Tag Archives: Maurice Hillman

John Enders: “The Father of Modern Vaccines”

John Enders (1897- 1985) was one of the subjects of a recent posting, Vaccine Research Using Children (1). In the 1950s, Enders used severely handicapped children at the Walter E. Fernald State School in Massachusetts to test his measles vaccine—a vaccine that may have saved well over 100 million lives. Irrespective of the ethical issues raised by the incident at the Fernald School, Nobel laureate John Enders was one of the most highly renowned of virologists, and there is much more to his story, some of which is told here.

John F. Enders, November 17, 1961
John F. Enders, November 17, 1961

Enders grew up in West Hartford, Connecticut. His father, who was CEO of the Hartford National Bank, left the Enders family a fortune of $19 million when he passed away. Thus, John Enders became financially independent, which may help to account for his rather atypical path to a career in biomedical research.

Enders was under no pressure to decide on a vocation, and had no particular objective in mind when he enrolled at Yale University in 1915. In 1917 (during the First World War) he interrupted his Yale studies to enlist in the Naval Reserve. He became a Navy pilot and then a flight instructor. After three years of naval service, Enders returned to Yale to complete his undergraduate studies.

After Enders graduated from Yale he tried his hand at selling real estate in Hartford. However, selling real estate troubled him, in part because he believed that people ought to know whether or not they wanted to buy a house, rather than needing to be sold (2, 3). Thus, Enders considered other callings, finally deciding to prepare for a career teaching English literature.

What might have motivated that particular choice? Here is one possibility. During the years when Enders was growing up in West Hartford, his father handled the financial affairs of several celebrated New England writers, including Mark Twain. [The young Enders always admired Twain’s immaculate white suits whenever he visited the Enders home (3).] So, perhaps Enders’ early exposure to eminent writers among his father’s clients planted the seed for his interest in literature. In any case, Enders enrolled at Harvard to pursue graduate studies in preparation for his new calling.

Enders received his M.A. degree in English Literature from Harvard in 1922. Moreover, he was making substantial progress towards his Ph.D., when his career took yet another rather dramatic turn; one reminiscent of that taken later by Harold Varmus, who likewise did graduate studies in English literature at Harvard, with the intent of becoming an English teacher (4).

The changes in the career plans of both Enders and Varmus—from teaching English literature to biomedical research—were prompted by the friends each had who were at Harvard Medical School. Varmus’ friends were his former classmates from Amherst College. Enders first met his friends from among his fellow boarders at his Brookline rooming house.

Dr. Hugh Ward, an instructor in Harvard’s Department of Bacteriology and Immunology, was one of the friends Enders met at his rooming house. Enders wrote, “We soon became friends, and thus I fell into the habit of going to the laboratory with him in the evening and watching him work (5).” Enders was singularly impressed by Ward’s enthusiasm for his research (5).

During one of the trips that Ward and Enders made to the laboratory, Ward introduced Enders to Hans Zinsser, Head of Harvard’s Department of Bacteriology and Immunology. Zinsser was an eminent microbiologist, best known for isolating the typhus bacterium and for developing a vaccine against it.

Enders soon became fascinated by the research in Zinsser’s lab. So, at 30-years-of-age, and on the verge of completing his Ph.D. in English Literature, Enders changed career plans once again; this time to begin studies toward a doctorate in bacteriology and immunology, under Zinsser’s mentorship.

Zinsser, a distinguished microbiologist, was also a sufficiently accomplished poet to have some of his verses published in The Atlantic Monthly. That aspect of Zinsser likely impressed the literate Enders, who described his mentor as: “A man of superlative energy. Literature, politics, history, and science-all he discussed with spontaneity and without self-consciousness. Everything was illuminated by an apt allusion drawn from the most diverse sources, or by a witty tale. Voltaire seemed just around the corner, and Laurence Sterne upon the stair. . . . Under such influences, the laboratory became much more than a place just to work and teach; it became a way of life (3).”

Enders was awarded his Ph.D. in Bacteriology and Immunology in 1930. Afterwards, he remained at Harvard, as a member of the teaching staff, until 1946, when he established his own laboratory at the Children’s Medical Center in Boston.

Why might Enders have been satisfied staying so long at Harvard, for the most part as Zinsser’s underling? Perhaps that too might be explained by his financial independence. In any case, in 1939, while Enders was still at Harvard, he initiated the singularly significant course of research for which he is best remembered.

In 1939, in collaboration with Dr. Alto Feller and Thomas Weller (then a senior medical student), Enders began to develop procedures to propagate vaccinia virus in cell culture. After achieving that goal, the Enders team applied their cell culture procedures to propagate other viruses, including influenza and mumps viruses.

Enders and his coworkers were not the first researchers to grow viruses in cell culture. However, they were the first to do so consistently and routinely. Thus, the Enders lab launched the “modern” era of virus research in vitro. Virology could now advance much more quickly than before, since most virologists would no longer need to grow, or study their viruses only in live animals.

A recurrent theme on the blog is that key scientific discoveries may well be serendipitous. The case in point here was the unforeseen 1949 discovery by Enders and his young collaborators, Tom Weller and Frederick Robbins, that poliovirus could be grown in cultured cells. That crucial discovery made it possible for Jonas Salk and Albert Sabin to generate a virtually unlimited amount of poliovirus and, thus, to create their polio vaccines. Importantly, the discovery happened at a time when polio researchers believed that poliovirus could grow only in nerve cells. Their dilemma was that nerve cells could not be cultured in the laboratory.

Enders, Weller, and Robbins were not working on polio, nor did they have any immediate intention of working on polio when they made their finding. In fact, when the thirty-year-old Robbins (see Aside 1) came to work with Enders, he proclaimed that he wanted to work on any virus, except polio (6).

[Aside 1: Weller was one year older than Robbins. Both had been Army bacteriologists during the Second World War, and they were classmates and roommates at Harvard Medical School when they came to Enders for research experience. Robbins’ father-in-law, John Northrop, shared the 1946 Nobel Prize in chemistry with James Sumner and Wendell Stanley (7). In 1954, Robbins joined his father-in-law as a Nobel laureate (see below).]

The Enders team was trying to grow varicella (the chicken pox virus) when, on a whim; they made their critical discovery. It happened as follows. While attempting to propagate varicella virus in a mixed culture of human embryonic skin and muscle cells, they happened to have some extra flasks of the cell cultures at hand. And, since they also had a sample of poliovirus nearby in their lab storage cabinet; they just happened to inoculate the extra cell cultures with polio virus.

The poliovirus-infected cultures were incubated for twenty days, with three changes of media. Then, Enders, Weller, and Robbins asked whether highly diluted extracts of the cultures might induce paralysis in their test mice. When those highly diluted extracts indeed caused paralysis in the mice, they knew that poliovirus had grown in the cultures. See Aside 2.

[Aside 2: Whereas Enders, Weller, and Robbins did not have pressing plans to test whether poliovirus might grow in non-neuronal cells, they probably were aware of already available evidence that poliovirus might not be strictly neurotropic. For instance, large amounts of poliovirus had been found in the gastrointestinal tract.]

Despite the exceptional significance of their discovery, Robbins said, “It was all very simple (6).” Weller referred to the discovery as a “fortuitous circumstance (6).” Enders said, “I guess we were foolish (6)”—rather modest words from a scholar of language and literature. See Aside 3.

[Aside 3: Current researchers and students might note that Enders’ entire research budget amounted to a grand total of two hundred dollars per year! The lab did not have a technician, and Weller and Robbins spent much of their time preparing cells, media, and reagents, as well as washing, plugging, and sterilizing their glassware.]

In 1954, Enders, Weller, and Robbins were awarded the Nobel Prize for Physiology or Medicine for their polio discovery. Interestingly, they were the only polio researchers to receive the Nobel award. The more famous Salk and Sabin never received that honor (8).

If Enders were so inclined, might he have produced a polio vaccine before Salk and Sabin? Weller and Robbins wanted to pursue the vaccine project, and Enders agreed that they had the means to do so. In fact, Weller actually had generated attenuated poliovirus strains by long-term propagation of the virus in culture; a first step in the development of a vaccine (3). Yet for reasons that are not clear, Enders counseled his enthusiastic young colleagues to resist the temptation (6). See Aside 4.

[Aside 4: Enders may have spared Weller and Robbins the sort of anguish that Salk experienced when some of his killed vaccine lots, which contained incompletely inactivated poliovirus, caused paralytic poliomyelitis in some 260 children (8).]

The Enders poliovirus group began to disperse, beginning in 1952 when Robbins became a professor of pediatrics at Western Reserve. Weller left in 1954 to become chairman of the Department of Tropical Public Health at Harvard.

Regardless of whether Enders might have regretted not pursuing the polio vaccine, he soon would play a hands-on role in the development of the measles vaccine. The first critical step in that project occurred in1954, at the time when the Salk polio vaccine was undergoing field trials. It was then that Enders and a new young coworker, pediatric resident Thomas Peebles (Aside 5), succeeded in cultivating measles virus in cell culture for the first time.

[Aside 5: Enders was known for nurturing bright young investigators. His latest protégé, Tom Peebles, spent four years in the Navy, as a pilot, before enrolling at Harvard Medical School. Peebles graduated from medical school in 1951, and then did an internship at Mass General, before coming to the Enders lab to do research on infectious diseases in children. When Enders suggested to Peebles that he might try working on measles, Peebles eagerly accepted.]

Here is a piece of the measles vaccine story that happened before Peebles’ success growing the virus in cell culture. At the very start of the vaccine project, Enders and Peebles were stymied in their attempts to get hold of a sample of measles virus to work with. Their quest for the virus began with Peebles searching the Enders laboratory freezers for a sample. Finding none there, Peebles next inquired at Boston area health centers; still without success. After several more months of fruitless searching, Peebles received an unexpected phone call from the school physician at the Fay School (a private boarding school for Boys in a Boston suburb), telling him about a measles outbreak at the school. Peebles immediately rushed to the school, where he took throat swabs, as well as blood and stool samples from several of the school’s young patients. He then rushed back to the Enders laboratory, where he immediately inoculated human infant kidney cells with his samples. [Enders obtained the cells from a pediatric neurosurgeon colleague, who treated hydrocephalus in infants by excising a kidney, and shunting cerebrospinal fluid directly to the urethra.]

Peebles monitored the inoculated kidney cell cultures for the next several weeks, hoping for a sign of a virus replicating in them. Seeing no such indication of a virus in the cultures, Peebles made a second trip to the Fay School, which, like the first trip, was unproductive.

On a third trip to the school, Peebles obtained a sample from an 11-year-old boy, David Edmonston. The sample from young Edmonston indeed seemed to affect the kidney cell cultures. Still, Peebles needed to carry out several additional experiments before he could convince a skeptical Enders and Weller—first, that a virus had replicated in the cultures and, second, that it was measles. Peebles convinced the two doubters by demonstrating that serum from each of twelve convalescing measles patients prevented the virus from causing cytopathic effects in the inoculated cell cultures. That is, the convalescent serum neutralized the virus. The measles virus growing in those cultures was named for its source. It is the now famous Edmonston strain.

Enders, in collaboration with Drs.Milan Milovanovic and Anna Mitus, next showed that the Edmonston strain could be propagated in chick embryos (3). Then, working with Dr. Samuel Katz (1), Enders showed that the egg-adapted virus could be propagated in chicken cell cultures.

By 1958, Enders, Katz, and Dr. Donald Medearis showed that the Edmonston measles virus could be attenuated by propagating it in chicken cells. Moreover, the attenuated virus produced immunity in monkeys, while not causing disease (3). Thus, the attenuated Edmonston strain became the first measles vaccine. [Tests of the vaccine in humans led to the episode at the Fernald School (1).]

The Enders measles vaccine was attenuated further by Maurice Hilleman at Merck (9). In 1971 it was incorporated into the Merck MMR combination vaccine against measles, mumps, and rubella (9, 10).

The MMR vaccine has had a remarkable safety record, and it was widely accepted until 1997; the time when the now discredited claim that the vaccine is linked to autism first emerged (10). However, even prior to the MMR/autism controversy, vaccine non-compliance was already a problem. But, in that earlier time, parents were declining to have their children vaccinated, not because of safety issues, but rather because they questioned the severity of measles. Ironically, that was why David Edmonston refused to have his own son receive the vaccine.

Despite receiving the Nobel Prize for his polio work, Enders maintained that developing the measles vaccine was more personally satisfying to him and more socially significant (3).

References:

  1. Vaccine Research Using Children, Posted on the blog July 7, 2016.
  2. John F. Enders-Biographical, The Nobel Prize in Physiology or Medicine 1954. From Nobel Lectures, Physiology or Medicine 1942-1962, Elsevier Publishing Company, Amsterdam, 1964.
  3. Weller TH, Robbins FC, John Franklin Enders 1897-1995, A Biographical Memoir www.nasonline.org/publications/…/endersjohn.pdf [An excellent review of Enders’ life and career.]
  4. Harold Varmus: From English Literature Major to Nobel Prize-Winning Cancer Researcher, Posted on the blog January 5, 2016.
  5. John F. Enders, “Personal recollections of Dr. Hugh Ward,” Australian Journal of Experimental Biology 41:(1963):381-84. [This is the source of the quotation in the text. I found it in reference 3.]
  6. Greer Williams, Virus Hunters, Alfred A. Knopf, 1960.
  7. Wendell Stanley: First to Crystallize a Virus, Posted on the blog April 23, 2015.
  8. .Jonas Salk and Albert Sabin: One of the Great Rivalries of Medical Science, Posed on the blog March 27, 2014.
  9.  Maurice Hilleman: Unsung Giant of Vaccinology, Posted on the blog April 24, 2014.
  10.  Andrew Wakefield and the Measles Vaccine Controversy, Posted on the blog February 9, 2015.

 

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Baruch Blumberg: The Hepatitis B Virus and Vaccine

Hepatitis B virus (HBV), one of mankind’s most important pathogens, infects about 2 billion people worldwide, and more than 500 million individuals are life-long carriers of the virus; with most in Asia. HBV causes acute and chronic cirrhosis, as well as hepatocellular carcinoma. In point of fact, HBV is the 10th leading cause of death in the world! The serendipitous discovery of HBV, and the development of the first HBV vaccine, happened as follows. [See Note 1 for a brief review of the remarkable HBV replication strategy].

In the early 1940’s, during World War II, British doctor, F. O. MacCallum, was the first to suggest that an infectious agent might cause hepatitis. MacCallum was assigned to produce a yellow fever vaccine for British soldiers. That was how he happened to notice that soldiers tended to come down with hepatitis a few months after receiving the yellow fever vaccine.

It was fortunate that MacCallum also knew of hepatitis cases in children who received inoculations of serum from patients convalescing from measles and mumps (a means of protection against those viruses before vaccines were available), and of hepatitis cases in blood transfusion recipients, and of cases following treatments with unsterilized reused syringes.

To explain these coincidences, MacCallum hypothesized that hepatitis might be transmitted by a factor in human blood. And, since hepatitis could be transmitted by inoculation with serum that had been filtered, MacCallum proposed that the hepatitis factor might be a virus. [In 1947 MacCallum reported that hepatitis could be spread by food and water that had been contaminated with fecal material, as well as by blood. He coined the term hepatitis A for the form of the disease spread by food and water, and hepatitis B for the form transmitted via blood.] See Aside 1.

[Aside 1: The following episode, described in MacCallum’s own words (1), occurred in England during World War II: “One day in 1942, I received a message to go to Whitehall to see one of the senior medical advisers and when I arrived I was asked ‘What is this yellow fever vaccine and how dangerous is it?’ After explaining its constitution and the possibility of a mild reaction four to five days after inoculation, I was told that the Cabinet was at that moment debating whether or not Mr. Churchill should be allowed to go to Moscow, which he wished to do in a few days’ time. The yellow fever vaccine was theoretically essential before he could fly through the Middle East, but I explained that no antibody would be produced before seven to ten days so that there would be little point in giving the vaccine. It was finally decided that the vaccine would not be used, and the administrators would take care of the situation. Several months later I received an irate call from the Director of Medical Services of the RAF, who had been inoculated with the same batch of vaccine which would have been used for Mr. Churchill, and was informed that the D. G. had spent a very mouldy Christmas with hepatitis about 66 days after his inoculation…I will leave it to you to speculate on what might possibly have been the effect on the liver of our most famous statesman and our ultimate fate if  he had received the icterogenic vaccine.”]

With the advent of cell culture in the 1950s, researchers hoped that a hepatitis agent might soon be cultivated in vitro. Nonetheless, HBV was not discovered until 1966. What’s more, the discovery did not involve growing the virus in cell culture. And, reminiscent of the case of MacCallum above, the discovery was made by a researcher, Baruch S. Blumberg, who was not even working on hepatitis. Rather, Blumberg was interested in why individuals varied in their susceptibilities to various illnesses.

Nobel Laureate Baruch Blumberg
Nobel Laureate Baruch Blumberg

Blumberg sought to answer that question by identifying possibly relevant genetic differences between population groups, which, in the pre-molecular biology era, might be revealed by differences in their blood proteins. Thus, in the early 1950s, Blumberg, then working at the NIH, began collecting a panel of blood samples from diverse populations throughout the world.

Blumberg looked for serum protein variations (i.e., serum protein polymorphisms) by asking if sera from multiply-transfused individuals (defined by Blumberg as persons who received 25 units of blood or more) might contain antibodies that reacted with proteins in the serum samples of his panel. His rational, in his own words, was as follows: “We decided to test the hypothesis that patients who received large numbers of transfusions might develop antibodies against one or more of the polymorphic serum proteins (either known or unknown) which they themselves had not inherited, but which the blood donors had (2).” In other words, patients who received multiple transfusions were more likely than others to have antibodies against polymorphic serum proteins in donor blood, and those antibodies might also react with polymorphic serum proteins in the samples from his panel. See Aside 2.

[Aside 2: Blumberg used the Ouchterlony double-diffusion agar gel technique in these experiments. Serum samples to be tested against each other were placed in opposite wells of a gel. The proteins they contained could then diffuse through the gel. Antigen-antibody complexes that formed between the two samples appeared as white lines in the gel.]

Hemophilia and leukemia patients were well-represented in Blumberg’s collection of serum samples from multiply-transfused individuals. And, a serendipitous aspect of Blumberg’s experimental approach was that he used these samples to probe for serum protein polymorphisms in samples from geographically diverse populations. Thus it happened that Blumberg detected a cross-reaction between a New York hemophilia patient’s serum and a serum sample from an Australian aborigine. But what could these two individuals have had in common that might have triggered the cross-reaction?

His curiosity thus aroused, Blumberg and collaborator, Harvey Alter, of the NIH Blood Bank, tested the hemophilia patient’s serum against thousands of other serum samples. Blumberg and Alter may have been surprised to find that whatever the antigen in the Aborigine’s serum was that reacted with the hemophilia patient’s serum, reactivity against that antigen was common (one in ten) in leukemia patients, but rare (one in 1,000) in normal individuals. In any case, because the antigen was first identified in an Australian aborigine, it was termed the Australia antigen.

Bear in mind that Blumberg’s original purpose was to explain why individuals differed in their susceptibilities to various illnesses. Thus, Blumberg at first believed that he detected an inherited blood-protein that predisposes people to leukemia. However, additional experiments showed that the antigen was more common in older individuals than in younger ones; a finding more consistent with the possibility that the antigen might be associated with an infectious agent.

Blumberg’s first clue that the Australia antigen might be associated with hepatitis came to light when he tested serum samples from a 12-year old boy with Down syndrome. The first time that the boy was tested for the Australia antigen, he was negative. However, several months later, when retested, the boy was positive. Moreover, sometime during that interim, the boy also developed hepatitis.

Blumberg, and other researchers, carried out additional experiments, which confirmed that the Australia antigen indeed associated with hepatitis. In addition, the antigen was more frequently detected in hepatitis sufferers than in individuals with other liver diseases. Thus, the Australia antigen was a marker of hepatitis in particular and not of liver pathology in general. See Aside 3.

[Aside 3: Blumberg had a personal reason motivating him to identify the cause of hepatitis. His technician (later Dr. Barbara Werner) became ill with hepatitis, which she almost certainly acquired in the laboratory. Fortunately, she underwent a complete recovery.]

In 1970, British pathologist David Dane and colleagues at Middlesex Hospital in London, and K. E. Anderson and colleagues in New York, provided corroborating evidence  that hepatitis is an infectious disease. Using electron microscopy, they observed 42-nm “virus-like particles” in the sera of patients who were positive for the Australia antigen. In addition, they saw these same particles in liver cells of patients with hepatitis.

What then is the Australia antigen? Actually, it is the surface protein of the 42-nm HBV particles; now known as the hepatitis B surface antigen (HBsAg). Since HBV particles per se were described for the first time by David Dane, they are sometimes referred to as Dane particles.

Now we can explain Blumberg’s early finding, that individuals who received multiple transfusions (e.g., leukemia and hemophilia patients) were more likely than the general population to have antibodies against the Australia antigen. Those individuals were more likely than the general population to have received donated blood and, thus, were more likely to have been recipients of blood contaminated with HBV. At that time, a large percentage of the blood supply came from paid donors, at least some of whom were syringe-sharing, intravenous drug abusers and, consequently, more likely than most to be HBV carriers. In 1972 it became law in the United States that all donated blood be screened for HBV. See Note 2.

But it was important to protect all people from HBV; not just transfusion recipients. In 1968, Blumberg, now at the Fox Chase Cancer Center in Philadelphia, and collaborator Irving Millman, hypothesized that HBsAg might provoke an immune response that would protect people against HBV and, consequently, that a vaccine could be made using HBsAg purified from the blood of HBV carriers. In Blumberg’s own words: “Irving Millman and I applied separation techniques for isolating and purifying the surface antigen and proposed using this material as a vaccine. To our knowledge, this was a unique approach to the production of a vaccine; that is, obtaining the immunizing antigen directly from the blood of human carriers of the virus (1).”  The Fox Chase Cancer Center filed a patent for the process in 1969.

Blumberg was willing to share his method and the patent with any pharmaceutical company willing to develop an HBV vaccine for widespread use. Nonetheless, the scientific establishment was somewhat slow to accept his experimental findings and his proposal for making the vaccine. Then, in 1971, Merck accepted a license from Fox Chase to develop the vaccine. In 1982, after more years of research and testing, Maurice Hillman (3) and colleagues at Merck turned out the first commercial HBV vaccine (“Heptavax”). Producing an HBV vaccine, without having to cultivate the virus in vitro, was considered one of the major medical achievements of the day. See Notes 3 and 4.

The consequences of Blumberg’s vaccine were immediate and striking. For instance, in China the rate of chronic HBV infection among children fell from 15% to around 1% in less than a decade. And, in the United States, and in many other countries, post-transfusion hepatitis B was nearly eradicated.

Moreover, Blumberg’s HBV vaccine was, in a real sense, the world’s first anti-cancer vaccine since it prevented HBV-induced hepatocellular carcinoma, which accounts for 80% of all liver cancer; the 9th leading cause of death. Jonathan Chernoff (the scientific director of the Fox Chase Cancer Center, where Blumberg spent most of his professional life) stated: “I think it’s fair to say that Barry (Blumberg) prevented more cancer deaths than any person who’s ever lived (4).”

In 1976 Blumberg was awarded the Nobel Prize in Physiology or Medicine for “discoveries concerning new mechanisms for the origin and dissemination of infectious diseases.” He shared the award with Carlton Gajdusek, who won his portion for discoveries regarding the epidemiology of kuru (5). See Note 5.

Blumberg claimed that saving lives was the whole point of his career. “This is what drew me to medicine. There is, in Jewish thought, this idea that if you save a single life, you save the whole world, and that affected me (7).” See Aside 4.

[Aside 4: Blumberg received his elementary school education at an orthodox yeshiva in Brooklyn, and he attended weekly Talmud discussion classes until his death. Interestingly, Blumberg graduated from Far Rockaway High School in Queens, N.Y.; also the alma mater of fellow Nobel laureates, physicists Burton Richter and Richard Feynman.]

As we’ve seen, Blumberg’s landmark discovery of HBV sprang from a basic study of human genetic polymorphisms. In Blumberg’s own words, “… it is clear that I could not have planned the investigation at its beginning to find the cause of hepatitis B. This experience does not encourage an approach to basic research which is based exclusively on specific-goal-directed programs for the solution of biological problems (1).”

Saul Krugman (Note 4) had this to say about Blumberg’s discovery: “It is well known that Blumberg’s study that led to the discovery of Australia antigen was not designed to discover the causative agent of type B hepatitis. If he had included this objective in his grant application, the study section would have considered him either naïve or out of his mind. Yet the chance inclusion of one serum specimen from an Australian aborigine in a panel of 24 sera that was used in his study of polymorphisms in serum proteins…led to detection of an antigen that subsequently proved to be the hepatitis B surface antigen (1).” See Note 6.

In 1999, Blumberg’s scientific career took a rather curious turn when he accepted an appointment by NASA administrator, Dan Goldin, to head the NASA Astrobiology Institute. There, Blumberg helped to establish NASA’s search for extraterrestrial life. Blumberg also served on the board of the SETI Institute in Mountain View, Calif.

Blumberg passed away on April 5, 2011, at 85 years of age.

Notes:

[Note 1:  HBV is the prototype virus for the hepadnavirus family, which displays the most remarkable, and perhaps bizarre, viral replication strategy known. In brief, in the cell nucleus, the cellular RNA polymerase II enzyme transcribes the hepadnavirus circular, double-stranded DNA genome, thereby generating several distinct species of viral RNA transcripts, all of which are exported to the cytoplasm. The largest of these viral transcripts is the pregenomic RNA; a transcript of the entire circular viral DNA genome, as well as an additional terminal redundant sequence. Remarkably, the pregenomic RNA is then packaged in nascent virus capsids, within which it is reverse transcribed by a virus-encoded reverse transcriptase activity, thereby becoming an encapsulated progeny hepadnavirus double-stranded DNA genome. Thus, reverse transcription is a crucial step in the replication cycle of the hepadnaviruses, as it is in the case of the retroviruses. But, while the retroviruses replicate their RNA genomes via a DNA intermediate, the hepadnaviruses replicate their DNA genomes via an RNA intermediate.]

[Note 2: The highly sensitive radioimmunoassay (RIA) technique, developed by Rosalyn Yallow and Solomon Berson, is the basis for the test that screens the blood supply for the Australia antigen. The story behind this assay is worthy of note here because it is yet another example of serendipity in the progress of science. In brief, Yallow and Berson sought to develop an assay to measure insulin levels in diabetics. Towards that end, they happened to find that radioactively-labeled insulin disappeared more slowly from the blood samples of people previously given an injection of insulin than from the blood samples of untreated patients. That observation led them to conclude that the treated patients had earlier generated an insulin-binding antibody. And, from that premise they hit upon the RIA procedure. Using their insulin test as an example, they would add increasing amounts of an unlabelled insulin sample to a known amount of antibody bound to radioactively labeled insulin. They would then measure the amount label displaced from the antibody, from which they could calculate the amount of unlabelled insulin in the test sample. Their procedure has since been applied to hundreds of other substances. RIA is simpler to carry out and also about 1,000-fold more sensitive than the double-diffusion agar gel procedure that Blumberg used to identify the Australia antigen. Yallow and Berson refused to patent their RIA procedure, despite its huge commercial value. Yallow received a share of the 1977 Nobel Prize in Physiology or Medicine for her role in its development. Berson, died in 1972 and did not share in the award.]

[Note 3: Making Heptavax directly from the blood of human HBV carriers was somewhat hindered because it required a continuing and uncertain supply of suitable donor blood. Moreover, there was concern that even after purifying the HBsAg, and treating it with formalin to inactivate any infectivity, the vaccine might yet contain other live dangerous viruses. Concern increased in the early 1980s with the emergence of HIV/AIDS, since much of the HBV-infected serum came from donors who later developed AIDS. Thus, in 1990 Heptavax was replaced in the United States by a safer genetically engineered (i.e., DNA recombinant) HBV vaccine, which contained no virus whatsoever. That vaccine was the first to be made using recombinant DNA technology. Moreover, it was yet another instance in which Hilleman played a key role in the development of a vaccine (3).]

[Note 4: In 1971, Saul Krugman, working at NYU, was actually the first researcher to make a “vaccine” against HBV. Krugman’s accomplishment began as a straightforward inquiry into whether heat (boiling) might kill HAV (see Note 5). Finding that it did, Krugman repeated his experiments; this time to determine whether boiling might likewise kill HBV in the serum of HBV carriers. As Krugman expected, boiling indeed destroyed HBV infectivity. But, to his surprise, while the heated serum was no longer infectious, it did induce incomplete, but statistically significant protection against challenge with live HBV. Krugman considers his “vaccine” discovery, like Blumberg’s discovery of HBV, to have resulted from “pure serendipity” (1).

Krugman could not answer whether HBsAg per se in his crude vaccine induced immunity. However, Hilleman, in 1975, using purified HBsAg, as per Blumberg’s concept, showed that HBsAg indeed induced immunity against an intravenous challenge with HBV.

Krugman also carried out key studies on the epidemiology of hepatitis, demonstrating that “infectious” (type A) hepatitis is transmitted by the fecal-oral route, while the more serious “serum” (type B) hepatitis is transmitted by blood and sexual contact.

Krugman reputation was somewhat tarnished because he used institutionalized disabled children as test subjects in the experiments that led to his vaccine. While that practice astonishes us today, it was not unheard-of in the day. In any event, it did not prevent Krugman’s election in 1972 as president of the American Pediatric Society, or his 1983 Lasker Public Service Award.]

[Note 5: Gajdusek’s reputation was later sullied when he was convicted of child molestation (5).]

[Note 6: In 1973 and 1974, research groups led by Stephen Feinstone and Maurice Hilleman (3) discovered hepatitis A virus (HAV), a picornavirus.

After the discoveries of HAV and HBV, it became clear that blood samples cleared of HAV and HBV could still transmit hepatitis. In 1983 Mikhail Balayan identified a virus, now known a hepatitis E virus (the prototype of a new family of RNA viruses), as the cause of a non-A, non-B infectious hepatitis (6).

In 1989, a mysterious non-A, non-B hepatitis agent, now known as hepatitis C virus (a flavivirus), was identified by a team of molecular biologists using the cutting-edge molecular biology techniques of the day (8).]

References:

  1. Krugman, S. 1976. Viral Hepatitis: Overview and Historical Perspectives. The Yale Journal of Biology and Medicine 49:199-203.
  1. Blumberg, B, Australia Antigen and the Biology of Hepatitis B, Nobel Lecture, December 13, 1976.
  1. Maurice Hilleman: Unsung Giant of Vaccinology, Posted on the blog April 24, 20143.
  1. Emma Brown (6 April 2011). “Nobelist Baruch Blumberg, who discovered hepatitis B, dies at 85”. The Washington Post.
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