Citizendia

Virology, often considered a part of microbiology or of pathology, is the study of biological viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their potential uses in research and therapy. Microbiology (from Greek grc μῑκρος mīkros, "small" grc βίος bios, " Life " and grc -λογία Pathology (from Greek grc πάθος pathos, "fate harm" and grc -λογία -logia) is the study and A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called

Contents

Virus structure and classification

A major branch of virology is virus classification. Virus classification involves naming and placing Viruses into a taxonomic system Viruses can be classified according to the host cell they infect: animal viruses, plant viruses, fungal viruses, and bacteriophages (viruses infecting bacteria, which include the most complex viruses). Plant viruses are Viruses affecting Plants.Plant viruses like all other viruses are obligate intracellular Parasites that do not have the molecular A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ This article is about a biological infectious particle for other uses see Phage (disambiguation. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Another classification uses the geometrical shape of their capsid (often a helix or an icosahedron) or the virus's structure (e. For the leaf bug see Miridae. A capsid is the protein shell of a virus. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i In Geometry, an icosahedron ( Greek: eikosaedron, from eikosi twenty + hedron seat /ˌaɪ g. presence or absence a lipid envelope). Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble Many Viruses (eg influenza and many animal viruses have viral envelopes covering their protein Capsids The envelopes are typically derived from portions of Viruses range in size from about 30 nm to about 450 nm, which means that most of them cannot be seen with light microscopes. The optical microscope, often referred to as the "light microscope" is a type of Microscope which uses Visible light and a system of lenses to The shape and structure of viruses can be studied with electron microscopy, with NMR spectroscopy, and most importantly with X-ray crystallography. An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters

The most useful and most widely used classification system distinguishes viruses according to the type of nucleic acid they use as genetic material and the viral replication method they employ to coax host cells into producing more viruses:

In addition virologists also study subviral particles, infectious entities even smaller than viruses: viroids (naked circular RNA molecules infecting plants), satellites (nucleic acid molecules with or without a capsid that require a helper virus for infection and reproduction), and prions (proteins that can exist in a pathological conformation that induces other prion molecules to assume that same conformation). Viroids are Plant Pathogens that consist of a short stretch (a few hundred nucleobases) of highly complementary circular single-stranded A Satellite is a Subviral agent composed of Nucleic acid that depends on the Coinfection of a host cell with a helper or master Virus for their A prion (ˈpriːɒn is thought to be an infectious agent that according to current scientific consensus is comprised entirely of a propagated, mis-folded Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl

The latest report by the International Committee on Taxonomy of Viruses (2005) lists 5450 viruses, organized in over 2,000 species, 287 genera, 73 families and 3 orders. The International Committee on Taxonomy of Viruses ( ICTV) is a committee which authorizes and organizes the taxonomic classification of Viruses They have

The taxa in virology are not necessarily monophyletic. A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor In fact, the evolutionary relationships of the various virus groups remain unclear, and three hypotheses regarding their origin exist:

  1. Viruses arose from non-living matter, separately from and in parallel to other life forms, possibly in the form of self-reproducing RNA ribozymes similar to viroids. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units A ribozyme (from ribo nucleic acid en' zyme', also called RNA Enzyme or catalytic RNA is an RNA Molecule that catalyzes Viroids are Plant Pathogens that consist of a short stretch (a few hundred nucleobases) of highly complementary circular single-stranded
  2. Viruses arose from earlier, more competent cellular life forms that became parasites to host cells and subsequently lost most of their functionality; examples of such tiny parasitic prokaryotes are Mycoplasma and Nanoarchaea. Mycoplasma is a Genus of bacteria which lack a Cell wall. Without a cell wall they are unaffected by many common Antibiotics such Nanoarchaeum equitans is a species of tiny Microbe, discovered in 2002 in a Hydrothermal vent off the coast of Iceland by Karl
  3. Viruses arose as parts of the genome of cells, most likely transposons or plasmids, that acquired the ability to "break free" from the host cell and infect other cells. Transposons are sequences of DNA that can move around to different positions within the Genome of a single cell, a process called transposition A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA

It is of course possible that different alternatives apply to different virus groups.

Of particular interest here is mimivirus, a giant virus that infects amoebae and carries much of the molecular machinery traditionally associated with bacteria. Mimivirus is a viral genus containing a single identified species named Acanthamoeba polyphaga mimivirus (APMV The Amoebozoa are a major group of Amoeboid protozoa including the majority that move by means of internal Cytoplasmic flow Is it a simplified version of a parasitic prokaryote, or did it originate as a simpler virus that acquired genes from its host?

The evolution of viruses, which often occurs in concert with the evolution of their hosts, is studied in the field of viral evolution. Viral evolution is a subfield of Evolutionary biology that is specifically concerned with the Evolution of Viruses Many Viruses in particular

While viruses reproduce and evolve, they don't engage in metabolism and depend on a host cell for reproduction. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. The often-debated question of whether they are alive or not is a matter of definition that does not affect the biological reality of viruses.

Viral diseases and host defenses

One main motivation for the study of viruses is the fact that they cause many important infectious diseases, among them the common cold, influenza, rabies, measles, many forms of diarrhea, hepatitis, yellow fever, polio, smallpox and AIDS. Acute viral nasopharyngitis or acute coryza, usually known as the common cold, is a highly contagious viral Infectious disease of the Rabies (from rabies “madness rage fury” Also known as “ hydrophobia ” is a viral Zoonotic neuroinvasive disease that Measles (rubeola is a Disease caused by a virus specifically a Paramyxovirus of the genus Morbillivirus. In Medicine, diarrhea, also spelled diarrhoea (see spelling differences) is frequent loose or liquid Bowel movements Acute diarrhea Hepatitis (plural hepatitides) implies injury to the Liver characterized by the presence of Inflammatory cells in the tissue of Yellow fever (also called yellow jack, black vomit or sometimes American Plague) is an acute viral disease Poliomyelitis, often called polio or infantile paralysis, is an acute viral Infectious disease spread from person to person primarily via Smallpox is an Infectious disease unique to humans caused by either of two virus variants named Variola major and Variola minor. Some viruses, known as oncoviruses, contribute to certain forms of cancer; the best studied example is the association between Human papillomavirus and cervical cancer. An oncovirus is a Virus associated with Cancer. Oncoviruses come in two different forms viruses with a DNA Genome, such as Adenovirus Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled A human papillomavirus ( HPV) is a Papillomavirus that infects the skin and Mucous membranes of Humans Approximately 130 HPV types have been Cervical cancer is Malignant Cancer of the Cervix uteri or cervical area Some subviral particles also cause disease: Kuru and Creutzfeldt-Jakob disease are caused by prions, and hepatitis D is due to a satellite virus. Kuru is a disease which affects the Brain. It was endemic among the Fore tribe of Papua New Guinea and was universally fatal Creutzfeldt-Jakob disease ( CJD) is a very rare and incurable degenerative neurological disorder ( Brain Disease) that is ultimately Hepatitis D is a Disease caused by a small circular RNA virus ( Hepatitis delta virus or hepatitis D virus, HDV)

The study of the manner in which viruses cause disease is viral pathogenesis. Viral pathogenesis is the study of how biological Viruses cause diseases in their target hosts usually carried out at the cellular or molecular level The degree to which a virus causes disease is its virulence. Virulence (also called pestiferousness) refers to the degree of Pathogenicity of a Microbe, or in other words the relative ability of a Microbe

When the immune system of a vertebrate encounters a virus, it produces specific antibodies which bind to the virus and mark it for destruction. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily The presence of these antibodies is often used to determine whether a person has been exposed to a given virus in the past, with tests such as ELISA. Enzyme-Linked ImmunoSorbent Assay, also called ELISA, Enzyme ImmunoAssay or EIA, is a biochemical technique used mainly in Immunology Vaccinations protect against viral diseases, in part, by eliciting the production of antibodies. Vaccination is the administration of Antigenic material (the Vaccine) to produce immunity to a disease Specifically constructed monoclonal antibodies can also be used to detect the presence of viruses, with a technique called fluorescence microscopy. Monoclonal antibodies ( mAb or moAb) are monospecific antibodies that are identical because they are produced by one type of immune cell A fluorescence microscope (colloquially synonymous with epifluorescent microscope) is a light Microscope used to study properties of organic or inorganic substances

A second defense of vertebrates against viruses, cell-mediated immunity, involves immune cells known as T cells: the body's cells constantly display short fragments of their proteins on the cell's surface, and if a T cell recognizes a suspicious viral fragment there, the host cell is destroyed and the virus-specific T-cells proliferate. Cell-mediated immunity is an Immune response that does not involve Antibodies or complement but rather involves the activation of Macrophages T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. This mechanism is jump-started by certain vaccinations.

RNA interference, an important cellular mechanism found in plants, animals and many other eukaryotes, most likely evolved as a defense against viruses. RNA interference ( RNAi) is a mechanism that inhibits Gene expression at the stage of translation or by hindering the transcription of specific Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex An elaborate machinery of interacting enzymes detects double-stranded RNA molecules (which occur as part of the life cycle of many viruses) and then proceeds to destroy all single-stranded versions of those detected RNA molecules.

Every lethal viral disease presents a paradox: killing its host is obviously of no benefit to the virus, so how and why did it evolve to do so? Today it is believed that most viruses are relatively benign in their natural hosts; the lethal viral diseases are explained as resulting from an "accidental" jump of the virus from a species in which it is benign to a new one that is not accustomed to it (see zoonosis). A zoonosis (ˌzoʊəˈnoʊsɨs or zoonose is any Infectious disease that is able to be transmitted (by a vector) from other Animals both wild and domestic For example, serious influenza viruses probably have pigs or birds as their natural host, and HIV is thought to derive from the benign monkey virus SIV. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome

While it has been possible to prevent (certain) viral diseases by vaccination for a long time, the development of antiviral drugs to treat viral diseases is a comparatively recent development. Antiviral drugs are a class of Medication used specifically for treating viral Infections Like Antibiotics for Bacteria, specific antivirals The first such drug was interferon, a substance that is naturally produced by certain immune cells when an infection is detected and stimulates other parts of the immune system. Interferons ( IFN s are natural Proteins produced by the cells of the Immune system of most Vertebrates in response to challenges by foreign agents

Molecular biology research and viral therapy

Bacteriophages, the viruses which infect bacteria, can be relatively easily grown as viral plaques on bacterial cultures. This article is about a biological infectious particle for other uses see Phage (disambiguation. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A viral plaque is a visible structure formed within a Cell culture, such as bacterial cultures within some nutrient medium (e A microbiological culture, AKA microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory Bacteriophages occasionally move genetic material from one bacterial cell to another in a process known as transduction, and this horizontal gene transfer is one reason why they served as a major research tool in the early development of molecular biology. Transduction is the process by which DNA is transferred from one Bacterium to another by a Virus. Molecular biology is the study of Biology at a molecular level The genetic code, the function of ribozymes, the first recombinant DNA and early genetic libraries were all arrived at using bacteriophages. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins A ribozyme (from ribo nucleic acid en' zyme', also called RNA Enzyme or catalytic RNA is an RNA Molecule that catalyzes Recombinant DNA is a form of synthetic DNA that is engineered through the combination or insertion of one or more DNA strands thereby combining DNA sequences In Molecular biology, a library is a collection of molecules in a stable form that represents some aspect of an organism Certain genetic elements derived from viruses, such as highly effective promoters, are commonly used in molecular biology research today. In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene.

Growing animal viruses outside of the living host animal is more difficult. Classically, fertilized chicken eggs have often been used, but cell cultures are increasingly employed for this purpose today. Cell culture is the process by which prokaryotic, or eukaryotic cells are grown under controlled conditions

Since viruses that infect eukaryotes need to transport their genetic material into the host cell's nucleus, they are attractive tools for introducing new genes into the host (known as transformation or transfection). Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed In Molecular biology, transformation is the genetic alteration of a cell resulting from the uptake genomic incorporation and expression of foreign Transfection is the process of introducing nucleic acids into cells by non-viral methods. Modified retroviruses are often used for this purpose, as they integrate their genes into the host's chromosomes. A chromosome is an organized structure of DNA and Protein that is found in cells.

This approach of using viruses as gene vectors is being pursued in the gene therapy of genetic diseases. Gene therapy is the insertion of Genes into an individual's cells and tissues to treat a Disease, and Hereditary diseases in which a An obvious problem to be overcome in viral gene therapy is the rejection of the transforming virus by the immune system.

Phage therapy, the use of bacteriophages to combat bacterial diseases, was a popular research topic before the advent of antibiotics and has recently seen renewed interest. Phage therapy is the Therapeutic use of Bacteriophages to treat Pathogenic Bacterial infections In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa

Oncolytic viruses are viruses that preferably infect cancer cells. An oncolytic virus is a Virus that is able to infect and Lyse cancer cells while leaving normal cells unharmed making them potentially useful in cancer therapy Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled While early efforts to employ these viruses in the therapy of cancer failed, there have been reports in 2005 and 2006 of encouraging preliminary results. [1]

Other uses of viruses

See: Materials science and nanotechnology

A new application of genetically engineered viruses in nanotechnology was recently described. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Nanotechnology, sometimes shortened to nanotech, refers to a field of Applied science whose theme is the control of matter on an Atomic and Molecular

History

A very early form of vaccination known as variolation was developed several thousand years ago in China. Inoculation is the placement of something to where it will grow or reproduce and is most commonly used in respect of the introduction of a serum Vaccine, or antigenic substance It involved the application of materials from smallpox sufferers in order to immunize others. Smallpox is an Infectious disease unique to humans caused by either of two virus variants named Variola major and Variola minor. In 1717 Lady Mary Wortley Montagu observed the practice in Istanbul and attempted to popularize it in Britain, but encountered considerable resistance. The Lady Mary Wortley Montagu ( 26 May 1689 &ndash 21 August 1762) was an English aristocrat and writer Istanbul (historically Byzantium and later Constantinople; see the other Names of Istanbul) is the largest city of Turkey In 1796 Edward Jenner developed a much safer method, using cowpox to successfully immunize a young boy against smallpox, and this practice was widely adopted. Edward Jenner, FRS, ( May 17 1749 – January 26 1823) was an English scientist who studied his natural surroundings in Berkeley Cowpox is a Disease of the skin that is caused by a Virus known as the Cowpox virus. Vaccinations against other viral diseases followed, including the successful rabies vaccination by Louis Pasteur in 1886. Rabies (from rabies “madness rage fury” Also known as “ hydrophobia ” is a viral Zoonotic neuroinvasive disease that Louis Pasteur (27 December 1822 – 28 September 1895 a French Chemist and Microbiologist, is best known for remarkable breakthroughs in the causes and The nature of viruses however was not clear to these researchers.

In 1892 Dimitri Ivanovski showed that a disease of tobacco plants, tobacco mosaic disease, could be transmitted by extracts that were passed through filters fine enough to exclude even the smallest known bacteria. Tobacco is an Agricultural product recognized as an addictive drug processed from the fresh Leaves of plants in the genus Nicotiana. Tobacco mosaic virus (TMV is an RNA virus that infects Plants especially Tobacco and other members of the family Solanaceae. In 1898 Martinus Beijerinck, also working on tobacco plants, found that this "filterable agent" grew in the host and was thus not a mere toxin. Martinus Willem Beijerinck ( March 16, 1851 - January 1, 1931) was a Dutch Microbiologist and Botanist A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low The question of whether the agent was a "living fluid" or a particle was however still open.

In 1903 it was suggested for the first time that transduction by viruses might cause cancer. Such an oncovirus in chickens was described by Francis Peyton Rous in 1911; it was later called Rous sarcoma virus 1 and understood to be a retrovirus. (Francis Peyton Rous ( October 5, 1879 &ndash February 16, 1970) born in Baltimore Maryland in 1879 and received his B Rous sarcoma virus is a Retrovirus and is the first Oncovirus to have been described it causes Sarcoma in chickens Several other cancer-causing retroviruses have since been described.

The existence of viruses that infect bacteria was first recognized by Frederick Twort in 1911, and, independently, by Felix d'Herelle in 1917. Frederick William Twort (1877-1950 was an English Bacteriologist. Félix d'Herelle ( April 25, 1873 &ndash February 22, 1949) was a French-Canadian microbiologist, the co-discoverer of Since bacteria could be grown easily in culture, this led to an explosion of virology research. An important investigator in this area, Max Delbrück, described the basic life cycle of a virus in 1937: rather than "growing", a virus particle is assembled from its constituent pieces in one step; eventually it leaves the host cell to infect other cells. Max Ludwig Henning Delbrück ( September 4, 1906 &ndash March 9, 1981) was a German-American Biophysicist and Nobel The Hershey-Chase experiment in 1952 showed that only DNA and not protein enters a bacterial cell upon infection with bacteriophage T2. The Hershey-Chase experiments were a series of Experiments conducted in 1952 by Alfred Hershey and Martha Chase, confirming that DNA Enterobacteria phage T2 is a virulent bacteriophage of the T4-like viruses genus in the family Myoviridae. Transduction of bacteria by bacteriophages was first described in the same year. Transduction is the process by which DNA is transferred from one Bacterium to another by a Virus.

While plant viruses and bacteriophages can be grown comparatively easily, animal viruses normally require a living host animal, which complicates their study immensely. In 1931 it was shown that influenza virus could be grown in fertilized chicken eggs, a method that is still used today to produce vaccines. The Orthomyxoviridae (Derivation of name orthos is Greek for straight myxa is Greek for Mucus) are a family of RNA viruses that In 1937, Max Theiler managed to grow the yellow fever virus in chicken eggs and produced a vaccine from an attenuated virus strain; this vaccine saved millions of lives and is still being used today. Max Theiler ( January 30, 1899 &ndash August 11, 1972) was a South African Swiss virologist.

In 1949 John F. Enders, Thomas Weller and Frederick Robbins reported that they had been able to grow poliovirus in cultured human embryonal cells, the first significant example of an animal virus grown outside of animals and chicken eggs. John Franklin Enders ( February 10 1897 &ndash September 8 1985) was an American medical scientist and Nobel laureate. For the Nobel Prize winning virologist see Thomas Huckle Weller Thomas Christian Weller (born November 4, 1980) is a Frederick Chapman Robbins ( August 25, 1916 &ndash August 4, 2003) was an American pediatrician and virologist Poliovirus, the causative agent of Poliomyelitis, is a human Enterovirus and member of the family of Picornaviridae. This work aided Jonas Salk in deriving a polio vaccine from killed polio viruses; this vaccine was shown to be effective in 1955. Jonas Edward Salk ( October 28 1914 &ndash June 23, 1995) was an American Biologist and Physician best

The first virus which could be crystalized and whose structure could therefore be elucidated in detail was tobacco mosaic virus (TMV), the virus that had been studied earlier by Ivanovski and Beijerink. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Tobacco mosaic virus (TMV is an RNA virus that infects Plants especially Tobacco and other members of the family Solanaceae. In 1935, Wendell Stanley achieved its crystallization for electron microscopy and showed that it remains active even after crystallization. Wendell Meredith Stanley ( August 16, 1904 &ndash June 15, 1971) was an American biochemist, virologist An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image Clear X-ray diffraction pictures of the crystallized virus were obtained by Bernal and Fankuchen in 1941. X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystallographic structure chemical composition Based on such pictures, Rosalind Franklin proposed the full structure of the tobacco mosaic virus in 1955. Rosalind Elsie Franklin ( 25 July, 1920 Notting Hill, London – 16 April, 1958 Chelsea London) was an Also in 1955, Heinz Fraenkel-Conrat and Robley Williams showed that purified TMV RNA and its capsid (coat) protein can assemble by themselves to form functional viruses, suggesting that this simple mechanism is likely the natural assembly mechanism within the host cell. Heinz Ludwig Fraenkel-Conrat ( July 29, 1910 &ndash April 10, 1999) was a biochemist, famous for his viral research Robley Cook Williams ( 1908 - January 3, 1995) was an early Biophysicist and Virologist. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units For the leaf bug see Miridae. A capsid is the protein shell of a virus.

In 1963, the Hepatitis B virus was discovered by Baruch Blumberg who went on to construct a vaccine against Hepatitis B. Baruch Samuel Blumberg (born July 28, 1925) is an American scientist and recipient of the 1976

In 1965, Howard Temin described the first retrovirus: an RNA-virus that was able to insert its genome in the form of DNA into the host's genome. Howard Martin Temin ( December 10, 1934 &ndash February 9, 1994) was a U A retrovirus is any Virus belonging to the viral family Retroviridae. Reverse transcriptase, the key enzyme that retroviruses use to translate their RNA into DNA, was first described in 1970, independently by Howard Temin and David Baltimore. In Biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase Enzyme that transcribes David Baltimore (born March 7, 1938) is an American biologist The first retrovirus infecting humans was identified by Robert Gallo in 1974. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Robert Charles Gallo (born March 23, 1937) is a US biomedical researcher Later it was found that reverse transcriptase is not specific to retroviruses; retrotransposons which code for reverse transcriptase are abundant in the genomes of all eukaryotes. Retrotransposons (also called transposons via RNA intermediates are genetic elements that can amplify themselves in a Genome and are ubiquitous components of the About 10-40% of the human genome derives from such retrotransposons.

In 1975 the functioning of oncoviruses was clarified considerably. Until that time, it was thought that these viruses carried certain genes called oncogenes which, when inserted into the host's genome, would cause cancer. An oncogene is a protein encoding Gene, which — when deregulated — participates in the onset and development of Cancer. Michael Bishop and Harold Varmus showed that the oncogene of Rous sarcoma virus is in fact not specific to the virus but is contained in healthy animals of many species. John Michael Bishop (born February 22, 1936) is an American Immunologist and Microbiologist who won the 1989 Nobel Prize in Physiology Harold Elliot Varmus (born December 18, 1939) is an American Nobel prize winning scientist The oncovirus can switch this pre-existing benign proto-oncogene on, turning it into a true oncogene.

1976 saw the first recorded outbreak of Ebola hemorrhagic fever, a highly lethal virally transmitted disease. Ebola is the common term for a group of Viruses belonging to genus Ebolavirus, family Filoviridae, and for the disease which they

In 1977, Frederick Sanger achieved the first complete sequencing of the genome of any organism, the bacteriophage Phi X 174. Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby The phi X 174 (or phi X) Bacteriophage was the first DNA-based Genome to be sequenced by Fred Sanger and his team in 1977. In the same year, Richard Roberts and Phillip Sharp independently showed that the genes of adenovirus contain introns and therefore require gene splicing. Sir Richard John Roberts (born September 6, 1943 in Derby) is an English Biochemist and molecular biologist. Phillip Allen Sharp (born June 6, 1944) is an American Geneticist and molecular biologist who co-discovered gene splicing Adenoviruses are medium-sized (90–100 nm) Nonenveloped (naked Icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into Genetic engineering, Recombinant DNA technology, genetic modification/manipulation (GM and gene splicing are terms that apply to the direct It was later realized that almost all genes of eukaryotes have introns as well.

A world-wide vaccination campaign lead by the UN World Health Organization lead to the eradication of smallpox in 1979.

In 1982, Stanley Prusiner discovered prions and showed that they cause scrapie. Stanley Ben Prusiner (born May 28, 1942 In this work he coined the term prion, which comes from "proteinaceous infectious particle that lacks A prion (ˈpriːɒn is thought to be an infectious agent that according to current scientific consensus is comprised entirely of a propagated, mis-folded Scrapie is a fatal degenerative Disease that affects the Nervous systems of Sheep and Goats It is one of several Transmissible spongiform

The first cases of AIDS were reported in 1981, and HIV, the retrovirus causing it, was identified in 1983 by Robert Gallo and Luc Montagnier. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome Robert Charles Gallo (born March 23, 1937) is a US biomedical researcher Luc Montagnier (born August 18 1932 is a French virologist and joint recipient with Françoise Barré-Sinoussi and Harald zur Hausen of the Tests detecting HIV infection by detecting the presence of HIV antibody were developed. Subsequent tremendous research efforts turned HIV into the best studied virus. Human Herpes Virus 8, the cause of Kaposi's sarcoma which is often seen in AIDS patients, was identified in 1994. Kaposi's sarcoma-associated herpesvirus ( KSHV) is the eighth human Herpesvirus; its formal name according to the International Committee on Taxonomy of Viruses is Kaposi's sarcoma (KS is a tumor caused by Human herpesvirus 8 ( HHV8) also known as Kaposi's sarcoma-associated herpesvirus (KSHV Several anti-retroviral drugs were developed in the late 1990s, decreasing AIDS mortality dramatically in developed countries.

The Hepatitis C virus was identified using novel molecular cloning techniques in 1987, leading to screening tests that dramatically reduced the incidence of post-transfusion hepatitis. This page is for the virus For the disease see Hepatitis C. Hepatitis C virus ( HCV) is a small (50 nm in size Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it In vivo. Blood transfusion is the process of transferring Blood or blood-based products from one person into the Circulatory system of another Hepatitis (plural hepatitides) implies injury to the Liver characterized by the presence of Inflammatory cells in the tissue of [2]

The first attempts at gene therapy involving viral vectors began in the early 1980s, when retroviruses were developed that could insert a foreign gene into the host's genome. Gene therapy is the insertion of Genes into an individual's cells and tissues to treat a Disease, and Hereditary diseases in which a They contained the foreign gene but did not contain the viral genome and therefore could not reproduce. Tests in mice were followed by tests in humans, beginning in 1989. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The first human studies attempted to correct the genetic disease severe combined immunodeficiency (SCID), but clinical success was limited. Severe combined immunodeficiency ( SCID) or Boy in the Bubble Syndrome is a genetic disorder in which both "arms" ( B cells and T cells In the period from 1990 to 1995, gene therapy was tried on several other diseases and with different viral vectors, but it became clear that the initially high expectations were overstated. In 1999 a further setback occurred when 18-year-old Jesse Gelsinger died in a gene therapy trial. Jesse Gelsinger ( June 18 1981 - September 17 1999) was the first person publicly identified as having died in a clinical trial for Gene He suffered a severe immune response after having received an adenovirus vector. Adenoviruses are medium-sized (90–100 nm) Nonenveloped (naked Icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA Success in the gene therapy of two cases of X-linked SCID was reported in 2000. Severe combined immunodeficiency ( SCID) or Boy in the Bubble Syndrome is a genetic disorder in which both "arms" ( B cells and T cells [3]

In 2002 it was reported that poliovirus had been synthetically assembled in the laboratory, representing the first synthetic organism. Poliovirus, the causative agent of Poliomyelitis, is a human Enterovirus and member of the family of Picornaviridae. Assembling the 7741-base genome from scratch, starting with the virus's published RNA sequence, took about two years. In 2003 a faster method was shown to assemble the 5386-base genome of the bacteriophage Phi X 174 in 2 weeks. The phi X 174 (or phi X) Bacteriophage was the first DNA-based Genome to be sequenced by Fred Sanger and his team in 1977.

The giant mimivirus, in some sense an intermediate between tiny prokaryotes and ordinary viruses, was described in 2003 and sequenced in 2004. Mimivirus is a viral genus containing a single identified species named Acanthamoeba polyphaga mimivirus (APMV The term DNA sequencing encompasses biochemical methods for determining the order of the Nucleotide bases Adenine, Guanine, Cytosine

The strain of Influenza A virus subtype H1N1 that killed up to 50 million people during the Spanish flu pandemic in 1918 was reconstructed in 2005. H1[[Neuraminidase N1]] is a subtype of the species Influenza A virus. The 1918 flu pandemic (commonly referred to as the Spanish flu) was an Influenza Pandemic that spread to nearly every part of the world Sequence information was pieced together from preserved tissue samples of flu victims; viable virus was then synthesized from this sequence. [4]

Two vaccines protecting against several cervical cancer-causing strands of human papillomavirus (HPV) were released in 2006. Cervical cancer is Malignant Cancer of the Cervix uteri or cervical area A human papillomavirus ( HPV) is a Papillomavirus that infects the skin and Mucous membranes of Humans Approximately 130 HPV types have been

In 2006 and 2007 it was reported that introducing a small number of specific transcription factor genes into normal skin cells of mice or humans can turn these cells into pluripotent stem cells, known as Induced Pluripotent Stem Cells. In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Pluripotency in the broad sense refers to "having more than one potential outcome Stem cells are cells found in most if not all multi-cellular Organisms. Induced pluripotent stem cells Unfortunately one of the four genes used (namely c-Myc is Oncogenic, and 20% of the chimeric mice developed cancer The technique uses modified retroviruses to transform the cells; this is a potential problem for human therapy since these viruses integrate their genes at a random location in the host's genome, which can interrupt other genes and potentially causes cancer. [5]

See also

References

  1. ^ Viruses: The new cancer hunters, IsraCast, 1 March 2006
  2. ^ 2000 Albert Lasker Award for Clinical Medical Research, The Lasker Foundation. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Virus classification involves naming and placing Viruses into a taxonomic system This is a list of biological viruses See also List of computer viruses This is a list of biological Viruses and types of viruses The study of animal viruses is important from a veterinary viewpoint and many of these viruses cause diseases that are economically devastating Human Infectious diseases grouped by causative agent and alphabetically arranged Anatomy Commentary on Anatomy in Avicenna's Canon Accessed 20 February 2008
  3. ^ Zeger Debyser. A Short Course on Virology / Vectorology / Gene Therapy, Current Gene Therapy, 2003, 3, 495-499
  4. ^ Kolata, Gina. "Experts Unlock Clues to Spread of 1918 Flu Virus", The New York Times, 2005-10-06. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 105 BC - Battle of Arausio: The Cimbri inflict the heaviest defeat on the Roman army of Gnaeus Mallius Maximus Retrieved on 2008-02-03. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1112 - Ramon Berenguer III of Barcelona and Douce I of Provence marry uniting the fortunes of those two states  
  5. ^ Stem Cells—This Time without the Cancer, Scientific American News, 30 November 2007

External links and sources

Dictionary

virology

-noun

  1. The branch of microbiology that deals with the study of viruses and viral diseases.
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