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Thursday, February 16, 2023
Liberal conservatism
Liberal conservatism is a political ideology combining conservative policies with liberal stances, especially on economic issues but also on social and ethical matters, representing a brand of political conservatism strongly influenced by liberalism.
The ideology incorporates the classical liberal view of minimal government intervention in the economy, according to which individuals should be free to participate in the market and generate wealth without government interference. However, liberal conservatives also hold that individuals cannot be thoroughly depended on to act responsibly in other spheres of life; therefore, they believe that a strong state is necessary to ensure law and order and that social institutions are needed to nurture a sense of duty and responsibility to the nation. Liberal conservatives also support civil liberties, along with some socially conservative positions. Liberal conservatives differ on social issues with some being more socially conservative while others taking a more liberal approach. They generally support the rule of law regarding civil rights, social equality and the environment. This is equated with the creation of a cohesive and tolerant society with increased levels of individual responsibility and less inequality.
Liberal conservatism shares the classical liberal tenets of a commitment to individualism, belief in negative freedom, a lightly regulated free market, and a minimal rule of law state. A number of commentators have stated that many conservative currents in the 1980s, such as Thatcherism, were rejuvenated classical liberals in all but name. However, in contrast to classical liberalism there is a stronger social agenda and support for a greater degree of state intervention especially in certain areas of social life which liberal conservatives believe should not be subject to market forces. Particularly in regards to the family, sexuality, health and education, these should either always be periodically regulated or minimally protected by the state.
In Europe, liberal conservatism is the dominant form of modern conservatism and centre-right politics. Most European liberal-conservative parties adhere to the European People's Party, originally formed by Christian democrats.
Overview, definitions and usage
Both conservatism and liberalism have had different meanings over time in different centuries. The term liberal conservatism has been used in quite different ways. It usually contrasts with aristocratic conservatism, which deems the principle of equality as something discordant with human nature and emphasizes instead the idea of natural inequality. As conservatives in democratic countries have embraced typical liberal institutions such as the rule of law, private property, the market economy and constitutional representative government, the liberal element of liberal conservatism became consensual among conservatives. In some countries such as the United Kingdom and the United States, the term liberal conservatism came to be understood simply as conservatism in popular culture, prompting some conservatives who embraced more strongly classical-liberal values to call themselves libertarians instead. However, there are differences between classical liberals and libertarians.
In their embracement of liberal and free market principles, European liberal conservatives are clearly distinguishable from those holding national-conservative, fully socially conservative and/or outright populist views, let alone a right-wing populist posture. Being liberal often involves stressing free market economics and the belief in individual responsibility together with the defense of civil rights and support for a limited welfare state. Compared to other centre-right political traditions such as Christian democracy, liberal conservatives are less socially conservative and more economically liberal, favouring low taxes and minimal state intervention in the economy. Some regional varieties and peculiarities can be observed:
- In much of Central and Northwestern Europe, especially in Germanic and traditionally Protestant countries as well as the United Kingdom and Belgium, a divide persists between liberal conservatives (including Christian democrats) and liberals (including conservative liberals and social liberals).
- In most Nordic countries, liberal conservatives, Christian democrats and liberals form distinct political families and have each their own party. The largest liberal parties are the Nordic agrarian parties, which are traditionally agrarian.
- In most countries where Romance languages are spoken and where Catholicism is or has been dominant as well as in Greece and Poland, liberal conservative movements, often encompassing Christian democrats and liberals, have more recently gained traction and the terms conservative and liberal may be understood as synonymous.
At the European level, Christian democrats and most liberal conservatives are affiliated to the European People's Party (EPP), while liberals (including conservative and social liberals) to the Alliance of Liberals and Democrats for Europe Party (ALDE Party). In this context, some traditionally Christian-democratic parties (such as Christian-Democratic and Flemish in Belgium, the Christian Democratic Appeal in the Netherlands, the Christian Democratic Union in Germany and the People's Party in Austria) have become almost undistinguishable from other liberal-conservative parties. On the other hand, newer liberal-conservative parties (such as New Democracy in Greece, the Social Democratic Party in Portugal, the People's Party in Spain, Forza Italia/The People of Freedom/Forza Italia in Italy, the Union for a Popular Movement/The Republicans in France and most centre-right parties from countries once belonging to the Eastern Bloc and Yugoslavia) have not adopted traditional labels, but their ideologies are also a mixture of conservatism, Christian democracy and liberalism.
In the modern European discourse, liberal conservatism usually encompasses centre-right political outlooks that reject at least to some extent social conservatism. This position is also associated with support for moderate forms of social safety net and environmentalism (see also green conservatism and green liberalism). This variety of liberal conservatism has been espoused by Nordic conservatives (the Moderate Party in Sweden, the Conservative Party in Norway and the National Coalition Party in Finland) which have been fending off competition from right-wing populists to their right and do not include Christian democrats; and at times the British Conservative Party. In an interview shortly after taking office as Prime Minister in 2010, David Cameron introduced himself as a liberal conservative. During his first speech to a party conference in 2006, Cameron had defined this as believing in individual freedom and human rights, but being skeptical of "grand schemes to remake the world".
Relation to American conservatism
In the United States, conservatives often combine the economic individualism of classical liberals with a Burkean form of conservatism that emphasizes the natural inequalities between men, the irrationality of human behavior as the basis for the human drive for order and stability and the rejection of natural rights as the basis for government. From a different perspective, American conservatism (a "hybrid of conservatism and classical liberalism") has exalted three tenets of Burkean conservatism, namely the diffidence toward the power of the state, the preference of liberty over equality and for patriotism while rejecting the three remaining tenets, namely loyalty to traditional institutions and hierarchies, scepticism regarding progress and elitism. Consequently, the term liberal conservatism is not used in the United States. Modern American liberalism happens to be quite different from European liberalism and occupies the centre-left of the political spectrum, in contrast to many European countries where liberalism is often more associated with the centre and centre-right while social democracy makes up a substantial part of the centre-left. The opposite is true in Latin America, where economically liberal conservatism is often labelled under the rubric of neoliberalism both in popular culture and academic discourse.
American libertarian conservatism focuses more on libertarian economic principles and conservative cultural principles, but social stances of European liberal conservatism, on the other hand, are more closely related to relative progressivism than traditional conservatism. American neoconservatism is sometimes described as the same or similar to liberal conservatism in Europe. However, Peter Lawler regarded neoconservatism in the United States as conservative liberalism and distinguished it from liberal conservatism. Fiscal conservatism is also an idea rooted in classical liberalism.
Classical conservatism and economic liberalism
Historically, conservatism in the 18th and 19th centuries comprised a set of principles based on concern for established tradition, respect for authority and religious values. This form of traditionalist or classical conservatism is often considered to be exemplified by the writings of Joseph de Maistre in the post-Enlightenment age. Contemporaneous liberalism, now recalled as classical liberalism, advocated both political freedom for individuals and a free market in the economic sphere. Ideas of this sort were promulgated by John Locke, Montesquieu, Voltaire, Jean-Jacques Rousseau, Ben Franklin, Thomas Jefferson, Thomas Paine, Edward Gibbon, David Hume, Adam Smith, Jeremy Bentham and John Stuart Mill, who are respectively remembered as the fathers of liberalism, including economic liberalism, the separation of church and state, social liberalism and utilitarianism.
According to scholar Andrew Vincent, the maxim of liberal conservatism is "economics is prior to politics". Others emphasize the openness of historical change and a suspicion of tyrannical majorities behind the hailing of individual liberties and traditional virtues by authors such as Edmund Burke and Alexis de Tocqueville as the basis of current liberal conservatism which can be seen both in the works of Raymond Aron and Michael Oakeshott. However, there is general agreement that the original liberal conservatives were those who combined conservative social attitudes with an economically liberal outlook, adapting a previous aristocratic understanding of natural inequalities between men to the rule of meritocracy, without directly criticizing privileges of birth as long as individual liberties were guaranteed. Over time, the majority of conservatives in the Western world came to adopt free market economic ideas as the Industrial Revolution progressed and the aristocracy lost its power, to the extent that such ideas are now generally considered as part of conservatism. Nonetheless, the term liberal is used in most countries to describe those with free-market economic views. This is the case in continental Europe, Australia and Latin America.
Retrovirus
Retroviridae | |
---|---|
HIV retrovirus schematic of cell infection, virus production and virus structure | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Pararnavirae |
Phylum: | Artverviricota |
Class: | Revtraviricetes |
Order: | Ortervirales |
Family: | Retroviridae |
Subfamilies and genera | |
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus. Many retroviruses cause serious diseases in humans, other mammals, and birds.
Retroviruses have many subfamilies in three basic groups.
- Oncoretroviruses (cancer-causing retroviruses) include human T-lymphotropic virus (HTLV) causing a type of leukemia in humans, and murine leukemia viruses (MLVs) in mice.
- Lentiviruses (slow viruses) include HIV-1 and HIV-2, the cause of acquired immune deficiency syndrome (AIDS) in humans.
- Spumaviruses (foamy viruses) are benign and not linked to any disease in humans or animals.
The specialized DNA-inflitration enzymes in retroviruses make them valuable research tools in molecular biology, and they have been used successfully in gene delivery systems.
Evidence from endogenous retroviruses (inherited provirus DNA in animal genomes) suggests that retroviruses have been infecting vertebrates for at least 450 million years.
Structure
Virions, viruses in the form of independent particles of retroviruses, consist of enveloped particles about 100 nm in diameter. The outer lipid envelope consists of glycoprotein. The virions also contain two identical single-stranded RNA molecules 7–10 kilobases in length. The two molecules are present as a dimer, formed by base pairing between complementary sequences. Interaction sites between the two RNA molecules have been identified as a "kissing stem-loop". Although virions of different retroviruses do not have the same morphology or biology, all the virion components are very similar.
The main virion components are:
- Envelope: composed of lipids (obtained from the host plasma membrane during the budding process) as well as glycoprotein encoded by the env gene. The retroviral envelope serves three distinct functions: protection from the extracellular environment via the lipid bilayer, enabling the retrovirus to enter/exit host cells through endosomal membrane trafficking, and the ability to directly enter cells by fusing with their membranes.
- RNA: consists of a dimer RNA. It has a cap at the 5' end and a poly(A) tail at the 3' end. Genomic RNA (gRNA) is produced as a result of host RNA polymerase II (Pol II) activity and by adding a 5' methyl cap and a 3' poly-A tail is processed as a host mRNA. The RNA genome also has terminal noncoding regions, which are important in replication, and internal regions that encode virion proteins for gene expression. The 5' end includes four regions, which are R, U5, PBS, and L. The R region is a short repeated sequence at each end of the genome used during the reverse transcription to ensure correct end-to-end transfer in the growing chain. U5, on the other hand, is a short unique sequence between R and PBS. PBS (primer binding site) consists of 18 bases complementary to 3' end of tRNA primer. L region is an untranslated leader region that gives the signal for packaging of the genome RNA. The 3' end includes three regions, which are PPT (polypurine tract), U3, and R. The PPT is a primer for plus-strand DNA synthesis during reverse transcription. U3 is a sequence between PPT and R, which serves as a signal that the provirus can use in transcription. R is the terminal repeated sequence at 3' end.
- Proteins: consisting of gag proteins, protease (PR), pol proteins, and env proteins.
- Group-specific antigen (gag) proteins are major components of the viral capsid, which are about 2000–4000 copies per virion. Gag possesses two nucleic acid binding domains, including matrix (MA) and nucleocapsid (NC). Specifically recognizing, binding, and packaging the retroviral genomic RNA into assembling virions is one of the important functions of Gag protein. Gag interactions with cellular RNAs also regulate aspects of assembly. The expression of gag alone gives rise to assembly of immature virus-like particles that bud from the plasma membrane. In all retroviruses the Gag protein is the precursor to the internal structural protein.
- Protease (pro) is expressed differently in different viruses. It functions in proteolytic cleavages during virion maturation to make mature gag and pol proteins. Retroviral Gag proteins are responsible for coordinating many aspects of virion assembly.
- Pol proteins are responsible for synthesis of viral DNA and integration into host DNA after infection.
- Env proteins play a role in association and entry of virions into the host cell. Possessing a functional copy of an env gene is what makes retroviruses distinct from retroelements. The ability of the retrovirus to bind to its target host cell using specific cell-surface receptors is given by the surface component (SU) of the Env protein, while the ability of the retrovirus to enter the cell via membrane fusion is imparted by the membrane-anchored trans-membrane component (TM). Thus it is the Env protein that enables the retrovirus to be infectious.
- Several protein species are associated with the RNA in the retrovirus virion. Nucleocapsid (NC) protein is the most abundant protein, which coats the RNA; while other proteins, present in much smaller amounts and have enzyme activities. Some enzyme activities that are present in the retrovirus virion includes RNA-dependent DNA polymerase (reverse transcriptase; RT), DNA-dependent DNA polymerase, Ribonuclease H (RNase H) Integrase and Protease. The retroviral RNases H encoded by all retroviruses, including HIV have been demonstrated to show three different modes of cleavage: internal, DNA 3′ end-directed, and RNA 5′ end-directed. All three modes of cleavage constitute roles in reverse transcription. Therefore, The RNase H activity is essential in several aspects of reverse transcription. The use of an RNase H activity during retroviral replication displays a unique strategy to copy a single-stranded RNA genome into a double-stranded DNA, since the minus-strand DNA are complementary and make base pairing to retrovirus genome in the first cycle of DNA synthesis. The RNase H ribonuclease activity is also required in the retroviral life cycle, since it generates and removes primers essential by the Reverse Transcriptase (RT) for the initiation of DNA synthesis. Retroviruses that are lacking RNase H activity are noninfectious.
Genomic structure
The retroviral genome is packaged as viral particles. These viral particles are dimers of single-stranded, positive-sense, linear RNA molecules.
Retroviruses (and orterviruses in general) follow a layout of 5'–gag–pro–pol–env–3' in the RNA genome. gag and pol encode polyproteins, each managing the capsid and replication. The pol region encodes enzymes necessary for viral replication, such as reverse transcriptase, protease and integrase. Depending on the virus, the genes may overlap or fuse into larger polyprotein chains. Some viruses contain additional genes. The lentivirus genus, the spumavirus genus, the HTLV / bovine leukemia virus (BLV) genus, and a newly introduced fish virus genus are retroviruses classified as complex. These viruses have genes called accessory genes, in addition to gag, pro, pol and env genes. Accessory genes are located between pol and env, downstream from the env, including the U3 region of LTR, or in the env and overlapping portions. While accessory genes have auxiliary roles, they also coordinate and regulate viral gene expression. In addition, some retroviruses may carry genes called oncogenes or onc genes from another class. Retroviruses with these genes (also called transforming viruses) are known for their ability to quickly cause tumors in animals and transform cells in culture into an oncogenic state.
The polyproteins are cleaved into smaller proteins each with their own function. The nucleotides encoding them are known as subgenes.
Multiplication
When retroviruses have integrated their own genome into the germ line, their genome is passed on to a following generation. These endogenous retroviruses (ERVs), contrasted with exogenous ones, now make up 5–8% of the human genome. Most insertions have no known function and are often referred to as "junk DNA". However, many endogenous retroviruses play important roles in host biology, such as control of gene transcription, cell fusion during placental development in the course of the germination of an embryo, and resistance to exogenous retroviral infection. Endogenous retroviruses have also received special attention in the research of immunology-related pathologies, such as autoimmune diseases like multiple sclerosis, although endogenous retroviruses have not yet been proven to play any causal role in this class of disease.
While transcription was classically thought to occur only from DNA to RNA, reverse transcriptase transcribes RNA into DNA. The term "retro" in retrovirus refers to this reversal (making DNA from RNA) of the usual direction of transcription. It still obeys the central dogma of molecular biology, which states that information can be transferred from nucleic acid to nucleic acid but cannot be transferred back from protein to either protein or nucleic acid. Reverse transcriptase activity outside of retroviruses has been found in almost all eukaryotes, enabling the generation and insertion of new copies of retrotransposons into the host genome. These inserts are transcribed by enzymes of the host into new RNA molecules that enter the cytosol. Next, some of these RNA molecules are translated into viral proteins. The proteins encoded by the gag and pol genes are translated from genome-length mRNAs into Gag and Gag–Pol polyproteins. In example, for the gag gene; it is translated into molecules of the capsid protein, and for the pol gene; it is translated into molecules of reverse transcriptase. Retroviruses need a lot more of the Gag proteins than the Pol proteins and have developed advanced systems to synthesize the required amount of each. As an example, after Gag synthesis nearly 95 percent of the ribosomes terminate translation, while other ribosomes continue translation to synthesize Gag–Pol. In the rough endoplasmic reticulum glycosylation begins and the env gene is translated from spliced mRNAs in the rough endoplasmic reticulum, into molecules of the envelope protein. When the envelope protein molecules are carried to the Golgi complex, they are divided into surface glycoprotein and transmembrane glycoprotein by a host protease. These two glycoprotein products stay in close affiliation, and they are transported to the plasma membrane after further glycosylation.
It is important to note that a retrovirus must "bring" its own reverse transcriptase in its capsid, otherwise it is unable to utilize the enzymes of the infected cell to carry out the task, due to the unusual nature of producing DNA from RNA.
Industrial drugs that are designed as protease and reverse-transcriptase inhibitors are made such that they target specific sites and sequences within their respective enzymes. However these drugs can quickly become ineffective due to the fact that the gene sequences that code for the protease and the reverse transcriptase quickly mutate. These changes in bases cause specific codons and sites with the enzymes to change and thereby avoid drug targeting by losing the sites that the drug actually targets.
Because reverse transcription lacks the usual proofreading of DNA replication, a retrovirus mutates very often. This enables the virus to grow resistant to antiviral pharmaceuticals quickly, and impedes the development of effective vaccines and inhibitors for the retrovirus.
One difficulty faced with some retroviruses, such as the Moloney retrovirus, involves the requirement for cells to be actively dividing for transduction. As a result, cells such as neurons are very resistant to infection and transduction by retroviruses. This gives rise to a concern that insertional mutagenesis due to integration into the host genome might lead to cancer or leukemia. This is unlike Lentivirus, a genus of Retroviridae, which are able to integrate their RNA into the genome of non-dividing host cells.
Recombination
Two RNA genomes are packaged into each retrovirus particle, but, after an infection, each virus generates only one provirus. After infection, reverse transcription occurs and this process is accompanied by recombination. Recombination involves template strand switching between the two genome copies (copy choice recombination) during reverse transcription. From 5 to 14 recombination events per genome occur at each replication cycle. Genetic recombination appears to be necessary for maintaining genome integrity and as a repair mechanism for salvaging damaged genomes.
Transmission
- Cell-to-cell
- Fluids
- Airborne, like the Jaagsiekte sheep retrovirus.
Provirus
The DNA formed after reverse transcription (the provirus) is longer than the RNA genome because each of the terminals have the U3 - R - U5 sequences called long terminal repeat (LTR). Thus, 5' terminal has the extra U3 sequence, while the other terminal has the U5 sequence. LTRs are able to send signals for vital tasks to be carried out such as initiation of RNA production or management of the rate of transcription. This way, LTRs can control replication, hence, the entire progress of the viral cycle. Although located in the nucleus, the non-integrated retroviral cDNA is a very weak substrate for transcription. For this reason, an integrated provirus is a necessary for permanent and an effective expression of retroviral genes.
This DNA can be incorporated into host genome as a provirus that can be passed on to progeny cells. The retrovirus DNA is inserted at random into the host genome. Because of this, it can be inserted into oncogenes. In this way some retroviruses can convert normal cells into cancer cells. Some provirus remains latent in the cell for a long period of time before it is activated by the change in cell environment.
Early evolution
Studies of retroviruses led to the first demonstrated synthesis of DNA from RNA templates, a fundamental mode for transferring genetic material that occurs in both eukaryotes and prokaryotes. It has been speculated that the RNA to DNA transcription processes used by retroviruses may have first caused DNA to be used as genetic material. In this model, the RNA world hypothesis, cellular organisms adopted the more chemically stable DNA when retroviruses evolved to create DNA from the RNA templates.
An estimate of the date of evolution of the foamy-like endogenous retroviruses placed the time of the most recent common ancestor at > 450 million years ago.
Gene therapy
Gammaretroviral and lentiviral vectors for gene therapy have been developed that mediate stable genetic modification of treated cells by chromosomal integration of the transferred vector genomes. This technology is of use, not only for research purposes, but also for clinical gene therapy aiming at the long-term correction of genetic defects, e.g., in stem and progenitor cells. Retroviral vector particles with tropism for various target cells have been designed. Gammaretroviral and lentiviral vectors have so far been used in more than 300 clinical trials, addressing treatment options for various diseases. Retroviral mutations can be developed to make transgenic mouse models to study various cancers and their metastatic models.
Cancer
Retroviruses that cause tumor growth include Rous sarcoma virus and mouse mammary tumor virus. Cancer can be triggered by proto-oncogenes that were mistakenly incorporated into proviral DNA or by the disruption of cellular proto-oncogenes. Rous sarcoma virus contains the src gene that triggers tumor formation. Later it was found that a similar gene in cells is involved in cell signaling, which was most likely excised with the proviral DNA. Nontransforming viruses can randomly insert their DNA into proto-oncogenes, disrupting the expression of proteins that regulate the cell cycle. The promoter of the provirus DNA can also cause over expression of regulatory genes. Retroviruses can cause diseases such as cancer and immunodeficiency. If viral DNA is integrated into host chromosomes, it can lead to permanent infections. It is therefore important to discover the body's response to retroviruses. Exogenous retroviruses are especially associated with pathogenic diseases. For example, mice have mouse mammary tumor virus (MMTV), which is a retrovirus. This virus passes to newborn mice through mammary milk. When they are 6 months old, the mice carrying the virus get mammary cancer because of the retrovirus. In addition, leukemia virus I (HTLV-1), found in human T cell, has been found in humans for many years. It is estimated that this retrovirus causes leukemia in the ages of 40 and 50. It has a replicable structure that can induce cancer. In addition to the usual gene sequence of retroviruses, HTLV-1 contains a fourth region, PX. This region encodes Tax, Rex, p12, p13 and p30 regulatory proteins. The Tax protein initiates the leukemic process and organizes the transcription of all viral genes in the integrated HTLV proviral DNA.
Classification
Exogenous
Exogenous retroviruses are infectious RNA- or DNA-containing viruses that are transmitted from one organism to another. In the Baltimore classification system, which groups viruses together based on their manner of messenger RNA synthesis, they are classified into two groups: Group VI: single-stranded RNA viruses with a DNA intermediate in their life cycle, and Group VII: double-stranded DNA viruses with an RNA intermediate in their life cycle.
Group VI viruses
All members of Group VI use virally encoded reverse transcriptase, an RNA-dependent DNA polymerase, to produce DNA from the initial virion RNA genome. This DNA is often integrated into the host genome, as in the case of retroviruses and pseudoviruses, where it is replicated and transcribed by the host.
Group VI includes:
- Order Ortervirales
- Family Belpaoviridae
- Family Metaviridae
- Family Pseudoviridae
- Family Retroviridae – Retroviruses, e.g. HIV
- Family Caulimoviridae – a VII group virus family (see below)
The family Retroviridae was previously divided into three subfamilies (Oncovirinae, Lentivirinae, and Spumavirinae), but are now divided into two: Orthoretrovirinae and Spumaretrovirinae. The term oncovirus is now commonly used to describe a cancer-causing virus. This family now includes the following genera:
- Subfamily Orthoretrovirinae:
- Genus Alpharetrovirus; including Avian leukosis virus and Rous sarcoma virus
- Genus Betaretrovirus; including Mouse mammary tumour virus
- Genus Gammaretrovirus; including Murine leukemia virus and Feline leukemia virus
- Genus Deltaretrovirus; including Bovine leukemia virus and the cancer-causing Human T-lymphotropic virus
- Genus Epsilonretrovirus
- Genus Lentivirus; including Human immunodeficiency virus 1 and Simian and Feline immunodeficiency viruses
- Subfamily Spumaretrovirinae:
- Genus Bovispumavirus
- Genus Equispumavirus
- Genus Felispumavirus
- Genus Prosimiispumavirus
- Genus Simiispumavirus
Note that according to ICTV 2017, genus Spumavirus has been divided into five genera, and its former type species Simian foamy virus is now upgraded to genus Simiispumavirus with not less than 14 species, including new type species Eastern chimpanzee simian foamy virus.
Group VII viruses
Both families in Group VII have DNA genomes contained within the invading virus particles. The DNA genome is transcribed into both mRNA, for use as a transcript in protein synthesis, and pre-genomic RNA, for use as the template during genome replication. Virally encoded reverse transcriptase uses the pre-genomic RNA as a template for the creation of genomic DNA.
Group VII includes:
- Family Caulimoviridae — e.g. Cauliflower mosaic virus
- Family Hepadnaviridae — e.g. Hepatitis B virus
The latter family is closely related to the newly proposed
- Family Nackednaviridae — e.g. African cichlid nackednavirus (ACNDV), formerly named African cichlid hepatitis B virus (ACHBV).
whilst families Belpaoviridae, Metaviridae, Pseudoviridae, Retroviridae, and Caulimoviridae constitute the order Ortervirales.
Endogenous
Endogenous retroviruses are not formally included in this classification system, and are broadly classified into three classes, on the basis of relatedness to exogenous genera:
- Class I are most similar to the gammaretroviruses
- Class II are most similar to the betaretroviruses and alpharetroviruses
- Class III are most similar to the spumaviruses.
Controversy
Retroviruses have been the focus of several recent claims and assertions which have been largely discredited by the science community. An initial study in 2009 seemed to make new findings which might change some of the established knowledge on this topic. However, although later research disproved some of the claims made about retroviruses, there are several controversial figures who continue to make claims which overall are considered to not have any valid basis or consensus in support of these claims.
Treatment
Antiretroviral drugs are medications for the treatment of infection by retroviruses, primarily HIV. Different classes of antiretroviral drugs act on different stages of the HIV life cycle. Combination of several (typically three or four) antiretroviral drugs is known as highly active antiretroviral therapy (HAART).
Treatment of veterinary retroviruses
Feline leukemia virus and Feline immunodeficiency virus infections are treated with biologics, including the only immunomodulator currently licensed for sale in the United States, Lymphocyte T-Cell Immune Modulator (LTCI).
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