Trait Offers Malaria Immunity to Children

The blood cell abnormality, sickle cell trait, gives an increasing amount of protection against malaria as young children grow during their first 10 years of life, new research has revealed.

Between the ages of 2 and 10 immunity to the disease, which kills up to 2 million people a year, rises rapidly, a Wellcome Trust funded study has found.

The project involved more than 1,000 people living on the coast of Kenya, where malaria is rife. Those taking part were aged from three months to 84 years, although most were under 10. The research, which is reported by the Public Library of Science today, was carried out over six years, and compared the incidence of mild malaria in those with sickle cell trait and those without.

The trait causes blood cells to deform into the shape of a scythe but does not cause sickle cell disease, which, in its worst form, can cause anemia, lung problems and strokes. People with the trait, which is inherited, lead normal lives.

The study, which was led by Dr. Tom Williams of the Kenya Medical Research Institute/Wellcome Trust Research Programme in Kilifi, found that the increased protection from sickle cell trait (HbAS) rose from 20 percent in the first two years of life to more than 50 percent by the age of 10.

Williams comments, It has been known for some time that sickle cell trait offers this protection but the accelerated level of immunity in the first years of life has not been revealed before. There are several possible reasons why this happens and further research will be required before we find the full answer. But one explanation may be that HbAS causes the malaria infection to stay in the body a long time, so allowing the immune system time to build up a proper defense. Our research concentrated on mild malaria, which causes fever, but does not kill. We do not know if our findings can be applied to severe forms of malaria, which can lead to death.

Sickle Cell Trait occurs when someone inherits a normal haemoglobin blood protein gene (HbA) from one parent and a sickle haemoglobin gene (HbS) from the other --  resulting in HbAS. Children with sickle cell trait do not usually display symptoms; however, children who inherit a double dose of the sickle gene suffer from sickle cell disease (HbSS), which in its worst form causes chronic ill health and can result in early mortality.

The Wellcome Trust is an independent research-funding charity established in 1936 under the will of tropical medicine pioneer Sir Henry Wellcome. The Trusts mission is to promote research with the aim of improving human and animal health.

Source: The Wellcome Trust