View source for Polydnaviriformidae

{{Short description|Family of viruses}}
{{Use dmy dates|date=April 2017}}
{{Virusbox
| name = Polydnavirus
| image = GiBV-em.jpg
| image_caption = Electron micrograph of a bracovirus
| taxon = Polydnaviriformidae
| subdivision = 
* ''[[Bracovirus|Bracoviriform]]''
* ''[[Ichnovirus|Ichnoviriform]]''
| synonyms =
* ''Polydnaviriformidae'' <small>ICTV 2021</small>
* ''Polydnaviridae'' <small>ICTV 1984</small>
}}

'''''Polydnaviriformidae''''' ({{IPAc-en|p|ɒ|ˈ|l|ɪ|d|n|ə|v|ɪ|r|ə|,|f|O:|m|ɪ|d|ɛ}} '''PDV''')<ref>{{cite web |title=Taxon Details: Polydnaviriformidae |url=https://ictv.global/taxonomy/taxondetails?taxnode_id=202204352&taxon_name=Polydnaviriformidae |website=ictv.global |quote=Proposal: 2021.006D.R.Polydnaviriformidae_1renfam_3rensp}}</ref> is a [[family (biology)|family]] of [[insect]] [[viriform]]s; members are known as '''polydnaviruses'''. There are two genera in the family: ''[[Bracovirus|Bracoform]]'' and ''[[Ichnovirus|Ichnoviriform]]''. Polydnaviruses form a [[symbiotic relationship]] with [[parasitoid wasps]]. [[ichnovirus|Ichnoviriform]]s (IV) occur in [[ichneumonidae|Ichneumonid wasps]] and [[bracovirus|Bracoviriform]]s (BV) in [[braconidae|Braconid wasps]]. The larvae of wasps in both of those groups are themselves parasitic on [[Lepidoptera]] (moths and butterflies), and the polydnaviruses are important in circumventing the immune response of their parasitized hosts.<ref name=ViralZone>{{cite web|title=Viral Zone|url=https://viralzone.expasy.org/147|publisher=ExPASy|access-date=15 June 2015}}</ref><ref name=ICTV>{{cite web |title=Virus Taxonomy: 2020 Release |url=https://ictv.global/taxonomy |publisher=International Committee on Taxonomy of Viruses (ICTV) |date=March 2021 |access-date=24 May 2021}}</ref> Little or no [[sequence homology]] exists between BV and IV, suggesting that the two genera have been evolving independently for a long time.

==Taxonomy==
Bracoviriform
{{div col|colwidth=18em}}
* Bracoviriform altitudinis
* Bracoviriform argentifrontis
* Bracoviriform blackburni
* Bracoviriform canadense
* Bracoviriform congregatae
* Bracoviriform crassicornis
* Bracoviriform croceipedis
* Bracoviriform curvimaculati
* Bracoviriform demolitoris
* Bracoviriform ectdytolophae
* Bracoviriform facetosae
* Bracoviriform flavicoxis
* Bracoviriform flavipedis
* Bracoviriform flavitestaceae
* Bracoviriform fumiferanae
* Bracoviriform glomeratae
* Bracoviriform hyphantriae
* Bracoviriform inaniti
* Bracoviriform indiense
* Bracoviriform insularis
* Bracoviriform kariyai
* Bracoviriform liparidis
* Bracoviriform marginiventris
* Bracoviriform melanoscelae
* Bracoviriform nigricipitis
* Bracoviriform ornigis
* Bracoviriform paleacritae
* Bracoviriform quadridentatae
* Bracoviriform rubeculae
* Bracoviriform schaeferi
* Bracoviriform texani
{{div col end}}
Ichnoviriform
{{div col|colwidth=18em}}
* Ichnoviriform acronyctae
* Ichnoviriform annulipedis
* Ichnoviriform aprilis
* Ichnoviriform arjunae
* Ichnoviriform benefactoris
* Ichnoviriform eribori
* Ichnoviriform exiguae
* Ichnoviriform flavicinctae
* Ichnoviriform forcipatae
* Ichnoviriform fugitivi
* Ichnoviriform fumiferanae
* Ichnoviriform geniculatae
* Ichnoviriform infestae
* Ichnoviriform interrupti
* Ichnoviriform lymantriae
* Ichnoviriform montani
* Ichnoviriform pilosuli
* Ichnoviriform rivalis
* Ichnoviriform rostralis
* Ichnoviriform sonorense
* Ichnoviriform tenuifemoris
* Ichnoviriform terebrantis
{{div col end}}
==Structure==
Viruses in ''Polydnaviridae'' are [[viral envelope|enveloped]], with [[prolate]] [[ellipsoid]] and cylindrical geometries. [[Genomes]] are circular and segmented, composed of multiple segments of double-stranded, [[superhelical DNA]] packaged in [[capsid]] [[proteins]]. They are around 2.0–31kb in length.<ref name=ViralZone/>

{| class="wikitable sortable" style="text-align:center"
|-
! Genus !! Structure || Symmetry !! Capsid !! Genomic arrangement !! Genomic segmentation
|-
|''Ichnoviriform''||Prolate ellipsoid||||Enveloped||Circular||Segmented
|-
|''Bracoviriform''||Prolate ellipsoid||||Enveloped||Circular||Segmented
|}

==Life cycle==
Viral replication is nuclear. DNA-templated [[transcription (biology)|transcription]] is the method of transcription. The virus exits the host cell by [[Nuclear_pore#Export_of_proteins|nuclear pore export]].

Parasitoid wasps serve as hosts for the virus, and Lepidoptera serve as hosts for these wasps. The female wasp injects one or more eggs into its host along with a quantity of virus. The virus and wasp are in a [[mutualism (biology)|mutualistic]] [[symbiotic]] relationship: expression of viral genes prevents the wasp's host's immune system from killing the wasp's injected egg and causes other physiological alterations that ultimately cause the parasitized host to die. Transmission routes are parental.<ref name=ViralZone/>

{| class="wikitable sortable" style="text-align:center"
|-
! Genus !! Host details !! Tissue tropism !! Entry details !! Release details !! Replication site !! Assembly site !! Transmission
|-
|''Ichnoviriform''||Parasitoid wasps (Ichneumonidae)||Hemocytes; fat bodies||Unknown||Budding through cell membrane<ref name=ViralZone/><ref name=webb/>||Nucleus||Nucleus||Unknown
|-
|''Bracoviriform''||Parasitoid wasps (Braconidae)||Hemocytes; fat bodies||Unknown||[[Lysis]]<ref name=ViralZone/>||Nucleus||Nucleus||Unknown
|}

==Biology==
[[File:Pdv-host.svg|thumb|288px|right|Diagram of a PDV host association]]

These viruses are part of a unique biological system consisting of an endoparasitic wasp ([[parasitoid]]), a host (usually [[lepidoptera]]n) larva, and the virus. The full [[genome]] of the virus is [[endogenous]], dispersed among the genome of the wasp. The virus only replicates in a particular part of the ovary, called the [[Calyx_(anatomy)#Insects|calyx]], of pupal and adult female wasps. The virus is injected along with the wasp egg into the body cavity of a lepidopteran host caterpillar and infects cells of the caterpillar. The infection does not lead to replication of new viruses; rather, it affects the caterpillar's [[immune system]], as the virion carries virulence genes instead of viral replication genes.<ref name="pmid25670535">{{cite journal |last1=Strand |first1=MR |last2=Burke |first2=GR |title=Polydnaviruses: From discovery to current insights. |journal=Virology |date=May 2015 |volume=479-480 |pages=393–402 |doi=10.1016/j.virol.2015.01.018 |pmid=25670535 |pmc=4424053 |doi-access=free}}</ref> It can be considered a type of [[viral vector]].<ref name=vec/>

Without the virus infection, [[phagocyte|phagocytic]] [[hemocyte (invertebrate immune system cell)|hemocytes]] (blood cells) will encapsulate and kill the wasp egg and larvae, but the immune suppression caused by the virus allows survival of the wasp egg and larvae, leading to hatching and complete development of the immature wasp in the caterpillar. Additionally, genes expressed from the polydnavirus in the parasitised host alter host development and metabolism to be beneficial for the growth and survival of the parasitoid larva.<ref name=webb>Webb, B. A. (1998). ''Polydnavirus biology, genome structure, and evolution''. In Miller, L.K., Ball, L.A., Eds. ''The Insect Viruses''. Plenum Publishing Corporation. pp. 105–139.</ref><ref>{{cite journal |last1= Roossinck |first1= M. J. |year= 2011 |title= Changes in population dynamics in mutualistic versus pathogenic viruses |journal= Viruses |volume= 3 |issue= 1|pages= 12–19 |doi=10.3390/v3010012 |pmid= 21994724 |pmc= 3187592|doi-access= free }}</ref>

===Potential carrier subfamilies===
*[[Ichneumonoidea]] 
** [[Braconidae]]
***[[Microgastrinae]]<ref name=webb/><ref>{{cite journal|last1=Murphy|first1=Nicholas|last2=Banks|first2=Jonathan C.|last3=Whitfield|first3=James B.|last4=Austin|first4=Andrew D.|date=2008-04-01|title=Phylogeny of the parasitic microgastroid subfamilies (Hymenoptera: Braconidae) based on sequence data from seven genes, with an improved time estimate of the origin of the lineage|journal=Molecular Phylogenetics and Evolution|volume=47|issue=1|pages=378–395|doi=10.1016/j.ympev.2008.01.022|pmid=18325792}}</ref>
***[[Miracinae]]
***[[Cheloninae]]<ref name=webb/>
***[[Cardiochilinae]]<ref name=webb/>
***[[Mendeselinae]]
***[[Khoikhoiinae]]
**[[Ichneumonidae]]
***[[Campopleginae]]<ref name=webb/>
***[[Banchinae]]<ref name=webb/><ref name=vec>{{cite journal|last1=Burke|first1=Gaelen R.|last2=Strand|first2=Michael R.|date=2012-01-31|title=Polydnaviruses of Parasitic Wasps: Domestication of Viruses To Act as Gene Delivery Vectors|journal=Insects|language=en|volume=3|issue=1|pages=91–119|doi=10.3390/insects3010091|pmc=4553618|pmid=26467950|doi-access=free}}</ref>

==Characteristics==
Both genera of PDV share certain characteristics:

*the virus particles of each contain multiple segments of dsDNA (double-strand, or "normal" DNA, as contrasted with positive- or negative-sense single-strand DNA or RNA, as found in some other viruses) with each segment containing only part of the full genome (much like chromosomes in [[Eukaryote|eukaryotic organisms]])
*the genome of the virus has eukaryotic characteristics such as the presence of [[Intron|introns]] (common for insect genes but rare for viruses) and a low coding density<ref name="virology_2006">{{cite journal |author1=Webb, B. A. |author2=Strand, M. R. |author3=Dickey, S. E. |author4=Beck, M. H. |author5=Hilgarth, R. S. |author6=Barney, W. E. |author7=Kadash, K. |author8=Kroemer, J. A. |author9=Lindstrom, K. G. |author10=Rattanadechakul, W. |author11=Shelby, K. S. |author12=Thoetkiattikul, H. |author13=Turnbull, M. W. |author14=Witherell, R. A. |title= Polydnavirus genomes reflect their dual roles as mutualists and pathogens |journal=Virology |year=2006 |volume=347 |pages= 160–174 |doi= 10.1016/j.virol.2005.11.010 |pmid=16380146 |issue=1|display-authors=etal|doi-access=free}}</ref>
*the genome of each virus is integrated into the host wasp genome<ref name="integrated_1991">{{cite journal |author1=Fleming, J.-A. G. W. |author2=Summers, M. D. |name-list-style=amp |title= Polydnavirus DNA is integrated in the DNA of its parasitoid wasp host |journal= Proceedings of the National Academy of Sciences |year= 1991 |volume=88 |pages= 9770–9774 |doi= 10.1073/pnas.88.21.9770 |pmid= 1946402 |issue=21 |pmc=52802|bibcode=1991PNAS...88.9770F|doi-access=free }}</ref>
*the genome is organized in several multiple-member genes families (which differ between Bracoviruses and Ichnoviruses)
*the virus particles are only produced in specific cell types in the female wasp's reproductive organs

The morphologies of the two genera are different when observed by electron microscopy. Ichnoviruses tend to be ovoid while bracoviruses are short rods. The virions of Bracoviruses are released by [[Lysis|cell lysis]]; the virions of Ichnoviruses are released by budding.

==Evolution==
[[Nucleic acid]] analysis suggests a very long association of the viruses with the wasps (estimated 73.7 million years ± 10 million).<ref>{{cite journal |author=Whitfield, J. B. |title= Estimating the age of the polydnavirus-braconid wasp symbiosis |journal=Proceedings of the National Academy of Sciences |year= 2002 |volume=99 |pages=7508–7513 |doi= 10.1073/pnas.112067199 |pmid= 12032313 |issue=11 |pmc=124262|bibcode= 2002PNAS...99.7508W|doi-access= free }}</ref>

=== Older wasp-derived theory ===
Two proposals have been advanced for how the wasp/virus association developed. The first suggests that the virus is derived from wasp genes. Many parasitoids that do not use PDVs inject proteins that provide many of the same functions, that is, a suppression of the immune response to the parasite egg. In this model, the braconid and ichneumonid wasps packaged genes for these functions into the viruses—essentially creating a gene-transfer system that results in the caterpillar producing the immune-suppressing factors. In this scenario, the PDV structural proteins (capsids) were probably "borrowed" from existing viruses.<ref name=Reineke2006/>

=== Current endogenous virus theory ===
{{see also|Endogenous viral element}}
The alternative proposal suggests that ancestral wasps developed a beneficial association with an existing virus that eventually led to the integration of the virus into the wasp's genome. Following integration, the genes responsible for virus replication and the capsids were (eventually) no longer included in the PDV genome. This hypothesis is supported by the distinct morphology differences between IV and BV, suggesting different ancestral viruses for the two genera. BV has likely evolved from a [[nudivirus]], specifically a betanudivirus,<ref name="pmid28728099">{{cite journal |last1=Drezen |first1=JM |last2=Leobold |first2=M |last3=Bézier |first3=A |last4=Huguet |first4=E |last5=Volkoff |first5=AN |last6=Herniou |first6=EA |title=Endogenous viruses of parasitic wasps: variations on a common theme. |journal=Current Opinion in Virology |date=August 2017 |volume=25 |pages=41–48 |doi=10.1016/j.coviro.2017.07.002 |pmid=28728099}}</ref> ~{{Ma|100}}.<ref name=Herniou2013>{{cite journal |vauthors=Herniou EA, Huguet E, Thézé J, Bézier A, Periquet G, Drezen JM |year= 2013 |title= When parasitic wasps hijacked viruses: genomic and functional evolution of polydnaviruses |journal= Philos Trans R Soc Lond B Biol Sci |volume= 368 |issue= 1626 |page= 20130051 |doi= 10.1098/rstb.2013.0051 |pmid= 23938758 |pmc= 3758193}}</ref> IV has a less clear origin: although earlier reports found a protein p44/p53 with structural similarities to [[ascovirus]], the link was not confirmed in later studies.<ref>{{cite journal |last1=Volkoff |first1=AN |last2=Jouan |first2=V |last3=Urbach |first3=S |last4=Samain |first4=S |last5=Bergoin |first5=M |last6=Wincker |first6=P |last7=Demettre |first7=E |last8=Cousserans |first8=F |last9=Provost |first9=B |last10=Coulibaly |first10=F |last11=Legeai |first11=F |last12=Béliveau |first12=C |last13=Cusson |first13=M |last14=Gyapay |first14=G |last15=Drezen |first15=JM |title=Analysis of virion structural components reveals vestiges of the ancestral ichnovirus genome. |journal=PLOS Pathogens |date=27 May 2010 |volume=6 |issue=5 |pages=e1000923 |doi=10.1371/journal.ppat.1000923 |doi-access=free |pmid=20523890|pmc=2877734}}</ref> As a result, the current opinion is that IV originated from a yet-unidentified novel viral family,<ref name="pmid28728099"/> with a weak link to the [[NCLDV]]s.<ref name="pmid26085165">{{cite journal |last1=Béliveau |first1=C |last2=Cohen |first2=A |last3=Stewart |first3=D |last4=Periquet |first4=G |last5=Djoumad |first5=A |last6=Kuhn |first6=L |last7=Stoltz |first7=D |last8=Boyle |first8=B |last9=Volkoff |first9=AN |last10=Herniou |first10=EA |last11=Drezen |first11=JM |last12=Cusson |first12=M |title=Genomic and Proteomic Analyses Indicate that Banchine and Campoplegine Polydnaviruses Have Similar, if Not Identical, Viral Ancestors. |journal=Journal of Virology |date=September 2015 |volume=89 |issue=17 |pages=8909–21 |doi=10.1128/JVI.01001-15 |doi-access=free |pmid=26085165|pmc=4524098 }}</ref> In either case, both genera were formed through a single integration event in their respective wasp lineages.<ref name="pmid25670535"/>

The two groups of viruses in the family are not in fact phylogenetically related suggesting that this taxon may need revision.<ref name=Dupuy2006>{{cite journal |vauthors=Dupuy C, Huguet E, Drezen JM |year= 2006 |title= Unfolding the evolutionary story of polydnaviruses |journal= Virus Res |volume= 117 |issue= 1 |pages= 81–89 |doi=10.1016/j.virusres.2006.01.001 |pmid= 16460826}}</ref>

==Effect on host immunity==
In the host, several mechanisms of the insect immune system can be triggered when the wasp lays its eggs and when the parasitic wasp is developing. When a large body (wasp egg or small particle used experimentally) is introduced into an insect's body, the classic immune reaction is the encapsulation by hematocytes. An encapsulated body can also be melanised in order to asphyxiate it, thanks to another type of hemocyte, which uses the [[phenoloxidase]] pathway to produce melanin. Small particles can be phagocytosed, and macrophage cells can then be also melanised in a nodule. Finally, insects can also respond with production of [[Antimicrobial_peptides|antiviral peptides]].<ref name=Virologie>{{cite journal|author1=JM. Drezen |author2=S. Savary |author3=M. Poirier |author4=G. Periquet |title=Polydnaviruses, viral entities domesticated by the parasitoid wasps|journal=Virologie|year= 1999|volume= 3|issue= 1|pages=11–21}}</ref>

PolyDNAvirus protect the hymenopteran larvae from the host immune system, acting at different levels.

*First they can disable or destroy hematocytes. The polyDNAvirus associated with ''Cotesia rubecula'', code for a protein CrV1 that denatures actin filaments in hematocytes, so those cells become less able to move and adhere to the larvae.<ref name=Virologie/> ''Microplitis demolitor'' Bracovirus (MdBV) induce apoptosis of hematocytes, thanks to its gene PTP-H2.<ref name=Virologie/> It also decreases the adhesion capacity of hematocytes, thanks to its gene Glc1.8. The gene also inhibits phagocytosis.<ref>{{cite journal|author1=Markus Beck |author2=Michael R. Strand |name-list-style=amp |title=Glc1.8 from Microplitis demolitor Bracovirus Induces a Loss of Adhesion and Phagocytosis in Insect High Five and S2 Cells|journal=Journal of Virology|date=February 2005|volume= 79|issue= 3|pages=1861–1870|doi=10.1128/jvi.79.3.1861-1870.2005 |pmid=15650210 |pmc=544146}}</ref>
*PolyDNAvirus can also act on melanisation, MdBV interferes with the production of [[phenoloxidase]].<ref>{{cite journal|author1=Lu Zhiqiang |author2=Beck Markus H. |author3=Wang Yang |author4=Jiang Haobo |author5=Strand Michael R |title=The Viral Protein Egf1.0 Is a Dual Activity Inhibitor of Prophenoloxidase-activating Proteinases 1 and 3 from ''Manduca sexta''|journal=Journal of Biological Chemistry|date=August 2008|volume=283|issue=31|pages=21325–21333 |doi=10.1074/jbc.M801593200|pmid=18519564 |pmc=2490783 |doi-access=free}}</ref>
*Finally, polyDNAvirus can also produce viral [[ankyrin]]s, that interfere with production of antiviral peptides.<ref>{{cite journal|author1=Bae Sungwoo |author2=Kim Yonggyun |title=IkB genes encoded in Cotesia plutellae bracovirus suppress an antiviral response and enhance baculovirus pathogenicity against the diamondback moth, Plutella xylostella.|journal=Journal of Invertebrate Pathology|date=2009-09-01|volume= 102|issue= 1|pages= 79–87|pmid=19559708|issn= 0022-2011|doi=10.1016/j.jip.2009.06.007}}</ref> In some Ichnoviruses, Vankyrin can also prevent apoptosis, the extreme reaction of a cell to block viral propagation.<ref>{{cite journal|author1=Fath-Goodin A. |author2=Kroemer J. A. |author3=Webb B. A |title=The Campoletis sonorensis ichnovirus vankyrin protein P-vank-1 inhibits apoptosis in insect Sf9 cells|journal=Insect Molecular Biology|date=August 2009|volume= 18|issue= 4|pages=497–506|doi=10.1111/j.1365-2583.2009.00892.x|pmid=19453763|s2cid=31146050 }}</ref><ref name=Clavijo2011>{{cite journal |vauthors=Clavijo G, Dorémus T, Ravallec M, Mannucci MA, Jouan V, Volkoff AN, Darboux I |year= 2011 |title= Multigenic families in Ichnovirus: A tissue and host specificity study through expression analysis of vankyrins from ''Hyposoter didymator'' Ichnovirus |journal= PLOS ONE |volume= 6 |issue= 11 |page= e27522 |doi=10.1371/journal.pone.0027522 |pmid=22087334 |pmc=3210807|bibcode= 2011PLoSO...627522C|doi-access= free }}</ref>
*The Ichnoviruses produce some proteins called vinnexins which have been recognized as homologous to the [[Innexin|innexins]] of insects. They are responsible for the encoding of the structural units of the gap-junctions. These proteins may alter the intercellular communication which could explain the disruption of the [[encapsidation]] process.<ref>{{cite journal|author1=Marziano N.K. |author2=Hasegawa D.K. |author3=Phelan P. |author4=Turnbull M.W. |title= Functional Interactions between Polydnavirus and Host Cellular Innexins|journal= Journal of Virology|date=October 2011|volume= 85|issue=19|pages=10222–9 |doi=10.1128/jvi.00691-11 |pmid=21813607 |pmc=3196458}}</ref>

==Virus-like particles==
Another strategy used by parasitoid [[Hymenoptera]] to protect their offspring is production of [[virus-like particle]]s. VLPs are similar to viruses in their structure, but they don't carry any nucleic acid. For example, ''Venturia canescens'' ([[Ichneumonidae|Ichneumonidea]]) and ''[[Leptopilina]] sp.'' ([[Figitidae]]a) produce VLPs.

VLPs can be compared to PolyDNAvirus because they are secreted in the same way, and they both act to protect the larvae against the host's immune system. ''V. canescens''-VLPs (VcVLP1, VcVLP2, VcNEP ...) are produced in the calyx cells before they go to the oviducts. Work in 2006 did not find their link to any viruses and assumed a cellular origin.<ref name=Reineke2006/> More recent comparison links them to highly reshuffled domesticated [[Nudivirus]] sequences. This link produces the name ''Venturia canescens endogenous nudivirus'' (VcENV), an alphanudivirus closely related to NlENV found in ''[[Nilaparvata lugens]]''.<ref name=nv>{{cite journal |last1=Leobold |first1=Matthieu |last2=Bézier |first2=Annie |last3=Pichon |first3=Apolline |last4=Herniou |first4=Elisabeth A |last5=Volkoff |first5=Anne-Nathalie |last6=Drezen |first6=Jean-Michel |last7=Abergel |first7=Chantal |title=The Domestication of a Large DNA Virus by the Wasp Venturia canescens Involves Targeted Genome Reduction through Pseudogenization |journal=Genome Biology and Evolution |date=July 2018 |volume=10 |issue=7 |pages=1745–1764 |doi=10.1093/gbe/evy127 |pmid=29931159 |pmc=6054256 |doi-access=free}}</ref>

VLPs protect the Hymenoptera larvae locally, whereas polyDNAvirus can have a more global effect. VLPs allow the larvae to escape the immune system: the larva is not recognised as harmful by its host, or the immune cells can't interact with it thanks to the VLPs.<ref name=Reineke2006>{{cite journal|author1=Annette Reineke |author2=Sassan Asgari |author3=Otto Schmidt |name-list-style=amp |title=Evolutionary Origin of Venturia canescens Virus-Like Particles|journal=Archives of Insect Biochemistry and Physiology|year=2006|volume=61|issue=3 |pages=123–133|doi=10.1002/arch.20113|pmid=16482583}}</ref> ''Venturia canescens'' uses these instead of polydnaviruses because its ichnovirus has been deactivated.<ref name=nv/>

The wasp ''Leptopilina heterotoma'' secrete VLPs that are able to penetrate into the [[Hemocyte (invertebrate immune system cell)|lamellocyte]]s, thanks to specific receptors, and then modify the shape and surface properties of the lamellocytes so they become inefficient and the larvae are safe from encapsulation.<ref>{{cite journal|author1=R. M. Rizki |author2=T. M. Rizki |title=Parasitoid virus-like particles destroy Drosophila cellular immunity|journal=Proceedings of the National Academy of Sciences of the United States of America|date=November 1990|volume= 87|issue=21|pages=8388–8392|doi=10.1073/pnas.87.21.8388|pmid=2122461|pmc=54961|bibcode=1990PNAS...87.8388R|doi-access=free }}</ref> The ''Leptopilina'' VLPs or mixed-strategy extracellular vesicles (MSEVs) contain some secretion systems. Their evolutionary picture is less clear,<ref name="pmid28889977">{{cite journal |last1=Heavner |first1=ME |last2=Ramroop |first2=J |last3=Gueguen |first3=G |last4=Ramrattan |first4=G |last5=Dolios |first5=G |last6=Scarpati |first6=M |last7=Kwiat |first7=J |last8=Bhattacharya |first8=S |last9=Wang |first9=R |last10=Singh |first10=S |last11=Govind |first11=S |title=Novel Organelles with Elements of Bacterial and Eukaryotic Secretion Systems Weaponize Parasites of Drosophila |journal=Current Biology |date=25 September 2017 |volume=27 |issue=18 |pages=2869–2877.e6 |doi=10.1016/j.cub.2017.08.019 |pmid=28889977 |pmc=5659752 |doi-access=free}}</ref> but a recently reported virus, ''L. boulardi'' Filamentous Virus (LbFV), shows significant similarities.<ref name="pmid32080746">{{cite journal |last1=Di Giovanni |first1=D |last2=Lepetit |first2=D |last3=Guinet |first3=B |last4=Bennetot |first4=B |last5=Boulesteix |first5=M |last6=Couté |first6=Y |last7=Bouchez |first7=O |last8=Ravallec |first8=M |last9=Varaldi |first9=J |title=A Behavior-Manipulating Virus Relative as a Source of Adaptive Genes for Drosophila Parasitoids. |journal=Molecular Biology and Evolution |date=1 October 2020 |volume=37 |issue=10 |pages=2791–2807 |doi=10.1093/molbev/msaa030 |pmid=32080746|doi-access=free |biorxiv=10.1101/342758}}</ref>

== Micro-RNA ==
MicroRNA are small RNA fragments produced in the host cells thanks to a specific enzymatic mechanism. They promote viral RNA destruction. MicroRNA attach to viral-RNA because they are complementary. Then the complex is recognised by an enzyme that destroys it. This phenomenon is known as [[PTGS]] (for post transcriptional gene silencing)<ref>{{cite journal|author1=Li, H.W. |author2=Ding, S.W. |name-list-style=amp |title=Antiviral silencing in animals|journal=FEBS Lett.|year=2005|volume=579|issue=26 |pages=5965–5973|doi=10.1016/j.febslet.2005.08.034|pmid=16154568|pmc=1350842}}</ref> or RNAi ([[RNA interference]].)

It is interesting to consider the microRNA phenomenon in the polyDNAvirus context. Many hypotheses can be formulated:
*Braconidae carry [[nudivirus]]-related genes in their genome,<ref>{{cite journal|vauthors=Bézier A, Annaheim M, Herbinière J, Wetterwald C, Gyapay G, Bernard-Samain S, Wincker P, Roditi I, Heller M, Belghazi M, Pfister-Wilhem R, Periquet G, Dupuy C, Huguet E, Volkoff AN, Lanzrein B, Drezen JM |title=Polydnaviruses of braconid wasps derive from an ancestral nudivirus|journal=Science|date=13 February 2009|volume= 323|series=13|issue= 5916|pages=926–30|doi=10.1126/science.1166788|pmid=19213916|bibcode=2009Sci...323..926B|s2cid=6538583|url=https://zenodo.org/record/1134807}}</ref> so they may be able to produce microRNA against nudivirus, as an innate immunity.
*Wasps perhaps use microRNA to control the viral genes they carry.
*PolyDNAvirus can also use PTGS to interfere with the host's gene expression.
*PTGS is also used for organisms' development, using the same enzymes as antiviral gene silencing, so we can imagine that if the host uses PTGS against polyDNAvirus, perhaps it also affects its development.

==See also==
*[[Mutualism (biology)|Mutualism]]

==References==
{{Reflist}}
*ICTVdB Management (2006). 00.055. Polydnaviridae. In: ICTVdB—The Universal Virus Database, version 4. Büchen-Osmond, C. (Ed), Columbia University, New York, USA
*{{cite journal |author=Espagne, E. |title= Genome Sequence of a Polydnavirus: Insights into Symbiotic Virus Evolution |journal=Science |year=2004 |volume=306 |pages= 286–289 |doi= 10.1126/science.1103066 |pmid= 15472078 |bibcode= 2004Sci...306..286E |issue=5694 |s2cid= 12260572 |display-authors=etal |url=https://www.science.org/doi/10.1126/science.1103066}}

==External links==
*http://research.biology.arizona.edu/mosquito/willott/507/polydnaviruses.html
*[https://viralzone.expasy.org/147 '''Viralzone''': Polydnaviridae]
*[https://ictv.global/taxonomy '''ICTV''']
{{Baltimore (virus classification)}}

{{Taxonbar|from=Q1892353}}

[[Category:Polydnaviridae| ]]
[[Category:Symbiosis]]