Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Salk, Jonas

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immunity to polio with no harmful side effects. By this time,

however, the public and much of the scientific community

were committed to the Salk vaccine. Two scientists working

for Lederle Laboratories had also developed a live-virus vac-

cine. However, the Lederle vaccine was tested in Northern

Ireland in 1956 and proved dangerous, as it sometimes

reverted to a virulent state.

Although Sabin lacked backing for a large-scale clini-

cal trial in the United States, he remained undaunted. He was

able to convince the Health Ministry in the Soviet Union to

try his vaccine in massive trials. At the time, the Soviets were

mired in a polio epidemic that was claiming eighteen to

twenty thousand victims a year. By this time, Sabin was

receiving the political backing of the World Health

Organizationin Geneva, Switzerland, which had previously

been using Salk’s vaccine to control the outbreak of polio

around the world; they now believed that Sabin’s approach

would one day eradicate the disease.

Sabin began giving his vaccine to Russian children in

1957, inoculating millions over the next several years. Not to

be outdone by Salk’s public relations expertise, Sabin began

to travel extensively, promoting his vaccine through newspa-

per articles, issued statements, and scientific meetings. In

1960, the U.S. Public Health Service, finally convinced of

Sabin’s approach, approved his vaccine for manufacture in

the United States. Still, the PHS would not order its use and

the Salk vaccine remained the vaccine of choice until a pedi-

atrician in Phoenix, Arizona, Richard Johns, organized a

Sabin vaccine drive. The vaccine was supplied free of charge,

and many physicians provided their services without a fee on

a chosen Sunday. The success of this effort spread, and

Sabin’s vaccine soon became “the vaccine” to ward off polio.

The battle between Sabin and Salk persisted well into

the 1970s, with Salk writing an op-ed piece for the New York

Times in 1973 denouncing Sabin’s vaccine as unsafe and urg-

ing people to use his vaccine once more. For the most part,

Salk was ignored, and by 1993, health organizations began to

report that polio was close to extinction in the Western

Hemisphere.

Sabin continued to work vigorously and tirelessly into

his seventies, traveling to Brazil in 1980 to help with a new

outbreak of polio. He antagonized Brazilian officials, how-

ever, by accusing the government bureaucracy of falsifying

data concerning the serious threat that polio still presented in

that country. He officially retired from the National Institute of

Health in 1986. Despite his retirement, Sabin continued to be

outspoken, saying in 1992 that he doubted whether a vaccine

against the human immunodeficiency virus, or HIV, was feasi-

ble. Sabin died from congestive heart failure at the

Georgetown University Medical Center on March 3, 1993. In

an obituary in the Lancet,Sabin was noted as the “architect”

behind the eradication of polio from North and South

America. Salk issued a statement praising Sabin’s work to

vanquish polio.

See alsoAntibody and antigen; Antibody formation and kinet-

ics; History of immunology; History of public health;

Poliomyelitis and polio

SSaccharomyces cerevisiaeACCHAROMYCES CEREVISIAE

Unicellular Fungi(YeastPhylum) are one of the most studied

single-cell Eukaryotes. Among them, Saccharomyces cere-

visiaeis perhaps the biological model most utilized for decades

in order for scientists to understand the molecular anatomy and

physiology of eukaryotic cells, such as membrane and trans-

membrane receptors, cell cyclecontrols, and enzymesand pro-

teins involved in signal transductionto the nucleus.

Many strands of S. cerevisiaeare used by the wine and

beer industry for fermentation. S. cerevisiaeis a member of the

group of budding yeasts that replicate (reproduce) through the

formation of an outgrowth in the parental cell known as a bud.

After nuclear division into two daughter nuclei, one nucleus

migrates to the bud, which continues to grow until it breaks off

to form an independent daughter cell. Most eukaryotic cells

undergo symmetric cell division, resulting in two daughter

cells with the same size. In budding yeast, however, cell divi-

sion is asymmetric and produces at cell separation a large

parental cell and a small daughter cell. Moreover, after sepa-

ration, the parental cell starts the production of a new bud,

whereas the daughter cell continues to grow into its mature

size before producing its own bud. Cell cycle times are also

different between parental and young daughter cells. Parental

(or mother cells) have a cell cycle of 100 minutes, whereas

daughter cells in the growing process have a cycle time of 146

minutes from birth to first budding division.

The study of cell cycle controls, enzymatic systems of

DNArepair, programmed cell death, and DNAmutationsin S.

cerevisiaeand S. pombegreatly contributed to the understand-

ing of pre-malignant cell transformations and the identifica-

tion of genes involved in carcinogenesis. They constitute ideal

biological models for these studies because they change the

cellular shape in each phase of the cell cycle and in case of

genetic mutation, the position defect is easily identified and

related to the specific phase of the cell cycle. Such mutations

are known as cdc mutations (cell division cycle mutations).

See alsoCell cycle (eukaryotic), genetic regulation of; Yeast

genetics

SSalk, Jonas ALK, JONAS(1914-1995)

American physician

Jonas Salk was one of the United States’s best-known micro-

biologists, chiefly celebrated for his discovery of his polio

vaccine. Salk’s greatest contribution to immunologywas the

insight that a “killed virus” is capable of serving as an antigen,

prompting the body’s immune systemto produce antibodies

that will attack invading organisms. This realization enabled

Salk to develop a polio vaccine composed of killed polio

viruses, producing the necessary antibodies to help the body

to ward off the disease without itself inducing polio.

The eldest son of Orthodox Jewish-Polish immigrants,

Jonas Edward Salk was born in East Harlem, New York, on

October 28, 1914. His father, Daniel B. Salk, was a garment

worker, who designed lace collars and cuffs and enjoyed

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