Examples of Helper virus in the following topics:
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- Therefore, it is a defective virus and cannot replicate without the help of hepatitis B virus.
- satellites (nucleic acid molecules with or without a capsid that require a helper virus for infection and reproduction)
- Satellites depend on co-infection of a host cell with a helper virus for productive multiplication.
- Their nucleic acids have substantially distinct nucleotide sequences from either their helper virus or host.
- Therefore, it is a defective virus and cannot replicate without the help of hepatitis B virus.
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- The human pathogen Hepatitis D virus is similar to viroids.
- Since they depend on helper viruses, they are classified as satellites.
- Key features of replication include no helper virus required and no proteins are encoded for.
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- If a cell does not express these receptors then the virus cannot normally infect it.
- An example of this is the HIV virus, which exhibits tropism for CD4 related immune cells (e.g.
- T helper cells, macrophages or dendritic cells).
- These cells express a CD4 receptor, to which the HIV virus can bind, through the gp120 and gp41 proteins on its surface .
- In virology, Tissue tropism is the cells and tissues of a host that support growth of a particular virus or bacteria.
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- Immunodeficiency is also the hallmark of acquired immunodeficiency syndrome (AIDS) , caused by the human immunodeficiency virus (HIV).
- HIV directly infects a small number of T helper cells and also impairs other immune system responses indirectly.
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- CD4 cells or helper T cells provide protection against different pathogens.
- 1. activating antigen-specific cytotoxic T-lymphocytes that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens
- It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria.
- CD4+ helper T cells recognize antigen in a complex with Class 2 major histocompatibility complex.
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- Patients with Human Immunodeficiency Virus (HIV) are particularly susceptible to opportunistic infections.
- HIV can develop into Acquired Immune Deficiency Syndrome (AIDS), which infects and destroys helper T cells (specifically CD4+ T cells).
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- 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.
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- 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).
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- 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.
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- 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 .