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Virus

Retroviruses

Retroviruses are unique viruses. They are double-stranded RNA viruses that contain an enzyme called reverse transcriptase. Within the host cell, the virus uses reverse transcriptase to make a DNA copy from its RNA genome. In all other organisms, RNA is synthesized from DNA. Cells infected with retroviruses are the only living things that reverse this process.

The first retroviruses discovered were viruses that infect chickens. The Rous sarcoma virus, discovered in the 1950s by Peyton Rous (1879-1970), was also the first virus that was linked to cancer. But it was not until 1980 that the first human retrovirus was discovered. Called Human T-cell Leukemia Virus (HTLV), this virus causes a form of leukemia called adult T-cell leukemia. In 1983-4, another human retrovirus, Human Immunodefiency Virus, the virus responsible for AIDS, was discovered independently by two researchers. Both HIV and HTLV are transmitted in body fluids.

Resources

Books

Doerfler, Walter, and Petra Bohm, eds. Virus Strategies: Molecular Biology and Pathenogenesis. New York: VCH, 1993.

Flint, S.J., et al. Principles of Virology: Molecular Biology, Pathogenesis, and Control. Washington: American Society for Microbiology, 1999.

Kurstak, Edouard, ed. Control of Virus Diseases. New York: Marcel Dekker, 1993.

Richman, D.D., and R.J. Whitley. Clinical Virology. 2nd ed. Washington: American Society for Microbiology, 2002.

Thomas, D. Brian. Viruses and the Cellular Immune Response. New York: Marcel Dekker, 1993.

Periodicals

Appleton, Hazel. "Foodborne Viruses." The Lancet 336 (December 1990): 1362.

Berns, Kenneth I., and Michael R. Linden. "The Cryptic Life Style of Adeno-associated Virus." BioEssays 17 (March 1995): 237.

Bloch, Alan B., et al. "Recovery of Hepatitis A Virus from a Water Supply Responsible for a Common Source Outbreak of Hepatitis A." American Journal of Public Health 80 (April 1990): 428.

Cimons, M. "New Prospects on the HIV Vaccine Scene." ASM News no. 68 (January 2002): 19-22.

Dutton, Gail. "Biotechnology Counters Bioterrorism." Genetic Engineering News no. 21 (December 2000): 1-22ff.

Dybul, M., T.-K. Chun, C. Yoder, et al. "Short-cycle Structured Intermittent Treatment of Chronic HIV Infection with Highly Effective Antiretroviral Therapy: Effects on Virologic, Immunologic, and Toxicity Parameters." Proceedings of the National Academy of Sciences no. 98 (18 December 2001): 15161-15166.

Ganem, Don. "Oncogenic Viruses: Of Marmots and Men." Nature 347 (September 20, 1990): 230.

Slater, P. E., et al. "Poliomyelitis Outbreak in Israel in 1988: A Report with Two Commentaries." The Lancet: 335 (May 19, 1992): 1192.

Zur Hausen, Harald. "Viruses in Human Cancer." Science 254 (November 22, 1991): 1167.

Kathleen Scogna

KEY TERMS

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Bacteriophage: —A virus that infects bacteria.
Capsid: —The outer protein coat of a virus.
Deoxyribonucleic acid (DNA): —The genetic material in a cell; in the nucleus, DNA transcribes RNA for the synthesis of proteins.
Envelope: —The outermost covering of some viruses; it is composed of lipid and protein acquired from the host cell's plasma membrane as the virus buds out from the cell.
Eukaryote: —A cell whose genetic material is carried on chromosomes inside a nucleus encased in a membrane. Eukaryotic cells also have organelles that perform specific metabolic tasks and are supported by a cytoskeleton which runs through the cytoplasm, giving the cell form and shape.
Exocytosis: —The process by which a virus "buds out" from the host cell.
Genome: —The complete sequence of genes within a cell or virus.
Host cell: —The specific cell that a virus targets and infects.
Icosahedron: —A 20–sided polyhedron.
Lysogenic cycle: —A viral replication cycle in which the virus does not destroy the host cell but co-exists within it.
Lytic cycle: —A viral replication cycle in which the virus destroys the host cell.
Obligate intracellular parasite: —An organism or agent, such as a virus, that cannot reproduce unless it is inside a cell.
Oncogene: —A gene that encodes for growth factors; oncogenes are believed to cause the cancerous growth of cells.
Prokaryote: —A type of cell without a true nucleus, such as a bacterium.
Retrovirus: —A type of virus that inserts its genetic material into the chromosomes of the cells it infects.
Reverse transcriptase: —The enzyme that allows a retrovirus to transcribe DNA from RNA.
Ribonucleic acid: —RNA; the molecule translated from DNA in the nucleus that directs protein synthesis in the cytoplasm; it is also the genetic material of many viruses.

Additional topics

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