title: Phagosomal Acidification Prevents Macrophage Inflammatory Cytokine Production to Malaria, and Dendritic Cells Are the Major Source at the Early Stages of Infection: IMPLICATION FOR MALARIA PROTECTIVE IMMUNITY DEVELOPMENT.
abstract: Inflammatory cytokines produced at the early stages of malaria infection contribute to shaping protective immunity and pathophysiology. To gain mechanistic insight into these processes, it is important to understand the cellular origin of cytokines because both cytokine input and cytokine-producing cells play key roles. Here, we determined cytokine responses by monocytes, macrophages, and dendritic cells (DCs) to purified Plasmodium falciparum and Plasmodium berghei ANKA, and by spleen macrophages and DCs from Plasmodium yoelii 17NXL-infected and P. berghei ANKA-infected mice. The results demonstrate that monocytes and macrophages do not produce inflammatory cytokines to malaria parasites and that DCs are the primary source early in infection, and DC subsets differentially produce cytokines. Importantly, blocking of phagosomal acidification by inhibiting vacuolar-type H(+)-ATPase enabled macrophages to elicit cytokine responses. Because cytokine responses to malaria parasites are mediated primarily through endosomal Toll-like receptors, our data indicate that the inability of macrophages to produce cytokines is due to the phagosomal acidification that disrupts endosomal ligand-receptor engagement. Macrophages efficiently produced cytokines to LPS upon simultaneously internalizing parasites and to heat-killed Escherichia coli, demonstrating that phagosomal acidification affects endosomal receptor-mediated, but not cell surface receptor-mediated, recognition of Toll-like receptor agonists. Enabling monocytes/macrophages to elicit immune responses to parasites by blocking endosomal acidification can be a novel strategy for the effective development of protective immunity to malaria. The results have important implications for enhancing the efficacy of a whole parasite-based malaria vaccine and for designing strategies for the development of protective immunity to pathogens that induce immune responses primarily through endosomal receptors.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033.
authors.forename: Xianzhu
authors.initials: X
authors.lastname: Wu
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033.
authors.forename: Nagaraj M
authors.initials: NM
authors.lastname: Gowda
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 gowda@psu.edu.
authors.forename: D Channe
authors.identifier: http://orcid.org/0000-0002-6860-5108
authors.initials: DC
authors.lastname: Gowda
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D016207:Cytokines / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology* / Q000473:pathology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007249:Inflammation / Q000276:immunology / Q000473:pathology; D008288:Malaria / Q000276:immunology* / Q000473:pathology; D051379:Mice; D010588:Phagosomes / Q000276:immunology* / Q000473:pathology; D010961:Plasmodium / Q000276:immunology*; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000276:immunology
chemical_list: D016207:Cytokines; D025262:Vacuolar Proton-Translocating ATPases
keywords: cytokine induction; inflammation; innate immunity; macrophage; malaria; phagocytosis; plasmodium; vacuolar acidification