Flock House virus (FHV) is in the Alphanodavirus genus of the Nodaviridae family of viruses. Flock House virus was isolated from a grass grub (Costelytra zealandica) at the Flock House research station in Bulls, New Zealand. FHV is an extensively studied virus and is considered a model system for the study of other non-enveloped RNA viruses owing to its small size and genetic tractability, particularly to study the role of the transiently exposed hydrophobic gamma peptide and the metastability of the viral capsid.[1][2] FHV can be engineered in insect cell culture allowing for the tailored production of native or mutant authentic virions or virus-like-particles. FHV is a platform for nanotechnology and nanomedicine, for example, for epitope display and vaccine development.[3] Viral entry into host cells occurs via receptor-mediated endocytosis.[4] Receptor binding initiates a sequence of events during which the virus exploits the host environment in order to deliver the viral cargo in to the host cytosol. Receptor binding prompts the meta-stability of the capsid–proteins, the coordinated rearrangements of which are crucial for subsequent steps in the infection pathway. In addition, the transient exposure of a covalently-independent hydrophobic γ-peptide is responsible for breaching cellular membranes and is thus essential for the viral entry of FHV into host cells.[5]
Flock house virus genome and functional map of replicase protein A.
Flock House virus is a small, non-enveloped, icosahedral T=3 insect virus containing a bipartite positive sense ssRNA genome comprising two genes: RNA1 (3.1kb) an RNA2 (1.4kb). RNA1 encodes the RNA-dependent RNA polymerase and also contains a frame-shifted subgenomic RNA 3 (369 nts) that encodes protein B2, responsible for inhibition of RNAi pathways.[6] RNA2 encodes the capsid precursor, alpha, of which 180 copies form the viral capsid of FHV. Upon maturation, alpha undergoes an autocatalytic cleavage in its C-terminus to form beta, forming the main structural capsid component, and gamma, a short hydrophobic peptide required for endosome penetration that remains associated with the viral capsid. Virus-Like-Particles (VLPs) of FHV spontaneously form in S. frugiperda cell lines (e.g. Sf21) when RNA2 is expressed from a baculovirus vector and package cellular RNAs.[7][8]
Range
FHV was originally isolated from New Zealand grass grubs (Costelytra zealandica) in the former Flock House agricultural facility in Bulls, Ragnitikei, New Zealand.[9] Isolates were passaged in Drosophila cells in culture, which were subsequently shown to exhibit cell-death (cytopathic effect). FHV can also infect live flies.[10] FHV has been shown to infect medically important genera of insects: mosquitos, e.g. Anopheles gambiae; the tsetse fly; and the Chagas vector, Rhodnius prolixus Stal.[11][12] Infection of these organisms by FHV has been demonstrated to have similar characteristics in terms of viral titre, virus dissemination and mortality as has been shown for fruit fly infections.[citation needed]
Capsid structure
The structure and biophysical properties of authentic virions of FHV and of virus-like-particles (VLPs) have been extensively studied.[citation needed]
Other studies
FHV has provided a model system for the study of the emergence and evolution of defective-interfering RNAs (DI-RNAs).[citation needed]
References
↑ Odegard, A; Banerjee, M; Johnson, JE (2010). "Flock House Virus: A Model System for Understanding Non-Enveloped Virus Entry and Membrane Penetration". Cell Entry by Non-Enveloped Viruses. Current Topics in Microbiology and Immunology. Vol.343. pp.1–22. doi:10.1007/82_2010_35. ISBN978-3-642-13331-2. PMID20407886.
↑ Banerjee, M; Johnson, JE (February 2008). "Activation, exposure and penetration of virally encoded, membrane-active polypeptides during non-enveloped virus entry". Current Protein & Peptide Science. 9 (1): 16–27. doi:10.2174/138920308783565732. PMID18336320.
↑ Destito, G; Schneemann, A; Manchester, M (2009). "Biomedical Nanotechnology Using Virus-Based Nanoparticles". Viruses and Nanotechnology. Current Topics in Microbiology and Immunology. Vol.327. pp.95–122. doi:10.1007/978-3-540-69379-6_5. ISBN978-3-540-69376-5. PMID19198572.
↑ Dasgupta, R; Free, HM; Zietlow, SL; Paskewitz, SM; Aksoy, S; Shi, L; Fuchs, J; Hu, C; Christensen, BM (January 2007). "Replication of flock house virus in three genera of medically important insects". Journal of Medical Entomology. 44 (1): 102–10. doi:10.1603/0022-2585(2007)44[102:rofhvi]2.0.co;2. PMID17294927.
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