AIDS: SI virus is considered a precursor to HIV

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AIDS: SI virus is a precursor to HIV and is several tens of thousands of years old. The SIV is an archetype of HIV.

(09/17/2010) The precursor of the HIV virus (AIDS) is apparently several tens of thousands of years old. In the scientific community, the virus is called "Simian Immunodeficiency Virus (SIV)" and has apparently been transported in the organism of monkeys for thousands of years.

According to the latest scientific studies, the SI virus is a precursor to today's AIDS virus (HIV). Scientists have now found that the virus is much older than previously thought. So far, DNA tests have shown that the virus is only a few hundred years old. The virus is still very widespread among African monkeys.

Scientists led by biologist Michael Worobey from the US University of Arizona and virologist Preston Marx from the "Tulane National Primate Research Center" in Louisiana have discovered numerous variants of the so-called SI virus in samples of monkey meat from the island of Biko in Africa. In-depth analyzes have shown that the virus must be between 32 and 75 thousand years old. But how did the researchers come to this assumption?

The scientists came up with the assumption that the virus had to be older than previously thought using the argumentative double step method. The island of Biko was separated from the African continent around 10,000 years ago as the sea level rose. Since then, the monkeys have lived separately from the mainland and were isolated. However, since the animals were previously infected with the SI virus, the virus must be older than the separation of the island from the mainland.

Another interpretation is that the primates of the genus Bioko-Drills living on the island as well as the viruses have highly genetically related species on the mainland of Africa. A laboratory comparison of the DNA of the viruses showed that they mutate much more slowly than previously thought. Due to the approximately 10,000 year old separation of primates from the mainland, the DNA of the viruses showed very few changes. The so-called molecular clock ran slower than is otherwise the case if virus strains do not mutate in isolation. To substantiate the results, the researchers used empirical values ​​to determine the age of the last common ancestors from the course and number of genetic mutations. From the values, the age of the SI viruses could now be estimated to be at least 32,000 years.

Monkeys infected with the SI virus rarely develop AIDS, an immune deficiency disease. Because the SIV is rather harmless compared to HIV. "Unlike HIV, the Simiane immunodeficiency virus does not cause AIDS in most infected primates," explains Preston Marx.

According to scientists, the low virulence of the virus, i.e. the poor ability of a pathogen to actually cause a disease, may have developed over the past millennia. The SI virus coexists with the monkeys without causing any disease. The HI virus, on the other hand, is much younger and therefore more aggressive towards the host. Because of the small age of the AIDS pathogen, the researchers found that timely virulence was ruled out. Accordingly, it is “not to be expected so soon” that the HI virus will soon develop similarly. After all, the SI virus has only become harmless over thousands of years.

The research results now raise further questions in AIDS research. Why did the spread of the HIV virus only start in the 20th century when people have been in contact with SI-infected viruses for thousands of years? There are no answers yet. The study results were published in the science magazine “Science”.

More than 33 million people are infected with the deadly HI virus (HIV). About 2 million people die each year from the consequences of the immunodeficiency disease AIDS (acquired immunodeficiency syndrome). In Germany, 3000 new HIV diagnoses are made each year. Although modern medications relieve the course of the disease, effective active ingredients have not yet been developed. (sb)

Also read:
UN warns of rapid spread of AIDS
World AIDS Conference: Rights here and now
AIDS: no fate with correct antibodies?
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Photo credit: pixelio / Rolf van Melis

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