HIV Sub Type: Key to death risk - study

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Type of AIDS infection key to death risk - study

06 Feb 2006 19:25:16 GMT

Source: Reuters: By Maggie Fox, Health and Science Correspondent

DENVER, Feb 6 (Reuters) - Which particular kind of HIV virus an AIDS

patient has may be more important than other factors in how quickly

death comes, U.S. and Ugandan researchers reported on Monday.

They found that people infected with a clade, or subtype, of HIV

called D died more quickly that those with infections from the A

clade.

Clade was a better predictor than viral load -- how much virus can

be found in a patient's blood -- of rapid death from AIDS, the

researchers told a conference.

" Knowing a person's HIV subtype is important for the management of

the infection because the disease can progress more rapidly in those

infected with subtype D ... than in those with other subtypes, " said

Oliver Laeyendecker, a senior research associate at The s

Hopkins University School of Medicine who led the study.

If an HIV patient is fortunate enough to have medical care, DNA

testing to determine clade may be an important part of that care,

the researchers said.

More than 40 million people are infected with the incurable and

fatal human immunodeficiency virus. HIV killed more than 3 million

people in 2005 and infected 5 million new patients, according to

United Nations.

Africa is by far the worst-hit continent.

GEOGRAPHICAL BOUNDARIES

The virus has mutated into nine clades that correspond to rough

geographical boundaries. Clades A and D are common in Uganda, for

instance, while clade C circulates in Botswana, South Africa, India

and parts of China. Clade B is common in Europe and the United

States.

Researchers are not certain yet if clade is important for making

vaccines against AIDS.

Laeyendecker, Dr. Wawer, Dr. Quinn and colleagues were

studying the Rakai cohort, a group of 12,000 people in Uganda. The

volunteers get annual blood tests, so researchers know when each

patient becomes infected and can track the pattern of the epidemic

in Uganda.

They concentrated on 300 men and women newly infected between 1995

and 2001. Of them, 53 were infected with clade A HIV and 203

infected with clade D. Another 70 were infected with a virus that

had mixed genetic lineages of A and D.

Ten percent of those infected with subtype D died within three

years, while none with subtype A died that quickly, the researchers

told the Conference on Retroviruses and Opportunistic Infections in

Denver.

On average, the people infected with A lived 8.8 years, those with D

lived 6.9 years and those with the A-D mixture lived just 5.8 years.

VIRAL LOAD

In richer countries doctors usually keep track of HIV by measuring

viral load. Current drug cocktails that help control HIV infection

suppress the load to very low levels, and patients usually start to

become ill if it goes up.

But in the Rakai cohort, viral load varied greatly and was not a

good predictor of who died the soonest, the researchers said.

The s Hopkins team said clade D may be more virulent than A

because D uses multiple doorways, called receptors, to get into

human immune cells called T-cells that it infects.

Clade A HIV uses only one receptor called CCR5, to infect T-cells.

But the researchers found that 25 percent of clade D virus also used

a receptor called CXCR4. Two-thirds of the patients whose virus used

CXCR4 died within three years, the researchers said.

An earlier study done in Senegal found that women with clade C, D,

or G infections were more likely to progress to AIDS within 5 years

of infection than women with subtype A.

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