The worst outcome of infection with Plasmodium falciparum is death from Cerebral Malaria (CM). An estimated 445,000 people, mostly children, die yearly from CM and survivors often experience long- term neurological sequelae. The host response to infection causes encephalopathy. However, the causes of pathology are multi-factorial, and not well-defined, limiting development of strategies to treat patients and reduce mortality. Severe vascular congestion, coagulation, and increased inflammatory cytokines each correlate with poor CM outcomes. Mutations that promote low levels of the regulatory cytokine, IL-10, in response to parasite correlate with more severe disease, as do low serum levels. While both parasite and host variation are likely to contribute to pathogenesis, it is challenging to separate them experimentally. Therefore, we employ a model of hyper-inflammatory experimental CM (eCM), which is due to a normally non-virulent parasite strain that is not found sequestered in the brain, and yet causes many of the symptoms of CM in a hyper-inflammatory setting (IL-10 KO). This model, in combination with anti-coagulants, will allow us to examine the role of inflammatory cytokines and coagulation in a reductionist manner. In preliminary data, we found that hyper-inflammation drives formation of thrombi in the brain vasculature that contain inflammatory leukocytes. Furthermore, activated glia are attracted to these thrombotic sites suggesting amplification of inflammatory cytokines within or associated with these vascular foci. Strikingly, treatment with anti-coagulant resulted in reduced mortality from eCM, as well as reduced gliosis and behavioral symptoms. Therefore, we hypothesize that thrombus-associated events promote cytokine amplification and neuropathology, either by trapping immune cells, which interact within the vasculature, or by direct activation of glia, by fibrin(ogen) leaked from the site of thrombosis. We will determine the mechanisms of thrombus-associated neuropathology through the following specific aims: 1) Determine the pathogenic effects of thrombi and inflammatory cells on intravascular events in hyperinflammatory experimental Cerebral Malaria and 2) Determine mechanisms of Fibrinogen-driven neuropathology in malaria infection. This study will dissect the complimentary and overlapping mechanisms by which fibrin(ogen) contributes to inflammation and neuropathology in cerebral malaria. Understanding the interactions between inflammation and coagulation promoting neuropathology in eCM will drive identification of critical factors involved in cerebral pathology leading to potential therapeutic strategies in the future. The three collaborating investigators bring a cohesive team with complimentary knowledge and skills: immunology of malaria, neuroimmunology and cutting-edge imaging of the brain, to this multi-disciplinary project which will improve our understanding of this lethal multi-factorial disease.
Despite continued efforts at eradication, 1.4 billion people are still at risk of malaria infection, and an estimated 343,000 people die of cerebral malaria each year. Understanding how the immune system turns against the body while attempting to fight the parasite is critical for developing therapy for severe malaria. The goal of this proposal is to understand the contributions of inflammation and coagulation to brain pathology in this most lethal form of malaria.
