Stress may worsen HIV outcome
23 October 2001
LONDON By health-newswire.com reporters
Stress causes a more rapid spread of HIV in infected people and may prevent antiretroviral drugs from restoring immune system function, according to US researchers.
It has long been suspected that stress depresses the immune
system – and now researchers at the University College of Los Angeles (UCLA)
say they have identified the molecular mechanisms that link stress and HIV
infection.
Dr Steve Cole and his team took blood samples from 13 HIV-positive men, aged 25
to 54, who had not received a treatment of combination antiretroviral drugs, and
recorded each subject’s baseline AIDS viral load and CD-4 cell count.
To determine the men’s levels of autonomic nervous system (ANS) activity – a
measure of physiological stress – the researchers calculated the men’s blood
pressure, skin moisture, heart rate and pulse rate at rest.
“Persons with higher ANS activity tend to be more high-strung and easily
stressed out…We wanted to see what effect – if any – this had on our
subjects’ ability to fight HIV infection,” said Dr Jerome Zack, UCLA
professor of medicine and associate director for basic sciences at the UCLA AIDS
Institute.
After exposing the men to a series of stress-inducing exercises, the UCLA team
measured each man’s ANS activity and compared the results to the baseline
findings before giving all the participants a powerful antiretroviral drug
regimen to combat their HIV infection.
To gauge the extent of spread of HIV and the effectiveness of the immune system
in fighting the infection, the researchers again measured each man’s viral
load and CD-4 cell count, and discovered that the higher the man’s stress
level, the less likely he was to respond to antiretroviral treatment.
The average decline in viral load dropped more than 40 times for men with low
ANS activity, but dropped less than 10 times for men with high ANS activity, say
the team, who noted a similar pattern in CD-4 cell count recovery. Men with low
ANS activity showed the most noticeable cell-count increases while men with high
ANS activity displayed insignificant increases.
The hormone norepinephrine plays a key role in the effect of stress on the
immune system say the team. Norepinephrine, released by the nervous system into
the lymph nodes at times of stress, increases viral replication 10-fold, they
found.
Two mechanisms are responsible for this effect, say the team. First, the hormone
increases T-cells’ vulnerability to infection fivefold by increasing levels of
two co-receptor molecules that enable HIV to bind to the cell’s surface and
invade the T-cell. Secondly, norepinephrine increases HIV’s rate of viral gene
expression in the cells it has already infected – allowing the AIDS virus to
spread five times more quickly, they say.
Drs Cole and Zack believe their findings may hold broader implications for
future studies of the role stress plays in physical health.
Source: UCLA
© Health Media Ltd 2001
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