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	~~The complex world of virology introduces myriad viruses, some of which possess distinct abilities to aid the replication of other viral entities. One such~~ virus~~, known as a '''helper virus''', is crucial for facilitating the replication of helper~~-~~dependent viral vectors that lack the inherent capacity for self~~-~~replication. These viral vectors, although deficient in replication machinery, are often employed in scientific and therapeutic interventions, relying on helper viruses to achieve their replication.~~		{{DISPLAYTITLE:Helper Virus}}
			{{Infobox virus
			\| name = Helper Virus
			\| image = <!-- No image available -->
			\| image_caption = <!-- No image available -->
			\| virus_group = I
			\| familia = [[Parvoviridae]]
			\| genus = [[Dependoparvovirus]]
			\| species = Various
			}}

	~~=== Overview ===~~		A '''helper virus''' is a virus that enables the replication of another virus, known as a [[defective virus]], which is unable to replicate on its own. Helper viruses provide essential functions that the defective virus lacks, allowing it to complete its life cycle.
	A '''helper virus''' is ~~essential for~~ the replication of ~~certain viral vectors~~. ~~It provides~~ the ~~missing components necessary for the propagation of these vectors when they are used in various biomedical applications~~.

	* '''Helper ~~Dependent Viral Vector''': These~~ are ~~viral vectors that have been stripped~~ of ~~their replication capabilities, either naturally or through genetic manipulation. Although they can't replicate on their own, they can still infect cells~~ and ~~introduce their genetic material<ref>Palmer, D~~.~~, & Ng, P. (2005). Helper-dependent adenoviral~~ vectors for ~~gene therapy~~. ~~Human gene therapy, 16(1), 1-16~~.~~</ref>.~~		==Overview==
	~~=== Mechanism of Action ===~~		Helper viruses are crucial in the study of [[virology]] and [[gene therapy]]. They are often used in laboratory settings to propagate defective viruses that are used as vectors for delivering [[genetic material]] into cells. The relationship between helper viruses and defective viruses is a key example of viral [[symbiosis]].

	~~When cells are coinfected with both the helper-dependent viral vector and the helper virus, the following process ensues~~:		==Mechanism of Action==
			Helper viruses provide missing functions that defective viruses need for replication. These functions can include:

	* ~~'''Coinfection'''~~: ~~Both~~ the ~~helper virus and~~ the ~~helper-dependent~~ viral ~~vector infect the target cell.~~		* [[Replication enzymes]]: Enzymes necessary for the replication of the viral genome.
	* '''Genome Integration''': The viral vector introduces its genome ~~into the host cell~~.		* [[Structural proteins]]: Proteins required for the assembly of the viral capsid.
	* ~~'''Helper Virus's Role'''~~: ~~The helper virus provides the necessary enzymes and other replication machinery to facilitate~~ the ~~replication~~ of the viral ~~vector's genome<ref>Kotin, R. M., & Snyder, R. O. (2017). Manufacturing clinical grade recombinant adeno-associated virus using invertebrate cell lines. Human gene therapy, 28(4), 350-360.</ref>~~.		* [[Transcription factors]]: Proteins that facilitate the transcription of viral genes.
	* ~~'''Replication'''~~: ~~The~~ viral ~~vector's genome is replicated, leveraging the machinery provided by the helper virus~~.
	~~=== Applications ===~~

	~~Helper viruses~~, ~~alongside helper-dependent viral vectors~~, ~~have found utility in several biomedical fields:~~		The helper virus infects the same cell as the defective virus, and its gene products complement the missing functions of the defective virus, allowing it to replicate.

	* '''Gene Therapy''': Helper-dependent viral vectors, with their replication components removed, present a safer alternative for gene delivery as they minimize the risks associated with viral replication. They are, therefore, used to deliver therapeutic genes to target cells or tissues in gene therapy protocols<ref>Thomas, C. E., Ehrhardt, A., & Kay, M. A. (2003). Progress and problems with the use of viral vectors for gene therapy. Nature Reviews Genetics, 4(5), 346-358.</ref>.		==Examples==
	* '''Vaccine Development''': These vectors can also be employed in the creation of viral vaccines. They introduce a harmless version of a pathogenic virus into the host to stimulate an immune response without causing disease.
	==~~= Challenges and Considerations =~~==

	~~Despite their advantages, the use~~ of helper ~~viruses~~ and ~~dependent viral vectors is not without challenges:~~		===Adeno-Associated Virus (AAV)===
			[[Adeno-associated virus]] (AAV) is a well-known example of a defective virus that requires a helper virus for replication. AAV is a member of the [[Parvoviridae]] family and the [[Dependoparvovirus]] genus. It requires co-infection with a helper virus, such as [[adenovirus]] or [[herpes simplex virus]], to replicate.

	* '''Contamination''': One of the ~~primary concerns is~~ the ~~potential contamination~~ of ~~the~~ viral ~~vector preparation with the~~ helper virus, which ~~can lead to unintended consequences when introduced into~~ a ~~patient~~ or ~~experimental model<ref>Urabe, M~~., ~~Ding, C., & Kotin, R. M. (2002). Insect cells as a factory~~ to ~~produce adeno-associated~~ virus ~~type 2 vectors~~. ~~Human gene therapy, 13(16), 1935~~-~~1943.</ref>~~.		===Hepatitis D Virus (HDV)===
	* '''Optimization''': Achieving optimal levels of coinfection for efficient replication without promoting excessive helper virus propagation can be a delicate balance.		[[Hepatitis D virus]] (HDV) is another example of a defective virus that requires a helper virus. HDV is dependent on the [[Hepatitis B virus]] (HBV) for its replication. HDV uses the surface antigen of HBV to form its own viral particles.
	=== Conclusion ===
	Helper viruses ~~are indispensable tools~~ in the ~~world~~ of ~~virology, particularly~~ in ~~therapeutic applications where safety~~ and ~~precision are paramount~~. Understanding ~~their role, mechanism,~~ and ~~challenges~~ can ~~enable scientists~~ and ~~clinicians to harness their benefits while minimizing potential drawbacks~~.		==Applications in Gene Therapy==
	~~== References ==~~		Helper viruses are used in [[gene therapy]] to produce viral vectors that can deliver therapeutic genes to target cells. For example, AAV vectors are produced using a helper virus system in which the necessary replication functions are provided by a helper virus or plasmid.
	~~<references />~~
			==Safety Considerations==
			When using helper viruses in research and therapy, it is important to ensure that the helper virus does not cause disease or unwanted effects. Researchers often use modified helper viruses that are replication-deficient or have attenuated virulence.

			==Conclusion==
			Helper viruses play a vital role in the replication of defective viruses and have significant applications in biotechnology and medicine. Understanding the interactions between helper and defective viruses can lead to advancements in [[viral vector]] development and [[gene therapy]].

			{{Virus-stub}}
	[[Category:Virology]]		[[Category:Virology]]
	~~{{med stub}}~~		[[Category:Gene therapy]]
			[[Category:Viral vectors]]

Prab at 00:47, 28 September 2023

2023-09-28T00:47:26Z

New page

The complex world of virology introduces myriad viruses, some of which possess distinct abilities to aid the replication of other viral entities. One such virus, known as a '''helper virus''', is crucial for facilitating the replication of helper-dependent viral vectors that lack the inherent capacity for self-replication. These viral vectors, although deficient in replication machinery, are often employed in scientific and therapeutic interventions, relying on helper viruses to achieve their replication.

=== Overview ===
A '''helper virus''' is essential for the replication of certain viral vectors. It provides the missing components necessary for the propagation of these vectors when they are used in various biomedical applications.

* '''Helper Dependent Viral Vector''': These are viral vectors that have been stripped of their replication capabilities, either naturally or through genetic manipulation. Although they can't replicate on their own, they can still infect cells and introduce their genetic material<ref>Palmer, D., & Ng, P. (2005). Helper-dependent adenoviral vectors for gene therapy. Human gene therapy, 16(1), 1-16.</ref>.
=== Mechanism of Action ===

When cells are coinfected with both the helper-dependent viral vector and the helper virus, the following process ensues:

* '''Coinfection''': Both the helper virus and the helper-dependent viral vector infect the target cell.
* '''Genome Integration''': The viral vector introduces its genome into the host cell.
* '''Helper Virus's Role''': The helper virus provides the necessary enzymes and other replication machinery to facilitate the replication of the viral vector's genome<ref>Kotin, R. M., & Snyder, R. O. (2017). Manufacturing clinical grade recombinant adeno-associated virus using invertebrate cell lines. Human gene therapy, 28(4), 350-360.</ref>.
* '''Replication''': The viral vector's genome is replicated, leveraging the machinery provided by the helper virus.
=== Applications ===

Helper viruses, alongside helper-dependent viral vectors, have found utility in several biomedical fields:

* '''Gene Therapy''': Helper-dependent viral vectors, with their replication components removed, present a safer alternative for gene delivery as they minimize the risks associated with viral replication. They are, therefore, used to deliver therapeutic genes to target cells or tissues in gene therapy protocols<ref>Thomas, C. E., Ehrhardt, A., & Kay, M. A. (2003). Progress and problems with the use of viral vectors for gene therapy. Nature Reviews Genetics, 4(5), 346-358.</ref>.
* '''Vaccine Development''': These vectors can also be employed in the creation of viral vaccines. They introduce a harmless version of a pathogenic virus into the host to stimulate an immune response without causing disease.
=== Challenges and Considerations ===

Despite their advantages, the use of helper viruses and dependent viral vectors is not without challenges:

* '''Contamination''': One of the primary concerns is the potential contamination of the viral vector preparation with the helper virus, which can lead to unintended consequences when introduced into a patient or experimental model<ref>Urabe, M., Ding, C., & Kotin, R. M. (2002). Insect cells as a factory to produce adeno-associated virus type 2 vectors. Human gene therapy, 13(16), 1935-1943.</ref>.
* '''Optimization''': Achieving optimal levels of coinfection for efficient replication without promoting excessive helper virus propagation can be a delicate balance.
=== Conclusion ===
Helper viruses are indispensable tools in the world of virology, particularly in therapeutic applications where safety and precision are paramount. Understanding their role, mechanism, and challenges can enable scientists and clinicians to harness their benefits while minimizing potential drawbacks.
== References ==
<references />
[[Category:Virology]]
{{med stub}}

Helper virus - Revision history

Prab: CSV import

Prab at 00:47, 28 September 2023