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Thursday, 26 September, 2002, 18:02 GMT 19:02 UK
Secrets of Aids 'immunity'
Some patients can block the development of HIV
Some patients can block the development of HIV
Scientists have identified why some HIV patients are immune from developing full-blown Aids.

It has been known for some time that around 2% of HIV patients were protected in some way.

But now, American and Chinese researchers have identified a group of proteins in the body which naturally block HIV developing into Aids.

They say the discovery, detailed in the journal Science, could lead to better understanding of how the body fights HIV, and could potentially lead to the development of new treatments.


This discovery is a major step forward in our understanding of how the body fights HIV

Dr Linqi Zhang, Aaron Diamond Aids Research Center
A second study to be published in The Lancet on Friday shows that a common spermicide which had previously been proposed as a preventative agent against HIV infection is ineffective.

Nonoxynol-9 spermicide can be bought over-the-counter, and it has also been suggested it could protect against other sexually transmitted infections.

But Belgian researchers say Nonoxynol-9 could even increase HIV transmission if used frequently.

Proteins

Scientists have known since the mid-1980s that some people with HIV do not go on to develop Aids.

Immune cells, called CD8 T cells, were discovered to produce some unidentifiable factors which inhibited HIV cells from replicating.

In this research, scientists from the Aaron Diamond Aids Research Center in New York City compared CD8 T cells from HIV patients who had not developed Aids with those from patients whose immune systems were beginning to fail.

They found that those who remained healthy had the alpha-defensins -1, -2, -3 proteins.

The proteins appeared to suppress all strands of HIV, and the researchers suggest they could be developed to suppress HIV in the greater infected population.

To confirm their finding, the researchers artificially stripped the proteins from the cells of protected HIV patients.

They found that the cells ability to fight HIV was virtually eliminated.

Further research showed a synthesized versions of the proteins was 10 to 20 times less effective than the natural version.

Vaccination possibility

Dr Linqi Zhang, who led the research, told AFP news agency: "This discovery is a major step forward in our understanding of how the body fights HIV.

"By understanding how some people's immune systems are able to control HIV infection, we may be able to develop new treatments that take advantage of this phenomenon."

Keith Alcorn, editor at the UK National Aids Manual, told BBC News Online: "This is an interesting discovery, but as always the key issue is how well it will work in humans, and how easy it will be to synthesise it in the quantities needed to treat humans, given that the synthetic form is far less potent than the naturally occurring form".

"Another avenue for development of this discovery into a treatment might be to look for agents or vaccination strategies which stimulate the body's own production."

Lesions

Researchers from the Institute of Tropical Medicine in Antwerp, Belgium, looked at the effectiveness of Nonoxynol-9 spermicide gel by studying 765 HIV negative sex workers in South Africa, Côte d'Ivoire, Benin, and Thailand.

Around a third of women used the spermicide gel an average of three and a half times a day.

This was associated with a doubling of HIV infection compared with women using a dummy gel.

Researchers suggest this could have been because of the occurrence of vaginal lesions as a result of intensive use of the gel.

However, low use of the gel did not increase the risk of HIV infection.

There was also no differences in the incidence of other sexually transmitted diseases between Nonoxynol-9 and dummy gels.

Dr Lut Van Damme, who led the study, said: "Nonoxynol-9 no longer has a part to play in HIV-prevention.

"Our data show that low frequency use of nonoxynol-9 causes neither harm nor benefit; but that frequent use increases a woman's risk of HIV-1 infection by causing lesions."

But in an editorial in the Lancet, Dr David Wilkinson from the University of South Australia, Adelaide, Australia, said the findings should not mean that the search for methods to reduces the risk of acquiring HIV loses momentum."

Commenting on the study, Lisa Power, head of policy at the Terrence Higgins Trust, which is calling for the removal of Nonoxynol 9 from condoms and lubricants, said: "There is no basis for the use of Nonoxynol 9 as an anti-HIV agent.

"Research shows that in fact it is liable to increase the possibility of transmission.

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Dr David Ho
"It's been known for a long time that some people's cells release a protein that suppresses HIV"
See also:

26 Jan 00 | Health
01 May 02 | Health
10 Sep 02 | Health
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