We now have explicit evidence that a common retrovirus in cattle is transmitted to humans, and associated with lethal disease.
This falls short of academic standards for determining etiology, but that may not be very important when it points to a major risk factor. There are many risk factors doctors take very seriously which have yet to be conclusively tied to causation.
If you doubt a possible connection between leukemia and breast cancer you might make an on-line search for papers mentioning the two diseases together.
This is presented as late-breaking news, of the sort nobody suspected. Perhaps we should report this as seriously broken news.
Not only was there prior evidence in recent years, there was evidence going back before the discovery of the first human retrovirus. Here is Robert Gallo's account of that discovery.
(If anyone is interested in arguing about personalities involved I am quite willing to stipulate that Gallo can be abrasive, and managed to tick a lot of people off. This is irrelevant to the factual discussion.)
I'm going to quote selectively, but I do not think I am taking things out of context.
"...In this period (early 1970s) I began to study animal retroviruses because in several animals these kinds of viruses caused leukemias. Thus, no matter whether human retroviruses (leukemia-causing or otherwise) existed or not, a study of animal retroviruses, especially focused on learning their mechanisms of leukemia causation, might provide insights into the mechanisms involved in human leukemias. However, my co-workers and I also decided to search for human retroviruses, an unpopular goal at this time, considering the decades of attempts and failures..."
Comment: those decades of failures took place at a time when virtually all researchers were convinced that reverse transcription from RNA to DNA did not take place, and that viruses did not insert their genes in chromosomes. The term endogenous means something different w.r.t. DNA viruses than it does when used for endogenous retroviruses. Nobody was prepared to look for latent provirus in host chromosomes. The discovery of reverse transcriptase independently by Temin and Baltimore changed that in 1970. Nobody had found such human tumor viruses before because they were looking for viruses that did not have the defining characteristics of retroviruses.
"...Armed with these RT assays we did find a few cases of adult lymphocytic leukemias with RT showing all the characteristics of RT from a retrovirus (we had by then purified and characterized RT from many different animal retroviruses). We published on the one best characterized in Nature New Biology in 1972 [15]. We believed this was a "footprint" of a human retrovirus, but we failed to isolate virus from this patient. (Though we will never know, it is interesting to speculate whether this young adult had ATL because of some clinical similarities to ATL). We also thought it would attract wide interest and excitement in the field. It did not. It was clear that we had to isolate a replicating virus, one we could study, perpetuate, and give to others..."
"...We reasoned otherwise. Kawakami and colleagues had just discovered gibbon ape leukemia virus, and linked it to chronic myeloid leukemia in that species [21]. Later, we discovered a variant of that virus which caused T cell leukemia [22]. Bovine leukemia virus (BLV) was discovered [23,24], and it was noted that BLV replicated at very low levels thus putting to rest the notion of "extensive viremia always precedes animal retrovirus induced leukemias". The biased view came from the fact that the earlier small animal models were naturally selected for their utility. Consequently, models in which virus is difficult to detect would be selected against..."
Just what is Bovine Leukemia Virus? It is a delta retrovirus very similar to HTLV-1, which only tells you how humans have classified it. What does it do?
Quotes from the Wikipedia article:
"In general BLV causes only a benign mononucleosis-like disease in cattle. Only some animals later develop a B-cell leukemia called enzootic bovine leukosis. Under natural conditions the disease is transmitted mainly by milk to the calf. Infected lymphocytes transmit the disease too. So for artificial infection infected cells are used or the more stable and even heat resistant DNA."
"The variety of organs where white blood cells occur explains the many symptoms: enlargement of superficial lymph nodes, a digestive form, a cardiac form, a nervous form, a respiratory form, and others."
"Although several species can be infected by inoculation of the virus, natural infection occurs only in cattle (Bos taurus and Bos indicus), water buffaloes, and capybaras. Sheep are very susceptible to experimental inoculation and develop tumours more often and at a younger age than cattle. A persistent antibody response can also be detected after experimental infection in deer, rabbits, rats, guinea-pigs, cats, dogs, sheep, rhesus monkeys, chimpanzees, antelopes, pigs, goats and buffaloes."[5]
Now, has anyone reported evidence of a retrovirus resembling HTLV-1 in humans causing a disease which resembles mononucleosis followed by chronic disease?
As it happens Elaine DeFreitas reported this long ago in work done under the direction of the late Hilary Koprowski at Wistar Institute on samples from patients of Dr. David S. Bell. He had found a cluster of cases in children who had consumed unpasteurized goat's milk. They also suggested a similar retrovirus was behind some cases of MS. This is a small part of the story told in Osler's Web. What happened in response to that claim is hard to believe.
Apparently, nobody important was interested in following up clues that might lead to discovery of a known mammalian leukemia retrovirus infecting humans and causing other diseases. Had the patients shown convenient clinical signs, and dropped dead quickly, things might have been different.
This falls short of academic standards for determining etiology, but that may not be very important when it points to a major risk factor. There are many risk factors doctors take very seriously which have yet to be conclusively tied to causation.
If you doubt a possible connection between leukemia and breast cancer you might make an on-line search for papers mentioning the two diseases together.
This is presented as late-breaking news, of the sort nobody suspected. Perhaps we should report this as seriously broken news.
Not only was there prior evidence in recent years, there was evidence going back before the discovery of the first human retrovirus. Here is Robert Gallo's account of that discovery.
(If anyone is interested in arguing about personalities involved I am quite willing to stipulate that Gallo can be abrasive, and managed to tick a lot of people off. This is irrelevant to the factual discussion.)
I'm going to quote selectively, but I do not think I am taking things out of context.
"...In this period (early 1970s) I began to study animal retroviruses because in several animals these kinds of viruses caused leukemias. Thus, no matter whether human retroviruses (leukemia-causing or otherwise) existed or not, a study of animal retroviruses, especially focused on learning their mechanisms of leukemia causation, might provide insights into the mechanisms involved in human leukemias. However, my co-workers and I also decided to search for human retroviruses, an unpopular goal at this time, considering the decades of attempts and failures..."
Comment: those decades of failures took place at a time when virtually all researchers were convinced that reverse transcription from RNA to DNA did not take place, and that viruses did not insert their genes in chromosomes. The term endogenous means something different w.r.t. DNA viruses than it does when used for endogenous retroviruses. Nobody was prepared to look for latent provirus in host chromosomes. The discovery of reverse transcriptase independently by Temin and Baltimore changed that in 1970. Nobody had found such human tumor viruses before because they were looking for viruses that did not have the defining characteristics of retroviruses.
"...Armed with these RT assays we did find a few cases of adult lymphocytic leukemias with RT showing all the characteristics of RT from a retrovirus (we had by then purified and characterized RT from many different animal retroviruses). We published on the one best characterized in Nature New Biology in 1972 [15]. We believed this was a "footprint" of a human retrovirus, but we failed to isolate virus from this patient. (Though we will never know, it is interesting to speculate whether this young adult had ATL because of some clinical similarities to ATL). We also thought it would attract wide interest and excitement in the field. It did not. It was clear that we had to isolate a replicating virus, one we could study, perpetuate, and give to others..."
"...We reasoned otherwise. Kawakami and colleagues had just discovered gibbon ape leukemia virus, and linked it to chronic myeloid leukemia in that species [21]. Later, we discovered a variant of that virus which caused T cell leukemia [22]. Bovine leukemia virus (BLV) was discovered [23,24], and it was noted that BLV replicated at very low levels thus putting to rest the notion of "extensive viremia always precedes animal retrovirus induced leukemias". The biased view came from the fact that the earlier small animal models were naturally selected for their utility. Consequently, models in which virus is difficult to detect would be selected against..."
Just what is Bovine Leukemia Virus? It is a delta retrovirus very similar to HTLV-1, which only tells you how humans have classified it. What does it do?
Quotes from the Wikipedia article:
"In general BLV causes only a benign mononucleosis-like disease in cattle. Only some animals later develop a B-cell leukemia called enzootic bovine leukosis. Under natural conditions the disease is transmitted mainly by milk to the calf. Infected lymphocytes transmit the disease too. So for artificial infection infected cells are used or the more stable and even heat resistant DNA."
"The variety of organs where white blood cells occur explains the many symptoms: enlargement of superficial lymph nodes, a digestive form, a cardiac form, a nervous form, a respiratory form, and others."
"Although several species can be infected by inoculation of the virus, natural infection occurs only in cattle (Bos taurus and Bos indicus), water buffaloes, and capybaras. Sheep are very susceptible to experimental inoculation and develop tumours more often and at a younger age than cattle. A persistent antibody response can also be detected after experimental infection in deer, rabbits, rats, guinea-pigs, cats, dogs, sheep, rhesus monkeys, chimpanzees, antelopes, pigs, goats and buffaloes."[5]
Now, has anyone reported evidence of a retrovirus resembling HTLV-1 in humans causing a disease which resembles mononucleosis followed by chronic disease?
As it happens Elaine DeFreitas reported this long ago in work done under the direction of the late Hilary Koprowski at Wistar Institute on samples from patients of Dr. David S. Bell. He had found a cluster of cases in children who had consumed unpasteurized goat's milk. They also suggested a similar retrovirus was behind some cases of MS. This is a small part of the story told in Osler's Web. What happened in response to that claim is hard to believe.
Apparently, nobody important was interested in following up clues that might lead to discovery of a known mammalian leukemia retrovirus infecting humans and causing other diseases. Had the patients shown convenient clinical signs, and dropped dead quickly, things might have been different.
