Type of AIDS infection key to death risk: study

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.