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Type of AIDS infection key to death risk - study

Posted on: Monday, 6 February 2006, 15:17 CST

By Maggie Fox, Health and Science Correspondent

DENVER (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 Johns 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. Maria Wawer, Dr. Thomas 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 Johns 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.

Source: REUTERS

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