virus (rus. вирус) — (latin, virus from "poison") autonomous genetic structures that do not have their own metabolism and can reproduce only in cells of bacteria, plants or animals that are sensitive to them.

Description

Viruses are obligate parasites, i.e. they cannot reproduce outside of the cell. Many of them can form crystal-like structures outside of the cell. Based on these facts, many scientists believe that viruses lie on the boundary between animate and inanimate nature. Viruses vary in diameter from 20 to 300 nm.

Modern science knows viruses that multiply in the cells of plants, animals, fungi and bacteria (the latter usually referred to as bacteriophages). A virus that infects other viruses has also been discovered. Viruses form a major component in Earth’s biomass and outnumber all other forms of life by orders of magnitude. All living organisms contain viral genome, therefore viruses have an impact on the evolution of all living things.

Each virus particle is composed of an RNA or DNA, enclosed in a protein shell, called a capsid. Viruses may contain only one type of nucleic acid (double stranded or single-stranded DNA, double stranded or single-stranded RNA). A structurally mature infectious particle is called a virion. Some viruses (such as herpes or flu) have an additional lipoprotein envelope built from the plasma membrane of the host cell.

Viruses are natural nanocomplexes of biomolecules. Targeted genetic or chemical modifications of viruses enable the creation of the so-called recombinant viral nanoparticles (RVN). After the removal of the genes responsible for replication from the viral genome, a virus loses its ability to replicate and lyse the host cell. Yet, it retains the ability to infect target cells and avoid lysosomal degradation. Protein capsid modifications enable the creation of target-specific RVNs by replacing the protein of the capsid with structural components of other viruses or bacteria, or with specialised ligands. Currently, RVNs with various characteristics are derived from such viruses as papillomaviruses, adenovirus, herpes virus, virus of smallpox vaccine and others. RVNs are used both in diagnostics and therapy, including drug delivery , therapeutic nanoparticles, components of gene therapy to the target cells, as well as stimulation of the immune response through introduction of certain antigens.

Authors

  • Naroditsky Boris S.
  • Nesterenko Lyudmila N.

Sources

  1. Bernard R. Glick et al. Molecular biotechnology: principles and applications of recombinant DNA // Jack J. Pasternak, Cheryl L. Patten. - 4th ed. - ASM Press, 2009 - p.1018.
  2. Virus // Wikipedia, the free encyclopedia. - http://wikipedia.org/wiki/Virus(reference date: 12.12.2011).

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