[afro-nets] Bug uses 'sword and shield' to cause fatal diarrhoea

[Claudio Schuftan <claudio@hcmc.netnam.vn>]

Bug uses 'sword and shield' to cause fatal diarrhoea
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http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=1958&language=1
 
Catherine Brahic
25 February 2005
Source: SciDev.Net
 
The bacterium that causes dysentery uses a 'sword and shield' 
approach to attacks cells while protecting itself from the in-
flammation it triggers. The findings were published by Nicholas 
West and colleagues in Science this week.
 
Until now, how the bacterium, known as Shigella, is able to in-
fect cells while protecting itself from the inflammation that it 
triggers has remained a mystery.
 
The researchers ­ led by Christoph Tang of Imperial College Lon-
don, in the United Kingdom, and Philippe Sansonetti of the Pas-
teur Institute in France ­ found that Shigella protects itself 
using a shield of proteins that prevents the host's immune de-
fences from destroying it.
 
The results are important because Shigella bacteria, which cause 
more than one million deaths each year, mostly in developing 
countries, are increasingly showing signs of resistance to sev-
eral existing drugs.
 
Shigella infects the cells of the gut by pushing a 'molecular 
needle' into their membranes and injecting them with proteins. 
Once inside the cells, these proteins cause an inflammation.
 
Shigella's protective shield surrounds the molecular needle ­ 
seemingly preventing it from reaching its target gut cells. 
Tang's team showed, however, that Shigella is able to change the 
shape of the shield allowing the needle to stick out beyond it.
 
This allows Shigella to attack gut cells without compromising 
its protection.
 
Developing drugs and vaccines to target Shigella's shield could 
be difficult, as drug designers have never targeted the molecule 
it is made from before.
 
However, Sansonetti believes the findings do open the way for 
future treatments for dysentery and even vaccines against Shig-
ella.
 
"This molecule has not been targeted in current therapies and 
vaccines but they offer the potential for interventions in the 
future," says Tang.
 
Reference: Science 307, 1313 (2005)