title: Interrogating the Plasmodium Sporozoite Surface: Identification of Surface-Exposed Proteins and Demonstration of Glycosylation on CSP and TRAP by Mass Spectrometry-Based Proteomics.
abstract: Malaria parasite infection is initiated by the mosquito-transmitted sporozoite stage, a highly motile invasive cell that targets hepatocytes in the liver for infection. A promising approach to developing a malaria vaccine is the use of proteins located on the sporozoite surface as antigens to elicit humoral immune responses that prevent the establishment of infection. Very little of the P. falciparum genome has been considered as potential vaccine targets, and candidate vaccines have been almost exclusively based on single antigens, generating the need for novel target identification. The most advanced malaria vaccine to date, RTS,S, a subunit vaccine consisting of a portion of the major surface protein circumsporozoite protein (CSP), conferred limited protection in Phase III trials, falling short of community-established vaccine efficacy goals. In striking contrast to the limited protection seen in current vaccine trials, sterilizing immunity can be achieved by immunization with radiation-attenuated sporozoites, suggesting that more potent protection may be achievable with a multivalent protein vaccine. Here, we provide the most comprehensive analysis to date of proteins located on the surface of or secreted by Plasmodium falciparum salivary gland sporozoites. We used chemical labeling to isolate surface-exposed proteins on sporozoites and identified these proteins by mass spectrometry. We validated several of these targets and also provide evidence that components of the inner membrane complex are in fact surface-exposed and accessible to antibodies in live sporozoites. Finally, our mass spectrometry data provide the first direct evidence that the Plasmodium surface proteins CSP and TRAP are glycosylated in sporozoites, a finding that could impact the selection of vaccine antigens.
authors.affiliation: Institute for Systems Biology, Seattle, Washington, United States of America.
authors.forename: Kristian E
authors.identifier: 0000-0002-6756-4471
authors.initials: KE
authors.lastname: Swearingen
authors.affiliation: Center for Infectious Disease Research, formerly Seattle Biomedical Research Institute, Seattle, Washington, United States of America.|Center for Malaria Research, Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Lindner
authors.affiliation: Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Lirong
authors.initials: L
authors.lastname: Shi
authors.affiliation: Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Shears
authors.affiliation: Center for Infectious Disease Research, formerly Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Anke
authors.initials: A
authors.lastname: Harupa
authors.affiliation: Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Christine S
authors.initials: CS
authors.lastname: Hopp
authors.affiliation: Center for Infectious Disease Research, formerly Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Vaughan
authors.affiliation: Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Springer
authors.affiliation: Institute for Systems Biology, Seattle, Washington, United States of America.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Moritz
authors.affiliation: Center for Infectious Disease Research, formerly Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Stefan H I
authors.initials: SH
authors.lastname: Kappe
authors.affiliation: Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Photini
authors.initials: P
authors.lastname: Sinnis
mesh_terms: D000818:Animals; D009033:Culicidae; D005455:Fluorescent Antibody Technique; D006031:Glycosylation; D016778:Malaria, Falciparum / Q000378:metabolism*; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D030781:Organisms, Genetically Modified; D040901:Proteomics / Q000379:methods*; D015800:Protozoan Proteins / Q000032:analysis* / Q000378:metabolism*; D034101:Sporozoites / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D015800:Protozoan Proteins; C041595:circumsporozoite protein, Protozoan; C069428:thrombospondin-related adhesive protein, protozoan