{{Short description|Species of virus}} {{Virusbox | name = Flock House virus | image = | image_alt = | image_caption = | parent = Alphanodavirus | species = Alphanodavirus flockense | synonyms = | synonyms_ref = | subdivision_ranks = | subdivision = }}

'''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.<ref>{{Cite book|last1=Odegard|first1=A|last2=Banerjee|first2=M|last3=Johnson|first3=JE|chapter=Flock House Virus: A Model System for Understanding Non-Enveloped Virus Entry and Membrane Penetration|title=Cell Entry by Non-Enveloped Viruses|series=Current Topics in Microbiology and Immunology|date=2010|volume=343|pages=1–22|doi=10.1007/82_2010_35|pmid=20407886|isbn=978-3-642-13331-2}}</ref><ref>{{cite journal|last1=Banerjee|first1=M|last2=Johnson|first2=JE|title=Activation, exposure and penetration of virally encoded, membrane-active polypeptides during non-enveloped virus entry|journal=Current Protein & Peptide Science|date=February 2008|volume=9|issue=1|pages=16–27|pmid=18336320|doi=10.2174/138920308783565732}}</ref> 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.<ref>{{cite book|last1=Destito|first1=G|last2=Schneemann|first2=A|last3=Manchester|first3=M|title=Viruses and Nanotechnology|chapter=Biomedical Nanotechnology Using Virus-Based Nanoparticles|series=Current Topics in Microbiology and Immunology|date=2009|volume=327|pages=95–122|doi=10.1007/978-3-540-69379-6_5|pmid=19198572|isbn=978-3-540-69376-5}}</ref> Viral entry into host cells occurs via receptor-mediated endocytosis.<ref>{{cite journal|last1=Odegard|first1=AL|last2=Kwan|first2=MH|last3=Walukiewicz|first3=HE|last4=Banerjee|first4=M|last5=Schneemann|first5=A|last6=Johnson|first6=JE|title=Low endocytic pH and capsid protein autocleavage are critical components of Flock House virus cell entry|journal=Journal of Virology|date=September 2009|volume=83|issue=17|pages=8628–37|doi=10.1128/JVI.00873-09|pmid=19553341|pmc=2738175}}</ref> 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.<ref>{{cite journal|pmid=1404613|pmc=240169|year=1992|last1=Schneemann|first1=A|title=Maturation cleavage required for infectivity of a nodavirus|journal=Journal of Virology|volume=66|issue=11|pages=6728–34|last2=Zhong|first2=W|last3=Gallagher|first3=T. M|last4=Rueckert|first4=R. R|doi=10.1128/JVI.66.11.6728-6734.1992}}</ref>

== Genome == [[File:Elife-25940-fig1-v2.jpg|thumb|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.<ref>{{cite journal|last1=Chao|first1=JA|last2=Lee|first2=JH|last3=Chapados|first3=BR|last4=Debler|first4=EW|last5=Schneemann|first5=A|last6=Williamson|first6=JR|title=Dual modes of RNA-silencing suppression by Flock House virus protein B2|journal=Nature Structural & Molecular Biology|date=November 2005|volume=12|issue=11|pages=952–7|doi=10.1038/nsmb1005|pmid=16228003|s2cid=37878393}}</ref> 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.<ref>{{cite journal|last1=Schneemann|first1=A|last2=Dasgupta|first2=R|last3=Johnson|first3=JE|last4=Rueckert|first4=RR|title=Use of recombinant baculoviruses in synthesis of morphologically distinct viruslike particles of flock house virus, a nodavirus|journal=Journal of Virology|date=May 1993|volume=67|issue=5|pages=2756–63|doi=10.1128/JVI.67.5.2756-2763.1993|pmid=8474173|pmc=237599}}</ref><ref>{{cite journal|last1=Routh|first1=A|last2=Domitrovic|first2=T|last3=Johnson|first3=JE|title=Host RNAs, including transposons, are encapsidated by a eukaryotic single-stranded RNA virus|journal=Proceedings of the National Academy of Sciences of the United States of America|date=7 February 2012|volume=109|issue=6|pages=1907–12|doi=10.1073/pnas.1116168109|pmid=22308402|pmc=3277583|bibcode=2012PNAS..109.1907R|doi-access=free}}</ref>

==Range== FHV was originally isolated from New Zealand grass grubs (Costelytra zealandica) in the former Flock House agricultural facility in Bulls, Ragnitikei, New Zealand.<ref>{{cite journal|last1=Scotti|first1=PD|last2=Dearing|first2=S|last3=Mossop|first3=DW|title=Flock House virus: a nodavirus isolated from Costelytra zealandica (White) (Coleoptera: Scarabaeidae)|journal=Archives of Virology|date=1983|volume=75|issue=3|pages=181–9|pmid=6188442|doi=10.1007/BF01315272|s2cid=9853542}}</ref> Isolates were passaged in ''Drosophila'' cells in culture, which were subsequently shown to exhibit cell-death (cytopathic effect). FHV can also infect live flies.<ref>{{cite journal|last1=Goic|first1=B|last2=Vodovar|first2=N|last3=Mondotte|first3=JA|last4=Monot|first4=C|last5=Frangeul|first5=L|last6=Blanc|first6=H|last7=Gausson|first7=V|last8=Vera-Otarola|first8=J|last9=Cristofari|first9=G|last10=Saleh|first10=MC|title=RNA-mediated interference and reverse transcription control the persistence of RNA viruses in the insect model Drosophila|journal=Nature Immunology|date=April 2013|volume=14|issue=4|pages=396–403|doi=10.1038/ni.2542|pmid=23435119|s2cid=6690552|url=https://hal-pasteur.archives-ouvertes.fr/pasteur-01957212/file/ni.2542_to_AU_HAL-1.pdf}}</ref> 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.<ref name=dasgupta >{{cite journal|last1=Dasgupta|first1=R|last2=Cheng|first2=LL|last3=Bartholomay|first3=LC|last4=Christensen|first4=BM|title=Flock house virus replicates and expresses green fluorescent protein in mosquitoes|journal=The Journal of General Virology|date=July 2003|volume=84|issue=Pt 7|pages=1789–97|doi=10.1099/vir.0.18938-0|pmid=12810873|doi-access=free}}</ref><ref>{{cite journal|last1=Dasgupta|first1=R|last2=Free|first2=HM|last3=Zietlow|first3=SL|last4=Paskewitz|first4=SM|last5=Aksoy|first5=S|last6=Shi|first6=L|last7=Fuchs|first7=J|last8=Hu|first8=C|last9=Christensen|first9=BM|title=Replication of flock house virus in three genera of medically important insects|journal=Journal of Medical Entomology|date=January 2007|volume=44|issue=1|pages=102–10|pmid=17294927|doi=10.1603/0022-2585(2007)44[102:rofhvi]2.0.co;2|doi-access=}}</ref> 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.<ref name=dasgupta />

== References == {{reflist}}

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Category:Nodaviridae