Bad news for malaria

06 August 2009
Posted by Chris Smith.

Scientists have uncovered new insight into malaria, the deadly disease that affects around 500 million people every year. Sub Saharan African suffers the worst, with an annual death toll of 1 million people annually, mostly children aged between six months and three years.

A newborn babyIt was that statistic of the age-related risk that was the focus of this study in the journal PLoS Medicine, by Christopher King from Case Western Reserve University and his colleagues.

The research team followed up 586 babies born in Kenya from their birth up until their 3rd birthday.  They took samples of umbilical cord blood form the babies and also some blood from the mothers.

As we might expect, some of the mothers were infected with malaria at the time of delivery.  King and the team suspected that this would expose the baby to products made by the malaria parasites while still in the womb, and cause the babies' immune system to develop tolerance to malaria - a process by which the immune system learns what it should ignore when we are first born and what it should launch an attack on.

To test their ideas, they mixed malaria antigens with white blood cells from some of the babies with infected mothers and found that the cells reacted only very weakly to the malarial signal.

Babies whose mothers weren't infected, showed a very strong reaction and pumped out lots of inflammatory hormones.

This suggests that mothers that are infected with malaria pass trigger a tolerance to the malaria in their babies which means they ignore it rather than attack it.

Babies receive antibodies from their mother, which makes them protected from malaria for the first 6 months of life.  After that, the baby because vulnerable.  But if their immune system thinks that malaria is friend rather than foe, then the vaccines will have to tackle this re-programming error if they are going to work.

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