The Role of EphA2 in the Development of Cerebral Malaria

Emory University, Atlanta GA

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Abstract

PROJECT SUMMARY Malaria is a global disease responsible for over 200 million infections and nearly 500,000 deaths annually with two-thirds of deaths occurring in children under five years of age. While global efforts have led to an appreciable decrease in malaria incidence and mortality over the past few decades, cerebral malaria (CM) remains a devastating complication of severe Plasmodium falciparum malaria and is responsible for many of the malaria-associated deaths. There is currently a paucity of supplemental treatment options that have been shown to prevent or improve the outcome of cerebral malaria in particular. In order to improve CM disease treatment, it is necessary to better understand the underlying immunological causes of the disease. We propose to define the role of the receptor EphA2 in the development of cerebral malaria and determine its contribution to T cell sequestration and blood-brain barrier (BBB) breakdown in the context of malaria. The proposed research is highly innovative in that the role of EphA2 in malaria has never been described. The overall objective of this proposal is to determine the mechanism(s) by which EphA2 leads to CD8+ T cell sequestration and BBB breakdown during experimental cerebral malaria (ECM). We hypothesize that EphA2 functions as an adherence molecule for ephrin A ligand-expressing CD8+ T cells leading to CD8+ T cell sequestration on the brain endothelium and subsequent breakdown of the blood-brain barrier. To test this hypothesis, in Specific Aim 1 we will demonstrate the requirement for endothelial-expressed EphA2 in mediating CD8+ T cell retention in the brain during ECM. Using the ECM-inducing parasite strain Plasmodium berghei ANKA, we will demonstrate the requirement of EphA2 on the brain endothelium in CD8+ T cell retention through infections of bone marrow chimeras using EphA2-/- and EphA2+/+ mice. We will further determine if targeting ephrin A ligands on CD8+ T cells is a viable therapeutic strategy for preventing ECM. In Specific Aim 2, we will determine the contribution of EphA2 to BBB breakdown during ECM. We will assess the effect of blocking EphA2 activation on ECM-associated vascular leakage in the brain using a highly specific small molecule inhibitor of EphA2. We will further determine if targeting EphA2 on endothelial cells is a viable therapeutic strategy for preventing ECM. We are uniquely positioned to address these issues due to the expertise of the sponsor and co-sponsor in parasite immunology and brain immunopathology, respectively. Our long-term goal is to understand how EphA2 functions in ECM development in order to apply this information to cerebral malaria in humans and determine the suitability of EphA2 as a target for a novel adjunctive therapy for cerebral malaria. The proposed research has strong potential to significantly contribute to the understanding and cerebral malaria immunopathology and inform design of rational cerebral malaria therapeutics. Cerebral malaria remains a significant cause of mortality globally, and the identification of new targets and therapeutics to combat this severe disease manifestation is an urgent public health issue addressed by this proposal.