[afro-nets] Malaria gene 'defends mosquitoes'

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

Malaria gene 'defends mosquitoes'
---------------------------------

A gene may explain why mosquitoes do not develop malaria even
though they carry the disease, say US scientists.

Female mosquitoes become infected with the malaria parasite when
they draw blood from humans with malaria.

The insects can then pass this on to other humans they bite, but
do not get sick themselves.

The Johns Hopkins University team believe a gene called SPRN6
enables a mosquito to defend itself - a discovery that could
help fight human infection.

Scientist Dr Marcelo Jacobs-Lorena told Proceedings of the Na-
tional Academy of Sciences: "More research is needed, but we
plan to apply this knowledge in the development of new ap-
proaches to control the disease."

The scientists hope to develop chemical sprays that would en-
hance the switching on of the SPRN6 gene in infected mosquitoes.

These mosquitoes would no longer be a real threat to humans when
biting them, because they would not transmit the malaria para-
site Plasmodium, they believe.

Switched off

By looking at two types of mosquito, Anopheles stephensi and
Anopheles gambiae, Dr Jacobs-Lorena and colleagues found that
the SPRN6 gene is normally switched off.

However, when mosquitoes are infected with the malaria parasite
the gene is switched on.

  To find out the function of SPRN6 they looked at what happened
when they forced the gene to stay switched off.

The number of malaria parasites that developed in the stephensi
mosquitoes increased three-fold.

Removing the SPRN6 gene completely delayed the natural process
by which gambiae mosquitoes rid themselves of the malaria para-
site.

Dr Alister Craig, from the Liverpool School of Tropical Medi-
cine, said a number of genes had been found that appeared to
help mosquitoes defend themselves against the malaria parasite.

"Having multiple ways of stopping malaria is important. This
type of research is really helpful in that area. It's nice to
use mosquito immunity as well as other approaches, such as bed
nets and anti-malarial drugs, to beat the disease."

Professor Paul Eggleston, professor of molecular entomology at
Keele University, said: "This latest piece of work offers new
and important insights into the mechanisms by which mosquitoes
deal with malaria parasites.

"However, it remains to be seen whether manipulating the activ-
ity of SRPN6 in Anopheles gambiae could play a role in control-
ling transmission of the human disease.

"These organisms have had millions of years to refine their
game-play and we, as scientists, must expect to be equally ambi-
tious in our attempts to outwit them."

Dr Jo Lines, of the London School of Hygiene and Tropical Medi-
cine, said it was possible that the parasite might evolve and
find a way to overcome such a mechanism.

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