Stripping Down Science by Chris Smith, Dr Christorpher Smith Page B

mosquitoes.’
Still, it might be one to have in the bag for when times get really tough!

    FACT BOX
    Malaria in children: a case of mistaken identity
Mosquitoes are directly responsible for causing over 500 million cases of malaria per year, the annual death toll from which is over one million, mostly young babies and children aged between six months and three years in sub-Saharan Africa. Why does this disease hit this age group much harder than any other? The answer, it turns out, is a case of mistaking friend and foe.
Christopher King, a researcher from Case Western Reserve University in the US, 45 followed up 586 babies born in Kenya from the time they were born until the age of three. He collected umbilical cord blood samples from the babies and also took a specimen of blood from each of the babies’ mothers. Tests showed that some of the mothers were infected with malaria at the time when theygave birth, suggesting that the baby might also have been exposed to malarial antigens – chemical markers made by the parasite – which would have been circulating in the mother’s bloodstream.
King and his colleagues therefore suspected that this might be causing the babies’ immune systems to develop what is known as ‘tolerance’ to malaria. Tolerance is a process by which the immune system normally learns what it should befriend (and ignore) and what it should attack. If the malaria parasite is present when the baby is developing, the team reasoned, the baby’s immune system might be fooled into thinking that the parasite is a normal part of the body and so ignore it.
In keeping with this theory, when the team mixed malaria antigens with white blood cells from babies whose mothers were infected with malaria at the time of delivery, the babies’ cells reacted only very weakly. But white cells from babies who were not born to infected mothers, on the other hand, showed vigorous reactions and pumped out largeamounts of inflammatory hormones.
This suggests, say the team, that if a mother is infected with malaria when she is pregnant, the baby’s immune system is misled into becoming tolerant to the parasite rather than attacking it. This could have serious implications for the development of a successful vaccine, because the children who are most at risk are those who are already tolerant to malaria and therefore won’t make a very powerful immune response to a vaccine.
So why are children under six months less affected? This is because babies are initially protected from malaria by antibodies which are present in breast milk and are also added to the baby from the mother’s bloodstream during the final phase of pregnancy. These antibodies persist in the baby’s circulation for about six months, but once they are gone the child becomes vulnerable. And if the child is one that has developed tolerance to malaria, then it will develop far more severe malaria disease with a correspondingly increased risk of dying.

A saving grace is that researchers at least now know about this previously unappreciated part of the malarial parasitic puzzle. But as yet, the world is still waiting for an effective vaccine for one of the most common killers.

We often think of snow as a paragon of purity; it can transform even an ugly industrial landscape into a soothing sight that’s easy on the eye. But snow’s pristine image is something of a myth, because beneath its sparkling exterior lurks a dirty secret, the full scale of which is only now becoming apparent.
    Analysing samples of freshly fallen snow collected from a range of locations around the world, Louisiana State University scientist Brent Christner and his colleagues 46 found that the snow contained large numbers of bacteria which, it turned out, had quite literally come down in the last shower. Why were these bacteria turning up in pristine snow? Well, the results suggest that they were most likely hitching a ride around the