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Helper Virus
A helper virus is a virus that allows an otherwise-deficient coinfecting virus to replicate. These can be naturally occurring as with Hepatitis D virus, which requires Hepatitis B virus to coinfect cells in order to replicate. Helper viruses are also commonly used to replicate and spread viral vectors for gene expression and gene therapy Gene therapy is Health technology, medical technology that aims to produce a therapeutic effect through the manipulation of gene expression or through altering the biological properties of living cells. The first attempt at modifying human DNA .... See also * Helper dependent virus * Virophage References Virology {{virus-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 16,000 of the millions of List of virus species, virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or ''virions'', consisting of (i) genetic material, i.e., long ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis D Virus
Hepatitis D is a type of viral hepatitis caused by the hepatitis delta virus (HDV). HDV is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a satellite (a type of subviral agent) because it can propagate only in the presence of the hepatitis B virus (HBV). Transmission of HDV can occur either via simultaneous infection with HBV (coinfection) or superimposed on chronic hepatitis B or hepatitis B carrier state ( superinfection). HDV infecting a person with chronic hepatitis B (superinfection) is considered the most serious type of viral hepatitis due to its severity of complications. These complications include a greater likelihood of experiencing liver failure in acute infections and a rapid progression to liver cirrhosis, with an increased risk of developing liver cancer in chronic infections. In combination with hepatitis B virus, hepatitis D has the highest fatality rate of all the hepatitis infections, at 20%. A recent estimate from 2020 sugge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis B Virus
Hepatitis B virus (HBV) is a partially double-stranded DNA virus, a species of the genus '' Orthohepadnavirus'' and a member of the '' Hepadnaviridae'' family of viruses. This virus causes the disease hepatitis B. Classification Hepatitis B virus is classified in the genus '' Orthohepadnavirus'', which contains 11 other species. The genus is classified as part of the '' Hepadnaviridae'' family, which contains four other genera, '' Avihepadnavirus'', '' Herpetohepadnavirus'', '' Metahepadnavirus'' and '' Parahepadnavirus''. This family of viruses is the only member of the viral order ''Blubervirales''. Viruses similar to hepatitis B have been found in all apes (orangutans, gibbons, bonobos, gorillas and chimpanzees), in Old World monkeys, and in New World woolly monkeys (the woolly monkey hepatitis B virus), suggesting an ancient origin for this virus in primates. The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes present on it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Vector
A viral vector is a modified virus designed to gene delivery, deliver genetic material into cell (biology), cells. This process can be performed inside an organism or in cell culture. Viral vectors have widespread applications in basic research, agriculture, and medicine. Viruses have evolved specialized molecular mechanisms to transport their genomes into infected hosts, a process termed transduction (genetics), transduction. This capability has been exploited for use as viral vectors, which may integrate their genetic cargo—the transgene—into the host genome, although non-integrative vectors are also commonly used. In addition to agriculture and laboratory research, viral vectors are widely applied in gene therapy: as of 2022, all approved gene therapies were viral vector-based. Further, compared to traditional vaccines, the intracellular antigen expression enabled by viral vector vaccines offers more robust immune activation. Many types of viruses have been developed into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Therapy
Gene therapy is Health technology, medical technology that aims to produce a therapeutic effect through the manipulation of gene expression or through altering the biological properties of living cells. The first attempt at modifying human DNA was performed in 1980, by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989. The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990. Between 1989 and December 2018, over 2,900 clinical trials were conducted, with more than half of them in Phases of clinical research, phase I. In 2003, Gendicine became the first gene therapy to receive regulatory approval. Since that time, further gene therapy drugs were approved, such as alipogene tiparvovec (2012), Strimvelis (2016), tisagenlecleucel (2017), voretigene neparvovec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helper Dependent Virus
A helper dependent virus, also termed a gutless virus, is a synthetic viral vector dependent on the assistance of a helper virus in order to replicate, and can be used for purposes such as gene therapy. Naturally-occurring satellite viruses are also helper virus dependent, and can sometimes be modified to become viral vectors. Viral vector Since the genome of the gutless virus does not include genes encoding the enzymes and/or structural proteins required to replicate, it is deemed safe for use in gene therapy since an infection cannot occur except in the presence of a suitable helper virus. Well established protocols allow scientists to propagate helper dependent viruses in the lab. However, using an actual helper virus poses problems when it comes to purification of a desired transgenic virus. Therefore, lab methods often utilize minimal fragments of the helper DNA that can serve this purpose without creating unwanted virus. This process usually involves the introduction of thre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virophage
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for their own replication. One of the characteristics of virophages is that they have a parasitic relationship with the co-infecting virus. Their dependence upon the giant virus for replication often results in the deactivation of the giant viruses. The virophage may improve the recovery and survival of the host organism. Virophages constitute the class ''Virophaviricetes''. Discovery The first virophage was discovered in a cooling tower in Paris in 2008. It was discovered with its co-infecting giant virus, ''Acanthamoeba castellanii'' mamavirus (ACMV). The virophage was named Sputnik and its replication relied entirely on the co-infection of ACMV and its cytoplasmic replication machinery. Sputnik was also discovered to have an inhibitory e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
