Paramyxoviridae; Pneumovirinae; Vaccine Development; Viral Proteins; Viral Vaccines
PubMed: 35598506
DOI: 10.1016/j.coi.2022.102209 -
Journal of Virology Sep 2022The genus (family ) currently comprises seven viruses, four of which have demonstrated prior evidence of zoonotic capacity. These include the biosafety level 4 agents...
The genus (family ) currently comprises seven viruses, four of which have demonstrated prior evidence of zoonotic capacity. These include the biosafety level 4 agents Hendra (HeV) and Nipah (NiV) viruses, which circulate naturally in pteropodid fruit bats. Here, we describe and characterize Angavokely virus (AngV), a divergent henipavirus identified in urine samples from wild, Madagascar fruit bats. We report the nearly complete 16,740-nucleotide genome of AngV, which encodes the six major henipavirus structural proteins (nucleocapsid, phosphoprotein, matrix, fusion, glycoprotein, and L polymerase). Within the phosphoprotein (P) gene, we identify an alternative start codon encoding the AngV C protein and a putative mRNA editing site where the insertion of one or two guanine residues encodes, respectively, additional V and W proteins. In other paramyxovirus systems, C, V, and W are accessory proteins involved in antagonism of host immune responses during infection. Phylogenetic analysis suggests that AngV is ancestral to all four previously described bat henipaviruses-HeV, NiV, Cedar virus (CedV), and Ghanaian bat virus (GhV)-but evolved more recently than rodent- and shrew-derived henipaviruses, Mojiang (MojV), Gamak (GAKV), and Daeryong (DARV) viruses. Predictive structure-based alignments suggest that AngV is unlikely to bind ephrin receptors, which mediate cell entry for all other known bat henipaviruses. Identification of the AngV receptor is needed to clarify the virus's potential host range. The presence of V and W proteins in the AngV genome suggest that the virus could be pathogenic following zoonotic spillover. Henipaviruses include highly pathogenic emerging zoonotic viruses, derived from bat, rodent, and shrew reservoirs. Bat-borne Hendra (HeV) and Nipah (NiV) are the most well-known henipaviruses, for which no effective antivirals or vaccines for humans have been described. Here, we report the discovery and characterization of a novel henipavirus, Angavokely virus (AngV), isolated from wild fruit bats in Madagascar. Genomic characterization of AngV reveals all major features associated with pathogenicity in other henipaviruses, suggesting that AngV could be pathogenic following spillover to human hosts. Our work suggests that AngV is an ancestral bat henipavirus that likely uses viral entry pathways distinct from those previously described for HeV and NiV. In Madagascar, bats are consumed as a source of human food, presenting opportunities for cross-species transmission. Characterization of novel henipaviruses and documentation of their pathogenic and zoonotic potential are essential to predicting and preventing the emergence of future zoonoses that cause pandemics.
Topics: Animals; Chiroptera; Genome, Viral; Glycoproteins; Henipavirus; Henipavirus Infections; Humans; Madagascar; Nipah Virus; Phylogeny; Urine; Zoonoses
PubMed: 36040175
DOI: 10.1128/jvi.00921-22 -
Viruses Dec 2021All paramyxoviruses, which include the mumps virus, measles virus, Nipah virus, Newcastle disease virus, and Sendai virus, have non-segmented single-stranded... (Review)
Review
All paramyxoviruses, which include the mumps virus, measles virus, Nipah virus, Newcastle disease virus, and Sendai virus, have non-segmented single-stranded negative-sense RNA genomes. These RNA genomes are enwrapped throughout the viral life cycle by nucleoproteins, forming helical nucleocapsids. In addition to these helical structures, recombinant paramyxovirus nucleocapsids may occur in other assembly forms such as rings, clam-shaped structures, and double-headed nucleocapsids; the latter two are composed of two single-stranded helices packed in a back-to-back pattern. In all of these assemblies, the neighboring nucleoprotein protomers adopt the same domain-swapping mode via the N-terminal arm, C-terminal arm, and recently disclosed N-hole. An intrinsically disordered region in the C-terminal domain of the nucleoproteins, called the N-tail, plays an unexpected role in regulating the transition among the different assembly forms that occurs with other viral proteins, especially phosphoprotein. These structures, together with the helical nucleocapsids, significantly enrich the structural diversity of the paramyxovirus nucleocapsids and help explain the functions of these diverse assemblies, including RNA genome protection, transcription, and replication, as well as encapsulation.
Topics: Models, Molecular; Nucleocapsid; Nucleocapsid Proteins; Paramyxovirinae; Protein Conformation; Protein Domains; Protein Structure, Quaternary; Protein Subunits
PubMed: 34960748
DOI: 10.3390/v13122479 -
Viruses May 2023Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic species from the genus within the paramyxovirus family and are harbored by Flying Fox species....
Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic species from the genus within the paramyxovirus family and are harbored by Flying Fox species. Henipaviruses cause severe respiratory disease, neural symptoms, and encephalitis in various animals and humans, with human mortality rates exceeding 70% in some NiV outbreaks. The henipavirus matrix protein (M), which drives viral assembly and budding of the virion, also performs non-structural functions as a type I interferon antagonist. Interestingly, M also undergoes nuclear trafficking that mediates critical monoubiquitination for downstream cell sorting, membrane association, and budding processes. Based on the NiV and HeV M X-ray crystal structures and cell-based assays, M possesses a putative monopartite nuclear localization signal (NLS) (residues KRKKIR; NLS1 HeV), positioned on an exposed flexible loop and typical of how many NLSs bind importin alpha (IMPα), and a putative bipartite NLS (RR-10X-KRK; NLS2 HeV), positioned within an α-helix that is far less typical. Here, we employed X-ray crystallography to determine the binding interface of these M NLSs and IMPα. The interaction of both NLS peptides with IMPα was established, with NLS1 binding the IMPα major binding site, and NLS2 binding as a non-classical NLS to the minor site. Co-immunoprecipitation (co-IP) and immunofluorescence assays (IFA) confirm the critical role of NLS2, and specifically K258. Additionally, localization studies demonstrated a supportive role for NLS1 in M nuclear localization. These studies provide additional insight into the critical mechanisms of M nucleocytoplasmic transport, the study of which can provide a greater understanding of viral pathogenesis and uncover a potential target for novel therapeutics for henipaviral diseases.
Topics: Animals; Humans; Nuclear Localization Signals; Active Transport, Cell Nucleus; Nipah Virus; alpha Karyopherins; Hendra Virus; Henipavirus Infections; Protein Binding
PubMed: 37376602
DOI: 10.3390/v15061302 -
Microbes and Infection 2019Nipah virus is an emerging zoonotic paramyxovirus that causes severe and often fatal respiratory and neurological disease in humans. The virus was first discovered after... (Review)
Review
Nipah virus is an emerging zoonotic paramyxovirus that causes severe and often fatal respiratory and neurological disease in humans. The virus was first discovered after an outbreak of encephalitis in pig farmers in Malaysia and Singapore with subsequent outbreaks in Bangladesh or India occurring almost annually. Due to the highly pathogenic nature of NiV, its pandemic potential, and the lack of licensed vaccines or therapeutics, there is a requirement for research and development into highly sensitive and specific diagnostic tools as well as antivirals and vaccines to help prevent and control future outbreak situations.
Topics: Animals; Antiviral Agents; Clinical Laboratory Techniques; Disease Outbreaks; Henipavirus Infections; Humans; Models, Biological; Nipah Virus; Viral Vaccines; Zoonoses
PubMed: 30817995
DOI: 10.1016/j.micinf.2019.02.002 -
Viruses Dec 2021Viruses of the family share a common and complex molecular machinery for transcribing and replicating their genomes. Their non-segmented, negative-strand RNA genome is... (Review)
Review
Viruses of the family share a common and complex molecular machinery for transcribing and replicating their genomes. Their non-segmented, negative-strand RNA genome is encased in a tight homopolymer of viral nucleoproteins (N). This ribonucleoprotein complex, termed a nucleocapsid, is the template of the viral polymerase complex made of the large protein (L) and its co-factor, the phosphoprotein (P). This review summarizes the current knowledge on several aspects of paramyxovirus transcription and replication, including structural and functional data on (1) the architecture of the nucleocapsid (structure of the nucleoprotein, interprotomer contacts, interaction with RNA, and organization of the disordered C-terminal tail of N), (2) the encapsidation of the genomic RNAs (structure of the nucleoprotein in complex with its chaperon P and kinetics of RNA encapsidation in vitro), and (3) the use of the nucleocapsid as a template for the polymerase complex (release of the encased RNA and interaction network allowing the progress of the polymerase complex). Finally, this review presents models of paramyxovirus transcription and replication.
Topics: Gene Expression Regulation, Viral; Humans; Nucleocapsid; Nucleocapsid Proteins; Paramyxoviridae Infections; Paramyxovirinae; Phylogeny; RNA, Viral
PubMed: 34960734
DOI: 10.3390/v13122465 -
Viruses Mar 2020Paramyxoviruses and pneumoviruses infect cells through fusion (F) protein-mediated merger of the viral envelope with target membranes. Members of these families include... (Review)
Review
Paramyxoviruses and pneumoviruses infect cells through fusion (F) protein-mediated merger of the viral envelope with target membranes. Members of these families include a range of major human and animal pathogens, such as respiratory syncytial virus (RSV), measles virus (MeV), human parainfluenza viruses (HPIVs), and highly pathogenic Nipah virus (NiV). High-resolution F protein structures in both the metastable pre- and the postfusion conformation have been solved for several members of the families and a number of F-targeting entry inhibitors have progressed to advanced development or clinical testing. However, small-molecule RSV entry inhibitors have overall disappointed in clinical trials and viral resistance developed rapidly in experimental settings and patients, raising the question of whether the available structural information may provide a path to counteract viral escape through proactive inhibitor engineering. This article will summarize current mechanistic insight into F-mediated membrane fusion and examine the contribution of structural information to the development of small-molecule F inhibitors. Implications are outlined for future drug target selection and rational drug engineering strategies.
Topics: Animals; Antiviral Agents; Binding Sites; Drug Discovery; Humans; Models, Molecular; Paramyxoviridae Infections; Paramyxovirinae; Pneumovirus; Pneumovirus Infections; Protein Binding; Structure-Activity Relationship; Virus Internalization
PubMed: 32245118
DOI: 10.3390/v12030342 -
The Lancet. Infectious Diseases Jan 2022Henipaviruses, including Nipah virus, are regarded as pathogens of notable epidemic potential because of their high pathogenicity and the paucity of specific medical... (Review)
Review
Henipaviruses, including Nipah virus, are regarded as pathogens of notable epidemic potential because of their high pathogenicity and the paucity of specific medical countermeasures to control infections in humans. We review the evidence of medical countermeasures against henipaviruses and project their cost in a post-COVID-19 era. Given the sporadic and unpredictable nature of henipavirus outbreaks, innovative strategies will be needed to circumvent the infeasibility of traditional phase 3 clinical trial regulatory pathways. Stronger partnerships with scientific institutions and regulatory authorities in low-income and middle-income countries can inform coordination of appropriate investments and development of strategies and normative guidelines for the deployment and equitable use of multiple medical countermeasures. Accessible measures should include global, regional, and endemic in-country stockpiles of reasonably priced small molecules, monoclonal antibodies, and vaccines as part of a combined collection of products that could help to control henipavirus outbreaks and prevent future pandemics.
Topics: Animals; COVID-19; Chiroptera; Clinical Trials, Phase III as Topic; Disease Outbreaks; Henipavirus; Henipavirus Infections; Humans; Medical Countermeasures; Nipah Virus; Public Health; SARS-CoV-2
PubMed: 34735799
DOI: 10.1016/S1473-3099(21)00400-X