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Adenoviruses
Transmission electron micrograph of two adenovirus particles
Transmission electron micrograph of two adenovirus particles
Virus classification
Group:Group I (dsDNA)
Family:Adenoviridae
Genera

Aviadenovirus
Atadenovirus
Mastadenovirus
Siadenovirus

Adenoviruses are medium-sized (90–100 nm), nonenveloped (naked) icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome. Virus classification involves naming and placing Viruses into a taxonomic system A DNA virus is a Virus that has DNA as its Genetic material and replicates using a DNA-dependent DNA polymerase. Aviadenovirus are Viruses that affect birds they represent one of four genera of the family Adenoviridae, the others being Mastadenovirus Types of Atadenovirus Referenced from SpeciesDB Bovine adenovirus D Bovine adenovirus 4 Bovine adenovirus 5 A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Many Viruses (eg influenza and many animal viruses have viral envelopes covering their protein Capsids The envelopes are typically derived from portions of In Geometry, an icosahedron ( Greek: eikosaedron, from eikosi twenty + hedron seat /ˌaɪ Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known There are over 52 different serotypes in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well. For the term's use in bacteriology see Serovar. Transplants between genetically non-identical humans induce the creation of antibodies in the recipient

Viruses of the family Adenoviridae infect various species of animals, including humans. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable In Biological classification, family ( Latin Adenoviruses were first isolated in human adenoids (tonsils), from which the name is derived, and are classified as group I under the Baltimore classification scheme. Adenoids (or pharyngeal tonsils, or nasopharyngeal tonsils) are a mass of Lymphoid tissue situated at the very back of the nose in the roof of the The Baltimore classification is a Virus classification system which groups Viruses into families depending on their type of Genome ( DNA Adenoviruses represent the largest nonenveloped viruses, because they are the maximum size able to be transported through the endosome (i. e. envelope fusion is not necessary). The virion also has a unique "spike" or fiber associated with each penton base of the capsid (see picture below) that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the host cell. Fiber or fibre is a class of Materials that are continuous filaments or are in discrete elongated pieces similar to lengths of thread. For the leaf bug see Miridae. A capsid is the protein shell of a virus. In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment 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 There are 51 immunologically distinct human adenovirus serotypes (6 species: Human adenovirus A through F) that can cause human infections ranging from respiratory disease (mainly species HAdV-B and C), and conjunctivitis (HAdV-B and D), to gastroenteritis (HAdV-F serotypes 40 and 41). Respiratory Disease is the term for Diseases of the Respiratory system. Adenoviruses are unusually stable to chemical or physical agents and adverse pH conditions, allowing for prolonged survival outside of the body and water. A chemical substance is a Material with a definite chemical composition. pH is the measure of the acidity or alkalinity of a Solution. Adenoviruses are primarily spread via respiratory droplets, however they can also be spread by fecal routes as well. Feces, faeces, or fæces (see spelling differences) is a waste product from an animal's digestive tract expelled through the Anus

Most infections with adenovirus result in infections of the upper respiratory tract. Adenovirus infections often show up as conjunctivitis, tonsilitis (which may look exactly like strep throat and cannot be distinguished from strep except by throat culture), an ear infection, or croup. Conjunctivitis (commonly called " Pink Eye " or " Red Eye " in North America and " Madras eye " in India) is an inflammation Tonsillitis is an Infection of the Tonsils and will often but not necessarily cause a Sore throat and Fever. Streptococcal pharyngitis or streptococcal sore throat ( Strep throat AmE) is a form of Group A streptococcal infection that affects the Otitis media is Inflammation of the Middle ear, or middle ear infection (the word otitis is Greek and it means “inflammation of the ear” and media Croup is a group of Respiratory diseases that often affect infants and children under age 6 Adenoviruses can also cause gastroenteritis (stomach flu). Gastroenteritis (also known as gastro, gastric flu, and stomach flu, although unrelated to Influenza) is Inflammation of the A combination of conjunctivitis and tonsilitis is particularly common with adenovirus infections. Some children (especially small ones) can develop adenovirus bronchiolitis or pneumonia, both of which can be severe. Bronchiolitis is inflammation of the Bronchioles the smallest air passages of the lungs Pneumonia is an inflammatory illness of the Lung. Frequently it is described as lung Parenchyma / alveolar inflammation and abnormal In babies, adenoviruses can also cause coughing fits that look almost exactly like whooping cough. Pertussis, also known as whooping cough, is a highly contagious Disease caused by the Bacterium Bordetella pertussis; it derived its Adenoviruses can also cause viral meningitis or encephalitis. Meningitis is Inflammation of the protective membranes covering the Brain and Spinal cord, known collectively as the Meninges. Encephalitis is an acute Inflammation of the Brain, commonly caused by a viral Infection. Rarely, adenovirus can cause cystitis (inflammation of the urinary bladder—a form of urinary tract infection—with blood in the urine). Cystitis is Inflammation of the Urinary bladder. The condition more often affects women but can affect either sex and all age groups A urinary tract infection ( UTI) is a bacterial Infection that affects any part of the Urinary tract.

Most people recover from adenovirus infections by themselves, but people with immunodeficiency sometimes die of adenovirus infections, and—rarely—even previously healthy people can die of these infections. In Medicine, immunodeficiency (or immune deficiency) is a state in which the Immune system 's ability to fight Infectious disease is compromised [1]

Adenoviruses are often transmitted by coughed-out droplets, but can also be transmitted by contact with an infected person, or by virus particles left on objects such as towels and faucet handles. Some people with adenovirus gastroenteritis may shed the virus in their stools for months after getting over the symptoms. The virus can be passed from one person to another through some sexual practices, and through water in swimming pools that do not have enough chlorine in them. As with many other illnesses, good handwashing is one way to lessen the spread of adenoviruses from one person to another. Heat and bleach will kill adenoviruses on objects. A bleach is a Chemical that removes color or whitens often via Oxidation.

Contents

Treatment and prevention

As with almost all viruses, there are no antibiotics that help with an adenoviral infection, so treatment is largely directed at the symptoms (such as acetaminophen for fever). A doctor may give antibiotic eyedrops for conjunctivitis, since it takes a while to test to see if the eye infection is bacterial or viral and to help prevent secondary bacterial infections.

In the past, US military recruits were vaccinated against two serotypes of adenotypes, with a corresponding decrease in illnesses caused by those serotypes. The vaccine is no longer manufactured, and there are currently no vaccines available to protect against the adenovirus. Good hygiene, including handwashing, is still the best way to avoid picking up the adenovirus from an infected person.

Genome

Schematic diagram of the linear adenovirus genome, showing Early genes (E) and Late genes (L).
Schematic diagram of the linear adenovirus genome, showing Early genes (E) and Late genes (L).

The adenovirus genome is linear, non-segmented double stranded (ds) DNA which is around 30–38 Kbp. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called This allows the virus to theoretically carry 30 to 40 genes. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Although this is significantly larger than other viruses in its Baltimore group it is still a very simple virus and is heavily reliant on the host cell for survival and replication. An interesting feature of this viral genome is that it has a terminal 55 kDa protein associated with each of the 5' ends of the linear dsDNA, these are used as primers in viral replication and ensure that the ends of the virus' linear genome are adequately replicated. The unified atomic mass unit ( u) or Dalton ( Da) or sometimes universal mass unit, is an unit of Mass used to express

Replication

Adenoviruses possess a linear dsDNA genome and are able to replicate in the nucleus of mammalian cells using the host’s replication machinery. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby See also Biological reproduction Self-replication is any process by which a thing might make a copy of itself In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands

The structure of adenovirus. 1 = penton capsomeres 2 = hexon capsomeres, and 3= viral genome (linear dsDNA)
The structure of adenovirus. 1 = penton capsomeres 2 = hexon capsomeres, and 3= viral genome (linear dsDNA)

Entry of adenoviruses into the host cell involves two sets of interactions between the virus and the host cell. Entry into the host cell is initiated by the knob domain of the fiber protein binding to the cell receptor. The two currently established receptors are: CD46 for the group B human adenovirus serotypes and the coxsackievirus adenovirus receptor (CAR) for all other serotypes. There are some reports suggesting MHC molecules and sialic acid residues functioning in this capacity as well. This is followed by a secondary interaction, where a specialized motif in the penton base protein interacts with an integrin molecule. Integrins are Cell surface receptors that interact with the Extracellular matrix (ECM and mediate various intracellular signals. It is the co-receptor interaction that stimulates internalization of the adenovirus. This co-receptor molecule is αv integrin. Binding to αv integrin results in endocytosis of the virus particle via clathrin-coated pits. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. Attachment to αv integrin stimulates cell signaling and thus induces actin polymerization resulting in entry of the virion into the host cell within an endosome. In Biology, an endosome is a membrane-bound compartment inside cells roughly 300-400 nm in diameter when fully mature [2]

Once the virus has successfully gained entry into the host cell the endosome acidifies, which alters virus topology by causing capsid components to disassociate. These changes as well as the toxic nature of the pentons results in the release of the virion into the cytoplasm. With the help of cellular microtubules the virus is transported to the nuclear pore complex whereby the adenovirus particle disassembles. Microtubules are one of the components of the Cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers Viral DNA is subsequently released which can enter the nucleus via the nuclear pore. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed Nuclear pores are large Protein complexes that cross the Nuclear envelope, which is the double membrane surrounding the eukaryotic [3] After this the DNA associates with histone molecules. In Biology, histones are the chief Protein components of Chromatin. Thus viral gene expression can occur and new virus particles can be generated.

The adenovirus life cycle is separated, by the DNA replication process, into two phases: an early and a late phase. A life cycle is a period involving 1 Generation of an Organism through means of Reproduction, whether through Asexual reproduction or Sexual DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules In both phases a primary transcript is generated which is alternatively spliced to generate monocistronic mRNAs compatible with the host’s ribosome, allowing for the products to be translated. A primary transcript is an RNA molecule that has not yet undergone any modification after its synthesis. Alternative splicing is the RNA splicing variation mechanism in which the Exons of the primary gene transcript the Pre-mRNA, are separated and reconnected Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression)

The early genes are responsible for expressing mainly non-structural, regulatory proteins. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl The goal of these proteins is threefold: to alter the expression of host proteins that are necessary for DNA synthesis; to activate other virus genes (such as the virus-encoded DNA polymerase); and to avoid premature death of the infected cell by the host-immune defenses (blockage of apoptosis, blockage of interferon activity, and blockage of MHC class I translocation and expression). A DNA Polymerase is an Enzyme that assists in DNA replication. Interferons ( IFN s are natural Proteins produced by the cells of the Immune system of most Vertebrates in response to challenges by foreign agents There are two primary classes of Major histocompatibility complex (MHC molecules class I and MHC class II.

Some adenoviruses under specialized conditions can transform cells using their early gene products. E1a (binds Retinoblastoma tumor suppressor protein) has been found to immortalize primary cells in vitro allowing E1b (binds p53 tumor suppressor) to assist and stably transform the cells. The retinoblastoma protein (abbreviated pRb or Rb) is a Tumor suppressor Protein that is dysfunctional in many types of Cancer p53 (also known as protein 53 or tumor protein 53) is a Transcription factor encoded by the TP53 gene Nevertheless, they are reliant upon each other to successfully transform the host cell and form tumors. See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic

DNA replication separates the early and late phases. Once the early genes have liberated adequate virus proteins, replication machinery and replication substrates, replication of the adenovirus genome can occur. A terminal protein that is covalently bound to the 5’ end of the adenovirus genome acts as a primer for replication. A primer is a strand of Nucleic acid that serves as a starting point for DNA replication. The viral DNA polymerase then uses a strand displacement mechanism, as opposed to the conventional Okazaki fragments used in mammalian DNA replication, to replicate the genome. An Okazaki fragment is a relatively short fragment of DNA (with an RNA primer at the 5' terminus created on the Lagging strand during DNA replication.

The late phase of the adenovirus life cycle is focused on producing sufficient quantities of structural protein to pack all the genetic material produced by DNA replication. Once the viral components have successfully been replicated the virus is assembled into its protein shells and released from the cell as a result of virally induced cell lysis. Lysis ( Greek, lysis from lyein = to separate refers to the death of a cell by breaking of the cellular membrane often by viral or osmotic

Genera

This family contains the following genera:

Adenoviruses in humans

Adenoviruses in animals

Two types of canine adenoviruses are well known, type 1 and 2. A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Aviadenovirus are Viruses that affect birds they represent one of four genera of the family Adenoviridae, the others being Mastadenovirus Types of Atadenovirus Referenced from SpeciesDB Bovine adenovirus D Bovine adenovirus 4 Bovine adenovirus 5 Human adenovirus 36 (HAdV-36 or AD-36 is one of 51 types of Adenoviruses known to infect Humans It was first shown to be associated with Obesity Adenovirus infections most commonly cause illness of the respiratory system however depending on the infecting serotype they may also cause various other illnesses such as Adenovirus serotype 14 ( Ad14) is a Serovar of adenovirus which unlike other adenovirus serovars is known to cause potentially fatal Adenovirus infections The Canidae (ˈkænədiː ′kanə′dē family is a part of the order Carnivora within the Mammals (Class Mammalia Type 1 causes infectious canine hepatitis, a potentially fatal disease involving vasculitis and hepatitis. Infectious canine hepatitis is an acute liver infection in dogs caused by canine adenovirus type-1 (CAV-1 Vasculitis (plural vasculitides) a group of diseases featuring Inflammation of the wall of Blood vessels including veins ( Phlebitis) arteries Hepatitis (plural hepatitides) implies injury to the Liver characterized by the presence of Inflammatory cells in the tissue of Type 1 infection also can cause respiratory and eye infections. Canine adenovirus 2 (CAdV-2) is one of the potential causes of kennel cough. Kennel cough or tracheobronchitis is a highly contagious canine illness characterized by inflammation of the upper Respiratory system. Core vaccines for dogs include attenuated live CAdV-2, which produces immunity to CAdV-1 and CAdV-2. A vaccine is a biological preparation which is used to establish or improve immunity to a particular disease The dog ( Canis lupus familiaris) is a domesticated Subspecies of the gray wolf, a Mammal of the Canidae family of the order CAdV-1 was initially used in a vaccine for dogs, but corneal edema was a common complication. The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. Oedema (or Edema in American English formerly known as dropsy or hydropsy, is the increase of Interstitial fluid in any organ &mdash swelling [4]

Adenoviruses are also known to cause respiratory infections in horses, cattle, pigs, sheep, and goats. The horse ( Equus caballus) is a hoofed ( Ungulate) Mammal, one of eight living species of the family Equidae. Cattle, colloquially referred to as cows, are domesticated Ungulates a member of the Subfamily Bovinae of the family Pigs, also called hogs or' swine', are Ungulates which have been domesticated as sources of food leather and similar products since ancient times The domestic goat ( Capra aegagrus hircus) is a subspecies of goat Domesticated from the Wild goat of Southwest Asia and Eastern Europe Equine adenovirus 1 can also cause fatal disease in immunocompromised Arabian foals, involving pneumonia and destruction of pancreatic and salivary gland tissue. The Arabian horse is a breed of Horse with a reputation for Intelligence, spirit and stamina The pancreas is a Gland organ in the digestive and Endocrine system of Vertebrates. The salivary glands in mammals are exocrine glands that produce saliva [4]

See also

Viruses templates

References

  1. ^ Amy Burkholder. Infectious canine hepatitis is an acute liver infection in dogs caused by canine adenovirus type-1 (CAV-1 "A killer cold? Even the healthy may be vulnerable", CNN, 2007-12-19. Cable News Network, usually referred to by its Initialism CNN, is a major English language Television network founded in 1980 by Ted Turner Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 324 - Licinius abdicates his position as Roman Emperor. Retrieved on 2007-12-19. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 324 - Licinius abdicates his position as Roman Emperor.  
  2. ^ Wu and Nemerow (2004). "Virus yoga: the role of flexibility in virus host cell recognition". Trends Microbiol 12: 162–168. doi:10.1016/j.tim.2004.02.005. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15051066.  
  3. ^ Meier and Greber (2004). "Adenovirus endocytosis". J Gene Med 6: S152-S163. doi:10.1002/jgm.553. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 14978758.  
  4. ^ a b Fenner, Frank J. ; Gibbs, E. Paul J. ; Murphy, Frederick A. ; Rott, Rudolph; Studdert, Michael J. ; White, David O. (1993). Veterinary Virology (2nd ed. ). Academic Press, Inc. ISBN 0-12-253056-X.  

Sources

Centers for Disease Control and Prevention--National Center for Diseases--Division of Viral and Rickettsial Diseases, Respiratory and Enteric Viruses Branch

External links

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