Black Queen Cell Virus

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Black Queen Cell Virus
Systematics
Classification : Viruses
Area : Riboviria
Order : Picornavirales
Family : Dicistroviridae
Genre : Triatovirus
Type : Black Queen Cell Virus
Taxonomic characteristics
Genome : (+) ssRNA linear
Baltimore : Group 4
Symmetry : icosahedral
Scientific name
Black queen cell virus
Short name
BQCV
Left

The Black Queen Cell Virus ( English Black Queen Cell Virus , BQCV ) is a virus that infects honey bees, in particular the species Apis mellifera (Western honey bee), Apis florea (dwarf honey bee ) and Apis dorsata (giant honey bee ). The infestation of the latter two species is more recent and can be attributed to genetic similarity and geographic proximity to the former. In addition, several species of bumblebee could also be infected (see below).

The virus is not only because of its relative abundance of importance, but above all because bees the most important pollinators of flowering plants ( angiosperms are). In particular, agriculture depends on pollination by bees in order to be able to work economically.

description

The black queen cell virus was originally described as early as 1977, but its genome was not sequenced until 2000. BQCV is most commonly found in Australia and parts of South Africa. BQCV has a noticeable effect on the pupae of queen bees by first turning yellow, then black and finally dying off. However, these visible symptoms only manifest themselves in the larvae. Therefore, the queen bees from which these pupae were derived appear to be healthy themselves and show no symptoms of infection with this virus. Even if only the larvae are visible affected by this disease, also can adult (adult) bees are infected but remain asymptomatic , d. H. without symptoms.

It is transmitted by a unicellular parasite called Nosema apis ( Microsporidia ), which lives in the honeybees' intestines. In addition, BQCV can also be transmitted from nurse bees to larvae during feeding; as well as from beehive to beehive when the bees move between them or when infected queen bees are distributed to other hives.

As with the other viral diseases of honey bees, there are no vaccines or forms of treatment available to treat bees infected with BQCV (as of January 2020). Hence, hygiene is the best way to prevent the spread. Hygiene practices include the replacement of the honeycomb in the hive and replacing the queen ( English requeening ). Requeening generally means that the queen of the beehive is replaced with a new one; in the case of infected beehives in particular by a guaranteed healthy one.

Systematics

The Black Queen Cell Virus belongs to the order Picornavirales ( Picorna -like viruses). Families within this order include the Picornaviridae , Comoviridae , Dicistroviridae , Iflaviridae , Marnaviridae, and Sequiviridae . BQCV belongs to the family of dicistroviridae that arthropods infected (arthropods). Within this family, a distinction is made between the genera Cripavirus , Aparavirus and Triatovirus (with BQCV).

construction

A virion (virus particle) of the black queen cell virus contains 60 copies of the proteins VP1, VP2 and VP3, which are all important capsid proteins. The capsid is the shell of the virus particle, inside of which is the genetic material of the virus. VP4 proteins can sometimes also occur in the capsid, but they do not affect the infectivity of the virus or its ability to transmit. The surface of the virion has large protrusions ( English protrusive ) which are formed from the proteins VP1 and VP3 and 3-fold between the 5- and the axis of the icosahedral are capsid. An icosahedral capsid consists of 20 triangular faces that are put together in such a way that they come close to a sphere. The axes ( axes of symmetry ) run through the opposite corner points of the icosahedron.

Because of the protrusions, BQCV is larger than most other picornaviruses. The capsid is also characterized by plateaus (around 3-fold axis) and depressions (around 2-fold axis).

Viruses with icosahedral symmetry are characterized by triangulation numbers . BQCV has a pseudo-T = 3 capsid, which means that mathematically it is a T = 1 symmetry. However, the structure of the capsid makes it look like T = 3.

Genome

The black queen cell virus is a non-enveloped RNA virus . The genome consists of a linear, single-stranded positive sense RNA enclosed in the icosahedral capsid (as described above).

The genome of this virus contains 8550 nucleotides and is polyadenylated . Nucleotides are organic molecules that serve as monomer units to form nucleic acid polymers such as deoxyribonucleic acid ( DNA ) and ribonucleic acid ( RNA ). There are four different canonical nucleotides that are commonly found in the genome. In BQCV, 29.2% of its genome consists of A-nucleotides , 30.6% of U-nucleotides , 18.5% of C-nucleotides and 21.6% of G-nucleotides . The genome is called polyadenylated if it has a poly (A) tail at the end. H. has a chain of only adenine bases. The Black Queen Cell Virus contains two open reading frames ( english open reading frames , ORFs). This is a continuous series of codons that contain a start codon (usually AUG) and a stop codon (usually UAA, UAG or UGA). ORF1 and ORF2 encode polyproteins that contain non-structural and structural (capsid-forming) subunits, respectively.

Propagation cycle

Replication takes place in principle as with all members of the Dicistroviridae family .

Entry into the host cell

The virus enters the host cell through clathrin- mediated endocytosis . Clathrin-mediated endocytosis is generally a process in which cells absorb metabolites , hormones , other proteins - and in some cases viruses - by budding inward from plasma membrane vesicles . This absorption begins after the virion binds to a receptor on the cell membrane. Once inside the cell, the virus particle is uncoated and the genome (RNA) is released into the cytoplasm .

Replication

After the virus has entered the host cell, it must replicate (multiply) its genome. In dicistroviruses, the 5'-VPg protein activates RNA synthesis and inhibits translation of cellular mRNA , thereby promoting translation of viral mRNA. The aforementioned ORF1 codes for the replication enzymes, in particular the RNA-dependent RNA polymerase , which helps with RNA replication. The genome of the virus has a positive strand of RNA that is used as a template to synthesize the negative strand of RNA. This negative strand is then used as a template to synthesize more genomic RNA (RNA of the genome).

Interaction with the host

The main host of the Black Queen Cell virus is the honey bee genus Apis ; but there are also several species of bumblebee that have since been identified as possible hosts for this virus.

In particular, the virus affects its host's ability to produce offspring. The offspring are still produced by infected individuals, but they do not survive. Another influence on the host (as mentioned) is that the virus disrupts cellular mRNA production in favor of its own mRNA production.

Another important interaction that BQCV has with its host is the virus' resistance to host cell mechanisms. This resistance is caused by a cap structure that the BQCV has at the 5 'end of its genome. This cap structure has many functions: it protects the virus mRNA from degradation, ensures efficient translation and helps the mRNA to get from the cytoplasm to the cell nucleus (the replication site). One can study these viral interactions with the host cells by creating mutations in the viral genome and analyzing the effects on the host cell.

Associated Diseases

There are many diseases or viruses that can be linked to the black queen cell virus . One such disease is Nosema disease. When a honey bee is infected with Nosema apis , the chances of the same bee developing BQCV are greatly increased. Nosema disease can be treated with Flumidil -B in infected honey bees . Another virus that can be associated with BQCV, the sacbrood virus ( English Sacbrood virus , SBV) in the family Iflaviridae the same virus order. This virus manifests itself with symptoms similar to BQCV, but affects the beehive workers instead of the queen bee.

The black queen cell virus is similar to several other viruses in the Dicistroviridae family . The genus Aparavirus with the species Kashmir bee virus (KBV), Israeli acute paralysis virus ( Israeli acute paralysis virus , IAPV) and Acute bee paralysis virus ( acute bee paralysis virus , ABPV) is closely related to the BQCV. However, these all have less clear symptoms.

Structurally, as a member of the genus Triatovirus, BQCV is most similar to the type species Triatoma virus (TrV), but also to the Iflaviruses (genus Iflavirus in the family Iflaviridae , including the species wing deformity virus ). Iflaviruses also infect insects, just like the Black Queen Cell Virus.

Human viruses that are closest to BQCV include the hepatitis A virus and parechovirus A (aka human parechovirus ). Both are also members of the Picornaviridae family and could form evolutionary intermediates between human viruses and insect viruses.

Interactions with other parasites

BQCV interacts with parasites , which increases the mortality ( death rate) of the beekeepers. Parasites, in particular the Varroa destructor mite , are often found in colonies of bees that are simultaneously infected with viruses. The parasites can activate the virus when it is latent (dormant) and they can also act as vectors (vectors) to transmit the virus to other uninfected bees. Both properties of this parasite lead to an increase in the mortality rate and infectivity in relation to the virus in these colonies.

Others

Some members of the Dicistroviridae family are used for pest control. Some examples include the control of the olive fruit fly with the kappapapilloma virus 2 (alias Shope papilloma virus , SPV or Cottontail rabbit papilloma virus , CrPV), as well as the control of the cotton bollard owl Helicoverpa armigera (from the owl butterfly family ) with the Helicoverpa armigera stunt virus ( HaSV, family Alphatetraviridae ). The Black Queen Cell virus is of course not used in this way, since bee colonies are beneficial insects for agriculture / economy and ecology .

Individual evidence

  1. ICTV Master Species List 2018b.v2 . MSL # 34, March 2019
  2. X. Zhang, SY He, JD Evans, JS Pettis, GF Yin, YP Chen: New evidence that deformed wing virus and black queen cell virus are multi-host pathogens . In: Journal of Invertebrate Pathology . 109, No. 1, January 1, 2012, pp. 156–159. doi : 10.1016 / j.jip.2011.09.010 .
  3. a b c d e f g h i j k l m n Radovan Spurny, Antonín Přidal, Lenka Pálková, Hoa Khanh Tran Kiem, Joachim R. de Miranda, Pavel Plevka: Virion Structure of Black Queen Cell Virus, a Common Honeybee Pathogen . In: Journal of Virology . 91, No. 6, February 28, 2017, ISSN  0022-538X . doi : 10.1128 / JVI.02100-16 . PMID 28077635 . PMC 5331821 (free full text).
  4. a b c d e f g h i j Bryony C. Bonning: The Dicistroviridae: An emerging family of invertebrate viruses . In: Virologica Sinica . 24, No. 5, October 1, 2009, ISSN  1674-0769 , pp. 415-427. doi : 10.1007 / s12250-009-3044-1 .
  5. a b c d e Mongi Benjeddou, Neil Leat, Mike Allsopp, Sean Davison: Development of infectious transcripts and genome manipulation of Black queen-cell virus of honey bees . In: Journal of General Virology . 83, No. 12, 2002, pp. 3139-3146. doi : 10.1099 / 0022-1317-83-12-3139 . PMID 12466491 .
  6. a b c d e f Neil Leat, Brenda Ball, Vandana Govan, Sean Davison: Analysis of the complete genome sequence of black queen-cell virus, a picorna-like virus of honey bees . In: Journal of General Virology . 81, No. 8, 2000, pp. 2111-2119. doi : 10.1099 / 0022-1317-81-8-2111 .
  7. a b c Black queen cell virus ( en-AU ) on BeeAware
  8. ^ A b Emily Pitts, Office of Communications: Honey Bee Disorders: Viral Diseases | Honey Bee Program | CAES Entomology | UGA ( en )
  9. Tibor I. Szabo: Requeening Honeybee Colonies with Queen Cells . In: Journal of Apicultural Research . 21, No. 4, January 1, 1982, ISSN  0021-8839 , pp. 208-211. doi : 10.1080 / 00218839.1982.11100543 .
  10. a b Andrea C. Baker, Declan C. Schroeder: The use of RNA-dependent RNA polymerase for the taxonomic assignment of Picorna-like viruses (order Picornavirales) infecting Apis mellifera L. populations . In: Virology Journal . 5, January 22, 2008, ISSN  1743-422X , p. 10. doi : 10.1186 / 1743-422X-5-10 . PMID 18211671 . PMC 2267166 (free full text).
  11. a b Olivier Le Gall, Peter Christian, Claude M. Fauquet, Andrew MQ King, Nick J. Knowles, Nobuhiko Nakashima, Glyn Stanway, Alexander E. Gorbalenya: Picornavirales, a proposed order of positive-sense single-stranded RNA viruses with a pseudo-T = 3 virion architecture . In: Archives of Virology . 153, No. 4, April 1, 2008, ISSN  0304-8608 , p. 715. doi : 10.1007 / s00705-008-0041-x . PMID 18293057 .
  12. a b Jane Flint, Vincent R. Racaniello, Glenn F. Rall, Anna Marie Skalka: Principles of Virology . ASM Press, Washington DC 2015, ISBN 9781555819330 , pp. 89-90.
  13. Pierre Fechter, George G. Brownlee: Recognition of mRNA cap structures by viral and cellular proteins . In: The Journal of General Virology . 86, No. Pt 5, May 2005, ISSN  0022-1317 , pp. 1239-1249. doi : 10.1099 / vir.0.80755-0 . PMID 15831934 .