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Microscopic
worms offer new clues to fatal fungal disease
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Nematodes
Caught in Fungal Loop
Magnification of a fungus
reveals its capture of parasitic nematodes.
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The life cycle of a
microscopic worm is offering scientists new insights into a
deadly fungal disease, which affects around 1 in 10 patients with
HIV.
Scientists at the University of
Birmingham are using nematode worms to examine the development of
the Cryptococcus fungus. Cryptococcus can cause severe infections
in patients with weakened immune systems and is therefore a
particular health problem for AIDS patients.
Understanding the effects
of the fungus in the nematode will help researchers to understand
how the infection develops in humans.
The research, which is
published online in Genetics, showed that resistance to the
fungus was linked to the natural lifespan of the worm. So worms
with a longer natural lifespan survived infection with
Cryptococcus for longer.
Dr Robin May who led the
research said: "The link between resistance and life-span
was extremely pronounced, so worms with a long lifespan, like the
New York strain (C. remanei, EM464), survived the fungus for
longer. This suggests that animals with a longer lifespan invest
more in their immune response to ensure they survive long enough
to reproduce. It is also interesting because it shows that
similar organisms show a markedly different immune response to
the fungus."
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Cryptococcus
Fungus
Cryptococcus neoformans fungus
cells, which cause cryptococcosis. A dangerous meningitis
commonly manifests when the fungus proliferates in the lungs,
enters the blood, and is carried to the meninges.
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The researchers found a
similar pattern when looking at the difference between the sexes
of nematode species exposed to Cryptococcus. In one of the most
commonly studied species (C. elegans) males live up to 20% longer
than hermaphrodite worms. The Birmingham team showed that males
also showed far stronger resistance to Cryptococcus than
hermaphrodites.
Because of the unique
biology of the nematode, the Birmingham team were able to show
that this immune response could be switched on and off by
changing pathways that determine the worm’s sex.
Dr May continues: "Cryptococcus
is a fascinating organism. Although it is a relatively common
yeast-like fungus, we still don’t understand why only a few
species are pathogenic to humans. By looking at the progress of
the fungus in the nematode, we are able to better understand the
biological processes at work. Our study showed that immunity to
the fungus was very variable and linked, in ways that we do not
yet understand, to the natural ageing process.
We are now taking this work on
to look at how human defence cells (macrophages) respond to the
fungus to develop an understanding of how the fungus operates in
humans. Hopefully by understanding the basic biology of
Cryptococcus, we can eventually find ways to reduce people's risk
of infection."
Source
/ credit: University of Birmingham
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