Genetic blood disorder proves resistant to malaria
EU-funded researchers have discovered the reason why people with the genetic blood disorder alpha-thalassaemia are resistant to malarial anaemia. Those suffering from this disorder can tolerate losing large numbers of red blood cells associated with malaria, because their bodies produce an increased number of smaller red blood cells. Alpha-thalassaemiais is caused by the mutation of two or more of the four genes responsible for the production of haemoglobin, the protein that carries oxygen in the blood. People with the condition develop mild anaemia as a result. A study conducted in the mid-1990s in children living in Papua New Guinea, where more than two-thirds of the population have alpha-thalassaemia, found that the disorder protects against severe malaria. Scientists originally thought that although the condition did not stop malaria, it managed to interfere with the malarial parasite's ability to enter the red blood cells, multiply and spread. This prevented children with malaria developing the related illness anaemia. The researchers in this latest study decided to re-analyse the data of the 800 children involved in the Papua New Guinea study. They looked at red blood cell counts in each child with malaria, and compared this with the children's genetic profiles. They discovered that the children with Alpha-thalassaemiais had smaller red blood cells, containing less haemoglobin, than healthy people. However, these children also had many more of these red blood cells - between 10% and 20% more than is normal. This meant that children with the blood disorder could handle losing more blood cells to malaria because they have more blood cells to begin with. 'Children with alpha-thalassaemia have adapted to the loss of red blood cells associated with malarial disease by making more of these cells with less haemoglobin,' says Professor Karen Day from New York University (NYU), who conducted the study. 'These children do better because they end up with more haemoglobin overall when they have a malaria attack compared to normal children. It is really remarkable and so simple.' Although the study only deals with one type of malaria parasite, the researchers speculate that the blood profile associated with alpha-thalassaemia might well prevent other malaria species causing anaemia. The results of the study are published in the latest edition of the open access journal PLoS Medicine.