title: Identification of pre-erythrocytic malaria antigens that target hepatocytes for killing in vivo and contribute to protection elicited by whole-parasite vaccination.
abstract: Pre-erythrocytic malaria vaccines, including those based on whole-parasite approaches, have shown protective efficacy in animal and human studies. However few pre-erythocytic antigens other than the immunodominant circumsporozoite protein (CSP) have been studied in depth with the goal of developing potent subunit malaria vaccines that are suited for use in endemic areas. Here we describe a novel technique to identify pre-erythrocytic malaria antigens that contribute to protection elicited by whole-parasite vaccination in the mouse model. Our approach combines immunization with genetically attenuated parasites and challenge with DNA plasmids encoding for potential protective pre-erythrocytic malaria antigens as luciferase fusions by hydrodynamic tail vein injection. After optimizing the technique, we first showed that immunization with Pyfabb/f-, a P. yoelii genetically attenuated parasite, induces killing of CSP-presenting hepatocytes. Depletion of CD8+ but not CD4+ T cells diminished the killing of CSP-expressing hepatocytes, indicating that killing is CD8+ T cell-dependent. Finally we showed that the use of heterologous prime/boost immunization strategies that use genetically attenuated parasites and DNA vaccines enabled the characterization of a novel pre-erythrocytic antigen, Tmp21, as a contributor to Pyfabb/f- induced protection. This technique will be valuable for identification of potentially protective liver stage antigens and has the potential to contribute to the understanding of immunity elicited by whole parasite vaccination, as well as the development of effective subunit malaria vaccines.
authors.affiliation: Department of Pathogenic Biology, Third Military Medical University, Chongqing, China; Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Gladys J
authors.initials: GJ
authors.lastname: Keitany
authors.affiliation: Department of Pathogenic Biology, Third Military Medical University, Chongqing, China; Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Peng
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Claire
authors.initials: C
authors.lastname: Gibson
authors.affiliation: Department of Pathology, University of Washington, Seattle, Washington, United States of America.
authors.forename: Isaac
authors.initials: I
authors.lastname: Mohar
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Marissa
authors.initials: M
authors.lastname: Vignali
authors.affiliation: Department of Pathology, University of Washington, Seattle, Washington, United States of America; Department of Immunology, University of Washington, Seattle, Washington, United States of America.
authors.forename: Ian N
authors.initials: IN
authors.lastname: Crispe
authors.affiliation: Department of Pathogenic Biology, Third Military Medical University, Chongqing, China.
authors.forename: Fusheng
authors.initials: F
authors.lastname: Huang
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, United States of America; Department of Global Health, University of Washington, Seattle, Washington, United States of America.
authors.forename: Ruobing
authors.initials: R
authors.lastname: Wang
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000276:immunology*; D005260:Female; D022781:Hepatocytes / Q000276:immunology*; D006801:Humans; D017780:Malaria Vaccines / Q000008:administration & dosage / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids; D010961:Plasmodium / Q000276:immunology*
chemical_list: D000953:Antigens, Protozoan; D017780:Malaria Vaccines