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The Journal of General Virology Sep 2015The members of the genus Alphavirus are positive-sense RNA viruses, which are predominantly transmitted to vertebrates by a mosquito vector. Alphavirus disease in humans... (Review)
Review
The members of the genus Alphavirus are positive-sense RNA viruses, which are predominantly transmitted to vertebrates by a mosquito vector. Alphavirus disease in humans can be severely debilitating, and depending on the particular viral species, infection may result in encephalitis and possibly death. In recent years, alphaviruses have received significant attention from public health authorities as a consequence of the dramatic emergence of chikungunya virus in the Indian Ocean islands and the Caribbean. Currently, no safe, approved or effective vaccine or antiviral intervention exists for human alphavirus infection. The molecular biology of alphavirus RNA synthesis has been well studied in a few species of the genus and represents a general target for antiviral drug development. This review describes what is currently understood about the regulation of alphavirus RNA synthesis, the roles of the viral non-structural proteins in this process and the functions of cis-acting RNA elements in replication, and points to open questions within the field.
Topics: Alphavirus; Alphavirus Infections; Animals; Humans; RNA, Viral; Viral Nonstructural Proteins
PubMed: 26219641
DOI: 10.1099/jgv.0.000249 -
Viruses Jun 2016Alphaviruses cause debilitating disease in humans and animals and are transmitted by blood-feeding arthropods, typically mosquitoes. With a traditional focus on two... (Review)
Review
Alphaviruses cause debilitating disease in humans and animals and are transmitted by blood-feeding arthropods, typically mosquitoes. With a traditional focus on two models, Sindbis virus and Semliki Forest virus, alphavirus research has significantly intensified in the last decade partly due to the re-emergence and dramatic expansion of chikungunya virus in Asia, Europe, and the Americas. As a consequence, alphavirus-host interactions are now understood in much more molecular detail, and important novel mechanisms have been elucidated. It has become clear that alphaviruses not only cause a general host shut-off in infected vertebrate cells, but also specifically suppress different host antiviral pathways using their viral nonstructural proteins, nsP2 and nsP3. Here we review the current state of the art of alphavirus host cell shut-off of viral transcription and translation, and describe recent insights in viral subversion of interferon induction and signaling, the unfolded protein response, and stress granule assembly.
Topics: Alphavirus; Alphavirus Infections; Animals; Host-Pathogen Interactions; Humans; Immune Evasion; Immunity, Innate; Viral Nonstructural Proteins; Virulence Factors
PubMed: 27294951
DOI: 10.3390/v8060166 -
Journal of Virology Mar 2022The impact of the host microbiota on arbovirus infections is currently not well understood. Arboviruses are viruses transmitted through the bites of infected arthropods,...
The impact of the host microbiota on arbovirus infections is currently not well understood. Arboviruses are viruses transmitted through the bites of infected arthropods, predominantly mosquitoes or ticks. The first site of arbovirus inoculation is the biting site in the host skin, which is colonized by a complex microbial community that could possibly influence arbovirus infection. We demonstrated that preincubation of arboviruses with certain components of the bacterial cell wall, including lipopolysaccharides (LPS) of some Gram-negative bacteria and lipoteichoic acids or peptidoglycan of certain Gram-positive bacteria, significantly reduced arbovirus infectivity . This inhibitory effect was observed for arboviruses of different virus families, including chikungunya virus of the genus and Zika virus of the genus, showing that this is a broad phenomenon. A modest inhibitory effect was observed following incubation with a panel of heat-inactivated bacteria, including bacteria residing on the skin. No viral inhibition was observed after preincubation of cells with LPS. Furthermore, a virucidal effect of LPS on viral particles was noticed by electron microscopy. Therefore, the main inhibitory mechanism seems to be due to a direct effect on the virus particles. Together, these results suggest that bacteria are able to decrease the infectivity of alphaviruses and flaviviruses. During the past decades, the world has experienced a vast increase in epidemics of alphavirus and flavivirus infections. These viruses can cause severe diseases, such as hemorrhagic fever, encephalitis, and arthritis. Several alpha- and flaviviruses, such as chikungunya virus, Zika virus, and dengue virus, are significant global health threats because of their high disease burden, their widespread (re-)emergence, and the lack of (good) anti-arboviral strategies. Despite the clear health burden, alphavirus and flavivirus infection and disease are not fully understood. A knowledge gap in the interplay between the host and the arbovirus is the potential interaction with host skin bacteria. Therefore, we studied the effect of (skin) bacteria and bacterial cell wall components on alphavirus and flavivirus infectivity in cell culture. Our results show that certain bacterial cell wall components markedly reduced viral infectivity by interacting directly with the virus particle.
Topics: Alphavirus; Animals; Arboviruses; Bacteria; Cell Wall; Chikungunya virus; Flavivirus; Lipopolysaccharides; Microbiota; Zika Virus
PubMed: 35107376
DOI: 10.1128/jvi.00060-22 -
Journal of Virology Jan 2022Alphaviruses and flaviviruses have class II fusion glycoproteins that are essential for virion assembly and infectivity. Importantly, the tip of domain II is...
Alphaviruses and flaviviruses have class II fusion glycoproteins that are essential for virion assembly and infectivity. Importantly, the tip of domain II is structurally conserved between the alphavirus and flavivirus fusion proteins, yet whether these structural similarities between virus families translate to functional similarities is unclear. Using evolution of Zika virus (ZIKV), we identified several novel emerging variants, including an envelope glycoprotein variant in β-strand c (V114M) of domain II. We have previously shown that the analogous β-strand c and the ij loop, located in the tip of domain II of the alphavirus E1 glycoprotein, are important for infectivity. This led us to hypothesize that flavivirus E β-strand c also contributes to flavivirus infection. We generated this ZIKV glycoprotein variant and found that while it had little impact on infection in mosquitoes, it reduced replication in human cells and mice and increased virus sensitivity to ammonium chloride, as seen for alphaviruses. In light of these results and given our alphavirus ij loop studies, we mutated a conserved alanine at the tip of the flavivirus ij loop to valine to test its effect on ZIKV infectivity. Interestingly, this mutation inhibited infectious virion production of ZIKV and yellow fever virus, but not West Nile virus. Together, these studies show that shared domains of the alphavirus and flavivirus class II fusion glycoproteins harbor structurally analogous residues that are functionally important and contribute to virus infection Arboviruses are a significant global public health threat, yet there are no antivirals targeting these viruses. This problem is in part due to our lack of knowledge of the molecular mechanisms involved in the arbovirus life cycle. In particular, virus entry and assembly are essential processes in the virus life cycle and steps that can be targeted for the development of antiviral therapies. Therefore, understanding common, fundamental mechanisms used by different arboviruses for entry and assembly is essential. In this study, we show that flavivirus and alphavirus residues located in structurally conserved and analogous regions of the class II fusion proteins contribute to common mechanisms of entry, dissemination, and infectious-virion production. These studies highlight how class II fusion proteins function and provide novel targets for development of antivirals.
Topics: A549 Cells; Alphavirus; Ammonium Chloride; Animals; Culicidae; Flavivirus; Humans; Interferon Type I; Mice; Mice, Mutant Strains; Mutation; Protein Domains; Viral Fusion Proteins; Viral Nonstructural Proteins; Virion; Virus Assembly; Virus Internalization; Virus Replication; Zika Virus; Zika Virus Infection
PubMed: 34757841
DOI: 10.1128/JVI.01774-21 -
Future Microbiology Sep 2009Alphaviruses are small, spherical, enveloped, positive-sense ssRNA viruses responsible for a considerable number of human and animal diseases. Alphavirus members include... (Review)
Review
Alphaviruses are small, spherical, enveloped, positive-sense ssRNA viruses responsible for a considerable number of human and animal diseases. Alphavirus members include Chikungunya virus, Sindbis virus, Semliki Forest virus, the western, eastern and Venezuelan equine encephalitis viruses, and the Ross River virus. Alphaviruses can cause arthritic diseases and encephalitis in humans and animals and continue to be a worldwide threat. The viruses are transmitted by blood-sucking arthropods, and replicate in both arthropod and vertebrate hosts. Alphaviruses form spherical particles (65-70 nm in diameter) with icosahedral symmetry and a triangulation number of four. The icosahedral structures of alphaviruses have been defined to very high resolutions by cryo-electron microscopy and crystallographic studies. In this review, we summarize the major events in alphavirus infection: entry, replication, assembly and budding. We focus on data acquired from structural and functional studies of the alphaviruses. These structural and functional data provide a broader perspective of the virus lifecycle and structure, and allow additional insight into these important viruses.
Topics: Alphavirus; Models, Biological; Models, Molecular; Viral Proteins; Virion; Virus Assembly; Virus Internalization; Virus Replication
PubMed: 19722838
DOI: 10.2217/fmb.09.59 -
Viruses Feb 2018Alphaviruses are enveloped positive sense RNA viruses and include serious human pathogens, such as the encephalitic alphaviruses and Chikungunya virus. Alphaviruses are... (Review)
Review
Alphaviruses are enveloped positive sense RNA viruses and include serious human pathogens, such as the encephalitic alphaviruses and Chikungunya virus. Alphaviruses are transmitted to humans primarily by mosquito vectors and include species that are classified as emerging pathogens. Alphaviruses assemble highly organized, spherical particles that bud from the plasma membrane. In this review, we discuss what is known about the alphavirus exit pathway during a cellular infection. We describe the viral protein interactions that are critical for virus assembly/budding and the host factors that are involved, and we highlight the recent discovery of cell-to-cell transmission of alphavirus particles via intercellular extensions. Lastly, we discuss outstanding questions in the alphavirus exit pathway that may provide important avenues for future research.
Topics: Alphavirus; Alphavirus Infections; Animals; Biological Transport; Host-Pathogen Interactions; Humans; Protein Binding; Virus Assembly; Virus Internalization; Virus Release; Virus Replication
PubMed: 29470397
DOI: 10.3390/v10020089 -
MBio Feb 2017Sindbis virus (SINV [genus , family ]) is an enveloped, mosquito-borne virus. Alphaviruses cause cytolytic infections in mammalian cells while establishing...
Sindbis virus (SINV [genus , family ]) is an enveloped, mosquito-borne virus. Alphaviruses cause cytolytic infections in mammalian cells while establishing noncytopathic, persistent infections in mosquito cells. Mosquito vector adaptation of alphaviruses is a major factor in the transmission of epidemic strains of alphaviruses. Though extensive studies have been performed on infected mammalian cells, the morphological and structural elements of alphavirus replication and assembly remain poorly understood in mosquito cells. Here we used high-resolution live-cell imaging coupled with single-particle tracking and electron microscopy analyses to delineate steps in the alphavirus life cycle in both the mammalian host cell and insect vector cells. Use of dually labeled SINV in conjunction with cellular stains enabled us to simultaneously determine the spatial and temporal differences of alphavirus replication complexes (RCs) in mammalian and insect cells. We found that the nonstructural viral proteins and viral RNA in RCs exhibit distinct spatial organization in mosquito cytopathic vacuoles compared to replication organelles from mammalian cells. We show that SINV exploits filopodial extensions for virus dissemination in both cell types. Additionally, we propose a novel mechanism for replication complex formation around glycoprotein-containing vesicles in mosquito cells that produced internally released particles that were seen budding from the vesicles by live imaging. Finally, by characterizing mosquito cell lines that were persistently infected with fluorescent virus, we show that the replication and assembly machinery are highly modified, and this allows continuous production of alphaviruses at reduced levels. Reemerging mosquito-borne alphaviruses cause serious human epidemics worldwide. Several structural and imaging studies have helped to define the life cycle of alphaviruses in mammalian cells, but the mode of virus replication and assembly in the invertebrate vector and mechanisms producing two disease outcomes in two types of cells are yet to be identified. Using transmission electron microscopy and live-cell imaging with dual fluorescent protein-tagged SINV, we show that while insect and mammalian cells display similarities in entry and exit, they present distinct spatial and temporal organizations in virus replication and assembly. By characterizing acutely and persistently infected cells, we provide new insights into alphavirus replication and assembly in two distinct hosts, resulting in high-titer virus production in mammalian cells and continuous virus production at reduced levels in mosquito cells-presumably a prerequisite for alphavirus maintenance in nature.
Topics: Aedes; Animals; Cell Line; DNA Replication; Humans; Kinetics; Life Cycle Stages; Luminescent Proteins; Microscopy, Energy-Filtering Transmission Electron; RNA, Viral; Sindbis Virus; Spatio-Temporal Analysis; Virus Assembly; Virus Replication; Red Fluorescent Protein
PubMed: 28196962
DOI: 10.1128/mBio.02294-16 -
Cell Reports May 2023Arboviruses are public health threats that cause explosive outbreaks. Major determinants of arbovirus transmission, geographic spread, and pathogenesis are the magnitude...
Arboviruses are public health threats that cause explosive outbreaks. Major determinants of arbovirus transmission, geographic spread, and pathogenesis are the magnitude and duration of viremia in vertebrate hosts. Previously, we determined that multiple alphaviruses are cleared efficiently from murine circulation by the scavenger receptor MARCO (Macrophage receptor with collagenous structure). Here, we define biochemical features on chikungunya (CHIKV), o'nyong 'nyong (ONNV), and Ross River (RRV) viruses required for MARCO-dependent clearance in vivo. In vitro, MARCO expression promotes binding and internalization of CHIKV, ONNV, and RRV via the scavenger receptor cysteine-rich (SRCR) domain. Furthermore, we observe species-specific effects of the MARCO SRCR domain on CHIKV internalization, where those from known amplification hosts fail to promote CHIKV internalization. Consistent with this observation, CHIKV is inefficiently cleared from the circulation of rhesus macaques in contrast with mice. These findings suggest a role for MARCO in determining whether a vertebrate serves as an amplification or dead-end host following CHIKV infection.
Topics: Animals; Mice; Chikungunya virus; Viremia; Macaca mulatta; Chikungunya Fever; Disease Outbreaks; Receptors, Immunologic
PubMed: 37083332
DOI: 10.1016/j.celrep.2023.112418 -
Viruses May 2021Alphavirus non-structural proteins 1-4 (nsP1, nsP2, nsP3, and nsP4) are known to be crucial for alphavirus RNA replication and translation. To date, nsP3 has been... (Review)
Review
The Putative Roles and Functions of Indel, Repetition and Duplication Events in Alphavirus Non-Structural Protein 3 Hypervariable Domain (nsP3 HVD) in Evolution, Viability and Re-Emergence.
Alphavirus non-structural proteins 1-4 (nsP1, nsP2, nsP3, and nsP4) are known to be crucial for alphavirus RNA replication and translation. To date, nsP3 has been demonstrated to mediate many virus-host protein-protein interactions in several fundamental alphavirus mechanisms, particularly during the early stages of replication. However, the molecular pathways and proteins networks underlying these mechanisms remain poorly described. This is due to the low genetic sequence homology of the nsP3 protein among the alphavirus species, especially at its 3' C-terminal domain, the hypervariable domain (HVD). Moreover, the nsP3 HVD is almost or completely intrinsically disordered and has a poor ability to form secondary structures. Evolution in the nsP3 HVD region allows the alphavirus to adapt to vertebrate and insect hosts. This review focuses on the putative roles and functions of indel, repetition, and duplication events that have occurred in the alphavirus nsP3 HVD, including characterization of the differences and their implications for specificity in the context of virus-host interactions in fundamental alphavirus mechanisms, which have thus directly facilitated the evolution, adaptation, viability, and re-emergence of these viruses.
Topics: Alphavirus; Animals; Binding Sites; Cell Line; Evolution, Molecular; Host-Pathogen Interactions; Humans; Mice; Viral Nonstructural Proteins; Virus Replication
PubMed: 34071712
DOI: 10.3390/v13061021 -
Viruses Aug 2023Chikungunya virus (CHIKV), an alphavirus transmitted by mosquitoes, has experienced a recent re-emergence in various regions of the world, leading to large-scale...
Chikungunya virus (CHIKV), an alphavirus transmitted by mosquitoes, has experienced a recent re-emergence in various regions of the world, leading to large-scale outbreaks [...].
Topics: Animals; Chikungunya virus; Culicidae; Disease Outbreaks
PubMed: 37632110
DOI: 10.3390/v15081768