Author Topic: HIV Quickly Evolving Among Large Groups  (Read 1333 times)

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Offline oyashango

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HIV Quickly Evolving Among Large Groups
« on: February 25, 2009, 04:27:13 pm »
                              HIV Quickly Evolving Among Large Groups

Wed Feb 25, 2009 2:25pm EST
By Michael Kahn

LONDON (Reuters) - The AIDS virus is quickly adapting across large groups of people to avoid triggering the human immune system, posing another challenge in the search for a potential vaccine, researchers said on Wednesday.

Scientists know the human immunodeficiency virus, or HIV, constantly mutates within individual people to find ways to attack cells.

But the study published in the journal Nature suggests changes that help the virus do this are increasingly passed on in the wider population.

"What was previously clear is the virus could evolve within each infected person but that doesn't really matter from a vaccine perspective if the virus at the population level is staying the same," said Philip Goulder, an immunologist at Oxford University who led the study.

"The implication is that once we have found an effective vaccine, it would likely need to be changed to keep pace with the rapidly evolving virus."

There is no cure for AIDS and 33 million people globally are infected with HIV. Cocktails of drugs can control the virus and keep patients healthy. AIDS has killed more than 25 million people since the early 1980s, mostly in sub-Saharan Africa.

Researchers are trying to find vaccines that either prevent infection or would control the virus so that patients are less likely to transmit it -- a so-called therapeutic vaccine.

"The process of the virus adapting is happening before our eyes at quite a speed, and it is something we need to take into account when making our vaccines," Goulder said.

HIV attacks the immune system, the body's natural defenses. Like other viruses, it cannot replicate on its own but must hijack a cell and turn it into a virus factory.

HIV must evade several genes to do this, including an immunity gene called HLA.

The team, which included researchers from Australia and Japan, analyzed the genetic sequences of HIV and versions of HLA genes known to control the virus in 2,800 people.

Some people have a version of the gene that is more protective. In the study, the researchers found that mutations that allow HIV to evade immune responses directed by HLA were more common in people with the protective variant of the gene.

This was strong evidence for HIV adaptation to the human immune system among the wider population, Goulder added in a telephone interview.

This means the so-called escape mutation is circulating in more and more people and accumulating in the wider population of those infected with HIV, he said.

"We saw similar effects in every mutation that we looked at," Goulder said. "This shows that HIV is extremely adept at adapting to the immune responses in human populations that are most effective at containing the virus."

(Editing by Will Dunham and Jon Boyle)

Offline TahoeBlue

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Re: HIV Quickly Evolving Among Large Groups
« Reply #1 on: February 25, 2009, 05:17:14 pm »
An older article describing the "adapting" effect of this biological weapon...

Genes involved in evolutionary fight with HIV discovered

9 December 2004
Researchers from Oxford, South Africa and Harvard have discovered exactly which human genes are principally involved in the evolutionary arms race with HIV, leading to a greater understanding of how some people can survive symptom free for years whilst others proceed rapidly to AIDS and death.

HIV infection in most people is a killer. However, in a small proportion of infected people, the virus is successfully controlled by the immune system. There is an evolutionary arms race occurring, in which HIV is mutating to avoid the immune defences mounted by the infected person, and, at the same time, the virus is driving evolution of human immune genes, because those genetic variations that are less successful at fighting the virus will have a lesser chance of survival. Normally we would expect this process of virus adapting to humans and humans adapting to virus to take thousands of years, but a study funded in part by the Wellcome Trust and published today in Nature suggests that in the case of HIV it is happening much more rapidly. Not only are human immune responses to HIV causing rapid changes in the virus, HIV is also causing rapid evolutionary changes in humans. Researchers from the Universities of Oxford, KwaZuluNatal in South Africa, and Harvard, set out to understand precisely how this evolutionary battle is being fought in order to pave the way for vaccine design.

Human leucocyte antigen (HLA) class I molecules play an essential role in the immune system’s fight against infection. Found on the surface of all nucleus-containing cells in the body, they identify to the immune system which cells are infected with HIV and should be destroyed. They do this by presenting tiny fragments of the virus on the surface of the infected cell, signalling to the body’s cytotoxic T lympohocytes, or “killer” T cells, that they should be destroyed.

There are three types of HLA molecule, termed A, B and C, which help the immune system to see virus-infected cells. Previous studies have shown that HLA-B genes are evolving more rapidly than HLA-A or HLA-C, for reasons that have been unclear. To investigate whether significant biological differences exist between HLA-B and the other HLA class I molecules, the team examined the role of HLA-B in control of HIV infection in Durban, South Africa. South Africa is afflicted by more HIV infections than any other country worldwide. In the antenatal clinics in Durban involved in the study, the proportion of mothers attending these clinics who are infected by HIV has risen from less than 1 per cent in 1990 to around 50 per cent today.

The data collected in South Africa showed that above all other types, HLA-B molecules are doing the best job of identifying HIV infected cells to the body’s “killer” T cells. Correspondingly, it is these immune responses against which HIV is adapting the fastest. The researchers found that the success of the immune response in controlling HIV infection, and therefore the speed of progression to AIDS, is primarily determined by the particular HLA-B genes that each individual possesses.

Dr Philip Goulder, a paediatrician and research scientist working within the Peter Medawar Building for Pathogen Research at the University of Oxford, and at Massachusetts General Hospital, was principal investigator on the study. He said: ‘We have known for some time that HLA-B molecules are evolving more rapidly than other types, but it has been unclear why this is happening. These data suggest an explanation for the more rapid evolution of HLA-B in response to other infectious diseases, not only HIV. This is an exciting time for infectious disease research because we are witnessing the evolutionary fight between the human immune system and the HIV virus happening right now, rather than over a period of thousands of years.

‘This study identifies the genetic battleground where the struggle between HIV and the human immune response occurs. The findings will help in understanding precisely how the immune system can succeed or fail against HIV, a prerequisite for a rational approach towards design of an HIV vaccine.’

Dr Mark Walport, Director of the Wellcome Trust, said: ‘Developing a vaccine to prevent transmission of HIV from person to person is a very high priority for the international scientific community. This study adds a key piece to the jigsaw that needs to be completed in order to develop a successful vaccine.’
Behold, happy is the man whom God correcteth: therefore despise not thou the chastening of the Almighty: For he maketh sore, and bindeth up: he woundeth, and his hands make whole ; He shall deliver thee in six troubles: yea, in seven there shall no evil touch thee. - Job 5