antiviral drug

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antiviral drug,

any of several drugs used to treat viral infections. The drugs act by interfering with a virus's ability to enter a host cell and replicate itself with the host cell's DNA. Some drugs block the virus's attachment or entry into the cell; others inhibit replication or prevent the virus from shedding the protein coat that surrounds the viral DNA. Antiviral drug development has been concurrent with advances in molecular biologymolecular biology,
scientific study of the molecular basis of life processes, including cellular respiration, excretion, and reproduction. The term molecular biology was coined in 1938 by Warren Weaver, then director of the natural sciences program at the Rockefeller Foundation.
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 and genetic engineeringgenetic engineering,
the use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. The techniques include the use of hybridomas (hybrids of rapidly multiplying cancer cells and of cells that make a
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 that allow study and definition of the genetic codes of viral DNA. Study at this level was not possible until electron microscopesmicroscope,
optical instrument used to increase the apparent size of an object. Simple Microscopes

A magnifying glass, an ordinary double convex lens having a short focal length, is a simple microscope. The reading lens and hand lens are instruments of this type.
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 became available and it is only since the 1980s that antiviral drugs have been on the market.

Antivirals are now available for a wide variety of viral diseases. Ribavirin, available since the mid-1980s, is used to treat respiratory syncytial virus (RSV), a cause of severe childhood respiratory infections. It is thought to inhibit messenger RNA. Ribavirin has few side effects, but is prohibitively expensive for all but the most serious cases. Amantadine and rimantadine, which are effective against strains of influenza A, act by interfering with viral uncoating.

Herpes simplexherpes simplex
, an acute viral infection of the skin characterized by one or more painful, itching blisters filled with clear fluid. It is caused by either of two herpes simplex viruses: Type 1, herpes labialis,
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 virus can now be treated by a highly selective drug, acyclovir (Zovirax), that interferes with an enzyme critical to the growth of the DNA chain. Although not a cure, the drug lessens the frequency and severity of outbreaks. Acyclovir is also used to lessen the pain and speed the healing of herpes zosterherpes zoster,
infection of a ganglion (nerve center) with severe pain and a blisterlike eruption in the area of the nerve distribution, a condition called shingles. The causative organism is varicella zoster, a common, filtrable virus that is also known to cause chicken pox.
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 (shingles).

The search for cures and palliatives for AIDSAIDS
or acquired immunodeficiency syndrome,
fatal disease caused by a rapidly mutating retrovirus that attacks the immune system and leaves the victim vulnerable to infections, malignancies, and neurological disorders. It was first recognized as a disease in 1981.
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 has yielded drugs such as zidovudine (AZTAZT
or zidovudine
, drug used to treat patients infected with the human immunodeficiency virus (HIV), which causes AIDS; also called azidothymidine. Originally developed in 1964 as an anticancer drug, AZT was never approved for that purpose.
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), which inhibits the transcription of RNA to DNA in human immunodeficiency virus (HIV). Ganciclovir and cidofovir are used in the treatment of cytomegalovirus (CMV), a virus that affects the eyes of immunosuppressed patients. Fomivirsen, which is an antisenseantisense,
DNA or RNA manipulated in a laboratory so that its components (nucleotides) form a complementary copy of normal, or "sense," messenger RNA (mRNA; see nucleic acid).
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 drug, is also used to treat CMV.

See also nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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, virusvirus,
parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Most viruses are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes.
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, retrovirusretrovirus,
type of RNA virus that, unlike other RNA viruses, reproduces by transcribing itself into DNA. An enzyme called reverse transcriptase allows a retrovirus's RNA to act as the template for this RNA-to-DNA transcription.
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.