Enders, john F. (1897-1985)

American virologist

John F. Enders' research on viruses and his advances in tissue culture enabled microbiologists Albert Sabin and Jonas Salk to develop vaccines against polio, a major crippler of children in the first half of the twentieth century. Enders' work also served as a catalyst in the development of vaccines against measles , mumps and chicken pox. As a result of this work, Enders was awarded the 1954 Nobel Prize in medicine or physiology.

John Franklin Enders was born February 10, 1897, in West Hartford, Connecticut. His parents were John Enders, a wealthy banker, and Harriet Whitmore Enders. Entering Yale in 1914, Enders left during his junior year to enlist in the U.S. Naval Reserve Flying Corps following America's entry into World War I in 1917. After serving as a flight instructor and rising to the rank of lieutenant, he returned to Yale, graduating in 1920. After a brief venture as a real estate agent, Enders entered Harvard in 1922 as a graduate student in English literature. His plans were sidetracked in his second year when, after seeing a roommate perform scientific experiments, he changed his major to medicine. He enrolled in Harvard Medical School, where he studied under the noted microbiologist and author Hans Zinsser. Zinsser's influence led Enders to the study of microbiology, the field in which he received his Ph.D. in 1930. His dissertation was on anaphylaxis , a serious allergic condition that can develop after a foreign protein enters the body. Enders became an assistant at Harvard's Department of Bacteriology in 1929, eventually rising to assistant professor in 1935, and associate professor in 1942.

Following the Japanese attack on Pearl Harbor, Enders came to the service of his country again, this time as a member of the Armed Forces Epidemiology Board. Serving as a consultant to the Department of War, he helped develop diagnostic tests and immunizations for a variety of diseases. Enders continued to work with the military after the war, offering his counsel to the U.S. Army's Civilian Commission on Virus and Rickettsial Disease, and the Secretary of Defense's Research and Development Board. Enders left his position at Harvard in 1946 to set up the Infectious Diseases Laboratory at Boston Children's Hospital, believing this would give him greater freedom to conduct his research. Once at the hospital, he began to concentrate on studying those viruses affecting his young patients. By 1948, he had two assistants, Frederick Robbins and Thomas Weller , who, like him, were graduates of Harvard Medical School. Although Enders and his colleagues did their research primarily on measles, mumps, and chicken pox, their lab was partially funded by the National Foundation for Infantile Paralysis, an organization set up to help the victims of polio and find a vaccine or cure for the disease. Infantile paralysis, a virus affecting the brain and nervous system was, at that time, a much-feared disease with no known prevention or cure. Although it could strike anyone, children were its primary victims during the periodic epidemics that swept through communities. The disease often crippled and, in severe cases, killed those afflicted.

During an experiment on chicken pox, Weller produced too many cultures of human embryonic tissue. So as not to let them go to waste, Enders suggested putting polio viruses in the cultures. To their surprise, the virus began growing in the test tubes. The publication of these results in a 1949 Science magazine article caused major excitement in the medical community. Previous experiments in the 1930s had indicated that the polio virus could only grow in nervous system tissues. As a result, researchers had to import monkeys in large numbers from India, infect them with polio, then kill the animals and remove the virus from their nervous system. This was extremely expensive and time-consuming, as a single monkey could provide only two or three virus samples, and it was difficult to keep the animals alive and in good health during transport to the laboratories.

The use of nervous system tissue created another problem for those working on a vaccine. Tissue from that system often stimulate allergic reactions in the brain, sometimes fatally, when injected into another body, and there was always the danger some tissue might remain in the vaccine serum after the virus had been harvested from the culture. The discovery that the polio virus could grow outside the nervous system provided a revolutionary breakthrough in the search for a vaccine. As many as 20 specimens could be taken from a single monkey, enabling the virus to be cultivated in far larger quantities. Because no nervous system tissue had to be used, there was no danger of an allergic reaction through inadvertent transmission of the tissue. In addition, the technique of cultivating the virus and studying its effects also represented a new development in viral research. Enders and his assistants placed parts of the tissues around the inside walls of the test tubes, then closed the tubes and placed the cultures in a horizontal position within a revolving drum. Because this method made it easier to observe reaction within the culture, Enders was able to discover a means of distinguishing between the different viruses in human cells. In the case of polio, the virus killed the cell, whereas the measles virus made the cells fuse together and grow larger.

Because his breakthrough made it possible to develop a vaccine against polio, Enders, Robbins, and Weller were awarded the Nobel Prize for medicine or physiology in 1954. Interestingly enough, Enders originally opposed Salk's proposal to vaccinate against polio by injecting killed viruses into an uninfected person to produce immunity . He feared that this would actually weaken the immunity of the general population by interfering with the way the disease developed. In spite of their disagreements, Salk expressed gratitude to Enders by stating that he could not have developed his vaccine without the help of Enders' discoveries.

Enders' work in the field of immunology did not stop with his polio research. Even before he won the Nobel Prize, he was working on a vaccine against measles, again winning the acclaim of the medical world when he announced the creation of a successful vaccine against this disease in 1957. Utilizing the same techniques he had developed researching polio, he created a weakened measles virus that produced the necessary antibodies to prevent infection. Other researchers used Enders' methodology to develop vaccines against German measles and chicken pox.

In spite of his accomplishments and hard work, Enders' progress in academia was slow for many years. Still an assistant professor when he won the Nobel Prize, he did not become a full professor until two years later. This may have resulted in his dislike for university life—he once said that he preferred practical research to the "arid scholarship" of academia. Yet, by the mid-fifties, Enders began receiving his due recognition. He was given the Kyle Award from the United States Public Health Service in 1955 and, in 1962, became a university professor at Harvard, the highest honor the school could grant. Enders received the Presidential Medal of Freedom in 1963, the same year he was awarded the American Medical Association's Science Achievement Award, making him one of the few non-physicians to receive this honor.

Enders married his first wife in 1927, and in 1943, she passed away. The couple had two children. He married again in 1951. Affectionately known as "The Chief" to students and colleagues, Enders took a special interest in those he taught, keeping on the walls of his lab portraits of those who became scientists. When speaking to visitors, he was able to identify each student's philosophy and personality. Enders wrote some 190 published papers between 1929 and 1970. Towards the end of his life, he sought to apply his knowledge of immunology to the fight against AIDS , especially in trying to halt the progress of the disease during its incubation period in the human body. Enders died September 8, 1985, of heart failure, while at his summer home in Waterford, Connecticut.

See also Antibody and antigen; Antibody formation and kinetics; Immunity, active, passive and delayed; Immunity, cell mediated; Immunity, humoral regulation; Immunization; Immunochemistry; Poliomyelitis and polio