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Yao Z, Ramachandran S, Huang S, Kim E, Jami-Alahmadi Y, Kaushal P, Bouhaddou M, Wohlschlegel JA, Li MM. Interaction of chikungunya virus glycoproteins with macrophage factors controls virion production. EMBO J 2024:10.1038/s44318-024-00193-3. [PMID: 39261662 DOI: 10.1038/s44318-024-00193-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 07/16/2024] [Accepted: 07/17/2024] [Indexed: 09/13/2024] Open
Abstract
Despite their role as innate sentinels, macrophages can serve as cellular reservoirs of chikungunya virus (CHIKV), a highly-pathogenic arthropod-borne alphavirus that has caused large outbreaks among human populations. Here, with the use of viral chimeras and evolutionary selection analysis, we define CHIKV glycoproteins E1 and E2 as critical for virion production in THP-1 derived human macrophages. Through proteomic analysis and functional validation, we further identify signal peptidase complex subunit 3 (SPCS3) and eukaryotic translation initiation factor 3 subunit K (eIF3k) as E1-binding host proteins with anti-CHIKV activities. We find that E1 residue V220, which has undergone positive selection, is indispensable for CHIKV production in macrophages, as its mutation attenuates E1 interaction with the host restriction factors SPCS3 and eIF3k. Finally, we show that the antiviral activity of eIF3k is translation-independent, and that CHIKV infection promotes eIF3k translocation from the nucleus to the cytoplasm, where it associates with SPCS3. These functions of CHIKV glycoproteins late in the viral life cycle provide a new example of an intracellular evolutionary arms race with host restriction factors, as well as potential targets for therapeutic intervention.
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Affiliation(s)
- Zhenlan Yao
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sangeetha Ramachandran
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
| | - Serina Huang
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Erin Kim
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Yasaman Jami-Alahmadi
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Prashant Kaushal
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
- Institute for Quantitative and Computational Biosciences, University of California, Los Angeles, Los Angeles, CA, USA
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, USA
| | - Mehdi Bouhaddou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
- Institute for Quantitative and Computational Biosciences, University of California, Los Angeles, Los Angeles, CA, USA
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, USA
| | - James A Wohlschlegel
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Melody Mh Li
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA.
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, USA.
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2
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Hodoameda P, Ebel GD, Mukhopadhyay S, Clem RJ. Extreme infectious titer variability in individual Aedes aegypti mosquitoes infected with Sindbis virus is associated with both differences in virus population structure and dramatic disparities in specific infectivity. PLoS Pathog 2024; 20:e1012047. [PMID: 38412195 PMCID: PMC10923411 DOI: 10.1371/journal.ppat.1012047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 03/08/2024] [Accepted: 02/13/2024] [Indexed: 02/29/2024] Open
Abstract
Variability in how individuals respond to pathogens is a hallmark of infectious disease, yet the basis for individual variation in host response is often poorly understood. The titer of infectious virus among individual mosquitoes infected with arboviruses is frequently observed to vary by several orders of magnitude in a single experiment, even when the mosquitoes are highly inbred. To better understand the basis for this titer variation, we sequenced populations of Sindbis virus (SINV) obtained from individual infected Aedes aegypti mosquitoes that, despite being from a highly inbred laboratory colony, differed in their titers of infectious virus by approximately 10,000-fold. We observed genetic differences between these virus populations that indicated the virus present in the midguts of low titer mosquitoes was less fit than that of high titer mosquitoes, possibly due to founder effects that occurred during midgut infection. Furthermore, we found dramatic differences in the specific infectivity or SI (the ratio of infectious units/viral genome equivalents) between these virus populations, with the SI of low titer mosquitoes being up to 10,000-fold lower than that of high titer mosquitoes. Despite having similar amounts of viral genomes, low titer mosquitoes appeared to contain less viral particles, suggesting that viral genomes were packaged into virions less efficiently than in high titer mosquitoes. Finally, antibiotic treatment, which has been shown to suppress mosquito antiviral immunity, caused an increase in SI. Our results indicate that the extreme variation that is observed in SINV infectious titer between individual Ae. aegypti mosquitoes is due to both genetic differences between virus populations and to differences in the proportion of genomes that are packaged into infectious particles.
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Affiliation(s)
- Peter Hodoameda
- Division of Biology, Kansas State University, Manhattan, Kansas United States of America
| | - Gregory D. Ebel
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado United States of America
| | - Suchetana Mukhopadhyay
- Department of Biology, Indiana University, Bloomington, Indiana United States of America
| | - Rollie J. Clem
- Division of Biology, Kansas State University, Manhattan, Kansas United States of America
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3
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Kaavya K, Tharakan J, Joshi CO, Aneesh EM. Role of vertically transmitted viral and bacterial endosymbionts of Aedes mosquitoes. Does Paratransgenesis influence vector-borne disease control? Symbiosis 2022. [DOI: 10.1007/s13199-022-00836-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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4
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Zhang Y, Dai Y, Wang J, Xu Y, Li Z, Lu J, Xu Y, Zhong J, Ding SW, Li Y. Mouse circulating extracellular vesicles contain virus-derived siRNAs active in antiviral immunity. EMBO J 2022; 41:e109902. [PMID: 35343600 PMCID: PMC9156966 DOI: 10.15252/embj.2021109902] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 02/24/2022] [Accepted: 03/04/2022] [Indexed: 12/29/2022] Open
Abstract
Induction and suppression of antiviral RNA interference (RNAi) has been observed in mammals during infection with at least seven distinct RNA viruses, including some that are pathogenic in humans. However, while the cell-autonomous immune response mediated by antiviral RNAi is gradually being recognized, little is known about systemic antiviral RNAi in mammals. Furthermore, extracellular vesicles (EVs) also function in viral signal spreading and host immunity. Here, we show that upon antiviral RNAi activation, virus-derived small-interfering RNAs (vsiRNAs) from Nodamura virus (NoV), Sindbis virus (SINV), and Zika virus (ZIKV) enter the murine bloodstream via EVs for systemic circulation. vsiRNAs in the EVs are biologically active, since they confer RNA-RNA homology-dependent antiviral activity in both cultured cells and infant mice. Moreover, we demonstrate that vaccination with a live-attenuated virus, rendered deficient in RNAi suppression, induces production of stably maintained vsiRNAs and confers protective immunity against virus infection in mice. This suggests that vaccination with live-attenuated VSR (viral suppressor of RNAi)-deficient mutant viruses could be a new strategy to induce immunity.
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Affiliation(s)
- Yuqiang Zhang
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Yunpeng Dai
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Jiaxin Wang
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Yan Xu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Zhe Li
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Jinfeng Lu
- Gertrude H. Sergievsky Center, Columbia University, New York, NY, USA.,Department of Microbiology and Plant Pathology, University of California, Riverside, CA, USA
| | - Yongfen Xu
- Unit of Viral Hepatitis, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Jin Zhong
- Unit of Viral Hepatitis, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Shou-Wei Ding
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA, USA
| | - Yang Li
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
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5
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Construction and characterization of a full-length infectious clone of Getah virus in vivo. Virol Sin 2022; 37:348-357. [PMID: 35288349 PMCID: PMC9243596 DOI: 10.1016/j.virs.2022.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 03/02/2022] [Indexed: 11/23/2022] Open
Abstract
Getah virus (GETV) is a mosquito-borne virus of the genus Alphavirus in the family Togaviridae and, in recent years, it has caused several outbreaks in animals. The molecular basis for GETV pathogenicity is not well understood. Therefore, a reverse genetic system of GETV is needed to produce genetically modified viruses for the study of the viral replication and its pathogenic mechanism. Here, we generated a CMV-driven infectious cDNA clone based on a previously isolated GETV strain, GX201808 (pGETV-GX). Transfection of pGETV-GX into BHK-21 cells resulted in the recovery of a recombinant virus (rGETV-GX) which showed similar growth characteristics to its parental virus. Then three-day-old mice were experimentally infected with either the parental or recombinant virus. The recombinant virus showed milder pathogenicity than the parental virus in the mice. Based on the established CMV-driven cDNA clone, subgenomic promoter and two restriction enzyme sites (BamHI and EcoRI) were introduced into the region between E1 protein and 3′UTR. Then the green fluorescent protein (GFP), red fluorescent protein (RFP) and improved light-oxygen-voltage (iLOV) genes were inserted into the restriction enzyme sites. Transfection of the constructs carrying the reporter genes into BHK-21 cells proved the rescue of the recombinant reporter viruses. Taken together, the establishment of a reverse genetic system for GETV provides a valuable tool for the study of the virus life cycle, and to aid the development of genetically engineered GETVs as vectors for foreign gene expression. Generation and recovery of a CMV-driven infectious cDNA clone of GETV isolate, GX201808 (pGETV-GX). The recombinant virus showed milder pathogenicity than the parental virus in a mouse model. The Getah virus infectious clone can be used as a vector for expressing reporter genes.
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6
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Investigation of Biological Factors Contributing to Individual Variation in Viral Titer after Oral Infection of Aedes aegypti Mosquitoes by Sindbis Virus. Viruses 2022; 14:v14010131. [PMID: 35062335 PMCID: PMC8780610 DOI: 10.3390/v14010131] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 12/21/2022] Open
Abstract
The mechanisms involved in determining arbovirus vector competence, or the ability of an arbovirus to infect and be transmitted by an arthropod vector, are still incompletely understood. It is well known that vector competence for a particular arbovirus can vary widely among different populations of a mosquito species, which is generally attributed to genetic differences between populations. What is less understood is the considerable variability (up to several logs) that is routinely observed in the virus titer between individual mosquitoes in a single experiment, even in mosquitoes from highly inbred lines. This extreme degree of variation in the virus titer between individual mosquitoes has been largely ignored in past studies. We investigated which biological factors can affect titer variation between individual mosquitoes of a laboratory strain of Aedes aegypti, the Orlando strain, after Sindbis virus infection. Greater titer variation was observed after oral versus intrathoracic infection, suggesting that the midgut barrier contributes to titer variability. Among the other factors tested, only the length of the incubation period affected the degree of titer variability, while virus strain, mosquito strain, mosquito age, mosquito weight, amount of blood ingested, and virus concentration in the blood meal had no discernible effect. We also observed differences in culture adaptability and in the ability to orally infect mosquitoes between virus populations obtained from low and high titer mosquitoes, suggesting that founder effects may affect the virus titer in individual mosquitoes, although other explanations also remain possible.
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7
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Xu Y, Zhong Z, Ren Y, Ma L, Ye Z, Gao C, Wang J, Li Y. Antiviral RNA interference in disease vector (Asian longhorned) ticks. PLoS Pathog 2021; 17:e1010119. [PMID: 34860862 PMCID: PMC8673602 DOI: 10.1371/journal.ppat.1010119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 12/15/2021] [Accepted: 11/16/2021] [Indexed: 11/18/2022] Open
Abstract
Disease vectors such as mosquitoes and ticks play a major role in the emergence and re-emergence of human and animal viral pathogens. Compared to mosquitoes, however, much less is known about the antiviral responses of ticks. Here we showed that Asian longhorned ticks (Haemaphysalis longicornis) produced predominantly 22-nucleotide virus-derived siRNAs (vsiRNAs) in response to severe fever with thrombocytopenia syndrome virus (SFTSV, an emerging tick-borne virus), Nodamura virus (NoV), or Sindbis virus (SINV) acquired by blood feeding. Notably, experimental acquisition of NoV and SINV by intrathoracic injection also initiated viral replication and triggered the production of vsiRNAs in H. longicornis. We demonstrated that a mutant NoV deficient in expressing its viral suppressor of RNAi (VSR) replicated to significantly lower levels than wildtype NoV in H. longicornis, but accumulated to higher levels after knockdown of the tick Dicer2-like protein identified by phylogeny comparison. Moreover, the expression of a panel of known animal VSRs in cis from the genome of SINV drastically enhanced the accumulation of the recombinant viruses. This study establishes a novel model for virus-vector-mouse experiments with longhorned ticks and provides the first in vivo evidence for an antiviral function of the RNAi response in ticks. Interestingly, comparing the accumulation levels of SINV recombinants expressing green fluorescent protein or SFTSV proteins identified the viral non-structural protein as a putative VSR. Elucidating the function of ticks’ antiviral RNAi pathway in vivo is critical to understand the virus-host interaction and the control of tick-borne viral pathogens. Tick-borne diseases (TBDs) are the most common illnesses transmitted by ticks, and the annual number of reported TBD cases continues to increase. The Asian longhorned tick, a vector associated with at least 30 human pathogens, is native to eastern Asia and recently reached the USA as an emerging disease threat. Newly identified tick-transmitted pathogens continue to be reported, raising concerns about how TBDs occur. Interestingly, tick can harbor pathogens without being affected themselves. For viral infections, ticks have their own immune systems that protect them from infection. Meanwhile, tick-borne viruses have evolved to avoid these defenses as they establish themselves within the vector. Here, we show in detail that infecting longhorned ticks with distinct arthropod-borne RNA viruses through two approaches natural blood feeding and injection, all induce the production of vsiRNAs. Dicer2-like homolog plays a role in regulating antiviral RNAi responses as knocking down of this gene enhanced viral replication. Furthermore, we demonstrate that tick antiviral RNAi responses are inhibited through expression heterologous VSR proteins in recombinant SINV. We identify both the virus and tick factors are critical components to understanding TBDs. Importantly, our study introduces a novel, in vivo virus-vector-mouse model system for exploring TBDs in the future.
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Affiliation(s)
- Yan Xu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Zhengwei Zhong
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Yanxin Ren
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Liting Ma
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Zhi Ye
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Chuang Gao
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Jingwen Wang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
- * E-mail: (JW); (YL)
| | - Yang Li
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
- * E-mail: (JW); (YL)
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8
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Zhang Y, Li Z, Ye Z, Xu Y, Wang B, Wang C, Dai Y, Lu J, Lu B, Zhang W, Li Y. The activation of antiviral RNA interference not only exists in neural progenitor cells but also in somatic cells in mammals. Emerg Microbes Infect 2021; 9:1580-1589. [PMID: 32576094 PMCID: PMC7473182 DOI: 10.1080/22221751.2020.1787798] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The RNA interference (RNAi) pathway directs an important antiviral immunity mechanism in plants and invertebrates. Recently, we and others have demonstrated that the antiviral RNAi response is also conserved in mammals, at least to five distinct RNA viruses, including Zika virus (ZIKV). ZIKV may preferentially infect neuronal progenitor cells (NPCs) in the developing foetal brain. Ex vivo ZIKV infection induces RNAi-mediated antiviral response in human NPCs, but not in the more differentiated NPCs or somatic cells. However, litter is known about the in vivo property or function of the virus-derived small-interfering RNAs (vsiRNAs) targeting ZIKV. Here we report a surprising observation: different from ex vivo observations, viral small RNAs (vsRNAs) targeting ZIKV were produced in vivo upon infection in both central neuron system (CNS) and muscle tissues. In addition, our findings demonstrate the production of canonical vsiRNAs in murine CNS upon antiviral RNAi activation by Sindbis virus (SINV), suggesting the possibility of antiviral immune strategy applied by mammals in the CNS.
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Affiliation(s)
- Yuqiang Zhang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Zhe Li
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Zhi Ye
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Yan Xu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Binbin Wang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Congcong Wang
- State Key Laboratory of Medical Neurobiology, School of Life Sciences, Fudan University, Shanghai, China
| | - Yunpeng Dai
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Jinfeng Lu
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Boxun Lu
- State Key Laboratory of Medical Neurobiology, School of Life Sciences, Fudan University, Shanghai, China
| | - Wanju Zhang
- Department of Pathogen Diagnosis and Biosafety, Shanghai Public Health Clinical Center, Fudan University, Shanghai, China
| | - Yang Li
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
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9
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Effects of Manipulating Fibroblast Growth Factor Expression on Sindbis Virus Replication In Vitro and in Aedes aegypti Mosquitoes. Viruses 2020; 12:v12090943. [PMID: 32858937 PMCID: PMC7552049 DOI: 10.3390/v12090943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/14/2020] [Accepted: 08/23/2020] [Indexed: 12/05/2022] Open
Abstract
Fibroblast growth factors (FGFs) are conserved among vertebrate and invertebrate animals and function in cell proliferation, cell differentiation, tissue repair, and embryonic development. A viral fibroblast growth factor (vFGF) homolog encoded by baculoviruses, a group of insect viruses, is involved in escape of baculoviruses from the insect midgut by stimulating basal lamina remodeling. This led us to investigate whether cellular FGF is involved in the escape of an arbovirus from mosquito midgut. In this study, the effects of manipulating FGF expression on Sindbis virus (SINV) replication and escape from the midgut of the mosquito vector Aedes aegypti were examined. RNAi-mediated silencing of either Ae. aegypti FGF (AeFGF) or FGF receptor (AeFGFR) expression reduced SINV replication following oral infection of Ae. aegypti mosquitoes. However, overexpression of baculovirus vFGF using recombinant SINV constructs had no effect on replication of these viruses in cultured mosquito or vertebrate cells, or in orally infected Ae. aegypti mosquitoes. We conclude that reducing FGF signaling decreases the ability of SINV to replicate in mosquitoes, but that overexpression of vFGF has no effect, possibly because endogenous FGF levels are already sufficient for optimal virus replication. These results support the hypothesis that FGF signaling, possibly by inducing remodeling of midgut basal lamina, is involved in arbovirus midgut escape following virus acquisition from a blood meal.
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Development of a rapid antiviral screening assay based on eGFP reporter virus of Mayaro virus. Antiviral Res 2019; 168:82-90. [PMID: 31150677 DOI: 10.1016/j.antiviral.2019.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 05/26/2019] [Accepted: 05/28/2019] [Indexed: 01/02/2023]
Abstract
Mayaro virus (MAYV) is a neglected mosquito-borne alphavirus that causes illness similar to Chikungunya (CHIKV), Dengue (DENV) and Zika virus (ZIKV). Currently, there is no specific treatment or vaccine against MAYV infection. To develop an efficient antiviral screening assay for MAYV, we constructed the infectious clones of MAYV strain BeAr 20290 and its eGFP reporter virus. The reporter virus exhibited high replication capacity indistinguishable with the wild type MAYV, and was genetically stable within at least five rounds of passages in BHK-21 cell. The expression of eGFP correlated well with the viral replication. Using the known inhibitor ribavirin, we confirmed that the MAYV-eGFP reporter virus could be used for antiviral screening to identify the specific inhibitors against MAYV. Using the MAYV-eGFP based antiviral assay, we found that the compound 6-Azauridine which had antiviral activity against CHIKV and SFV, showed a significant inhibitory effect on MAYV replication.
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11
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Carissimo G, Ng LFP. Understanding Molecular Pathogenesis with Chikungunya Virus Research Tools. Curr Top Microbiol Immunol 2019; 435:33-53. [PMID: 30888547 DOI: 10.1007/82_2019_158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Since its re-emergence in 2006, Chikungunya has been a major health concern in endemic areas. Transmitted by Aedes mosquitoes to mammalian hosts, Chikungunya leads to persistent debilitating symptoms in a high proportion of symptomatic human cases. In this review, we present several tools on the mosquito vector side as well as on the mammalian side that have been used to advance research on Chikungunya transmission and immunopathogenesis. These tools lead to key understandings of viral replication in both hosts, and innate and adaptive responses mediating virus clearance and pathology in mammals. This comprehension of viral mechanisms has allowed the development of promising treatment avenues in animal models that will need to be further explored. However, research efforts need to continue in order to develop better and unbiased tools to assess antiviral and treatment strategies as well as further understand immune mechanisms at play in human pathologies.
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Affiliation(s)
- Guillaume Carissimo
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore, Singapore
| | - Lisa F P Ng
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore, Singapore. .,Institute of Infection and Global Health, University of Liverpool, Liverpool, UK. .,Laboratory of Microbial Immunity, Singapore Immunology Network, 8A Biomedical Grove, #04-06, Immunos, Biopolis, 138648, Singapore.
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12
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Encapsidated Host Factors in Alphavirus Particles Influence Midgut Infection of Aedes aegypti. Viruses 2018; 10:v10050263. [PMID: 29772674 PMCID: PMC5977256 DOI: 10.3390/v10050263] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/08/2018] [Accepted: 05/11/2018] [Indexed: 12/25/2022] Open
Abstract
Transmission of mosquito-borne viruses requires the efficient infection of both a permissive vertebrate host and a competent mosquito vector. The infectivity of Sindbis virus (SINV), the type species of the Alphavirus genus, is influenced by both the original and new host cell. We have shown that infection of vertebrate cells by SINV, chikungunya virus (CHIKV), and Ross River virus (RRV) produces two subpopulations of virus particles separable based on density. In contrast, a single population of viral particles is produced by mosquito cells. Previous studies demonstrated that the denser vertebrate-derived particles and the mosquito-derived particles contain components of the small subunit of the host cell ribosome, whereas the less dense vertebrate-derived particles do not. Infection of mice with RRV showed that both particle subpopulations are produced in an infected vertebrate, but in a tissue specific manner with serum containing only the less dense version of the virus particles. Previous infectivity studies using SINV particles have shown that the denser particles (SINVHeavy) and mosquito derived particles SINVC6/36 are significantly more infectious in vertebrate cells than the less dense vertebrate derived particles (SINVLight). The current study shows that SINVLight particles, initiate the infection of the mosquito midgut more efficiently than SINVHeavy particles and that this enhanced infectivity is associated with an exacerbated immune response to SINVLight infection in midgut tissues. The enhanced infection of SINVLight is specific to the midgut as intrathoracically injected virus do not exhibit the same fitness advantage. Together, our data indicate a biologically significant role for the SINVLight subpopulation in the efficient transmission from infected vertebrates to the mosquito vector.
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13
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Li X, Meng K, Qiao J, Liu H, Zhong C, Liu Q. Identification of Aadnr1, a novel gene related to innate immunity and apoptosis in Aedes albopictus. Gene 2016; 587:18-26. [PMID: 27045774 DOI: 10.1016/j.gene.2016.03.046] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 03/24/2016] [Accepted: 03/25/2016] [Indexed: 12/01/2022]
Abstract
Innate immunity and apoptosis play critical roles in defending pathogens in insects. In Drosophila, Dnr1 was reported as a negative regulator of apoptosis and immune deficiency (Imd) pathway which belongs to innate immunity. Aedes albopictus is an important kind of arbovirus vector and becoming a significant threat to public health due to its rapid global expansion. Here we identified an ortholog of dnr1 from A. albopictus, named as Aadnr1. Aadnr1 encoded a putative protein containing an N-terminal FERM domain and a C-terminal RING domain. AaDnr1 shared high identity with dipteran insects Dnr1 orthologs. Phylogenetic analyses showed that the closest relative of AaDnr1 was Aedes aegypti Dnr1. Real-time PCR proved that Aadnr1 mRNA was expressed ubiquitously during developmental and adult stages. Transcriptional levels of Aadnr1 were decreased drastically in C6/36 cells underwent apoptosis induced by Actinomycin D (Act D) treatment. Partial silence of Aadnr1 enhanced Act D-induced caspase activity. When challenged by heat-inactivated E. coli, transcriptional level of Aadnr1 was also decreased dramatically in C6/36 cells. While when C6/36 cells were infected with Sindbis virus TE/GFP, transcriptional level of Aadnr1 was reduced and recovered repeatedly, with an overall decreasing trend. It was also shown in this study that similar to Drosophila Dnr1, RING domain destabilized AaDnr1 protein. Taken together, the study identified an innate immunity and apoptosis related gene Aadnr1 in A. albopictus.
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Affiliation(s)
- Xiaomei Li
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Kun Meng
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Jialu Qiao
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Hao Liu
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Chunyan Zhong
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Qingzhen Liu
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China.
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Franz AWE, Kantor AM, Passarelli AL, Clem RJ. Tissue Barriers to Arbovirus Infection in Mosquitoes. Viruses 2015; 7:3741-67. [PMID: 26184281 PMCID: PMC4517124 DOI: 10.3390/v7072795] [Citation(s) in RCA: 290] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Revised: 07/01/2015] [Accepted: 07/03/2015] [Indexed: 12/24/2022] Open
Abstract
Arthropod-borne viruses (arboviruses) circulate in nature between arthropod vectors and vertebrate hosts. Arboviruses often cause devastating diseases in vertebrate hosts, but they typically do not cause significant pathology in their arthropod vectors. Following oral acquisition of a viremic bloodmeal from a vertebrate host, the arbovirus disease cycle requires replication in the cellular environment of the arthropod vector. Once the vector has become systemically and persistently infected, the vector is able to transmit the virus to an uninfected vertebrate host. In order to systemically infect the vector, the virus must cope with innate immune responses and overcome several tissue barriers associated with the midgut and the salivary glands. In this review we describe, in detail, the typical arbovirus infection route in competent mosquito vectors. Based on what is known from the literature, we explain the nature of the tissue barriers that arboviruses are confronted with in a mosquito vector and how arboviruses might surmount these barriers. We also point out controversial findings to highlight particular areas that are not well understood and require further research efforts.
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Affiliation(s)
- Alexander W E Franz
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA.
| | - Asher M Kantor
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA.
| | | | - Rollie J Clem
- Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
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15
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Antiviral immunity of Anopheles gambiae is highly compartmentalized, with distinct roles for RNA interference and gut microbiota. Proc Natl Acad Sci U S A 2014; 112:E176-85. [PMID: 25548172 DOI: 10.1073/pnas.1412984112] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Arboviruses are transmitted by mosquitoes and other arthropods to humans and animals. The risk associated with these viruses is increasing worldwide, including new emergence in Europe and the Americas. Anopheline mosquitoes are vectors of human malaria but are believed to transmit one known arbovirus, o'nyong-nyong virus, whereas Aedes mosquitoes transmit many. Anopheles interactions with viruses have been little studied, and the initial antiviral response in the midgut has not been examined. Here, we determine the antiviral immune pathways of the Anopheles gambiae midgut, the initial site of viral infection after an infective blood meal. We compare them with the responses of the post-midgut systemic compartment, which is the site of the subsequent disseminated viral infection. Normal viral infection of the midgut requires bacterial flora and is inhibited by the activities of immune deficiency (Imd), JAK/STAT, and Leu-rich repeat immune factors. We show that the exogenous siRNA pathway, thought of as the canonical mosquito antiviral pathway, plays no detectable role in antiviral defense in the midgut but only protects later in the systemic compartment. These results alter the prevailing antiviral paradigm by describing distinct protective mechanisms in different body compartments and infection stages. Importantly, the presence of the midgut bacterial flora is required for full viral infectivity to Anopheles, in contrast to malaria infection, where the presence of the midgut bacterial flora is required for protection against infection. Thus, the enteric flora controls a reciprocal protection tradeoff in the vector for resistance to different human pathogens.
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Nasar F, Haddow AD, Tesh RB, Weaver SC. Eilat virus displays a narrow mosquito vector range. Parasit Vectors 2014; 7:595. [PMID: 25515341 PMCID: PMC4297418 DOI: 10.1186/s13071-014-0595-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 12/06/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Most alphaviruses are arthropod-borne and utilize mosquitoes as vectors for transmission to susceptible vertebrate hosts. This ability to infect both mosquitoes and vertebrates is essential for maintenance of most alphaviruses in nature. A recently characterized alphavirus, Eilat virus (EILV), isolated from a pool of Anopheles coustani s.I. is unable to replicate in vertebrate cell lines. The EILV host range restriction occurs at both attachment/entry as well as genomic RNA replication levels. Here we investigated the mosquito vector range of EILV in species encompassing three genera that are responsible for maintenance of other alphaviruses in nature. METHODS Susceptibility studies were performed in four mosquito species: Aedes albopictus, A. aegypti, Anopheles gambiae, and Culex quinquefasciatus via intrathoracic and oral routes utilizing EILV and EILV expressing red fluorescent protein (-eRFP) clones. EILV-eRFP was injected at 10(7) PFU/mL to visualize replication in various mosquito organs at 7 days post-infection. Mosquitoes were also injected with EILV at 10(4)-10(1) PFU/mosquito and virus replication was measured via plaque assays at day 7 post-infection. Lastly, mosquitoes were provided bloodmeals containing EILV-eRFP at doses of 10(9), 10(7), 10(5) PFU/mL, and infection and dissemination rates were determined at 14 days post-infection. RESULTS All four species were susceptible via the intrathoracic route; however, replication was 10-100 fold less than typical for most alphaviruses, and infection was limited to midgut-associated muscle tissue and salivary glands. A. albopictus was refractory to oral infection, while A. gambiae and C. quinquefasciatus were susceptible only at 10(9) PFU/mL dose. In contrast, A. aegypti was susceptible at both 10(9) and 10(7) PFU/mL doses, with body infection rates of 78% and 63%, and dissemination rates of 26% and 8%, respectively. CONCLUSIONS The exclusion of vertebrates in its maintenance cycle may have facilitated the adaptation of EILV to a single mosquito host. As a consequence, EILV displays a narrow vector range in mosquito species responsible for the maintenance of other alphaviruses in nature.
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Affiliation(s)
- Farooq Nasar
- Institute for Human Infections and Immunity, Center for Tropical Diseases, and Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
- Present Address: Virology Division, United States Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Frederick, MD, 21702, USA.
| | - Andrew D Haddow
- Present Address: Virology Division, United States Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Frederick, MD, 21702, USA.
| | - Robert B Tesh
- Institute for Human Infections and Immunity, Center for Tropical Diseases, and Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
| | - Scott C Weaver
- Institute for Human Infections and Immunity, Center for Tropical Diseases, and Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
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Steel JJ, Franz AWE, Sanchez-Vargas I, Olson KE, Geiss BJ. Subgenomic reporter RNA system for detection of alphavirus infection in mosquitoes. PLoS One 2013; 8:e84930. [PMID: 24367703 PMCID: PMC3868651 DOI: 10.1371/journal.pone.0084930] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 11/29/2013] [Indexed: 01/01/2023] Open
Abstract
Current methods for detecting real-time alphavirus (Family Togaviridae) infection in mosquitoes require the use of recombinant viruses engineered to express a visibly detectable reporter protein. These altered viruses expressing fluorescent proteins, usually from a duplicated viral subgenomic reporter, are effective at marking infection but tend to be attenuated due to the modification of the genome. Additionally, field strains of viruses cannot be visualized using this approach unless infectious clones can be developed to insert a reporter protein. To circumvent these issues, we have developed an insect cell-based system for detecting wild-type sindbis virus infection that uses a virus inducible promoter to express a fluorescent reporter gene only upon active virus infection. We have developed an insect expression system that produces sindbis virus minigenomes containing a subgenomic promoter sequence, which produces a translatable RNA species only when infectious virus is present and providing viral replication proteins. This subgenomic reporter RNA system is able to detect wild-type Sindbis infection in cultured mosquito cells. The detection system is relatively species specific and only detects closely related viruses, but can detect low levels of alphavirus specific replication early during infection. A chikungunya virus detection system was also developed that specifically detects chikungunya virus infection. Transgenic Aedes aegypti mosquito families were established that constitutively express the sindbis virus reporter RNA and were found to only express fluorescent proteins during virus infection. This virus inducible reporter system demonstrates a novel approach for detecting non-recombinant virus infection in mosquito cell culture and in live transgenic mosquitoes.
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Affiliation(s)
- J. Jordan Steel
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Alexander W. E. Franz
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, United States of America
| | - Irma Sanchez-Vargas
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Ken E. Olson
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Brian J. Geiss
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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ERK signaling couples nutrient status to antiviral defense in the insect gut. Proc Natl Acad Sci U S A 2013; 110:15025-30. [PMID: 23980175 DOI: 10.1073/pnas.1303193110] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A unique facet of arthropod-borne virus (arbovirus) infection is that the pathogens are orally acquired by an insect vector during the taking of a blood meal, which directly links nutrient acquisition and pathogen challenge. We show that the nutrient responsive ERK pathway is both induced by and restricts disparate arboviruses in Drosophila intestines, providing insight into the molecular determinants of the antiviral "midgut barrier." Wild-type flies are refractory to oral infection by arboviruses, including Sindbis virus and vesicular stomatitis virus, but this innate restriction can be overcome chemically by oral administration of an ERK pathway inhibitor or genetically via the specific loss of ERK in Drosophila intestinal epithelial cells. In addition, we found that vertebrate insulin, which activates ERK in the mosquito gut during a blood meal, restricts viral infection in Drosophila cells and against viral invasion of the insect gut epithelium. We find that ERK's antiviral signaling activity is likely conserved in Aedes mosquitoes, because genetic or pharmacologic manipulation of the ERK pathway affects viral infection of mosquito cells. These studies demonstrate that ERK signaling has a broadly antiviral role in insects and suggest that insects take advantage of cross-species signals in the meal to trigger antiviral immunity.
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19
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Effects of manipulating apoptosis on Sindbis virus infection of Aedes aegypti mosquitoes. J Virol 2012; 86:6546-54. [PMID: 22438551 DOI: 10.1128/jvi.00125-12] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Improved control of vector-borne diseases requires an understanding of the molecular factors that determine vector competence. Apoptosis has been shown to play a role in defense against viruses in insects and mammals. Although some observations suggest a correlation between apoptosis and resistance to arboviruses in mosquitoes, there is no direct evidence tying apoptosis to arbovirus vector competence. To determine whether apoptosis can influence arbovirus replication in mosquitoes, we manipulated apoptosis in Aedes aegypti mosquitoes by silencing the expression of genes that either positively or negatively regulate apoptosis. Silencing of the A. aegypti anti-apoptotic gene iap1 (Aeiap1) caused apoptosis in midgut epithelium, alterations in midgut morphology, and 60 to 70% mosquito mortality. Mortality induced by Aeiap1 silencing was rescued by cosilencing the initiator caspase gene Aedronc, indicating that the mortality was due to apoptosis. When mosquitoes which had been injected with Aeiap1 double-stranded RNA (dsRNA) were orally infected with Sindbis virus (SINV), increased midgut infection and virus dissemination to other organs were observed. This increase in virus infection may have been due to the effects of widespread apoptosis on infection barriers or innate immunity. In contrast, silencing the expression of Aedronc, which would be expected to inhibit apoptosis, reduced SINV midgut infection and virus dissemination. Thus, our data suggest that some level of caspase activity and/or apoptosis may be necessary for efficient virus replication and dissemination in mosquitoes. This is the first study to directly test the roles of apoptosis and caspases in determining mosquito vector competence for arboviruses.
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Waldock J, Olson KE, Christophides GK. Anopheles gambiae antiviral immune response to systemic O'nyong-nyong infection. PLoS Negl Trop Dis 2012; 6:e1565. [PMID: 22428080 PMCID: PMC3302841 DOI: 10.1371/journal.pntd.0001565] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Accepted: 01/31/2012] [Indexed: 12/30/2022] Open
Abstract
Background Mosquito-borne viral diseases cause significant burden in much of the developing world. Although host-virus interactions have been studied extensively in the vertebrate host, little is known about mosquito responses to viral infection. In contrast to mosquitoes of the Aedes and Culex genera, Anopheles gambiae, the principal vector of human malaria, naturally transmits very few arboviruses, the most important of which is O'nyong-nyong virus (ONNV). Here we have investigated the A. gambiae immune response to systemic ONNV infection using forward and reverse genetic approaches. Methodology/Principal Findings We have used DNA microarrays to profile the transcriptional response of A. gambiae inoculated with ONNV and investigate the antiviral function of candidate genes through RNAi gene silencing assays. Our results demonstrate that A. gambiae responses to systemic viral infection involve genes covering all aspects of innate immunity including pathogen recognition, modulation of immune signalling, complement-mediated lysis/opsonisation and other immune effector mechanisms. Patterns of transcriptional regulation and co-infections of A. gambiae with ONNV and the rodent malaria parasite Plasmodium berghei suggest that hemolymph immune responses to viral infection are diverted away from melanisation. We show that four viral responsive genes encoding two putative recognition receptors, a galectin and an MD2-like receptor, and two effector lysozymes, function in limiting viral load. Conclusions/Significance This study is the first step in elucidating the antiviral mechanisms of A. gambiae mosquitoes, and has revealed interesting differences between A. gambiae and other invertebrates. Our data suggest that mechanisms employed by A. gambiae are distinct from described invertebrate antiviral immunity to date, and involve the complement-like branch of the humoral immune response, supressing the melanisation response that is prominent in anti-parasitic immunity. The antiviral immune response in A. gambiae is thus composed of some key conserved mechanisms to target viral infection such as RNAi but includes other diverse and possibly species-specific mechanisms. Mosquito-borne viral diseases are found across the globe and are responsible for numerous severe human infections. In order to develop novel methods for prevention and treatment of these diseases, detailed understanding of the biology of viral infection and transmission is required. Little is known about invertebrate responses to infection in mosquito hosts. In this study we used a model system of Anopheles gambiae mosquitoes and O'nyong-nyong virus to study mosquito immune responses to infection. We examined the global transcriptional responses of A. gambiae to viral infection of the mosquito blood equivalent (the hemolymph) identifying a number of genes with immune functions that are switched on or off in response to infection, including complement-like proteins that circulate in the mosquito hemolymph. The switching on of these genes combined with co-infection experiments with malaria parasites suggests that viral infection inhibits the melanisation pathway. Through silencing the function of a selection of viral responsive genes, we identified four genes that have roles in A. gambiae anti-viral immunity; two putative recognition receptors (a galectin and an MD2-like receptor); two effector lysozymes. These molecules have previously non-described roles in antiviral immunity, and suggest uncharacterised mechanisms for targeting viral infection in A. gambiae mosquitoes.
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Affiliation(s)
- Joanna Waldock
- Division of Cell and Molecular Biology, Department of Life Sciences, Imperial College, London, United Kingdom
| | - Kenneth E. Olson
- Arthropod Infectious Diseases Laboratory, Colorado State University, Fort Collins, Colorado, United States of America
| | - George K. Christophides
- Division of Cell and Molecular Biology, Department of Life Sciences, Imperial College, London, United Kingdom
- * E-mail:
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Steel JJ, Henderson BR, Lama SBC, Olson KE, Geiss BJ. Infectious alphavirus production from a simple plasmid transfection+. Virol J 2011; 8:356. [PMID: 21771308 PMCID: PMC3156776 DOI: 10.1186/1743-422x-8-356] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 07/19/2011] [Indexed: 11/10/2022] Open
Abstract
We have developed a new method for producing infectious double subgenomic alphaviruses from plasmids transfected into mammalian cells. A double subgenomic Sindbis virus (TE3'2J) was transcribed from a cytomegalovirus PolII promoter, which results in the production of infectious virus. Transfection of as little as 125 ng of plasmid is able to produce 1 × 108 plaque forming units/ml (PFU/ml) of infectious virus 48 hours post-transfection. This system represents a more efficient method for producing recombinant Sindbis viruses.
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Affiliation(s)
- J Jordan Steel
- Department of Microbiology, Immunology, and Pathology, 1682 Campus Delivery, Colorado State University, Fort Collins, CO 80523, USA
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Phillips A, Mossel E, Sanchez-Vargas I, Foy B, Olson K. Alphavirus transducing system: tools for visualizing infection in mosquito vectors. J Vis Exp 2010:2363. [PMID: 21178952 DOI: 10.3791/2363] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Alphavirus transducing systems (ATSs) are important tools for expressing genes of interest (GOI) during infection. ATSs are derived from cDNA clones of mosquito-borne RNA viruses (genus Alphavirus; family Togaviridae). The Alphavirus genus contains about 30 different mosquito-borne virus species. Alphaviruses are enveloped viruses and contain single-stranded RNA genomes (~11.7 Kb). Alphaviruses transcribe a subgenomic mRNA that encodes the structural proteins of the virus required for encapsidation of the genome and maturation of the virus. Alphaviruses are usually highly lytic in vertebrate cells, but persistently infect susceptible mosquito cells with minimal cytopathology. These attributes make them excellent tools for gene expression in mosquito vectors. The most common ATSs in use are derived from Sindbis virus (SINV). The broad species tropism of SINV allows for infection of insect, avian, and mammalian cells8. However, ATSs have been derived from other alphaviruses as well. Foreign gene expression is made possible by the insertion of an additional viral subgenomic RNA initiation site or promoter. ATSs in which an exogenous gene sequence is positioned 5' to the viral structural genes is used for stable protein expression in insects. ATSs, in which a gene sequence is positioned 3' to the structural genes, is used to trigger RNAi and silence expression of that gene in the insect. ATSs have proven to be valuable tools for understanding vector-pathogen interactions, molecular details of viral replication and maintenance infectious cycles. In particular, the expression of fluorescent and bioluminescent reporters has been instrumental tracking the viral infection in the vector and virus transmission. Additionally, the vector immune response has been described using two strains of SINV engineered to express GFP(2,9). Here, we present a method for the production of SINV containing a fluorescent reporter (GFP) from the cDNA infectious clone. Infectious, full-length RNA is transcribed from the linearized cDNA clone. Infectious RNA is introduced into permissive target cells by electroporation. Transfected cells generate infectious virus particles expressing the GOI. Harvested virus is used to infect mosquitoes, as described here, or other host species (not shown herein). Vector competence is assessed by detecting fluorescence outside the midgut or by monitoring virus transmission. Use of a fluorescent reporter as the GOI allows for convenient estimation of virus spread throughout a cell culture, for determination of rate of infection, dissemination in exposed mosquitoes, virus transmission from the mosquito and provides a rapid gauge of vector competence.
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Affiliation(s)
- Aaron Phillips
- Microbiology, Immunology, and Pathology, Colorado State University, USA
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McGee CE, Shustov AV, Tsetsarkin K, Frolov IV, Mason PW, Vanlandingham DL, Higgs S. Infection, dissemination, and transmission of a West Nile virus green fluorescent protein infectious clone by Culex pipiens quinquefasciatus mosquitoes. Vector Borne Zoonotic Dis 2010; 10:267-74. [PMID: 19619041 DOI: 10.1089/vbz.2009.0067] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We report the construction and comparative characterization of a full-length West Nile virus (WNV) cDNA infectious clone (ic) that contains a green fluorescent protein (GFP) expression cassette fused within the viral open reading frame. Virus derived from WNV-GFP ic stably infected Culex pipiens quinquefasciatus mosquitoes at comparable rates to virus derived from the parental (non-GFP) ic. However, insertion of this GFP cassette resulted in a temporal delay in in vivo replication kinetics and significantly decreased dissemination to head tissue. Consistent with previous reports of WNV-infected mosquito midguts, focal GFP expression was observed at 3 days post-infection (dpi), with the majority of posterior midgut epithelial cells being positive by 7 dpi. GFP foci were observed in one pair of salivary glands (1/15) dissected 14 dpi. Mice exposed to WNV-GFP-infected mosquitoes developed viremia, and GFP was detected in lymph node homogenates. These data demonstrate the effectiveness of our strategy to generate a replication competent construct with increased reporter gene stability that may be used to study early events in infection.
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Affiliation(s)
- Charles E McGee
- Department of Pathology, University of Texas Medical Branch , Galveston, Texas 77539-0609, USA
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Alphavirus vectors for cancer therapy. Virus Res 2010; 153:179-96. [PMID: 20692305 DOI: 10.1016/j.virusres.2010.07.027] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/27/2010] [Accepted: 07/28/2010] [Indexed: 11/23/2022]
Abstract
Alphaviruses contain a single strand RNA genome that can be easily modified to express heterologous genes at very high levels in a broad variety of cells, including tumor cells. Alphavirus vectors can be used as viral particles containing a packaged vector RNA, or directly as nucleic acids in the form of RNA or DNA. In the latter case alphavirus RNA is cloned within a DNA vector downstream of a eukaryotic promoter. Expression mediated by these vectors is generally transient due to the induction of apoptosis. The high expression levels, induction of apoptosis, and activation of type I IFN response are the key features that have made alphavirus vectors very attractive for cancer treatment and vaccination. Alphavirus vectors have been successfully used as vaccines to induce protective and therapeutic immune responses against many tumor-associated antigens in animal models of mastocytoma, melanoma, mammary, prostate, and virally induced tumors. Alphavirus vectors have also shown a high antitumoral efficacy by expressing antitumoral molecules in tumor cells, which include cytokines, antiangiogenic factors or toxic proteins. In these studies induction of apoptosis in tumor cells contributed to the antitumoral efficacy by the release of tumor antigens that can be uptaken by antigen presenting cells, enhancing immune responses against tumors. The potential use of alphaviruses as oncolytic agents has also been evaluated for avirulent strains of Semliki Forest virus and Sindbis virus. The fact that this latter virus has a natural tropism for tumor cells has led to many studies in which this vector was able to reach metastatic tumors when administered systemically. Other "artificial" strategies to increase the tropism of alphavirus for tumors have also been evaluated and will be discussed.
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Abstract
Characterization and noninvasive measurement of molecular pathways and biochemistry in living cells, animal models, and humans at the cellular and molecular level is now possible using remote imaging detectors. Positron and single photon emission tomography scanners, highly sensitive cameras for bioluminescence and fluorescence imaging, as well as high-magnetic-field magnetic resonance imaging scanners, can be used to study such diverse processes as signal transduction, receptor density and function, host response to pathogens, cell trafficking, and gene transfer. In many cases, images from more than one modality can be fused, allowing structure-function and multifunction relationships to be studied on a tissue-restricted or regional basis. "Molecular imaging" holds enormous potential for elucidating the molecular mechanisms of pulmonary disease and therapeutic response in intact animal models and humans.
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Traver BE, Anderson MAE, Adelman ZN. Homing endonucleases catalyze double-stranded DNA breaks and somatic transgene excision in Aedes aegypti. INSECT MOLECULAR BIOLOGY 2009; 18:623-33. [PMID: 19754740 PMCID: PMC3606018 DOI: 10.1111/j.1365-2583.2009.00905.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Aedes aegypti is a major vector of arthropod-borne viruses such as yellow fever virus and dengue viruses. Efforts to discern the function of genes involved in important behaviours, such as vector competence and host seeking through reverse genetics, would greatly benefit from the ability to generate targeted gene disruptions. Homing endonucleases are selfish elements which catalyze double-stranded DNA (dsDNA) breaks in a sequence-specific manner. In this report we demonstrate that the homing endonucleases I-PpoI, I-SceI, I-CreI and I-AniI are all able to induce dsDNA breaks in adult female Ae. aegypti chromosomes as well as catalyze the somatic excision of a transgene. These experiments provide evidence that homing endonucleases can be used to manipulate the genome of this important disease vector.
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Affiliation(s)
| | | | - Zach N. Adelman
- corresponding author: Zach N. Adelman, 305 Fralin Life Science Institute, West Campus Dr., Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, , 540 231-6614 (phone), 540 231-9931 (fax)
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Daubnerová I, Roller L, Žitňan D. Transgenesis approaches for functional analysis of peptidergic cells in the silkworm Bombyx mori. Gen Comp Endocrinol 2009; 162:36-42. [PMID: 19111552 PMCID: PMC2854327 DOI: 10.1016/j.ygcen.2008.11.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 11/14/2008] [Accepted: 11/18/2008] [Indexed: 10/21/2022]
Abstract
The domestic silkworm, Bombyx mori represents an insect model of great scientific and economic importance. Besides the establishment of a stable germline transformation using the PiggyBac vector, technically feasible methods for in vivo gene delivery and transient gene expression were developed using viral based vectors, especially Sindbis viruses and baculoviruses. The recombinant baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV), commonly used for large-scale protein production in permissive cell lines or insects, has been used for foreign gene transfer into specific peptidergic cells of B. mori in vivo. Since targeted gene expression is essential for functional analysis of neuropeptide genes and their receptors, the baculovirus-mediated gene transfer can serve as a reliable approach in reverse genetic studies in the silkworm. We review various strategies employing the baculovirus vector system for transient expression of molecular markers and transcription factors in specific peptidergic cells to investigate their roles in B. mori. We also use this system for functional analysis of neuropeptide signaling in the ecdysis behavioral sequence. Our data indicate that the AcMNPV vector is suitable for efficient delivery of foreign genes and their expression directed into specific peptidergic neurons and endocrine cells of B. mori larvae and pupae. However, some modifications of the vector and steps for optimization are necessary to minimize negative effects of viral infection on the host development. The transient gene expression using the AcMNPV and other virus vectors are promising tools for analysis of molecular mechanisms underlying various neuroendocrine processes during development of B. mori.
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Affiliation(s)
- Ivana Daubnerová
- Institute of Zoology, Slovak Academy of Sciences, SAV, Dúbravská cesta 9, 84506 Bratislava, Slovakia
- Department of Genetics, Faculty of Natural Sciences, Comenius University, 84205 Bratislava, Slovakia
| | - Ladislav Roller
- Institute of Zoology, Slovak Academy of Sciences, SAV, Dúbravská cesta 9, 84506 Bratislava, Slovakia
| | - Dušan Žitňan
- Institute of Zoology, Slovak Academy of Sciences, SAV, Dúbravská cesta 9, 84506 Bratislava, Slovakia
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Abstract
Horizontally transmitted mosquito-borne viruses enter the midgut with a blood meal then disseminate to infect the salivary glands. En route to the salivary glands, these viruses encounter the plasma (haemolymph) and blood cells (haemocytes). Haemocytes respond to a variety of micro-organisms, but their role in virus replication and dissemination has not been described. To look for a potential haemocyte tropism for an arbovirus, a Sindbis virus was injected intrathoracically into four species of mosquito. Virus infects haemocytes as early as 6 h post injection (p.i.) and infection was evident in these cells for as long as 4 days p.i. More than 90 % of haemocytes were infected, most often the phagocytic granulocytes. Virus titres in the haemolymph increased from 24 h p.i. through 60 h p.i. Similar results were found when Aedes aegypti mosquitoes were injected with orally infectious Sindbis. These data prove that an arbovirus infects, and replicates in, haemocytes.
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Affiliation(s)
- Grishma R Parikh
- Department of Entomology, College of Agriculture and Life Sciences, Iowa State University, Ames, IA 50011, USA
| | - Jonathan D Oliver
- Department of Entomology, College of Agriculture and Life Sciences, Iowa State University, Ames, IA 50011, USA
| | - Lyric C Bartholomay
- Department of Entomology, College of Agriculture and Life Sciences, Iowa State University, Ames, IA 50011, USA
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Wang H, Blair CD, Olson KE, Clem RJ. Effects of inducing or inhibiting apoptosis on Sindbis virus replication in mosquito cells. J Gen Virol 2009; 89:2651-2661. [PMID: 18931060 DOI: 10.1099/vir.0.2008/005314-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sindbis virus (SINV) is a mosquito-borne virus in the genus Alphavirus, family Togaviridae. Like most alphaviruses, SINVs exhibit lytic infection (apoptosis) in many mammalian cell types, but are generally thought to cause persistent infection with only moderate cytopathic effects in mosquito cells. However, there have been several reports of apoptotic-like cell death in mosquitoes infected with alphaviruses or flaviviruses. Given that apoptosis has been shown to be an antiviral response in other systems, we have constructed recombinant SINVs that express either pro-apoptotic or anti-apoptotic genes in order to test the effects of inducing or inhibiting apoptosis on SINV replication in mosquito cells. Recombinant SINVs expressing the pro-apoptotic genes reaper (rpr) from Drosophila or michelob_x (mx) from Aedes aegypti caused extensive apoptosis in cells from the mosquito cell line C6/36, thus changing the normal persistent infection observed with SINV to a lytic infection. Although the infected cells underwent apoptosis, high levels of virus replication were still observed during the initial infection. However, virus production subsequently decreased compared with persistently infected cells, which continued to produce high levels of virus over the next several days. Infection of C6/36 cells with SINV expressing the baculovirus caspase inhibitor P35 inhibited actinomycin D-induced caspase activity and protected infected cells from actinomycin D-induced apoptosis, but had no observable effect on virus replication. This study is the first to test directly whether inducing or inhibiting apoptosis affects arbovirus replication in mosquito cells.
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Affiliation(s)
- Hua Wang
- Molecular, Cellular, and Developmental Biology Program, Arthropod Genomics Center, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Carol D Blair
- Arthropod-Borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Ken E Olson
- Arthropod-Borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Rollie J Clem
- Molecular, Cellular, and Developmental Biology Program, Arthropod Genomics Center, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
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30
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Tseng JC, Daniels G, Meruelo D. Controlled propagation of replication-competent Sindbis viral vector using suicide gene strategy. Gene Ther 2008; 16:291-6. [PMID: 18818670 DOI: 10.1038/gt.2008.153] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A major concern of using viral gene therapy is the potential for uncontrolled vector propagation and infection that might result in serious deleterious effects. To enhance the safety, several viral vectors, including vectors based on Sindbis virus, were engineered to lose their capability to replicate and spread after transduction of target cells. Such designs, however, could dramatically reduce the therapeutic potency of the viral vectors, resulting in the need for multiple dosages to achieve treatment goals. Earlier, we showed that a replication-defective (RD) Sindbis vector achieved specific tumor targeting without any adverse effects in vivo. Here, we present a replication-competent Sindbis viral vector that has an hsvtk suicide gene incorporated into ns3, an indispensable non-structural gene for viral survival. The capability of viral propagation significantly increases tumor-specific infection and enhances growth suppression of tumor compared with the conventional RD vectors. Furthermore, in the presence of the prodrug ganciclovir, the hsvtk suicide gene serves as a safety mechanism to prevent uncontrolled vector propagation. In addition to suppressing vector propagation, toxic metabolites, generated by prodrug activation, could spread to neighboring uninfected tumor cells to further enhance tumor killing.
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Affiliation(s)
- J-C Tseng
- NYU Cancer Institute and the NYU Gene Therapy Center, Department of Pathology, NYU School of Medicine, New York University, New York, NY 10016, USA
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31
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Abstract
Alphavirus transducing systems (ATSs) are important tools for expressing genes of interest (GOI) in mosquitoes and nonvector insects. ATSs are derived from infectious cDNA clones of mosquito-borne RNA viruses (family Togaviridae). The most common ATSs in use are derived from Sindbis viruses; however, ATSs have been derived from other alphaviruses as well. ATSs generate viruses with genomes that contain GOI's that can be expressed from additional viral subgenomic promoters. ATSs in which an exogenous gene sequence is positioned 5' to the viral structural genes is used for stable protein expression in insects. ATSs in which a gene sequence is positioned 3' to the structural genes is used to trigger RNAi and silence expression of that gene in the insect. ATSs are proving to be invaluable tools for understanding vector-pathogen interactions, vector competence, and other components of vector-pathogen amplification and maintenance cycles in nature. These virus-based expression systems also facilitate the researcher's ability to decide which gene-based disease control strategies merit a further investment in time and resources in transgenic mosquitoes.
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32
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Adelman ZN, Anderson MAE, Morazzani EM, Myles KM. A transgenic sensor strain for monitoring the RNAi pathway in the yellow fever mosquito, Aedes aegypti. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2008; 38:705-13. [PMID: 18549956 PMCID: PMC2518454 DOI: 10.1016/j.ibmb.2008.04.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2008] [Revised: 04/10/2008] [Accepted: 04/13/2008] [Indexed: 05/24/2023]
Abstract
The RNA interference pathway functions as an antiviral defense in invertebrates. In order to generate a phenotypic marker which "senses" the status of the RNAi pathway in Aedes aegypti, transgenic strains were developed to express EGFP and DsRED marker genes in the eye, as well as double-stranded RNA homologous to a portion of the EGFP gene. Transgenic "sensor" mosquitoes exhibited robust eye-specific DsRED expression with little EGFP, indicating RNAi-based silencing. Cloning and high-throughput sequencing of small RNAs confirmed that the inverted-repeat transgene was successfully processed into short-interfering RNAs by the mosquito RNAi pathway. When the A. aegypti homologues of the genes DCR-2 or AGO-2 were knocked down, a clear increase in EGFP fluorescence was observed in the mosquito eyes. Knockdown of DCR-2 was also associated with an increase in EGFP mRNA levels, as determined by Northern blot and real-time PCR. Knockdown of AGO-3, a gene involved in the germline-specific piRNA pathway, did not restore EGFP expression at either the mRNA or protein level. This transgenic sensor strain can now be used to identify other components of the mosquito RNAi pathway and has the potential to be used in the identification of arboviral suppressors of RNAi.
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Affiliation(s)
- Zach N Adelman
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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33
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Genetic determinants of Sindbis virus mosquito infection are associated with a highly conserved alphavirus and flavivirus envelope sequence. J Virol 2007; 82:2966-74. [PMID: 18160430 DOI: 10.1128/jvi.02060-07] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wild-type Sindbis virus (SINV) strain MRE16 efficiently infects Aedes aegypti midgut epithelial cells (MEC), but laboratory-derived neurovirulent SINV strain TE/5'2J infects MEC poorly. SINV determinants for MEC infection have been localized to the E2 glycoprotein. The E2 amino acid sequences of MRE16 and TE/5'2J differ at 60 residue sites. To identify the genetic determinants of MEC infection of MRE16, the TE/5'2J virus genome was altered to contain either domain chimeras or more focused nucleotide substitutions of MRE16. The growth patterns of derived viruses in cell culture were determined, as were the midgut infection rates (MIR) in A. aegypti mosquitoes. The results showed that substitutions of MRE16 E2 aa 95 to 96 and 116 to 119 into the TE/5'2J virus increased MIR both independently and in combination with each other. In addition, a unique PPF/.GDS amino acid motif was located between these two sites that was found to be a highly conserved sequence among alphaviruses and flaviviruses but not other arboviruses.
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34
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Smith DR, Adams AP, Kenney JL, Wang E, Weaver SC. Venezuelan equine encephalitis virus in the mosquito vector Aedes taeniorhynchus: infection initiated by a small number of susceptible epithelial cells and a population bottleneck. Virology 2007; 372:176-86. [PMID: 18023837 DOI: 10.1016/j.virol.2007.10.011] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 09/28/2007] [Accepted: 10/10/2007] [Indexed: 11/17/2022]
Abstract
We evaluated infection of Aedes taeniorhynchus mosquitoes, vectors of Venezuelan equine encephalitis virus (VEEV), using radiolabeled virus and replicon particles expressing green (GFP) or cherry fluorescent protein (CFP). More epidemic VEEV bound to and infected mosquito midguts compared to an enzootic strain, and a small number of midgut cells was preferentially infected. Chimeric replicons infected midgut cells at rates comparable to those of the structural gene donor. The numbers of midgut cells infected averaged 28, and many infections were initiated in only 1-5 cells. Infection by a mixture of GFP- and CFP-expressing replicons indicated that only about 100 midgut cells were susceptible. Intrathoracic injections yielded similar patterns of replication with both VEEV strains, suggesting that midgut infection is the primary limitation to transmission. These results indicate that the structural proteins determine initial infection of a small number of midgut cells, and that VEEV undergoes population bottlenecks during vector infection.
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Affiliation(s)
- Darci R Smith
- Department of Pathology and Center for Tropical Diseases, University of Texas Medical, Branch, Galveston, TX 77555-0609, USA
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35
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Geiss BJ, Shimonkevitz LH, Sackal CI, Olson KE. Recombination-ready Sindbis replicon expression vectors for transgene expression. Virol J 2007; 4:112. [PMID: 17963504 PMCID: PMC2164957 DOI: 10.1186/1743-422x-4-112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Accepted: 10/26/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sindbis viruses have been widely used as tools to study gene function in cells. Despite the utility of these systems, the construction and production of alphavirus replicons is time consuming and inefficient due to potential additional restriction sites within the insert region and lack of directionality for insert ligation. In this report, we present a system useful for producing recombinant Sindbis replicons that uses lambda phage recombination technology to rapidly and specifically construct replicon expression plasmids that contain insert regions in the desired orientation. RESULTS Recombination of the gene of interest with the replicon plasmid resulted in nearly 100% recombinants, each of which contained a correctly orientated insert. Replicons were easily produced in cell culture and packaged into pseudo-infectious viral particles. Insect and mammalian cells infected with pseudo-infectious viral particles expressed various transgenes at high levels. Finally, inserts from persistently replicating replicon RNA were easily isolated and recombined back into entry plasmids for sequencing and subsequent analysis. CONCLUSION Replication-ready replicon expression plasmids make the use of alphavirus replicons fast and easy as compared to traditional replicon production methods. This system represents a significant step forward in the utility and ease of use of alphavirus replicons in the study of gene function.
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Affiliation(s)
- Brian J Geiss
- Arthropod-Borne and Infectious Diseases Laboratory, Department of Molecular Biology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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36
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Pierro DJ, Powers EL, Olson KE. Genetic determinants of Sindbis virus strain TR339 affecting midgut infection in the mosquito Aedes aegypti. J Gen Virol 2007; 88:1545-1554. [PMID: 17412985 DOI: 10.1099/vir.0.82577-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mosquito midgut epithelial cells (MEC) play a major role in determining whether an arbovirus can successfully infect and be transmitted by mosquitoes. The Sindbis virus (SINV) strain TR339 efficiently infects Aedes aegypti MEC but the SINV strain TE/5'2J poorly infects MEC. SINV determinants for MEC infection have been localized to the E2 glycoprotein. The E2 amino acid sequences of TR339 and TE/5'2J differ at two sites, E2-55 and E2-70. We have altered the TE/5'2J virus genome by site-directed mutagenesis to contain two TR339 residues, E2-55 H-->Q (histidine to glutamine) and E2-70 K-->E (lysine to glutamic acid). We have characterized the growth patterns of derived viruses in cell culture and determined the midgut infection rate (MIR) in A. aegypti mosquitoes. Our results clearly show that the E2-55 H-->Q and the E2-70 K-->E mutations in the TE/5'2J virus increase MIR both independently and in combination. TE/5'2J virus containing both TR339 E2 residues had MIRs similar to the parental TR339 virus. In addition, SINV propagated in a mammalian cell line had a significantly lower A. aegypti midgut 50 % infectious dose than virus propagated in a mosquito cell line.
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Affiliation(s)
- Dennis J Pierro
- Arthropod-Borne and Infectious Disease Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA
| | - Erik L Powers
- Arthropod-Borne and Infectious Disease Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA
| | - Ken E Olson
- Arthropod-Borne and Infectious Disease Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA
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37
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Tsetsarkin K, Higgs S, McGee CE, De Lamballerie X, Charrel RN, Vanlandingham DL. Infectious clones of Chikungunya virus (La Réunion isolate) for vector competence studies. Vector Borne Zoonotic Dis 2007; 6:325-37. [PMID: 17187566 DOI: 10.1089/vbz.2006.6.325] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The recent outbreak of Chikungunya virus (CHIKV) on several islands in the Indian Ocean and in India has focused attention on this reemerging virus and highlighted the need for development of new tools to study vector-virus-host interactions. We have constructed and characterized, in cell culture, Aedes aegypti and Ae. albopictus mosquitoes, infectious cDNA clones of CHIKV using a recent isolate from La Réunion Island. Comparison of the growth kinetics and infection rates of the viral isolate CHIKV strain LR2006 OPY1 (CHIKV-LR) and a full-length infectious clone (CHIKV-LR ic) indicate that the infectious clone has retained the viral phenotypes of the original isolate. Infectious clones that express green fluorescent protein (GFP) were also produced and characterized in cell culture and in Aedes mosquitoes. The CHIKV-LR 5'GFP infected Ae. aegypti and Ae. albopictus mosquitoes at a similar rate to the original virus and to the full length infectious clone. The CHIKV-LR 3'GFP only infected Ae. albopictus mosquitoes at similar rates. The development of these authentic infectious clones will enable targeted studies of the molecular determinants of infection, pathogenesis and transmission competence by Ae. aegypti and Ae. albopictus mosquitoes.
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Affiliation(s)
- Konstantin Tsetsarkin
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77539-0609, USA
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38
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Beaty BJ. Control of arbovirus diseases: is the vector the weak link? ARCHIVES OF VIROLOGY. SUPPLEMENTUM 2006:73-88. [PMID: 16358423 DOI: 10.1007/3-211-29981-5_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Arthropod-borne virus (arbovirus) diseases (ABVDs) remain major threats to human health and well-being and, as an epidemiologic group, inflict an unacceptable health and economic burden on humans and animals, including livestock. The developed world has been fortunate to have escaped much of the burden that arboviruses and their arthropod vectors inflict on humans in disease endemic countries, but the introduction and rapid spread of West Nile virus in the Western Hemisphere demonstrated that we can no longer be complacent in the face of these emerging and resurging vector-borne diseases. Unfortunately, as the burdens and threats of ABVDs have increased, the U.S. and international public health capacity to address them has decreased. Vaccines are not available for most of these agents. Previously successful strategies to control ABVDs emphasized vector control, but source reduction and vector control strategies using pesticides have not been sustainable. New insights into vector biology and vector pathogen interactions, and the novel targets that likely will be forthcoming in the vector post-genomics era, provide new targets and opportunities for vector control and disease reduction programs. These findings and approaches must be incorporated into existing strategies if we are to control these important pathogens.
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Affiliation(s)
- B J Beaty
- Department of Microbiology, Immunology, and Pathology, Arthropod-Borne and Infectious Diseases Laboratory, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
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39
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Sim C, Hong YS, Vanlandingham DL, Harker BW, Christophides GK, Kafatos FC, Higgs S, Collins FH. Modulation of Anopheles gambiae gene expression in response to o'nyong-nyong virus infection. INSECT MOLECULAR BIOLOGY 2005; 14:475-81. [PMID: 16164603 PMCID: PMC3840949 DOI: 10.1111/j.1365-2583.2005.00578.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
To determine if gene expression of An. gambiae is modulated in response to o'nyong-nyong virus (ONNV) infection, we utilized cDNA microarrays including about 20 000 cDNAs. Gene expression levels of ONNV-infected female mosquitoes were compared to that of the uninfected control females harvested at 14 days postinfection. In response to ONNV infection, expression levels of 18 genes were significantly modulated, being at least two-fold up- or down-regulated. Quantitative real-time PCR analysis (qRT-PCR) further substantiated the differential expression of six of these genes in response to ONNV infection. These genes have similarity to a putative heat shock protein 70, DAN4, agglutinin attachment subunit, elongation factor 1 alpha and ribosomal protein L35. One gene, with sequence similarity to mitochondrial ribosomal protein L7, was down-regulated in infected mosquitoes. The expression levels and annotation of the differentially expressed genes are discussed in the context of host/virus interaction including host translation/replication factors, and intracellular transport pathways.
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Affiliation(s)
- C Sim
- Center for Tropical Disease Research and Training, University of Notre Dame, Notre Dame, IN 46556, USA
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40
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Vanlandingham DL, Tsetsarkin K, Hong C, Klingler K, McElroy KL, Lehane MJ, Higgs S. Development and characterization of a double subgenomic chikungunya virus infectious clone to express heterologous genes in Aedes aegypti mosquitoes. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2005; 35:1162-70. [PMID: 16102421 DOI: 10.1016/j.ibmb.2005.05.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Revised: 05/20/2005] [Accepted: 05/20/2005] [Indexed: 05/04/2023]
Abstract
Three full-length infectious cDNA clones based on the alphavirus chikungunya (CHIKV) were developed and characterized in vitro and in vivo. The full-length clone retained the viral phenotypes of CHIKV in both cell culture and in mosquitoes and should be a valuable tool for the study of virus interactions in an epidemiologically significant natural vector, Aedes aegypti. Two additional infectious clones were constructed that express green fluorescent protein (EGFP) in the midgut, salivary glands, and nervous tissue of Aedes aegypti mosquitoes following oral infection. The two constructs differed in the placement of the subgenomic promoter and the gene encoding EGFP. Viruses derived from the pCHIKic EGFP constructs (5' CHIKV EGFP and 3' CHIKV EGFP) expressed EGFP in 100% of the Ae. aegypti mosquitoes tested on days 7 and 14 post infection (p.i.). The 5' CHIKV EGFP disseminated to 90% of the salivary glands and nervous tissue by day 14 p.i. Dissemination rates of this new viral vector exceeds those of previous systems, thus expanding the repertoire and potential for gene expression studies on this important vector species.
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Affiliation(s)
- Dana L Vanlandingham
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, USA
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41
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Goldsmith MR, Shimada T, Abe H. The genetics and genomics of the silkworm, Bombyx mori. ANNUAL REVIEW OF ENTOMOLOGY 2005; 50:71-100. [PMID: 15355234 DOI: 10.1146/annurev.ento.50.071803.130456] [Citation(s) in RCA: 324] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We review progress in applying molecular genetic and genomic technologies to studies in the domesticated silkworm, Bombyx mori, highlighting its use as a model for Lepidoptera, and in sericulture and biotechnology. Dense molecular linkage maps are being integrated with classical linkage maps for positional cloning and marker-assisted selection. Classical mutations have been identified by a candidate gene approach. Cytogenetic and sequence analyses show that the W chromosome is composed largely of nested full-length long terminal repeat retrotransposons. Z-chromosome-linked sequences show a lack of dosage compensation. The downstream sex differentiation mechanism has been studied via the silkworm homolog of doublesex. Expressed sequence tagged databases have been used to discover Lepidoptera-specific genes, provide evidence for horizontal gene transfer, and construct microarrays. Physical maps using large-fragment bacterial artificial chromosome libraries have been constructed, and whole-genome shotgun sequencing is underway. Germline transformation and transient expression systems are well established and available for functional studies, high-level protein expression, and gene silencing via RNA interference.
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Affiliation(s)
- Marian R Goldsmith
- Biological Sciences Department, University of Rhode Island, Kingston, Rhode Island 02881, USA.
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42
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Moncayo AC, Fernandez Z, Ortiz D, Diallo M, Sall A, Hartman S, Davis CT, Coffey L, Mathiot CC, Tesh RB, Weaver SC. Dengue emergence and adaptation to peridomestic mosquitoes. Emerg Infect Dis 2004; 10:1790-6. [PMID: 15504265 PMCID: PMC3323252 DOI: 10.3201/eid1010.030846] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Phylogenetic evidence suggests that endemic and epidemic dengue viruses (DENV), transmitted among humans by the anthropophilic mosquitoes Aedes aegypti and Ae. albopictus, emerged when ancestral, sylvatic DENV transmitted among nonhuman primates by sylvatic Aedes mosquitoes adapted to these peridomestic vectors. We tested this hypothesis by retrospectively examining evidence for adaptation of epidemic and endemic versus sylvatic strains of DENV-2 to Ae. albopictus and Ae. aegypti. First and second-generation offspring of mosquitoes from different geographic regions in the Americas and Southeast Asia were tested for their susceptibility to epidemic/endemic and sylvatic DENV-2 isolates from West Africa, Southeast Asia, and Oceania. Both Aedes species were highly susceptible (up to 100% infected) to endemic/epidemic DENV-2 strains after ingesting artificial blood meals but significantly less susceptible (as low as 0%) to sylvatic DENV-2 strains. Our findings support the hypothesis that adaptation to peridomestic mosquito vectors mediated dengue emergence from sylvatic progenitor viruses.
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43
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Brault AC, Foy BD, Myles KM, Kelly CLH, Higgs S, Weaver SC, Olson KE, Miller BR, Powers AM. Infection patterns of o'nyong nyong virus in the malaria-transmitting mosquito, Anopheles gambiae. INSECT MOLECULAR BIOLOGY 2004; 13:625-635. [PMID: 15606811 DOI: 10.1111/j.0962-1075.2004.00521.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Arthropod-borne alphaviruses transmitted by mosquitoes almost exclusively use culicines; however, the alphavirus o'nyong-nyong (ONNV) has the unusual characteristic of being transmitted primarily by anopheline mosquitoes. This unusual attribute makes ONNV a valuable tool in the characterization of mosquito determinants of infection as well as a useful expression system in Anopheles species. We developed a series of recombinant alphaviruses, based upon the genome of ONNV, designed for the expression of heterologous genes. The backbone genome is a full-length infectious cDNA clone of ONNV from which wild-type virus can be rescued. Additional constructs are variants of the primary clone and contain the complete genome plus a duplicated subgenomic promoter element with a multiple cloning site for insertion of heterologous genes. We inserted a green fluorescent protein (GFP) gene downstream of this promoter and used it to characterize infection and dissemination patterns of ONNV within An. gambiae mosquitoes. These experiments allowed us to identify atypical sites of initial infection and dissemination patterns in this mosquito species not frequently observed in comparable culicine infections. The utility of these ONNVs for studies in anopheline mosquitoes includes the potential for identification of vector infection determinants and to serve as tools for antimalaria studies. Viruses that can express a heterologous gene in a vector and rapidly and efficiently infect numerous tissues in An. gambiae mosquitoes will be a valuable asset in parasite-mosquito interaction and interference research.
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Affiliation(s)
- A C Brault
- Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80522, USA
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44
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Kramer MG. Recent advances in transgenic arthropod technology. BULLETIN OF ENTOMOLOGICAL RESEARCH 2004; 94:95-110. [PMID: 15153293 DOI: 10.1079/ber2003290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The ability to insert foreign genes into arthropod genomes has led to a diverse set of potential applications for transgenic arthropods, many of which are designed to advance public health or improve agricultural production. New techniques for expressing foreign genes in arthropods have now been successfully used in at least 18 different genera. However, advances in field biology are lagging far behind those in the laboratory, and considerable work is needed before deployment in nature can be a reality. A mechanism to drive the gene of interest though a natural population must be developed and thoroughly evaluated before any field release, but progress in this area has been limited. Likewise, serious consideration of potential risks associated with deployment in nature has been lacking. This review gives an overview of the most promising techniques for expressing foreign genes in arthropods, considers the potential risks associated with their deployment, and highlights the areas of research that are most urgently needed for the field to advance out of the laboratory and into practice.
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Affiliation(s)
- M G Kramer
- US Environmental Protection Agency, Office of Science Coordination and Policy, Washington, DC 20460, USA.
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45
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Piwnica-Worms D, Schuster DP, Garbow JR. Molecular imaging of host-pathogen interactions in intact small animals. Cell Microbiol 2004; 6:319-31. [PMID: 15009024 DOI: 10.1111/j.1462-5822.2004.00379.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Characterization and non-invasive measurement of host-pathogen interactions in living cells, animal models and humans at the cellular and molecular levels is now possible using remote imaging detectors. Positron emission tomography scanners, highly sensitive cooled charge-coupled device cameras for bioluminescence and fluorescence imaging as well as high-magnetic-field magnetic resonance imaging scanners can be used to study such diverse processes as pathogen tropism, pathogen life cycle, signal transduction, host response, cell trafficking and gene transfer. In many cases, images from more than one modality can be fused, allowing structure-function and multifunction relationships to be studied on a tissue-restricted or regional basis. These new instruments, when used in conjunction with targeted contrast agents, reporter substrates and radiopharmaceuticals, enable "molecular imaging" with enormous potential for elucidating host-pathogen interactions in intact animal models.
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Affiliation(s)
- David Piwnica-Worms
- Molecular Imaging Center, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Blvd, Box 8225, Washington University, St Louis, MO 63110, USA.
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46
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Foy BD, Myles KM, Pierro DJ, Sanchez-Vargas I, Uhlírová M, Jindra M, Beaty BJ, Olson KE. Development of a new Sindbis virus transducing system and its characterization in three Culicine mosquitoes and two Lepidopteran species. INSECT MOLECULAR BIOLOGY 2004; 13:89-100. [PMID: 14728670 DOI: 10.1111/j.1365-2583.2004.00464.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Alphavirus transducing systems (ATSs) are alphavirus-based tools for expressing genes in insects. Here we describe an ATS (5'dsMRE16ic) based entirely on Sindbis MRE16 virus. GFP expression was used to characterize alimentary tract infections and dissemination in three Culicine and two Lepidopteran species. Following per os infection, 5'dsMRE16ic-EGFP efficiently infected Aedes aegypti and Culex tritaeniorhynchus, but not Culex pipiens pipiens. Ae. aegypti clearly showed accumulation of green fluorescent protein (GFP) in the posterior midgut and foregut/midgut junction within 2-3 days postinfection. Following parenteral infection of larvae, Bombyx mori had extensive GFP expression in larvae and adults, but Manduca sexta larvae were mostly resistant. 5'dsMRE16ic should be a valuable tool for gene expression in several important insect species that are otherwise difficult to manipulate genetically.
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Affiliation(s)
- B D Foy
- Arthropod-Borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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Uhlirova M, Foy BD, Beaty BJ, Olson KE, Riddiford LM, Jindra M. Use of Sindbis virus-mediated RNA interference to demonstrate a conserved role of Broad-Complex in insect metamorphosis. Proc Natl Acad Sci U S A 2003; 100:15607-12. [PMID: 14668449 PMCID: PMC307615 DOI: 10.1073/pnas.2136837100] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The transcription factor Broad-Complex (BR-C) is required for differentiation of adult structures as well as for the programmed death of obsolete larval organs during metamorphosis of the fruit fly Drosophila melanogaster. Whether BR-C has a similar role in other holometabolous insects could not be proven without a loss-of-function genetic test, performed in a non-drosophilid species. Here we use a recombinant Sindbis virus as a tool to silence BR-C expression in the silkmoth Bombyx mori. The virus expressing a BR-C antisense RNA fragment reduced endogenous BR-C mRNA levels in infected tissues (adult wing and leg primordia) via RNA interference (RNAi). The RNAi knock-down of BR-C resulted in the failure of animals to complete the larval-pupal transition or in later morphogenetic defects, including differentiation of adult compound eyes, legs, and wings from their larval progenitors. BR-C RNAi also perturbed the programmed cell death of larval silk glands. These developmental defects correspond to loss-of-function phenotypes of BR-C Drosophila mutants in both the morphogenetic and degenerative aspects, suggesting that the critical role of BR-C in metamorphosis is evolutionarily conserved. We also demonstrate that the Sindbis virus is a useful vehicle for silencing of developmental genes in new insect models.
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Affiliation(s)
- Mirka Uhlirova
- Department of Molecular Biology, University of South Bohemia and Institute of Entomology, the Czech Academy of Sciences, Ceske Budejovice, 37005 Czech Republic
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Myles KM, Pierro DJ, Olson KE. Deletions in the putative cell receptor-binding domain of Sindbis virus strain MRE16 E2 glycoprotein reduce midgut infectivity in Aedes aegypti. J Virol 2003; 77:8872-81. [PMID: 12885905 PMCID: PMC167217 DOI: 10.1128/jvi.77.16.8872-8881.2003] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Sindbis virus (Alphavirus; Togaviridae) strain MRE16 efficiently infects Aedes aegypti mosquitoes that ingest a blood meal containing 8 to 9 log(10) PFU of virus/ml. However, a small-plaque variant of this virus, MRE16sp, poorly infects mosquitoes after oral infection with an equivalent titer. To determine the genetic differences between MRE16 and MRE16sp viruses, we have sequenced the MRE16sp structural genes and found a 90-nucleotide deletion in the E2 glycoprotein that spans the 3' end of the coding region for the putative cell-receptor binding domain (CRBD). We examined the role of this deletion in oral infection of mosquitoes by constructing infectious clones pMRE16icDeltaE200-Y229 and pMRE16ic, representing MRE16 virus genomes with and without the deletion, respectively. A third infectious clone, pMRE16icDeltaE200-C220, was also constructed that contained a smaller deletion extending only to the 3' terminus of the CRBD coding region. Virus derived from pMRE16ic replicated with the same efficiency as parental virus in vertebrate (BHK-21) and mosquito (C6/36) cells and orally infected A. aegypti. Viruses derived from pMRE16icDeltaE200-Y229 and pMRE16icDeltaE200-C220 replicated 10- to 100-fold less efficiently in C6/36 and BHK-21 cells than did MRE16ic virus. Each deletion mutant poorly infected A. aegypti and dramatically reduced midgut infectivity and dissemination. However, all viruses generated nearly equal titers (approximately 6.0 log(10) PFU/ml) in mosquitoes 4 days after infection by intrathoracic inoculation. These results suggest that the deleted portion of the E2 CRBD represents an important determinant of MRE16 virus midgut infectivity in A. aegypti.
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Affiliation(s)
- Kevin M Myles
- Arthropod-Borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80526, USA
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