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The bacterium that causes whooping cough
is mutating to develop resistance
to the vaccine used to immunize Dutch schoolchildren
against the disease.
It seems like the bacterium is changing
part of its coat, thereby disguising itself. In recent years
whooping cough has been making
something of a comeback in the Netherlands, the
United States and elsewhere. Comparing old and new strains
of the Bordetella pertussis bacterium under the microscope,
investigators found that, over
time, at least two proteins located on the outside of the
bacterium have been changed.
Since vaccines work by "priming"
the human immune system to recognize (and attack) such proteins,
these changes could explain why the pertussis vaccine now
provides Dutch children with weaker protection against whooping
cough than it did in years past.
This theory was supported by further studies in mice. After
administering the vaccine to a group of mice, the researchers
infected them with either an older or present-day version
of the whooping cough bacterium. The result? More mice infected
with current strains of pertussis showed signs of illness
than those infected with strains dominant in years past.
Annual meeting
of the American Society for Microbiology Orlando, FA May 22,
2000
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