[afro-nets] Malaria in pregnancy 'more complex than thought'

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

Malaria in pregnancy 'more complex than thought'
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http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=3080&language=1

Malaria in pregnancy 'more complex than thought'
Tissue from a malaria-infected placenta

Marta Paterlini
4 September 2006
Source: SciDev.Net

The way in which the malaria parasite infects pregnant women is
more complex than previously thought, with implications for
vaccine research, say scientists.

A joint study between the Karolinska Institutet in Sweden and
Makerere University in Uganda looked at how blood cells infected
with the malaria parasite Plasmodium falciparum invade the
placenta.

Malaria affects many millions of pregnant women each year,
mostly young African women during their first pregnancy when
they lose the semi-immunity normally found in adults.

In these young mothers, the parasite accumulates in the
placenta, causing them to become anemic. The children of
infected mothers often have lower birth weights.

Until recently, scientists believed that red blood cells
infected with the malaria parasite attached to the placenta
through a single protein on the blood cell surface, which bound
to the CSA protein on placental cells.

This one-to-one binding would have made it easier to design a
vaccine for pregnant mothers.

But the research using blood samples taken from pregnant mothers
in Uganda shows that things are not so simple.

"Most of the parasites we studied could bind to three different
receptors in the placenta," says author Niloofar Rasti of the
Karolinska Institutet. "This would mean that a future vaccine
cannot be based on the principle of one protein to one receptor,
as was previously believed."

The researchers say their findings suggest that the success of
malaria vaccines for pregnant mothers will depend on an in-depth
understanding of the binding interactions between infected blood
cells and the placenta.

Stephen Rogerson, a professor at the Department of Medicine,
Melbourne University, Australia says, "Wahlgren's finding goes
rather against the prevailing dogma, which suggests that only
adhesion to CSA is of major importance in placental malaria."

"We urgently need new medications to treat and prevent malaria
in pregnant women, as resistance to the few drugs that are safe
for pregnancy has risen to dangerous levels," he says.

And although testing such vaccines can be controversial,
Rogerson says that "future strategies should include both
pregnancy-specific vaccines, and possibly vaccines aimed at the
whole malaria-exposed population".

The study was led by Mats Wahlgren of the Karolinska Institutet,
and was published online by Proceedings of the National Academy
of Sciences last week (28 August).

Link to abstract of paper in Proceedings of the National Academy
of Sciences
http://www.pnas.org/cgi/content/abstract/0601519103v1