From: http://www.smh.com.au/articles/2003/05/16/1052885392603.html
Boston: Much of SARS victims' life-threatening lung damage appears to result
from an overly aggressive counterattack by their own bodies, suggesting that
virus-killing drugs alone may fail to stop the disease.
Researchers are testing drugs already on the shelf and creating new ones
in an effort to find something that will destroy the virus and arrest the
disease, which can wreck the lungs. However, many worry that the body's own
attempt to fight off the virus is part of the problem, and a study released
today supports that concern.
Researchers examining victims' lungs found two sources of damage: the virus
itself and the white blood cells summoned to fight it. This combination of
offence and misguided defence plays a part in many infectious diseases, and
the researchers said finding it so prominently in SARS supports the strategy
of subduing patients' immune systems to help them get better.
In fact, some doctors treating SARS in Hong Kong and elsewhere already routinely
give steroid drugs to patients to restrain their immune defences and protect
them from a flood of potentially harmful chemicals, called cytokines, aimed
at the virus. However, this approach is controversial, and some question
whether it could do more harm than good by dulling patients' virus-fighting
edge.
The latest evidence, based on lung samples taken from six people who died
of SARS, was released on the internet today by the British journal Lancet.
The study was conducted by Dr John M Nicholls and others at the University
of Hong Kong.
No drugs are proven to kill the SARS virus inside the body. However, with
nothing else to offer, some doctors have used a combination of ribavirin,
which works against some other respiratory infections, and steroids.
Enthusiasm for ribavirin has waned, especially after lab tests found no sign
it kills the virus. And some doctors said the latest study should not prompt
further use of steroids, at least until there is evidence in animal studies
that the approach improves recovery.
"With a few patients, you cannot make those kinds of recommendations," said
Dr. Sherif Zaki, pathology chief at the US Centres for Disease Control and
Prevention. "You are dealing with human life. You have to have evidence."
The debate also went on in this week's issue of the New England Journal of
Medicine, which published five SARS reports released earlier on the internet.
Dr. Yuji Oba of the University of Missouri in Kansas City wrote a letter
calling steroids potentially hazardous in SARS, while Drs Nelson Lee and
Joseph Sung of Chinese University of Hong Kong responded that the treatment
has been given "to suppress the cytokine storm ... and, in fact, in many
cases, it did".
The Lancet report showed evidence of extensive destruction triggered by blood
cells called macrophages. These cells produce a variety of chemicals that
fight infection but also trigger dangerous inflammation.
The doctors said some of the resulting lung damage is similar to what was
seen in the bird flu outbreak, which killed several people in Hong Kong in
1997. They said this suggests that large amounts of inflammatory chemicals
produced by macrophages in the air sacs of the lungs help explain why both
diseases can be lethal.
"If this is true, it's possible one could intervene at the very early stages
of SARS and use anti-inflammatory agents," such as steroids and other immune-suppressing
drugs, said Dr. Zab Mosenifar, pulmonology chief at Cedars-Sinai Medical
Center in Los Angeles.
However, he and several other doctors said they would be reluctant to suppress
patients' immune defences unless they could also give them effective virus-fighting
drugs.
Dr Michael Worthington, chief of infectious diseases at Caritas St Elizabeth's
Medical Centre in Boston, noted that a variety of sudden, untreatable lung
infections cause damage "that looks a lot like this. It's hard to show a
benefit of steroids, and sometimes they are harmful."
AP
|
|