Microbiology and Immunology

Rous, Peyton WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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tumor viruses is the presence of a protein that coats the viral

RNA. The gag gene codes for this latter protein. The protein

encoded by the gag gene is also found in the envelope. The

presence of these two protein species in RNA tumor viruses

is being explored as a target for therapy to prevent RNA

virus-induced cancer.

Another hallmark of RNA tumor viruses is the presence

of a gene that is designated pol. The products of the pol gene

include reverse transcriptase, another enzyme that helps inte-

grate the viral genetic material into the host genome, and

other enzymesthat help process the genetic material and viral

proteins so as to permit assembly of new virus. These essen-

tial functions have made the pol gene the target of antiviral

strategies.

The infection process begins with the binding of the

virus particles to a specific molecule on the surface of the host

cell. Generically, such molecules are termed receptors. Once

the virus is bound, it can be taken into the host by the process

of endocytosis. Blocking the viral recognition of the host

receptor and binding of the virus is yet another strategy to pre-

vent tumor development.

The molecular basis for the transformationof cells by

RNA tumor viruses was revealed by a number of scientists,

including the Nobel laureate Harold Varmus. He and the oth-

ers demonstrated that the cancer genes (oncogenes) of the

viruses were similar or the same as certain genes with the

nucleic acid of the host cell. When a virus infects the host, the

host gene may become part of a new virus particle following

viral replication. Over time, the host gene may become altered

in subsequent rounds of viral replication. Eventually, this

altered host gene may end up replacing a normal gene in a new

host cell. The altered gene produces a protein that is involved

in over-riding the controls on the division process of the host

cell. The result is the uncontrolled cell division that is the hall-

mark of a cancer cell.

See alsoAIDS, recent advances in research and treatment;

Immunodeficiency; Viral genetics

RRous, Peyton OUS, PEYTON(1879-1970)

American physician

Francis Peyton Rous was a physician-scientist at the

Rockefeller Institute for Medical Research (later the

Rockefeller University) for over sixty years. In 1966, Rous

won the Nobel Prize for his 1910 discovery that a virus can

cause cancer tumors. His other contributions to scientific med-

icine include creating the first blood bank, determining major

functions of the liver and gall bladder, and identifying factors

that initiate and promote malignancy in normal cells.

Rous was born in Baltimore, Maryland, to Charles

Rous, a grain exporter, and Frances Wood, the daughter of a

Texas judge. His father died when Rous was eleven, and his

mother chose to stay in Baltimore. His sisters were profes-

sionally successful, one a musician, the other a painter.

Rous, whose interest in natural science was apparent at

an early age, wrote a “flower of the month” column for the

Baltimore Sun. He pursued his biological interests at Johns

Hopkins University, receiving a B.A. in 1900 and an M.D. in

1905. After a medical internship at Johns Hopkins, however,
      he decided (as recorded in Les Prix Nobel en 1966) that he was
      “unfit to be a real doctor” and chose instead to concentrate on
      research and the natural history of disease. This led to a full
      year of studying lymphocytes with Aldred Warthin at the
      University of Michigan and a summer in Germany learning
      morbid anatomy (pathology) at a Dresden hospital.
      After Rous returned to the United States, he developed
      pulmonary tuberculosisand spent a year recovering in an
      Adirondacks sanatorium. In 1909, Simon Flexner, director of
      the newly founded Rockefeller Institute in New York City,
      asked Rous to take over cancer research in his laboratory. A
      few months later, a poultry breeder brought a Plymouth Rock
      chicken with a large breast tumor to the Institute and Rous,
      after conducting numerous experiments, determined that the
      tumor was a spindle-cell sarcoma. When Rous transferred a
      cell-free filtrate from the tumor into healthy chickens of the
      same flock, they developed identical tumors. Moreover, after
      injecting a filtrate from the new tumors into other chickens, a
      malignancy exactly like the original formed. Further studies
      revealed that this filterable agent was a virus, although Rous
      carefully avoided this word. Now called the Rous sarcoma
      virus RSV) and classed as an RNAretrovirus, it remains a pro-
      totype of animal tumor virusesand a favorite laboratory
      model for studying the role of genes in cancer.
      Rous’s discovery was received with considerable disbe-
      lief, both in the United States and in the rest of the world. His
      viral theory of cancer challenged all assumptions, going back
      to Hippocrates, that cancer was not infectious but rather a
      spontaneous, uncontrolled growth of cells and many scientists
      dismissed his finding as a disease peculiar to chickens.
      Discouraged by his failed attempts to cultivate virusesfrom
      mammal cancers, Rous abandoned work on the sarcoma in


1906. Nearly two decades passed before he returned to cancer
      research.
      After the onset of World War I, Rous, J. R. Turner, and
      O. H. Robertson began a search for emergency blood transfu-
      sion fluids. Nothing could be found that worked without red
      blood corpuscles so they developed a citrate-sugar solution
      that preserved blood for weeks as well as a method to trans-
      fuse the suspended cells. Later, behind the front lines in
      Belgium and France, they created the world’s first blood bank
      from donations by army personnel. This solution was used
      again in World War II, when half a million Rous-Turner blood
      units were shipped by air to London during the Blitz.
      During the 1920s, Rous made several contributions to
      physiology. With P. D. McMaster, Rous demonstrated the
      concentrating activity of bile in the gall bladder, the acid-
      alkaline balance in living tissues, the increasing permeability
      along capillaries in muscle and skin, and the nature of gall-
      stone formation. In conducting these studies, Rous devised
      culturetechniques that have become standard for studying
      living tissues in the laboratory. He originated the method for
      growing viruses on chicken embryos, now used on a mass
      scale for producing viral vaccines, and found a way to isolate
      single cells from solid tissues by using the enzyme trypsin.

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