The origin of the AIDS virus

The origin of the AIDS virus

Where there was virus Human immunodeficiency is still not completely clear, although the history of the epidemic has been studied quite well. It is known that the disease came from somewhere in the African jungle, but until recently stayed in the wilds of Africa, all of the studies. At this, the initial, phase concentrated efforts of researchers at the University of Alabama at Birmingham, Beatrice Hahn and George Shaw.

At first there were monkeys … and not only do they

The generally accepted view is that AIDS originated among the chimpanzees. A few decades ago, the disease spread to humans, causing a worldwide epidemic, after several sick animals were killed and eaten by locals.

Evidence in favor of this view are considered three captured in Africa chimpanzee, infected with the virus, it is very close to that causes AIDS in humans. Also were found four chimpanzees infected virus, genetically related, but not identical to HIV. It is not known where these animals lived before they were caught, but Han et al believe that these animals are not native to the western part of central Africa, because the virus that hit them, too genetically distinct from that species, that struck the first three chimpanzees.

Now we have four different simian virus — says Khan — three of them are very close to each other as well as human species. But they are very different from the fourth sample. Thus, we conclude that the western part of central Africa is the most likely birthplace of the microbe that hit the planet today.

There are a number of professionals who are not convinced of such evidence. Dr Khan says: "Many have said four chimpanzees in cages — is not enough. You do not quite understand what goes on in the wild. " Hahn and Shaw, from large-scale studies in the African jungle, were almost sure that will find widespread virus that affects many monkeys, not causing them serious illness.

The possibility of such a state has been proven over a decade ago when Marlo Brown, a resident of Petaluma, California, the owner of a shelter for cats, was surprised by the fact that several of its animals showed simtomy, very similar to the symptoms of AIDS. Miss Brown went along with her cats to the vet, who was unable to say anything definite. In the end, Niels Pedersen, a specialist in viral diseases of animals at University of California, acknowledged that cats suffer from AIDS.

A year later, Pedersen, along with a colleague, Janet Yamamoto, succeeded in isolating virus. He was quite close with HIV, but is not dangerous to humans. The mystery remained a source of infection. It was not clear also affects whether virus wild cats. And, if so, whether the damage is not due to the virus die made in the red book lions and pumas? Stephen O'Brien, an expert on cats, who heads the laboratory of genetic diversity at the National Cancer Institute in Frederick, Maryland, was extremely intrigued and concerned by these reports. He immediately began to study the storage of tissue samples of thousands of wild cats, cheetahs, lions, ocelots, pumas. Much to his surprise, the virus was detected in almost all samples. That is, one could say that the majority of feral cats suffer from a disease very similar to human AIDS. "All cats were hit by a virus that can destroy the immune system — said O'Brien. — But some animals were not even sick. " "We spent a lot of time looking for signs of disease, but could not find anything — said the researcher. — The impression that the wild cat somehow learned to live with the virus and do not get sick. However, domestic cats have been subjected to infection by this microbe were defenseless and quickly died. "

Thus, primates could expect the same situation. It was found that at least 20 species of African monkeys infected but not blown SPIDopodobnymi viruses. Asian monkeys, in contrast, are not infected. And when the Asian primates in the laboratory infected with a virus from African intentionally or accidentally, being lodged in one cell — they are sick and dying from the present AIDS. "All African primates have on the virus — says Jonathan Allan, a virologist at the Southwest Foundation of Biomedical Research in San Antonio. Some species of monkeys are carriers of viruses for thousands of years. And the natural hosts of these microbes never get sick. "

Expecting one thing and got another

So, given these facts, the researchers had to develop a technique that allows to detect HIV-like viruses in wild chimpanzee, which are listed in the Red Book of endangered species and are. It is forbidden not only to catch these animals and keep in captivity, but even the subject of anesthesia, and take blood tests. Scientists have found a way to detect traces of the virus in faeces and urine of monkeys.

The technology has been tested on people who were more accessible material for study than animals. Khan said her students refused to work with a huge amount of human feces, which, according to the experimental conditions, it was possible to examine only hours or even days after receipt (after all, had to look for feces of monkeys in the forest, and they could not be fresh). The study was under threat. The situation was saved by the fact that the feces of monkeys, as it turned out, did not have such a bad smell, even in semi-decomposed state.

In the end, the team went on a wild jungle. There, a partnership was established with the primatologist who knew each animal colony. This allowed to determine the identity of each sample, checking the accuracy of the re-analysis of studies of material from the same animals. It was possible to obtain a series of samples of feces and urine samples from 58 chimpanzee colony in Taey forest, national park Côte d'Ivoire (Ivory Coast), Kibale National Park in Uganda and Gombe in Tanzania. The material was stored and transported in the United States.

The researchers expected that all chimpanzees, regardless of location, will be amazed by an infection, that is again the situation with cats and monkeys caught. However, to the surprise of the researchers, only one animal were affected by the virus. It was a healthy 23-year-old male from Gombe. And it was absolutely not a virus similar to the human. The microbe was rather similar to the fourth sample obtained from monkeys in captivity. This result was published in the same issue of the journal Science. All AIDS experts were amazed. "It's absolutely incredible," — said Edward Holmes of Oxford University.

Whether adaptation to the virus?

This scientist suggested three possible explanations for this incredible outcome of the study. He said that there are probably affected populations, but they are isolated so that infections do not share with animals available to researchers. Or the population of chimpanzees infected by a virus, yet extinct. Perhaps this was due to hunting local residents and habitat alteration, violated their reproduction. And finally, the most mysterious is the assumption that, indeed, a very small number of infected chimpanzees. However, if infected chimpanzee as little as the virus is passed to humans?

Khan said her group began to explore a completely wild chimpanzees living outside the studied populations. Now they are collecting stool in the wildest parts of the jungle. Now they can not determine which specific animal belong collected samples and cool if it is. But, nevertheless, this study will determine whether the virus is rare in wild apes.

Now researchers are looking for signs of AIDS infection in the wild and try to apply the data to understand the future of the epidemic among people. Why chimpanzees and feral cats so resistant to the virus and do not have AIDS, being infected?

Mark Feinberg, a professor of medicine, microbiology and immunology at Emory University, focused on one type of West African monkeys ar
e widely affected by the virus, HIV-2 is identical, the human AIDS virus affecting humans in West Africa, but has not caused a worldwide epidemic. Researchers have known for certain that the monkeys are perfectly healthy. It was expected that the monkey can somehow inhibit the development of viruses. And in the blood of monkeys did not show up a lot of germs, peculiar to people infected with HIV-2. However, the analysis of the blood of monkeys found that in every drop of blood of millions of virus particles. Then the assumption of the body's ability to suppress the virus monkeys had to be abandoned.

To explain the situation has been offered a version that viruses for some reason, breeding, do not kill the monkey cage. However, this assumption was not true. Viruses are constantly destroyed a significant number of cells. The monkeys were able to just make up for this loss. The same situation was found with the lions and pumas, said an expert on wild cat O'Brien. The animals found a huge number of viruses, constantly destroying red blood cells and the ability to compensate for this loss, without compromising health.

O'Brien said that the emergence of such an adaptation can be predicted theoretically. He also added that the observed features of hematopoiesis in infected populations are essential to combat the AIDS epidemic among people. Feinberg, as O'Brien thinks that the inevitable is that HIV will change humanity. So many people are infected in some parts of Africa, according to an expert on wild cats that future generations will have a disproportionate number of people with a genetic predisposition to living with the virus.

Thus evolutionary change happens. "It's bound to happen — says Feinberg. — The severity of the epidemic in some parts of the world is so great that it will necessarily have an impact on human evolution. In the past, — he added — the infection is not just influenced human evolution. " "Today — said Feinberg, — we have the opportunity to observe the situation with my own eyes."

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