Both Functional LTb Receptor and TNF Receptor 2 Are Required for the Development of Experimental Cerebral Malaria Dieudonne ´ e Togbe 1. , Paulo Loureiro de Sousa 2. , Mathilde Fauconnier 1 , Victorine Boissay 1 , Lizette Fick 3 , Stefanie Scheu 4 , Klaus Pfeffer 4 , Robert Menard 5 , Georges E. Grau 6 , Bich-Thuy Doan 2 , Jean Claude Beloeil 2 , Laurent Renia 6,8 , Anna M. Hansen 6 , Helen J. Ball 6 , Nicholas H. Hunt 6 , Bernhard Ryffel 1 *, Valerie F. J. Quesniaux 1 * 1 University of Orle ´ans and CNRS, Molecular Immunology and Embryology UMR6218, Orleans, France, 2 CNRS CBM (Centre de Biophysique Mole ´ culaire), Orleans, France, 3 Institute of Infectious Disease and Molecular Medicine, Cape Town, South Africa, 4 University of Duesseldorf, Duesseldorf, Germany, 5 Pasteur Institute Paris, Paris, France, 6 The University of Sydney, Department of Pathology, Camperdown, Australia, 7 Institut Cochin, Universite ´ Paris Descartes, CNRS (UMR 8104), Paris, France, 8 Inserm, U567, Paris, France Abstract Background: TNF-related lymphotoxin a (LTa) is essential for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The pathway involved has been attributed to TNFR2. Here we show a second arm of LTa-signaling essential for ECM development through LTb-R, receptor of LTa1b2 heterotrimer. Methodology/Principal Findings: LTbR deficient mice did not develop the neurological signs seen in PbA induced ECM but died at three weeks with high parasitaemia and severe anemia like LTab deficient mice. Resistance of LTab or LTbR deficient mice correlated with unaltered cerebral microcirculation and absence of ischemia, as documented by magnetic resonance imaging and angiography, associated with lack of microvascular obstruction, while wild-type mice developed distinct microvascular pathology. Recruitment and activation of perforin + CD8 + T cells, and their ICAM-1 expression were clearly attenuated in the brain of resistant mice. An essential contribution of LIGHT, another LTbR ligand, could be excluded, as LIGHT deficient mice rapidly succumbed to ECM. Conclusions/Significance: LTbR expressed on radioresistant resident stromal, probably endothelial cells, rather than hematopoietic cells, are essential for the development of ECM, as assessed by hematopoietic reconstitution experiment. Therefore, the data suggest that both functional LTbR and TNFR2 signaling are required and non-redundant for the development of microvascular pathology resulting in fatal ECM. Citation: Togbe D, Loureiro de Sousa P, Fauconnier M, Boissay V, Fick L, et al. (2008) Both Functional LTb Receptor and TNF Receptor 2 Are Required for the Development of Experimental Cerebral Malaria. PLoS ONE 3(7): e2608. doi:10.1371/journal.pone.0002608 Editor: Denise L. Doolan, Queensland Institute of Medical Research, Australia Received March 28, 2008; Accepted June 4, 2008; Published July 9, 2008 Copyright: ß 2008 Togbe et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Work supported by CNRS, the interdisciplinary program MIE from the French Research Minister, and European FP6 MPCM project. Competing Interests: The authors have declared that no competing interests exist. * E-mail: bryffel@cnrs-orleans.fr (BR); quesniaux@cnrs-orleans.fr (VFJQ) . These authors contributed equally to this work. Introduction Cerebral malaria is a frequent cause of death in children and young adults infected with Plasmodium falciparum [1], which is characterized by the sequestration of parasitized erythrocytes in cerebral blood vessels [2,3]. TNF has been originally implicated in pathogenesis of the neurological complication [4]. In patients with cerebral malaria disease severity has been correlated with TNF serum levels [5–7]. In experimental murine malaria the admin- istration of TNF neutralizing antibodies prevented experimental cerebral malaria (ECM) [8]. Mice with a combined inactivation of TNF and LTa were to be resistant to ECM development [9]. Recent data suggest that LTa rather than TNF is responsible for the development of microvascular damage resulting in the neurological malaria complication [10]. Lymphotoxin alpha is a member of TNF superfamily and the closest TNF relative. It exists as a soluble homotrimer (LTa3) or forms membrane-bound heterotrimers with the membrane associated lymphotoxin beta (LTb) [11,12]. Both homotrimeric TNF and LTa3 interact with two receptors, TNFR1 (CD120a) and TNFR2 (CD120b), whereas membrane bound LTab heterotrimers function through the engagement of LTbR [13,14]. LTbR binds not only LTab heterotrimers but also LIGHT homotrimers, another TNF family member. Both LIGHT and LTa3 bind herpes virus entry mediator (HVEM), a fourth member of TNFR superfamily. The role of soluble LTa3, of LTab and LIGHT in pathogenesis is not fully understood. Mice with complete inactivation of TNF or TNFR1 gene are unable to mount a protective response against various pathogens [15], but develop ECM, while TNFR2 deficient mice are resistant to PLoS ONE | www.plosone.org 1 July 2008 | Volume 3 | Issue 7 | e2608