virus

Examples of virus in the following topics:

• Host Range

  • A virus' host range is the range of cell types and host species a virus is able to infect.
  • The defenses mounted by the host may act directly on the virus or indirectly on virus replication by altering or killing the infected cell.
  • The host range of the virus will depend upon the presence of the receptors described above.
  • If a host lacks the receptor for a virus, or if the host cell lacks some component necessary for the replication of a virus, the host will inherently be resistant to that virus.
  • For example, mice lack the receptors for polio viruses and thus are resistant to polio virus.

• Viruses of Archaea

  • The second single stranded DNA virus infecting Archaea is Aeropyrum coil-shaped virus (ACV).
  • A virus infecting archaea was first described in 1974.
  • The crenarchaeal virus Sulfolobus turreted icosahedral virus has a similar structure.
  • The first archaeal ssDNA virus to be isolated is the Halorubrum pleomorphic virus 1, which has a pleomorphic enveloped virion and a circular genome.
  • The second single stranded DNA virus infecting Archaea is Aeropyrum coil-shaped virus (ACV).

• DNA Oncogenic Viruses

  • The Epstein-Barr virus has been linked to Burkitt's lymphoma.
  • This virus infects B cells of the immune system and epithelial cells.
  • Human herpes virus-8 has been linked to the development of Kaposi sarcoma.
  • These are the early control functions of the virus.
  • The first DNA tumor viruses to be discovered were rabbit fibroma virus and Shope papilloma virus, both discovered by Richard Shope in the 1930s.

• Shingles

  • Shingles, the common name for herpes zoster, is caused by latent varicella zoster virus, the same virus which causes chickenpox in children.
  • The initial infection with varicella zoster virus (VZV) causes the acute (short-lived) illness chickenpox which generally occurs in children and young people.
  • Exactly how the virus remains latent in the body, and subsequently re-activates is not understood.
  • It has become common practice to vaccinate children against the virus that causes both chickenpox and shingles.
  • Once vaccinated, most children will not become infected with the varicella zoster virus if exposed, and subsequently will not develop shingles later in life.

• Defective Viruses

  • The hepatitis delta virus of humans has an RNA genome similar to viroids, but has a protein coat derived from hepatitis B virus and cannot produce one of its own.
  • Therefore, it is a defective virus and cannot replicate without the help of hepatitis B virus.
  • The hepatitis delta virus of humans has an RNA genome similar to viroids, but has a protein coat derived from hepatitis B virus and cannot produce one of its own.
  • Therefore, it is a defective virus and cannot replicate without the help of hepatitis B virus.
  • Hepatitis D, also referred to as hepatitis D virus (HDV) and classified as Hepatitis delta virus, is a disease caused by a small circular enveloped RNA virus.

• Antiviral Agents that Prevent Virus Uncoating or Release

  • Different approches are used to target the initial and final steps of a virus life cycle.
  • A viral infection starts with entry of the virus into the cell.
  • Virus infection starts with a virus attaching to the host cell by binding to a receptor molecule.
  • Using receptor-like molecules to bind to the virus and inactivate it before it meets the cell.
  • Neuraminidase is an enzyme on the capsid of influenza virus .

• Replication of Herpes Simplex Virus

  • The early proteins transcribed are used in the regulation of genetic replication of the virus.
  • The late proteins form the capsid and the receptors on the surface of the virus.
  • The virus acquires its final envelope by budding into cytoplasmic vesicles.
  • The envelope covering the virus particle, when bound to specific receptors on the cell surface, will fuse with the host cell membrane and create an opening, or pore, through which the virus enters the host cell.
  • Structure of the conserved core of the herpes simplex virus transcriptional regulatory protein VP16.

• Plant Virus Life Cycles

  • Tobacco mosaic virus (TMV) and Cauliflower mosaic virus (CaMV) are frequently used in plant molecular biology.
  • Next, a virus must take control of the host cell's replication mechanisms.
  • Tobacco mosaic virus and Cauliflower mosaic virus (CaMV) are frequently used in plant molecular biology.
  • Tobacco mosaic virus (TMV) is a positive-sense single stranded RNA virus that infects plants, especially tobacco and other members of the family Solanaceae.
  • TMV was the first virus to be discovered.

• Viral Genomes

  • The viral genome is the complete genetic complement contained in a DNA or RNA molecule in a virus.
  • A virus has either DNA or RNA genes and is called a DNA virus or a RNA virus, respectively.
  • However, all segments are not required to be in the same virion for the virus to be infectious, as demonstrated by the brome mosaic virus and several other plant viruses.
  • The virus particles of some virus families, such as those belonging to the Hepadnaviridae, contain a genome that is partially double-stranded and partially single-stranded.

• Virus Classification

  • However, these earlier classification methods grouped viruses based on which features of the virus they were using to classify them.
  • The virus core contains the genome or total genetic content of the virus.
  • For example, the tobacco mosaic virus has a naked helical capsid .
  • (a) Rabies virus has a single-stranded RNA (ssRNA) core and an enveloped helical capsid, whereas (b) variola virus, the causative agent of smallpox, has a double-stranded DNA (dsDNA) core and a complex capsid.
  • The capsid of the (a) polio virus is naked icosahedral; (b) the Epstein-Barr virus capsid is enveloped icosahedral; (c) the mumps virus capsid is an enveloped helix; (d) the tobacco mosaic virus capsid is naked helical; and (e) the herpesvirus capsid is complex.