Early Tests Show SARS Vaccine May Be Possible
Experimental Treatments Could One Day Help Target Communities
June 24, 2004 -- Two new experimental treatments may eventually
be able to help protect humans from the threat of severe acute respiratory
syndrome. Researchers say initial animal tests show that it may be possible to
immunize humans against the potentially deadly SARS virus using a SARS vaccine
or other means of boosting the immune system's defenses.
Two studies published in this week's issue of The
Lancet, show a inhaled vaccine and an antibody injection were both
effective at protecting animals against developing the severe lung disease
caused by the SARS virus.
Although more research is needed before these approaches can be
tested in human, researchers say the results show the potential for development
of a SARS vaccine.
Potential for SARS Vaccine Revealed
In the first study, researchers looked at the effects of a
single dose of an intranasal vaccine derived from a pediatric flu vaccine in
preventing SARS in a group of African green monkeys. In their experiment, the
weakened flu virus contained in the pediatric vaccine was genetically altered
to have components of the SARS virus coating.
The study showed that monkeys who received the vaccine were
able to produce antibodies capable of fighting SARS infection. Later the
monkeys were exposed to the SARS virus and showed no evidence of having the
SARS virus in their lungs. The monkeys that did not get the experimental
vaccine showed evidence of the SARS virus within eight days after infection
with the virus.
Researchers say the monkeys who received the SARS vaccine had
developed antibodies against the SARS virus in their blood, which indicates
that the immune system had responded to the vaccination.
In the second study, researchers injected a group of ferrets
with an experimental antibody, a protein normally created by the immune system
to help defend against infection by foreign viruses or bacteria.
Researchers found that ferrets who received the injection were
not contagious; they did not shed the virus from their lungs after being
exposed to the SARS virus. The antibody injection also completely prevented the
development of SARS-related lung damage in exposed animals.
In a commentary that accompanies the studies, Ruth Foxwell of
the University of Canberra, Australia, and colleagues say both approaches show
promise for reducing the risk of death and disease caused by SARS.
"Whilst further studies are required before these concepts
can be applied to human beings, the findings provide exciting strategies for
the prevention of disease in target communities and treatment of at-risk
individuals," write Foxwell and colleagues.