Louis Pasteur, the Father of Immunology

From Wikipedia

Born in France on December 27, 1822, Louis Pasteur began life as an average student but with a strong desire to learn. At first, his interests were in pastel sketching and fishing, but he aspired to attend a teachers college called École Normale Supérieure. To pay his way, he earned money by teaching math and physical science to high school children. His interests in science began when he was fascinated by

Pasteur's first pastel drawing at age 13 (Institut Pasteur)

 lectures from French chemist Jean-Baptiste Dumas at the College of Sorbonne (Paris College of Theology). These were public lectures that attracted 600-700 people at a time. Pasteur was accepted to École Normale in 1843 where he took up chemistry.

Louis Pasteur had once been thought to be a slow learner, but the truth is, he simply concentrated very carefully on everything he studied: "...he never affirmed anything of which he was not absolutely sure" (translated quote from The Life of Pasteur, by Rene Vallery-Radot). It was said that he didn't even know what it was like to skim a book because he wanted to get everything out of it. He was never satisfied with just book knowledge, though. At college, for example, they taught that phosphorus comes from extracting the mineral from bone. But he was so curious about the method they described that he bought some bones, burned and crushed them, and did the extraction himself just to have a phosphorus sample of his own!

After getting his bachelor's degree in 1845, he taught as professor of physics at the Collège de Tournon, but returned to École Normale at the urging of an old teacher. There, he got his doctoral degree in sciences in 1848 with a dissertation in chemistry and in physics. His studies focused on optical properties of chemicals, especially crystals. Pasteur was then appointed professor of chemistry at the University of Strasbourg.

Pasteur, 1848 (Institut Pasteur)

His initial interests in chemistry were about the crystal structure of two chemicals and how they responded to polarized light. But he was also dedicated to showing students the practical side of their studies. As professor of chemistry and dean of the science faculty at the University of Lille, he arranged for factory tours so students could see firsthand iron foundries and steel & metal works factories, then ask questions to the foremen. This was his attempt to instill curiosity in students. His sentiments were reflected in a quote from a university speech, "In the fields of observation, chance only favors the mind which is prepared".

But he was as honest as any scientist could be. In his own experiments, he would scribble a note in his lab reports where he found mistakes had been made. If the hypothesis itself for the work was incorrect and lead to a false result, he would write "erroneous" when the experiment failed.

In 1854, he became dean of the new faculty of sciences at the University of Lille in northern France. At that time, fermentation of beer and wine was considered a chemical process, not something caused by the metabolism of yeast. As early as 1837, Cagniard de la Tour, Theodor Schwann, and Friedrich Kützing independently proposed that yeast was a living organism that multiplied during fermentation, but most people disagreed. The thought of the day was that the chemical change of sugars to alcohol was caused instead by some "vital" or "catalytic force", even by "unstabilizing vibrations" of the chemicals. But the three researches above observed yeast cells budding under the microscope and suggested its role in the process, but they couldn't explain further.

Yeast cells with new growths (buds) forming as they grow (Wikipedia)

In 1856, the head of a beetroot alcohol manufacturer asked Pasteur for advice because some of his batches had spoiled. Pasteur noticed that the yeast cells were nicely rounded when the fermentation went well, but they were elongated when it went bad with an accumulation of acetic acid (vinegar) instead of alcohol. Even though yeast weren't yet known to cause the alcohol production, this observation gave the manufacturer something to keep an eye on, and this was the start of Pasteur's interest in fermentation.

Pasteur's drawings of yeast cells, 1862 (Yeast Research: A Historical Review)

A year later, his attention was drawn to souring of milk, too. But he observed in beer and wine tiny globules even smaller than yeast were what was responsible for failed fermention into alcohol and instead generated acids. (These were eventually explained as bacteria.) His own university colleagues didn't read his paper for 3 months, so he grew dissatisfied at Lille and accepted a director position at the École Normale.

Pasteur showed how yeast were not only alive but that they actively changed sugar into alcohol.

• He noticed that yeast cells multiplied during the fermentation process.
• When he sterilized sugar solutions and prevented yeast from entering, no alcohol was made.
• As sugar was consumed, yeast cells grew in number, and alcohol and carbon dioxide were produced.
• The alcohol and other products in fermentation bent light in a way that only living organisms can do. 

In 1862, he heated fermentation mixtures for a few moments to 50-60º C, and the problem of spoiling was solved by killing the bacteria (tiny globules) without changing the taste of the wine. People didn't believe him until he assembled a panel of wine experts to support him. Thus was born the process of pasteurization, which he patented in 1865.

 

Patent on pasteurization (Institut Pasteur)

Pasteur then attacked the notion of spontaneous generation, that is, the formation of life from organic matter and not from a previous life. Lazzaro Spallanzani (1768) boiled broth and then sealed it; no bacteria grew in it, but critics said it needed air. Franz Schulze (1836) boiled broth and introduced air that had been bubbled through strong acids and alkali; nothing grew, but people claimed the "vital force" in air had been altered with the chemical treatment. Theodor Schwann (1837) repeated the work, then passed heated air into the boiled broth instead, but even though nothing grew, naysayers claimed the "vital force" in the air had still been changed by heating.

In 1859, Pasteur challenged these claims in a letter to naturalist Felix Archimede Pouchet, who believed in spontaneous generation:

"he wrote that the question of spontaneous generation was entirely open and still awaiting proof and that all of this was unknown and warranted experimentation" (Schwartz, The life and works of Louis Pasteur, 2001)

So, he himself set up 3 swan-necked flasks as shown below. The bent neck did not allow germ-filled air to enter, but air in the top of the flask was present and sterilized (top diagram). If the same broth was exposed to air after boiling (middle diagram), the broth became contaminated with room bacteria. The bottom diagram shows that by tilting the boiled flask enough to let liquid reach a non-sterile part of the neck, contamination got in. Pasteur wrote in 1864, “Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment. There is no known circumstance in which it can be confirmed that microscopic beings came into the world without germs, without parents similar to themselves." Despite this proof, the idea of spontaneous generation of diseases lingered into the early 1880s.

 Pasteur's experiment to debunk spontaneous generation (Bio.libretexts.org)

In 1849, the silk industry in France was decimated by a disease of the silkworms. A solution could not be found, and healthy silkworms could not be imported because the disease was worldwide. The

Healthy and sick silkworms (Frontiers in Microbiology)

French Department of Agriculture asked Pasteur to investigate even though he knew nothing about the industry nor that worms could even have diseases. From 1865 to 1870, he learned that there were two diseases, and only by selective breeding of eggs from worms that appeared healthy did he eliminate the problem and create fresh healthy stocks. But he also noticed that there were environmental factors that contributed to spreading the diseases, a point that stayed in his mind about other diseases. During his research at this time, Pasteur suffered a cerebral hemorrhage that paralyzed his left side. He was incapacitated for 3 months, during which time people had to read and write for him, but he kept pursuing the silkworm research.

Pasteur dictating a letter to his wife, about 1868 (Getty Images)

In addition to the pasteurization process, Pasteur is most widely known for his role in vaccine development. In the 1870s, scientists were still unsure about the cause of many diseases from bacteria or viruses. They couldn't understand how things so small could have such a large effect.

Around 1880, Pasteur was commissioned again by the Minister of Agriculture, this time to help resolve major problems with anthrax wiping out sheep and cattle in France. He first observed that they caught the disease only after grazing in certain fields, and that this was where sheep killed by anthrax had been buried. He tested earthworms above them and confirmed that they carried the anthrax bacteria after feeding on the sheep carcasses. As animals' mouths were cut by prickly vegetation, they became infected with earthworm excrement loaded with anthrax.

Pasteur already knew of Edward Jenner's success in vaccinating people against smallpox in 1796. But Jenner had not used smallpox virus to protect people; he used a related virus from cowpox instead. Pasteur didn't have that luxury, so he tried to weaken the anthrax bacteria chemically before reinjecting it into animals. A public demonstration in May-June, 1881 attracted 200 farmers and scientists. Half of 58 sheep, 2 goats and 10 cattle had been vaccinated, and when all were injected with anthrax bacteria, only the vaccinated ones survived, thus proving Pasteur's method worked.

Pasteur and team inoculating animals for the demonstration (History of Vaccine Development, Plotkin, 2011)

Recognizing the power of vaccines, he then searched for a disease that affected animals and humans, so he could do his testing on animals before using the final vaccine product on people. He chose rabies, which had been known for 4,000 years even though the exact cause (a virus) was not known. The disease reaches the nervous system and eventually causes death by encephalitis. 

People of Pasteur's day did not know how to culture viruses in the lab, and they are too small to see with regular microscopes. Previous research by others like Pierre-Victor Galtier suggested that injecting saliva from rabid dogs into rabbits could produce rabies, and by 1881 Galtier had demonstrated how he could protect sheep and goats against rabies virus by injecting tiny amounts of rabid saliva. That same year, Pasteur's co-researcher Émile Roux developed a model of injecting the virus directly into the brain. In 1883-1884, Paul Gibier showed that the virus lost its potency if it was dried out, so no chemical treatment was needed to weaken it.

Dogs were easier to obtain and were the main source of human infection, so Pasteur used them as test and control animals and followed all of the research of the day from 1880 to 1885. In 1884, he made his first test in dogs given weakened (dried) rabies virus from infected rabbits' spinal column. Data had shown that spinal material produced more consistent virus than saliva. The test on 50 dogs proved to be successful. 

Pasteur in his lab with dogs undergoing testing (Meisterdruke.uk)

Then, on July 6, 1865, a mother and her 9-year-old boy Joseph Meister arrived at his home after a 470-km journey. The boy had been bitten two days earlier by a rabid dog, and she sought Pasteur's help. He reluctantly instructed two doctors how to perform the 12 inoculations needed over the next ten days and worried so much that he could not work. But the boy survived, and the first human trial had been completed successfully.

Pasteur and Joseph Meister (awesome stories.com)

He later proposed building an institute specific for the administration of the vaccine, and it later grew into the prestigious Institut Pasteur which spread worldwide. He won many accolades throughout his life and died on 28 September 1895.

If you wish to see a movie about his life, starring the actor Paul Muni, go to this YouTube link.