Helper virus

(noun)

A helper virus is a virus used when producing copies of a helper dependent viral vector which does not have the ability to replicate on its own. The helper virus is used to coinfect cells alongside the viral vector and provides the necessary enzymes for replication of the genome of the viral vector.

Related Terms

Examples of Helper virus in the following topics:

  • Defective Viruses

    • 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.

  • Viroids

    • 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.

  • Tissue Tropism in Animal Viruses

    • 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.

  • Secondary Immunodeficiency Diseases

    • 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.

  • Type IV (Delayed Cell-Mediated) Reactions

    • 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.

  • Opportunistic Microorganisms

    • 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).

  • 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.

  • 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 .