THIS WEEK, Boston researchers said they may have one
explanation for why some patients infected with HIV survive for
years - without treatment and without getting sick.
In a study published in the journal Science, researchers
reported that an analysis of blood from a healthy Boston man
infected with HIV for 18 to 20 years shows he is protected by a
large number of immune system cells, called helper T-cells (or
CD4 cells), that specifically attack HIV.
Using this clue, the researchers at Massachusetts General
Hospital went on to find that these special helper T-cells may
be an essential difference between being well and getting sick.
If preserved, these cells can be a critical weapon in defeating
the virus over the long term.
"Our work provides an explanation of why a very small group of
people have been able to avoid getting sick from this virus
even though they are infected," said Dr. Bruce Walker, the
senior author of the study.
In the Boston study, four men who have been able to withstand
the virus for up to two decades were at the heart of the
The one who has survived the longest, and who first sparked
interest among the hospital researchers, is Robert Massie, an
Episcopal priest who was the Democratic nominee for lieutenant
governor in 1994. Massie has had HIV for nearly 20 years, but
the level of virus in his blood remains below detectable
Laboratory tests of blood from these patients found that those
with the strongest CD4 cell response to the HIV antigen had the
lowest amount of virus in their bloodstream, but those with
weak CD4 cell responses had high virus loads.
What made Massie and the other long-term survivors different is
that their helper cells somehow survived, built up to high
levels, and helped beat back HIV. High levels of these
HIV-specific CD4 cells may be essential for the body to hold
the AIDS virus in check, the scientists said.
CD4 cells direct the body's immune system. There is a variety
of the cells, and each type is primed to attack a specific
virus or other invader. As these cells detect the presence of a
target virus, they reproduce by the billions, flooding the
bloodstream with defenders. But HIV breaks down this defense.
Throughout the epidemic, an estimated 2 percent to 3 percent of
infected people have beaten the odds by showing no symptoms
even though they were not being treated. That fact intrigued
researchers at Massachusetts General, who set out four years
ago to find out what allowed people to survive.
The discovery - that CD4 cells somehow keep HIV in check -
suggested that the body might be able to control HIV if these
cells were somehow protected.
To test this idea, researchers used powerful antiviral drugs to
treat patients recently infected with HIV. Walker said the
drugs caused the virus load to drop quickly, and the patients'
immune systems then started producing CD4 cells that
specifically attacked HIV.
Significantly, the HIV-specific cells were not produced in the
bodies of patients who had been infected with HIV for more than
six months. Rescuing CD4 cells has been shown to work only with
patients who are at the earliest stages of infection, probably
the first several weeks.
And even with the early stage patients who have built back a
full complement of CD4 cells, researchers haven't completed the
experiments they feel are needed before they try to wean
patients from their drug regimen.
"This suggests that there is a window of time during the acute
phase of infection when antiviral treatment can rescue the
helper T-cell response to HIV," Walker said. If treatment is
delayed, he said, that natural protection may be lost forever.
There may be immune system elements other than helper T-cells
that are responsible for suppressing or extinguishing HIV
In research to be presented next Monday afternoon at a World
AIDS Day symposium in UC-San Francisco's Cole Hall, Dr. Jay
Levy will report that people who remain uninfected - despite
repeated exposures to HIV - have a unique immunologic ability
to marshal a different kind of T-cell, called "killer" or
"cytotoxic" T-cell (CD8 cell), to prevent replication of HIV.
In studying patients' blood in the laboratory, Levy found that
if he attempted to infect CD4 cells with HIV in the presence of
CD8 cells, viral replication was stopped. However, when the CD8
cells were removed, the virus grew again.
"We think it results from exposure to low amounts of virus,
which is enough to get the cellular immune antiviral response
going," said Levy.
Levy suggests that CD8 cells have an important antiviral
response, somehow linked to a naturally occurring protein
called CAF (CD8 antiviral factor), that blocks replication of
*The spread of HIV is so rampant in Africa that about 25
percent of adults in Botswana are infected, 22 percent in
Zimbabwe and 19 percent in Namibia, a United Nations official
told an International Planned Parenthood conference.
In some southern African cities, more than 40 percent of
pregnant women are infected, said Dr. Elhadjas Sy, head of the
Joint U.N. Program on HIV / AIDS.
*Nearly 40 million children in developing countries stand to
lose one or both parents to AIDS over the next 13 years, with
catastrophic results, according to a survey by the U.S. Agency
for International Development and the Census Bureau.
The AIDS epidemic is creating a lost generation of children at
risk of exploitation and disease, it concluded.
The report also predicted that life expectancy - which has been
steadily on the rise for the last three decades - will drop to
40 years or less in nine sub-Saharan countries by the year
. . . . . .Date . . . . . .reported. . Cases. . Deaths S.F.. .
. .11/1 . . . . 24,787 . 16,935 Calif.. . .11/1 . . . .103,562
. 65,942 U.S.. . . .11/1 . . . .612,078 .379,258 WHO(rprtd)
11/1 . . .8,400,000 6,400,000
Figures are cumulative since June 1981. Government officials
now compile and release statistics quarterly, not monthly.
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