''Dependoparvovirus'' (formerly ''Dependovirus'' or Adeno-associated virus group) is a genus in the subfamily ''

Parvovirinae ''Parvovirinae'' is a subfamily of viruses in the family ''Parvoviridae''. There are ten genera and 84 species assigned to this subfamily. Taxonomy The following 10 genera are recognized: *'' Amdoparvovirus'' *'' Artiparvovirus'' *'' Aveparvovi ...

'' of the

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Parvoviridae Parvoviruses are a family of animal viruses that constitute the family ''Parvoviridae''. They have linear, single-stranded DNA (ssDNA) genomes that typically contain two genes encoding for a replication initiator protein, called NS1, and the pr ...

''; they are Group II viruses according to the

Baltimore classification Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a d ...

. Some dependoparvoviruses are also known as adeno-associated viruses because they cannot replicate productively in their

host cell In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

without the cell being coinfected by a helper virus such as an adenovirus, a

herpesvirus ''Herpesviridae'' is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word ''ἕρπειν ...

, or a

vaccinia virus ''Vaccinia virus'' (VACV or VV) is a large, complex, enveloped virus belonging to the poxvirus family. It has a linear, double-stranded DNA genome approximately 190 kbp in length, which encodes approximately 250 genes. The dimensions of the ...

Species

There are eleven recognized species: * ''

Adeno-associated dependoparvovirus A Adeno-associated viruses (AAV) are small viruses that infect humans and some other Primate, primate species. They belong to the genus ''Dependoparvovirus'', which in turn belongs to the family (biology), family ''Parvoviridae''. They are small ( ...

'' * '' Adeno-associated dependoparvovirus B'' * ''

Anseriform dependoparvovirus 1 Derzsy's disease is caused by ''Anseriform dependoparvovirus 1'', in the '' Parvoviridae'' family. It affects geese and Muscovy ducks. The virus is shed in the faeces and thus transmission is horizontal, via the direct faecal-oral route and a ...

'' * '' Avian dependoparvovirus 1'' * '' Carnivore dependoparvovirus 1'' * '' Chiropteran dependoparvovirus 1'' * '' Pinniped dependoparvovirus 1'' * '' Rodent dependoparvovirus 1'' * '' Rodent dependoparvovirus 2'' * '' Squamate dependoparvovirus 1'' * '' Squamate dependoparvovirus 2''

Virology

Dependoparvoviruses have an

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

shape, measure 22 nm is composed of 60 wedge-shaped proteins triangulation number = 1). Three proteins (VP1, VP2 and VP3) are present in each capsomere. Each capsid is made from 5 VP1, 5 VP2, and 50 VP3 proteins. The capsid does not have an envelope. The genome is a single molecule of single stranded DNA with a length of 4.7 kilobases. It has only two open reading frames. The 3' open reading frame is the structural capsid protein, cap, which can be spliced to form two RNAs, one for virion protein 1 (VP1) and the other goes on to eventually make VP2 and VP3. The second gene, rep, can be spliced into four different, nonstructural, regulatory proteins that all aid in the genome replication. These proteins are named Rep 78, Rep68, Rep 52, and Rep 40 based on their molecular weight. Due to inverted terminal repeats (ITRs) at each end of the genome, a T shaped secondary structure is formed. The complementary areas leave a 3'

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

group single stranded for the replication to begin. This 3' hydroxyl group is used as a primer for the

leading strand In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...

synthesis. Both positive and negative sense strands of DNA are made. Double stranded intermediates are formed throughout the replication; this means the two strands, positive and negative sense, will be matched up.

Host range

These viruses are capable of replication within all vertebrates. They are only limited by the virus they must infect with, also known as the helper virus. These helper viruses are necessary for the replication of a dependoparvovirus. A common helper virus in humans is the adenovirus.

Gene therapy

''Dependoparvovirus'' is not infectious enough to trigger an

immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...

; this makes it a good virus to use as a gene therapy tool.

Gene therapy Gene therapy is a medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying human DN ...

is a possible treatment for a variety of disorders and diseases that are genetic in origin.

Viral vectors Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism (''in vivo'') or in cell culture (''in vitro''). Viruses have evolved specialized molecul ...

are currently being developed to transport genes into human cells. Since this virus does not stimulate an immune response it can be used multiple times effectively without being neutralized before infection . Another reason these viruses are reliable vectors is the known insertion point for the genome. This virus always inserts its contents into the same place on chromosome 19. This predictability can cut down on the chances of inserting into an important area that might disrupt normal gene function or increase the risk of developing cancer. At this time, one challenge using this virus as a therapy tool is the fact that the genome is fairly small. With less than 5kb in the genome the amount of genetic material that can fit into the capsid is limited. Work is currently being done to increase the amount of information this vector can deliver. This may be accomplished by the ITRs found at both the 5' and 3' end of the genome. Since the ITRs have the same sequence they will leave complementary strands exposed if they are removed. The complementary strands can undergo recombination and join two 5kb inserted fragments together.

References

External links

ViralZone: Dependoparvovirus
{{Authority control Parvovirinae Virus genera