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Nature Feb 2022Alphaviruses, like many other arthropod-borne viruses, infect vertebrate species and insect vectors separated by hundreds of millions of years of evolutionary history....
Alphaviruses, like many other arthropod-borne viruses, infect vertebrate species and insect vectors separated by hundreds of millions of years of evolutionary history. Entry into evolutionarily divergent host cells can be accomplished by recognition of different cellular receptors in different species, or by binding to receptors that are highly conserved across species. Although multiple alphavirus receptors have been described, most are not shared among vertebrate and invertebrate hosts. Here we identify the very low-density lipoprotein receptor (VLDLR) as a receptor for the prototypic alphavirus Semliki forest virus. We show that the E2 and E1 glycoproteins (E2-E1) of Semliki forest virus, eastern equine encephalitis virus and Sindbis virus interact with the ligand-binding domains (LBDs) of VLDLR and apolipoprotein E receptor 2 (ApoER2), two closely related receptors. Ectopic expression of either protein facilitates cellular attachment, and internalization of virus-like particles, a VLDLR LBD-Fc fusion protein or a ligand-binding antagonist block Semliki forest virus E2-E1-mediated infection of human and mouse neurons in culture. The administration of a VLDLR LBD-Fc fusion protein has protective activity against rapidly fatal Semliki forest virus infection in mouse neonates. We further show that invertebrate receptor orthologues from mosquitoes and worms can serve as functional alphavirus receptors. We propose that the ability of some alphaviruses to infect a wide range of hosts is a result of their engagement of evolutionarily conserved lipoprotein receptors and contributes to their pathogenesis.
Topics: Animals; LDL-Receptor Related Proteins; Ligands; Mice; Mosquito Vectors; Receptors, LDL; Semliki forest virus; Sindbis Virus
PubMed: 34929721
DOI: 10.1038/s41586-021-04326-0 -
Viruses Jun 2014Alphavirus vectors have demonstrated high levels of transient heterologous gene expression both in vitro and in vivo and, therefore, possess attractive features for... (Review)
Review
Alphavirus vectors have demonstrated high levels of transient heterologous gene expression both in vitro and in vivo and, therefore, possess attractive features for vaccine development. The most commonly used delivery vectors are based on three single-stranded encapsulated alphaviruses, namely Semliki Forest virus, Sindbis virus and Venezuelan equine encephalitis virus. Alphavirus vectors have been applied as replication-deficient recombinant viral particles and, more recently, as replication-proficient particles. Moreover, in vitro transcribed RNA, as well as layered DNA vectors have been applied for immunization. A large number of highly immunogenic viral structural proteins expressed from alphavirus vectors have elicited strong neutralizing antibody responses in multispecies animal models. Furthermore, immunization studies have demonstrated robust protection against challenges with lethal doses of virus in rodents and primates. Similarly, vaccination with alphavirus vectors expressing tumor antigens resulted in prophylactic protection against challenges with tumor-inducing cancerous cells. As certain alphaviruses, such as Chikungunya virus, have been associated with epidemics in animals and humans, attention has also been paid to the development of vaccines against alphaviruses themselves. Recent progress in alphavirus vector development and vaccine technology has allowed conducting clinical trials in humans.
Topics: Alphavirus; Alphavirus Infections; Animals; Cancer Vaccines; Clinical Trials as Topic; Genetic Vectors; Humans; Vaccines, DNA; Viral Vaccines
PubMed: 24937089
DOI: 10.3390/v6062392 -
Nature May 2018Arthritogenic alphaviruses comprise a group of enveloped RNA viruses that are transmitted to humans by mosquitoes and cause debilitating acute and chronic...
Arthritogenic alphaviruses comprise a group of enveloped RNA viruses that are transmitted to humans by mosquitoes and cause debilitating acute and chronic musculoskeletal disease . The host factors required for alphavirus entry remain poorly characterized . Here we use a genome-wide CRISPR-Cas9-based screen to identify the cell adhesion molecule Mxra8 as an entry mediator for multiple emerging arthritogenic alphaviruses, including chikungunya, Ross River, Mayaro and O'nyong nyong viruses. Gene editing of mouse Mxra8 or human MXRA8 resulted in reduced levels of viral infection of cells and, reciprocally, ectopic expression of these genes resulted in increased infection. Mxra8 bound directly to chikungunya virus particles and enhanced virus attachment and internalization into cells. Consistent with these findings, Mxra8-Fc fusion protein or anti-Mxra8 monoclonal antibodies blocked chikungunya virus infection in multiple cell types, including primary human synovial fibroblasts, osteoblasts, chondrocytes and skeletal muscle cells. Mutagenesis experiments suggest that Mxra8 binds to a surface-exposed region across the A and B domains of chikungunya virus E2 protein, which are a speculated site of attachment. Finally, administration of the Mxra8-Fc protein or anti-Mxra8 blocking antibodies to mice reduced chikungunya and O'nyong nyong virus infection as well as associated foot swelling. Pharmacological targeting of Mxra8 could form a strategy for mitigating infection and disease by multiple arthritogenic alphaviruses.
Topics: 3T3 Cells; Animals; Antibodies, Blocking; CRISPR-Cas Systems; Chikungunya virus; Chondrocytes; Fibroblasts; Humans; Immunoglobulins; Male; Membrane Proteins; Mice; Muscle, Skeletal; O'nyong-nyong Virus; Osteoblasts; Receptors, Fc; Receptors, Virus
PubMed: 29769725
DOI: 10.1038/s41586-018-0121-3 -
Cell May 2023Semliki Forest virus (SFV) is an alphavirus that uses the very-low-density lipoprotein receptor (VLDLR) as a receptor during infection of its vertebrate hosts and...
Semliki Forest virus (SFV) is an alphavirus that uses the very-low-density lipoprotein receptor (VLDLR) as a receptor during infection of its vertebrate hosts and insect vectors. Herein, we used cryoelectron microscopy to study the structure of SFV in complex with VLDLR. We found that VLDLR binds multiple E1-DIII sites of SFV through its membrane-distal LDLR class A (LA) repeats. Among the LA repeats of the VLDLR, LA3 has the best binding affinity to SFV. The high-resolution structure shows that LA3 binds SFV E1-DIII through a small surface area of 378 Å, with the main interactions at the interface involving salt bridges. Compared with the binding of single LA3s, consecutive LA repeats around LA3 promote synergistic binding to SFV, during which the LAs undergo a rotation, allowing simultaneous key interactions at multiple E1-DIII sites on the virion and enabling the binding of VLDLRs from divergent host species to SFV.
Topics: Alphavirus; Cryoelectron Microscopy; Semliki forest virus; Receptors, LDL; Receptors, Virus
PubMed: 37098345
DOI: 10.1016/j.cell.2023.03.032 -
Nature Reviews. Microbiology Jun 2023Alphaviruses are arthropod-transmitted RNA viruses that cause epidemics of human infection and disease on a global scale. These viruses are classified as either... (Review)
Review
Alphaviruses are arthropod-transmitted RNA viruses that cause epidemics of human infection and disease on a global scale. These viruses are classified as either arthritogenic or encephalitic based on their genetic relatedness and the clinical syndromes they cause. Although there are currently no approved therapeutics or vaccines against alphaviruses, passive transfer of monoclonal antibodies confers protection in animal models. This Review highlights recent advances in our understanding of the host factors required for alphavirus entry, the mechanisms of action by which protective antibodies inhibit different steps in the alphavirus infection cycle and candidate alphavirus vaccines currently under clinical evaluation that focus on humoral immunity. A comprehensive understanding of alphavirus entry and antibody-mediated protection may inform the development of new classes of countermeasures for these emerging viruses.
Topics: Animals; Humans; Alphavirus; Alphavirus Infections; Antibodies, Monoclonal
PubMed: 36474012
DOI: 10.1038/s41579-022-00825-7 -
Viruses Aug 2019Alphaviruses belong to a family of positive sense, single-stranded RNA viruses that are transmitted mainly by mosquitoes through a blood meal and cause arthritis and/or...
Alphaviruses belong to a family of positive sense, single-stranded RNA viruses that are transmitted mainly by mosquitoes through a blood meal and cause arthritis and/or encephalitis in humans and animals [...].
Topics: Animals; Arthritis; Chikungunya Fever; Chikungunya virus; Communicable Diseases, Emerging; Disease Outbreaks; Encephalitis; Humans; Mosquito Vectors
PubMed: 31450552
DOI: 10.3390/v11090779 -
Viruses May 2015Alphavirus vectors present an attractive approach for gene therapy applications due to the rapid and simple recombinant virus particle production and their broad range... (Review)
Review
Alphavirus vectors present an attractive approach for gene therapy applications due to the rapid and simple recombinant virus particle production and their broad range of mammalian host cell transduction. Mainly three types of alphavirus vectors, namely naked RNA, recombinant particles and DNA/RNA layered vectors, have been subjected to preclinical studies with the goal of achieving prophylactic or therapeutic efficacy, particularly in oncology. In this context, immunization with alphavirus vectors has provided protection against challenges with tumor cells. Moreover, alphavirus intratumoral and systemic delivery has demonstrated substantial tumor regression and significant prolonged survival rates in various animal tumor models. Recent discoveries of the strong association of RNA interference and disease have accelerated gene therapy based approaches, where alphavirus-based gene delivery can play an important role.
Topics: Alphavirus; Cancer Vaccines; Drug Carriers; Genetic Therapy; Humans; Neoplasms; Transduction, Genetic
PubMed: 25961488
DOI: 10.3390/v7052321 -
Science Translational Medicine May 2023Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes epidemics of acute and chronic musculoskeletal disease. Here, we analyzed the human B cell...
Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes epidemics of acute and chronic musculoskeletal disease. Here, we analyzed the human B cell response to a CHIKV-like particle-adjuvanted vaccine (PXVX0317) from samples obtained from a phase 2 clinical trial in humans (NCT03483961). Immunization with PXVX0317 induced high levels of neutralizing antibody in serum against CHIKV and circulating antigen-specific B cells up to 6 months after immunization. Monoclonal antibodies (mAbs) generated from peripheral blood B cells of three PXVX0317-vaccinated individuals on day 57 after immunization potently neutralized CHIKV infection, and a subset of these inhibited multiple related arthritogenic alphaviruses. Epitope mapping and cryo-electron microscopy defined two broadly neutralizing mAbs that uniquely bind to the apex of the B domain of the E2 glycoprotein. These results demonstrate the inhibitory breadth and activity of the human B cell response induced by the PXVX0317 vaccine against CHIKV and potentially other related alphaviruses.
Topics: Animals; Humans; Chikungunya virus; Chikungunya Fever; Vaccines, Virus-Like Particle; Cryoelectron Microscopy; Antibodies, Viral; Antibodies, Neutralizing; Antibodies, Monoclonal
PubMed: 37196061
DOI: 10.1126/scitranslmed.ade8273 -
Current Opinion in Virology Feb 2018Alphaviruses are important human pathogens that cause diseases ranging from acute and chronic polyarthralgia to encephalitis. Transmitted by mosquito vectors,... (Review)
Review
Alphaviruses are important human pathogens that cause diseases ranging from acute and chronic polyarthralgia to encephalitis. Transmitted by mosquito vectors, alphaviruses have high potential for emergence and have initiated several recent epidemics. The innate immune response is critical for controlling the acute phase of alphavirus disease, and the induction of type I interferon (IFN) is essential in this response. In this review, we discuss our current understanding of innate host sensors that initiate antiviral responses following alphavirus infection, and the IFN-induced effector proteins that limit alphavirus replication and dissemination.
Topics: Alphavirus; Alphavirus Infections; Animals; Humans; Immunity, Innate; Interferon Type I; Mice; Toll-Like Receptors; Virus Replication
PubMed: 29175515
DOI: 10.1016/j.coviro.2017.11.006 -
Viruses Mar 2018Alphavirus nucleocapsids are assembled in the cytoplasm of infected cells from 240 copies of the capsid protein and the approximately 11 kb positive strand genomic RNA.... (Review)
Review
Alphavirus nucleocapsids are assembled in the cytoplasm of infected cells from 240 copies of the capsid protein and the approximately 11 kb positive strand genomic RNA. However, the challenge of how the capsid specifically selects its RNA package and assembles around it has remained an elusive one to solve. In this review, we will summarize what is known about the alphavirus capsid protein, the packaging signal, and their roles in the mechanism of packaging and assembly. We will review the discovery of the packaging signal and how there is as much evidence for, as well as against, its requirement to specify packaging of the genomic RNA. Finally, we will compare this model with those of other viral systems including particular reference to a relatively new idea of RNA packaging based on the presence of multiple minimal packaging signals throughout the genome known as the two stage mechanism. This review will provide a basis for further investigating the fundamental ways of how RNA viruses are able to select their own cargo from the relative chaos that is the cytoplasm.
Topics: Alphavirus; Animals; Capsid Proteins; Humans; Models, Biological; Nucleocapsid; Virus Assembly; Virus Replication
PubMed: 29558394
DOI: 10.3390/v10030138