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Monkey Island: in search of the origin of the AIDS disease

The monkeys of the island of Yoko contributed to deciphering the true age of the ancestor of the HIV virus

Pictured: Black colobus, one of the species found to be positive for the SIV virus. Photo: Rich Bergl, North Carolina Zoo, and courtesy of Dr. Gail Hearn, Biodiversity Conservation Program (BBPP)
Pictured: Black colobus, one of the species found to be positive for the SIV virus. Photo: Rich Bergl, North Carolina Zoo, and courtesy of Dr. Gail Hearn, Biodiversity Conservation Program (BBPP)

Dina Volodarsky Galileo
The origin of the HIV virus, which causes the acquired immune deficiency syndrome (AIDS), is apparently its relative, a virus known as SIV that infects certain types of monkeys and chimpanzees. The popular explanation is that the SIV virus passed from monkeys to chimpanzees and from them to humans - and this was probably through hunters who contracted the virus while capturing infected chimpanzees and killing them. The transition of the virus from chimpanzees to humans apparently occurred at the beginning of the 20th century. It is less clear when the virus passed from monkeys to chimpanzees. Researcher Michael Worobey from the University of Arizona previously found evidence that this transition took place between the 13th and 17th centuries.

Woroby and his colleagues used the RNA changes of the SIV viruses to calculate their age, and their conclusion was that it was several hundreds of years. It is about the use of a molecular clock, a method that makes it possible to date with the help of genetic research the time when two species split from a common ancestor. It is very important to calibrate this method correctly to get accurate results.

And here, the virus researcher Preston Marx (Marx) from the Tulane Primate Research Center in Louisiana in the United States suspected that the transition of the SIV virus from monkeys to chimpanzees occurred tens of thousands of years ago, since these viruses are very common in chimpanzees throughout the African continent, a distribution that is not suitable for a period of only hundreds of years.

Marx, Warobi and their colleagues spotted the rare opportunity on the island of Bioko in Equatorial Guinea, a volcanic island off the coast of West Africa that was separated from the continent about 10,000 years ago when the sea level rose. The researchers collected blood samples from dead monkeys on the island of Yoko, tested the samples for the presence of SIV viruses, and conducted a phylogenetic analysis of the viruses. For the purpose of the study, 79 monkeys from six biological species were examined; Of these, 22 monkeys from four different species were found to be positive for the virus.

A virus tens of thousands of years old

The viruses in these monkeys were not similar to each other, but resembled the viruses residing in corresponding monkeys on the African continent. From this, the researchers concluded that the origin of the viruses on the island was before the separation of Yoko from Africa, and after the separation there was a separate development of the viruses on the continent and on the island of Yoko, meaning that the changes that occurred in the viruses occurred during the 10,000 years that the island was isolated. The researchers used this data to calibrate the molecular clock in the SIV virus. After the "recalibration" Marx's hypothesis was confirmed that the transition to chimpanzees happened much earlier than the accepted estimates, and it also turned out that the age of the virus is not a few hundred years, as previously thought, but 32,000-75,000 years and maybe even more!

The researchers published the findings in September 2010 in the science weekly Science, and they emphasize that the island of Yoko is a rare opportunity to calibrate and study and understand the molecular clock in viruses, since there are only a few hundred monkeys left on the island of the species tested and it may not be possible to carry out a similar calibration if the research was conducted in a few decades.

The study raises questions about the origin of the HIV virus, since if it originated from SIV, then humans have been exposed to it for thousands of years, as shown by the current study. If so, why did the AIDS epidemic only break out in the 20th century? Furthermore, the research findings have important implications regarding the interaction between humans and the HIV virus.

It is important to note that the SIV virus infects monkeys, but usually does not cause disease in them. The starting assumption is that the "reciprocity" between the SIV virus and the monkeys has reached a stage where they can exist side by side (that is, inside each other...), compared to the relationship between the HIV virus and humans who are still relatively new to each other, and where the virus Deadly for his host. However, the new findings indicate that the coexistence of the SIV virus and monkeys reached the current stage after tens of thousands of years, so that a similar period may pass before the HIV virus does not cause disease in humans.

Furthermore, another layer that the researchers do not refer to in the article is that, compared to the SIV virus in monkeys, the humans who become infected with HIV in many cases receive drug treatment that damages the virus. Man interferes in the relationship between the virus and the host, so it is impossible to conclude from the relationship between the SIV virus and monkeys about the relationship between the HIV virus and man. Therefore, it is possible that the state of life mentioned by the researchers, a state of "truce", will not arrive even in the distant future.

Dina Volodarsky has a master's degree in life sciences from the Weizmann Institute of Science and a bachelor's degree in life sciences from the Hebrew University.

The full article was published in Galileo magazine, November 2010

2 תגובות

  1. Living matter is characterized by being far from equilibrium.

    We may be able to curb viruses/diseases/disabilities
    by drugs/treatments
    But we probably won't be able to eliminate the pathogens
    And then in the event of a global economic disaster
    Not only our possessions will disappear
    but also large parts of humanity
    that depend on technology in order to survive and/or reproduce.

  2. The biological truce in question is an evolutionary situation that natural selection created, so that initially there were only very few monkeys who managed to live with the SIV virus while most of the other monkeys died from it. Later on, only the monkeys that survived through the generations after being attacked by the SIV are the ones that as a result could also contain the virus within them. It is known that a very small proportion of the human population can live with the HIV virus without drug treatment. Without man's intervention and his war on the HIV virus with the drug cocktail, it is possible that if all of humanity had been infected by it, almost everyone would have died and only a tiny percentage of people would have remained alive and they would have been the ones who would have succeeded after thousands of years in carrying the AIDS virus in their bodies unharmed.

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