Modification of dendritic cell function and priming of protective immunity by malaria blood-stage parasites

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Approximately 2 billion individuals live in areas where malaria is a risk. Children and naive individuals who get infected for the first time, usually travellers, are most at risk of dying from a Plasmodium falciparum infection, with an estimated 2 million children under 3 years of age killed each year. Surviving adults living in malarial areas have partial immunity after a series of infections. It is unclear how this protective immunity, particularly cellular immunity is acquired, and also unclear why it takes so long to develop. Recent advances in immunology have indicated that Dendritic Cells (DCs) are necesssary to induce effectively cellular immunity and prime memory responses. DCs take up foreign proteins and show them to T cells resulting in their activation. T cells are critical for the establishment of long-term protective immunity to malaria. However, it has not been known if DC can take up malaria parasites or malaria infected red-blood cells and process them to activate protective T cell responses. Our preliminary data shows that both human and mouse DC can take up parasitised red-cells, but that the interaction of parasite derived proteins on the surface of the red cell with DC receptors causes a defect in DC maturation. This defect may prevent effective priming of T cells during natural malaria infection, contributing to the poor development of immunity in malaria endemic areas. Given these novel fundamental findings, it is now important to elucidate: 1) The nature of the DC defect induced by the parasites 2) Assess whether this is a common feature of all Plasmodia, or whether it may relate to strain virulence 3) Determine the nature and extent of the malaria specific response induced by the defective DC. Understanding how parasites may be able to sabotage a critical inducing component of the immune system has wide implications for the use of any immuno-therapies in malaria endemic regions.