Behring Discovers the Diphtheria Antitoxin

Date December 11, 1890

Emil von Behring discovered that a toxin produced by the causative agent of diphtheria could be destroyed by blood serum derived from immunized animals. His discovery resulted in the development of a vaccine.

Locale Berlin, Prussia, German Empire (now in Germany)

Key Figures

• Emil von Behring (1854-1917), German bacteriologist
• Shibasaburo Kitasato (1852-1931), Japanese bacteriologist and Behring’s collaborator
• Paul Ehrlich (1854-1915), German bacteriologist and Behring’s collaborator
• Edward Jenner (1749-1823), English physician who developed the smallpox vaccine
• Edwin Klebs (1834-1913), German bacteriologist who isolated the diphtheria bacillus in 1883
• Friedrich August Johannes Löffler (1852-1915), German bacteriologist
• Pierre-Paul-Émile Roux (1853-1933), French bacteriologist
• Alexandre Yersin (1863-1943), Swiss bacteriologist and Roux’s collaborator
• Henry Sewall (1855-1936), American physiologist

Summary of Event

During the nineteenth century, there was an enormous growth of knowledge in the field of bacteriology. Much of the expansion resulted from discoveries by German bacteriologist Robert Koch and French chemistLouis Pasteur . The two scientists are considered the founders of modern medical bacteriology and were instrumental in demonstrating the relationship between exposure to bacteria and specific human and animal diseases. These diseases involved causative agents, or pathogens, such as bacteria, which would interact with human and animal hosts and induce illness caused by infection or toxicity. The illnesses were collectively classified as “communicable diseases” since they could be transmitted from one host to another.

Several scientists and physicians focused on prevention and eradication of communicable diseases. Diphtheria was a major communicable disease studied during this period since it was responsible for many deaths, especially among young children. It is transmissible mainly via direct contact with an infected host and ingestion of contaminated raw milk, and possibly via contact with contaminated articles. The disease is caused by a bacterium called Corynebacterium diphtheriae. Certain strains of these bacteria are susceptible to genetic alteration by a virus that causes the organisms to produce a toxin which is responsible for the onset of diphtheria and the related symptoms. Infection of humans with these bacteria and absorption of their toxin can result in the formation of lesions in the nasal, pharyngeal, and laryngeal regions of the upper respiratory system. The toxin can also negatively impact other organs and systems, such as the nerves, heart, and kidneys. If the disease is extensive, diphtheria is fatal; the probability of contracting the disease is increased under crowded conditions.

The prevalence of the disease increased concomitantly as population densities increased in cities around the world. The causative agent of the disease was not discovered until 1883, when a German bacteriologist, Edwin Klebs, isolated the bacteria from people with diphtheria. The discovery was not confirmed, however, until 1884, when a German bacteriologist, Friedrich August Johannes Löffler, demonstrated that pure cultures of these organisms would induce diphtheria in experimental animals. Indeed, the original name of the causative agent of diphtheria was Klebs-Löffler bacillus, later renamed to Corynebacterium diphtheriae.

Five years later, two other scientists, French bacteriologist Pierre-Paul-Émile Roux and Swiss bacteriologist Alexandre Yersin, were able to separate a chemical toxin from C. diphtheriae and demonstrate that the chemical was the actual factor that caused diphtheria. Thus, the foundation was established for development of a means for rendering the toxin innocuous in order to prevent the onset or eradicate the symptoms of the disease in people who were exposed to the toxin-producing bacteria.

The German bacteriologist Emil von Behring and his assistant, a Japanese bacteriologist, Shibasaburo Kitasato, focused on immunization of animals via vaccination. The scope of their research was influenced by concepts established by several other scientists, including an English physician named Edward Jenner , Pasteur, and the American physiologist Henry Sewall. Jenner developed the concept of vaccination during the late 1790’s. Jenner knew that people who had acquired cowpox and survived were immune against future outbreaks and a very fatal disease, called smallpox. Based on this premise, Jenner demonstrated that smallpox could be prevented in humans if they were injected with a small dose of fluid from an active cowpox lesion. He named this process “vaccination” from the Latin vaccinia, which means cowpox.

Pasteur applied Jenner’s concept to other diseases and developed vaccinations consisting of attenuated bacteria for the prevention of anthrax and rabies during the 1880’s. In turn, based on Pasteur’s success, Sewall applied the concept to develop a vaccine that would induce immunity against toxic snake venoms. In 1887, he was successful in demonstrating that an animal could be protected from the toxic venom if previously vaccinated with sublethal doses of the toxin.

Behring and Kitasato attempted to extend the already proven concept of immunization via vaccination and apply the technique for control of diphtheria. Thus, combined with data generated by Klebs, Löffler, Roux, and Yersin regarding the toxin-producing C. diphtheriae, Behring and Kitasato initiated a series of their own experiments. In 1889, Kitasato had discovered the causative agent of tetanus, which was also found to be a toxin-producing bacterium.

Behring’s experimental design involved preparing a pure culture of a live, toxin-producing strain of C. diphtheriae in a nutrient broth, separating the toxin generated by the bacteria in the broth from the organisms via filtration, and injecting graduated sublethal doses of the toxin under the skin of healthy rabbits and mice. Several days later, he injected the inoculated animals with live, active C. diphtheriae bacteria. Behring’s experiment was a success.

On December 11, 1890, Behring reported in a journal article that the animals vaccinated with C. diphtheriae toxin prior to injection with active C. diphtheriae bacteria did not develop diphtheria. Control animals which were not vaccinated, however, developed the disease subsequent to injection with active organisms. Thus, Behring demonstrated that the experimental animals were able to develop an induced immunity to the C. diphtheriae toxin via vaccination because of the formation of a protective toxin-destroying agent produced within their blood serum. (One week earlier, Behring and Kitasato had coauthored a journal article which reported similar findings for experiments using toxin produced by tetanus bacilli.) The two scientists referred to the protective toxin-destroying agent within the blood sera of immunized animals as an “antitoxin.”

Significance

As a result of Behring’s discovery of diphtheria antitoxin, the foundation was established to develop an efficient vaccine and to determine an optimal dose for human use. Progress was demonstrated within a year, because of experiments conducted by German bacteriologist Paul Ehrlich , whose work involved determining if serum derived from animals and humans known to contain the antitoxin could be injected in others to induce immunization. This concept became the foundation of what is called “serotherapy” to induce “passive immunity.” A person is considered to have been passively immunized when they become immune to toxin because of injection with serum containing antitoxin from another immunized person or animal. In other words, passive immunity implies the transfer of immunity from one host to another via vaccination with antitoxin instead of active toxin.

Ehrlich’s assistance to Behring was also instrumental in establishing some insight into the administration of safe and effective doses of vaccine for clinical use. Within a year of Behring’s discovery of the diphtheria antitoxin, clinical trials were established with humans to determine if diphtheria could be prevented and possibly cured. The clinical trials were successful; thus, the era of vaccinating humans, especially children, with diphtheria antitoxin had begun. The process, however, was not totally efficient, and scientific research continued. Nevertheless, immunization to prevent and cure diphtheria via vaccination was gaining widespread use, and a significant decline in the disease was apparent by the beginning of the twentieth century.

Behring’s discovery of the diphtheria antitoxin influenced several major advances in the area of medical science. The concept of serotherapy as a form of vaccination was developed to induce passive immunity against the C. diphtheriae toxin. The process was later applied by other scientists to control the impact of other bacterial and viral agents found to be pathogenic to humans and animals. Concomitantly, a greater understanding of the human immune system was gained, especially relative to the concept of antibody (for example, antitoxic protein in blood serum) response to antigen (for example, C. diphtheriae toxin). Finally, as a result of the vaccine, countless lives of people who were afflicted with the dreaded disease of diphtheria were saved, while even more people were spared the experience of contracting the illness. In acknowledgment of Behring’s discovery and its positive impact realized at that time and perceived for the future, he was awarded the first Nobel Prize in Physiology or Medicine in 1901.

Bibliography

Asimov, Isaac. Asimov’s Biographical Encyclopedia of Science and Technology. New rev. ed. Garden City, N.Y.: Doubleday, 1972. This reference provides biographical summaries of 1,195 great scientists, including those who established the foundation and influenced the discovery of the diphtheria antitoxin.

Chase, Allan. Magic Shots. New York: William Morrow, 1982. This book provides a historical perspective regarding discoveries of various vaccines that had a positive influence in medicine. The book refers the reader to several of the original journal articles that reported the discoveries.

Lagerkvist, Ulf. Pioneers of Microbiology and the Nobel Prize. River Edge, N.J.: World Scientific, 2003. Behring is one of the scientists prominently featured in this book about Nobel Prize-winning microbiologists. The book contains a section about Behring’s life and his scientific discoveries. One of the few books about Behring written in English.

Walker, M. E. M. Pioneers of Public Health. New York: Macmillan, 1930. This book contains a chapter about Hermann Biggs, an American physician instrumental in encouraging the use of the diphtheria antitoxin to prevent diphtheria. The chapter provides a historical account of the discovery of the antitoxin and development of vaccine.

Waller, John. The Discovery of the Germ: Twenty Years That Transformed the Way We Think About Disease. New York: Columbia University Press, 2002. Waller examines the breakthroughs in microbiology that occurred between 1879 and 1900, including the discoveries of Koch and Pasteur. Places Behring’s work in a larger medical and historical context.

Walsh, James Joseph. Makers of Modern Medicine. Reprint. Freeport, N.Y.: Books for Libraries Press, 1970. The book contains a chapter about Joseph O’Dwyer, an American physician who relentlessly studied the efficacy of using diphtheria antitoxin and eventually succeeded in demonstrating its true value.

Wood, William Barry. From Miasmas to Molecules. New York: Columbia University Press, 1961. The book provides a historical perspective as well as expanded scientific explanations of the diphtheria bacilli: antitoxin and immunity.