Polio Vaccines, What They Are and How They Work.

Salk and Sabin Developed Useful Vaccines to Prevent Poliomyelitis

May 8, 2009

Polio is a feared, paralytic disease that is caused by any one of three major types of an intestinal virus. New tissue culture methods made polio vaccines a reality.

Dr. Jonas Salk and Dr. Sabin each sought to develop polio vaccines. Each succeeded, but their final products were different. Salk's vaccine was a killed vaccine. Sabin's vaccine was live and attenuated.

Polioviruses, Nature, Origin and Characteristics

Polioviruses are obligate, intracellular pathogens. Viruses multiply only within living host cells. Polioviruses are enteroviruses. They are acquired by drinking or eating, infect mammalian gastrointestinal (GI) tracts, and multiply there. These enteroviruses may become blood-borne (viremia) and, occasionally, enter the nervous system where they attack portions of the spinal cord or brain. A CNS polio attack may cause complete, or partial, paralysis of muscles of the diaphragm or legs. Specialized respirators are needed for diaphragm-paralyzed patients.

Polio Vaccines, Mode of Action, and Tissue Culture

Earlier viral vaccines for smallpox and rabies were cultivated in animals. Viruses were extracted from the animals' tissues and used as immunogens. Jenner and Pasteur vaccinated against smallpox and rabies respectively, and were successful with these animal-derived vaccines. In vitro tissue cultures marked a significant change and step forward in medical research of mammalian cells and virology.

The National Foundation for Infantile Paralysis (March of Dimes) raised money for polio research. Shirley Temple and Eddie Cantor were among the notable fundraisers. Major funding went to Dr.Jonas Salk's lab at the University of Pittsburgh. Salk's team grew each all three types of polioviruses (1,2 and 3) in tissues, purified the viruses, inactivated and killed them. The pioneer volunteer vaccination program of Thomas Francis Jr. at the University of Michigan proved Salk's trivalent vaccine worked and on April 12, 1955, the first poliovirus vaccine was licensed in the USA.

Dr. Sabin, also funded by NFIP, took a different approach. Sabin produced vaccine that consisted of mutated and attenuated viruses.

Sabin used elevated temperatures and rapid tissue culture passages to select for weakened, aberrant polio viruses. Sabin's vaccine was alive, weakened, and ingestable (swallowed in syrup). A further benefit was survival and multiplication of the viruses within the GI tract, followed by release of viruses. This served to immunize others who accidentally ingested these attenuated viruses in water or food. There was only one problem, and it was big—occasionally, the virus would mutate back to a virulent form. Therefore, Sabin's vaccine fell into some disfavor despite its great successes, ease of administration and usefulness. Nevertheless, the vaccine is so valuable for eradication of paralytic polio type 1 that it is used for The Global Polio Eradication Initiative and Immunizations.

Each vaccine stimulates the immune system to produce protective antibodies and T-cells to the polioviruses and gives vacinees lifelong, acquired immunity.

Current Status of Polio Worldwide, 2009

Since 1994, no polio has existed in the Americas. Worldwide polio declines continue in Asia and Africa. The Global Polio Eradication Initiative and Immunizations (started in 1988 by the World Health Organization, Rotary International, the CDC and UNICEF) have reduced polio to1,652 cases in 2008 from 350,000 in 1988.

Infectious Diseases Only a Short Distance Away, Anywhere on Planet Earth

Polio, flu, and other vaccine-preventable diseases are only a plane trip away from anywhere on earth. Earth's diverse populations are knit tightly, and without vaccines humans are as vulnerable as any species on the planet to pandemic decimation, or extinction. Much is owed to those who developed vaccines against smallpox, polio and the flu. Literally, millions have survived and lived because of the wisdom and dedication of great scientists.

Consider a productive, rewarding career in science, health management, or medicine.

Sources

Brooks, G.F., J.S. Butel and S. A. Moore. 2004. Medical Microbiology. 23rd ed., Lange Medical Books, McGraw-Hill, New York. 818pp

The copyright of the article Polio Vaccines, What They Are and How They Work. in Immunology is owned by Donald Reinhardt. Permission to republish Polio Vaccines, What They Are and How They Work. in print or online must be granted by the author in writing.