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Advances in Virus Research 2022Alphaviruses are a large group (>30 species) of enveloped, positive-strand RNA viruses. The re-emergence of mosquito-transmitted alphaviruses associated with human... (Review)
Review
Alphaviruses are a large group (>30 species) of enveloped, positive-strand RNA viruses. The re-emergence of mosquito-transmitted alphaviruses associated with human diseases ranging from severe and potentially fatal neurological disease to chronic arthritic disease highlights the need to understand the biology and pathogenesis of alphaviruses. Here, we review the development and use of animal models of alphavirus transmission and human disease, and discuss areas for continued refinement of these models including possible avenues for future investigation.
Topics: Animals; Humans; Alphavirus Infections; Alphavirus; Disease Models, Animal
PubMed: 36307168
DOI: 10.1016/bs.aivir.2022.07.001 -
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 -
MBio Jun 2024Chikungunya virus (CHIKV) is an enveloped, positive-sense RNA virus that has re-emerged to cause millions of human infections worldwide. In humans, acute CHIKV infection...
Chikungunya virus (CHIKV) is an enveloped, positive-sense RNA virus that has re-emerged to cause millions of human infections worldwide. In humans, acute CHIKV infection causes fever and severe muscle and joint pain. Chronic and debilitating arthritis and joint pain can persist for months to years. To date, there are no approved antivirals against CHIKV. Recently, the ribonucleoside analog 4'-fluorouridine (4'-FlU) was reported as a highly potent orally available inhibitor of SARS-CoV-2, respiratory syncytial virus, and influenza virus replication. In this study, we assessed 4'-FlU's potency and breadth of inhibition against a panel of alphaviruses including CHIKV, and found that it broadly suppressed alphavirus production in cell culture. 4'-FlU acted on the viral RNA replication step, and the first 4 hours post-infection were the critical time for its antiviral effect. replication assays identified nsP4 as the target of inhibition. , treatment with 4'-FlU reduced disease signs, inflammatory responses, and viral tissue burden in mouse models of CHIKV and Mayaro virus infection. Treatment initiated at 2 hours post-infection was most effective; however, treatment initiated as late as 24-48 hours post-infection produced measurable antiviral effects in the CHIKV mouse model. 4'-FlU showed effective oral delivery in our mouse model and resulted in the accumulation of both 4'-FlU and its bioactive triphosphate form in tissues relevant to arthritogenic alphavirus pathogenesis. Together, our data indicate that 4'-FlU inhibits CHIKV infection and and is a promising oral therapeutic candidate against CHIKV infection.IMPORTANCEAlphaviruses including chikungunya virus (CHIKV) are mosquito-borne positive-strand RNA viruses that can cause various diseases in humans. Although compounds that inhibit CHIKV and other alphaviruses have been identified , there are no licensed antivirals against CHIKV. Here, we investigated a ribonucleoside analog, 4'-fluorouridine (4'-FlU), and demonstrated that it inhibited infectious virus production by several alphaviruses and reduced virus burden in mouse models of CHIKV and Mayaro virus infection. Our studies also indicated that 4'-FlU treatment reduced CHIKV-induced footpad swelling and reduced the production of pro-inflammatory cytokines. Inhibition in the mouse model correlated with effective oral delivery of 4'-FlU and accumulation of both 4'-FlU and its bioactive form in relevant tissues. In summary, 4'-FlU exhibits potential as a novel anti-alphavirus agent targeting the replication of viral RNA.
Topics: Virus Replication; Animals; Antiviral Agents; Mice; Chikungunya virus; Alphavirus; Uridine; Humans; Chikungunya Fever; Disease Models, Animal; Cell Line; Chlorocebus aethiops; Female; Vero Cells
PubMed: 38700353
DOI: 10.1128/mbio.00420-24 -
International Review of Cell and... 2022Self-replicating RNA viral vectors have been engineered for both prophylactic and therapeutic applications. Mainly the areas of infectious diseases and cancer have been...
Self-replicating RNA viral vectors have been engineered for both prophylactic and therapeutic applications. Mainly the areas of infectious diseases and cancer have been targeted. Both positive and negative strand RNA viruses have been utilized including alphaviruses, flaviviruses, measles viruses and rhabdoviruses. The high-level of RNA amplification has provided efficient expression of viral surface proteins and tumor antigens. Immunization studies in animal models have elicit robust neutralizing antibody responses. In the context of infectious diseases, immunization with self-replicating RNA viral vectors has provided protection against challenges with lethal doses of pathogens in animal models. Similarly, immunization with vectors expressing tumor antigens has resulted in tumor regression and eradication and protection against tumor challenges in animal models. The transient nature and non-integration of viral RNA into the host genome are ideal features for vaccine development. Moreover, self-replicating RNA viral vectors show great flexibility as they can be applied as recombinant viral particles, RNA replicons or DNA replicon plasmids. Several clinical trials have been conducted especially in the area of cancer immunotherapy.
Topics: Alphavirus; Animals; Antigens, Neoplasm; Genetic Vectors; Neoplasms; RNA
PubMed: 36064268
DOI: 10.1016/bs.ircmb.2022.03.006 -
Nature Communications Oct 2023Arthritogenic alphaviruses are positive-strand RNA viruses that cause debilitating musculoskeletal diseases affecting millions worldwide. A recent discovery identified...
Arthritogenic alphaviruses are positive-strand RNA viruses that cause debilitating musculoskeletal diseases affecting millions worldwide. A recent discovery identified the four-and-a-half-LIM domain protein 1 splice variant A (FHL1A) as a crucial host factor interacting with the hypervariable domain (HVD) of chikungunya virus (CHIKV) nonstructural protein 3 (nsP3). Here, we show that acute and chronic chikungunya disease in humans correlates with elevated levels of FHL1. We generated FHL1 mice, which when infected with CHIKV or o'nyong-nyong virus (ONNV) displayed reduced arthritis and myositis, fewer immune infiltrates, and reduced proinflammatory cytokine/chemokine outputs, compared to infected wild-type (WT) mice. Interestingly, disease signs were comparable in FHL1 and WT mice infected with arthritogenic alphaviruses Ross River virus (RRV) or Mayaro virus (MAYV). This aligns with pull-down assay data, which showed the ability of CHIKV and ONNV nsP3 to interact with FHL1, while RRV and MAYV nsP3s did not. We engineered a CHIKV mutant unable to bind FHL1 (CHIKV-ΔFHL1), which was avirulent in vivo. Following inoculation with CHIKV-ΔFHL1, mice were protected from disease upon challenge with CHIKV and ONNV, and viraemia was significantly reduced in RRV- and MAYV-challenged mice. Targeting FHL1-binding as an approach to vaccine design could lead to breakthroughs in mitigating alphaviral disease.
Topics: Animals; Humans; Mice; Arthritis; Chikungunya Fever; Chikungunya virus; Intracellular Signaling Peptides and Proteins; LIM Domain Proteins; Muscle Proteins; O'nyong-nyong Virus; Vaccines
PubMed: 37884534
DOI: 10.1038/s41467-023-42330-2 -
The Journal of Infectious Diseases Oct 2023The Togaviridae family, genus, Alphavirus, includes several mosquito-borne human pathogens with the potential to spread to near pandemic proportions. Most of these are...
The Togaviridae family, genus, Alphavirus, includes several mosquito-borne human pathogens with the potential to spread to near pandemic proportions. Most of these are zoonotic, with spillover infections of humans and domestic animals, but a few such as chikungunya virus (CHIKV) have the ability to use humans as amplification hosts for transmission in urban settings and explosive outbreaks. Most alphaviruses cause nonspecific acute febrile illness, with pathogenesis sometimes leading to either encephalitis or arthralgic manifestations with severe and chronic morbidity and occasional mortality. The development of countermeasures, especially against CHIKV and Venezuelan equine encephalitis virus that are major threats, has included vaccines and antibody-based therapeutics that are likely to also be successful for rapid responses with other members of the family. However, further work with these prototypes and other alphavirus pathogens should target better understanding of human tropism and pathogenesis, more comprehensive identification of cellular receptors and entry, and better understanding of structural mechanisms of neutralization.
Topics: Animals; Horses; Humans; Chikungunya virus; Culicidae; Research
PubMed: 37849399
DOI: 10.1093/infdis/jiac326 -
Journal of Virology Sep 2021Alphaviruses have positive-strand RNA genomes containing two open reading frames (ORFs). The first ORF encodes the nonstructural (ns) polyproteins P123 and P1234 that...
Alphaviruses have positive-strand RNA genomes containing two open reading frames (ORFs). The first ORF encodes the nonstructural (ns) polyproteins P123 and P1234 that act as precursors for the subunits of the viral RNA replicase (nsP1 to nsP4). Processing of P1234 leads to the formation of a negative-strand replicase consisting of nsP4 (RNA polymerase) and P123 components. Subsequent processing of P123 results in a positive-strand replicase. The second ORF encoding the structural proteins is expressed via the synthesis of a subgenomic RNA. Alphavirus replicase is capable of using template RNAs that contain essential -active sequences. Here, we demonstrate that the replicases of nine alphaviruses, expressed in the form of separate P123 and nsP4 components, are active. Their activity depends on the abundance of nsP4. The match of nsP4 to its template strongly influences efficient subgenomic RNA synthesis. nsP4 of Barmah Forest virus (BFV) formed a functional replicase only with matching P123, while nsP4s of other alphaviruses were compatible also with several heterologous P123s. The P123 components of Venezuelan equine encephalitis virus and Sindbis virus (SINV) required matching nsP4s, while P123 of other viruses could form active replicases with different nsP4s. Chimeras of Semliki Forest virus, harboring the nsP4 of chikungunya virus, Ross River virus, BFV, or SINV were viable. In contrast, chimeras of SINV, harboring an nsP4 from different alphaviruses, exhibited a temperature-sensitive phenotype. These findings highlight the possibility for formation of new alphaviruses via recombination events and provide a novel approach for the development of attenuated chimeric viruses for vaccination strategies. A key element of every virus with an RNA genome is the RNA replicase. Understanding the principles of RNA replicase formation and functioning is therefore crucial for understanding and responding to the emergence of new viruses. Reconstruction of the replicases of nine alphaviruses from nsP4 and P123 polyproteins revealed that the nsP4 of the majority of alphaviruses, including the mosquito-specific Eilat virus, could form a functional replicase with P123 originating from a different virus, and the corresponding chimeric viruses were replication-competent. nsP4 also had an evident role in determining the template RNA preference and the efficiency of RNA synthesis. The revealed broad picture of the compatibility of the replicase components of alphaviruses is important for understanding the formation and functioning of the alphavirus RNA replicase and highlights the possibilities for recombination between different alphavirus species.
Topics: Alphavirus; Alphavirus Infections; Animals; Base Sequence; Cell Line; DNA-Directed RNA Polymerases; Humans; Polyproteins; RNA, Viral; RNA-Dependent RNA Polymerase; Viral Nonstructural Proteins; Viral Replicase Complex Proteins; Virus Replication
PubMed: 34319783
DOI: 10.1128/JVI.00355-21 -
Journal of Virology Oct 2023Alphaviruses threaten public health continuously, and Getah virus (GETV) is a re-emerging alphavirus that can potentially infect humans. Approved antiviral drugs and...
Alphaviruses threaten public health continuously, and Getah virus (GETV) is a re-emerging alphavirus that can potentially infect humans. Approved antiviral drugs and vaccines against alphaviruses are few available, but several host antiviral factors have been reported. Here, we used GETV as a model of alphaviruses to screen for additional host factors. Tetrachlorodibenzo-p-dioxin-inducible poly(ADP ribose) polymerase was identified to inhibit GETV replication by inducing ubiquitination of the glycoprotein E2, causing its degradation by recruiting the E3 ubiquitin ligase membrane-associated RING-CH8 (MARCH8). Using GETV as a model virus, focusing on the relationship between viral structural proteins and host factors to screen antiviral host factors provides new insights for antiviral studies on alphaviruses.
Topics: Humans; Alphavirus; Glycoproteins; Host Microbial Interactions; Nucleoside Transport Proteins; Poly(ADP-ribose) Polymerases; Transcriptome; Ubiquitination; Viral Structural Proteins; Virus Replication
PubMed: 37768084
DOI: 10.1128/jvi.00591-23 -
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 -
Progress in Molecular Biology and... 2015Viruses have evolved to exploit the vast complexity of cellular processes for their success within the host cell. The entry mechanisms of enveloped viruses (viruses with... (Review)
Review
Viruses have evolved to exploit the vast complexity of cellular processes for their success within the host cell. The entry mechanisms of enveloped viruses (viruses with a surrounding outer lipid bilayer membrane) are usually classified as being either endocytotic or fusogenic. Different mechanisms have been proposed for Alphavirus entry and genome delivery. Indirect observations led to a general belief that enveloped viruses can infect cells either by protein-assisted fusion with the plasma membrane in a pH-independent manner or by endocytosis and fusion with the endocytic vacuole in a low-pH environment. The mechanism of Alphavirus penetration has been recently revisited using direct observation of the processes by electron microscopy under conditions of different temperatures and time progression. Under conditions nonpermissive for endocytosis or any vesicular transport, events occur which allow the entry of the virus genome into the cells. When drug inhibitors of cellular functions are used to prevent entry, only ionophores are found to significantly inhibit RNA delivery. Arboviruses are agents of significant human and animal disease; therefore, strategies to control infections are needed and include development of compounds which will block critical steps in the early infection events. It appears that current evidence points to an entry mechanism, in which alphaviruses infect cells by direct penetration of cell plasma membranes through a pore structure formed by virus and, possibly, host proteins.
Topics: Alphavirus; Animals; Genome; Host-Pathogen Interactions; Humans; Membrane Fusion; Models, Biological; Virus Internalization
PubMed: 25595800
DOI: 10.1016/bs.pmbts.2014.10.002