The mosquito-borne parasites that cause human malaria and make it particularly lethal have a unique ability to evade destruction by the body's immune system, diminishing its ability to develop immunity and fight the infection, a Yale study has found.
One of the biggest problems in controlling malaria in regions of high transmission, where it continues to account for over one million deaths yearly, is that protective immunity against re-infection does not occur.
It is believed that inadequate formation and maintenance of infection-fighting memory T-cells are at the root of this immune malfunction. This phenomenon also frustrates efforts to develop effective malaria vaccines.
It's known that malaria causes a highly inflammatory response in infected individuals that leads to the deadly clinical complications of anaemia and cerebral disease.
The Yale research team learned that the parasites produce their own version of a human cytokine, or immune hormone, which directs the inflammatory response during malaria. They also discovered that this cytokine, called PMIF, incapacitates the anti-malaria, memory T-cell immune response.
Using a genetically modified strain of the malaria parasite in mice, the Yale team found that PMIF causes host T-cells to develop into short-lived effector cells rather than protective memory cells.