title: Measurement of ex vivo ELISpot interferon-gamma recall responses to Plasmodium falciparum AMA1 and CSP in Ghanaian adults with natural exposure to malaria.
abstract: BACKGROUND
  Malaria eradication requires a concerted approach involving all available control tools, and an effective vaccine would complement these efforts. An effective malaria vaccine should be able to induce protective immune responses in a genetically diverse population. Identification of immunodominant T cell epitopes will assist in determining if candidate vaccines will be immunogenic in malaria-endemic areas. This study therefore investigated whether class I-restricted T cell epitopes of two leading malaria vaccine antigens, Plasmodium falciparum circumsporozoite protein (CSP) and apical membrane antigen-1 (AMA1), could recall T cell interferon-γ responses from naturally exposed subjects using ex vivo ELISpot assays.
  
  
  METHODS
  Thirty-five subjects aged between 24 and 43 years were recruited from a malaria-endemic urban community of Ghana in 2011, and their peripheral blood mononuclear cells (PBMCs) were tested in ELISpot IFN-γ assays against overlapping 15mer peptide pools spanning the entire CSP and AMA1 antigens, and 9-10mer peptide epitope mixtures that included previously identified and/or predicted human leukocyte antigen (HLA) class 1-restricted epitopes from same two antigens.
  
  
  RESULTS
  For CSP, 26 % of subjects responded to at least one of the nine 15mer peptide pools whilst 17 % responded to at least one of the five 9-10mer HLA-restricted epitope mixtures. For AMA1, 63 % of subjects responded to at least one of the 12 AMA1 15mer peptide pools and 51 % responded to at least one of the six 9-10mer HLA-restricted epitope mixtures. Following analysis of data from the two sets of peptide pools, along with bioinformatics predictions of class I-restricted epitopes and the HLA supertypes expressed by a subset of study subjects, peptide pools that may contain epitopes recognized by multiple HLA supertypes were identified. Collectively, these results suggest that natural transmission elicits ELISpot IFN-γ activities to class 1-restricted epitopes that are largely HLA-promiscuous.
  
  
  CONCLUSIONS
  These results generally demonstrate that CSP and AMA1 peptides recalled ELISpot IFN-γ responses from naturally exposed individuals and that both CSP and AMA1 contain diverse class 1-restricted epitopes that are HLA-promiscuous and are widely recognized in this population.
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. harini.d.ganeshan.ctr@mail.mil.
authors.forename: Harini
authors.initials: H
authors.lastname: Ganeshan
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. akusi@noguchi.ug.edu.gh.
authors.forename: Kwadwo A
authors.initials: KA
authors.lastname: Kusi
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. danum@noguchi.ug.edu.gh.
authors.forename: Dorothy
authors.initials: D
authors.lastname: Anum
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. michael.hollingdale.ctr@mail.mil.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hollingdale
authors.affiliation: La Jolla Institute for Allergy and Immunology, La Jolla, San Diego, CA, USA. bpeters@liai.org.
authors.forename: Bjoern
authors.initials: B
authors.lastname: Peters
authors.affiliation: La Jolla Institute for Allergy and Immunology, La Jolla, San Diego, CA, USA. ykim@liai.org.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. jtetteh@noguchi.ug.edu.gh.
authors.forename: John K A
authors.initials: JK
authors.lastname: Tetteh
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. mofori@noguchi.ug.edu.gh.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Ofori
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. bgyan@noguchi.ug.edu.gh.
authors.forename: Ben A
authors.initials: BA
authors.lastname: Gyan
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. kkoram@noguchi.ug.edu.gh.
authors.forename: Kwadwo A
authors.initials: KA
authors.lastname: Koram
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. jun.huang.ctr@mail.mil.
authors.forename: Jun
authors.initials: J
authors.lastname: Huang
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. maria.n.belmonte.ctr@mail.mil.
authors.forename: Maria
authors.initials: M
authors.lastname: Belmonte
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. joglenna.g.banania.ctr@mail.mil.
authors.forename: Jo Glenna
authors.initials: JG
authors.lastname: Banania
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana. ddodoo@noguchi.ug.edu.gh.
authors.forename: Daniel
authors.initials: D
authors.lastname: Dodoo
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. eileen.d.villasante.civ@mail.mil.
authors.forename: Eileen
authors.initials: E
authors.lastname: Villasante
authors.affiliation: Malaria Department, Naval Medical Research Center, Silver Spring, MD, USA. martha.sedegah.civ@mail.mil.
authors.forename: Martha
authors.initials: M
authors.lastname: Sedegah
mesh_terms: D000328:Adult; D019295:Computational Biology; D058501:Enzyme-Linked Immunospot Assay; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D008288:Malaria / Q000276:immunology* / Q000378:metabolism*; D008297:Male; D010963:Plasmodium falciparum / Q000276:immunology*; D015800:Protozoan Proteins / Q000276:immunology*; D055815:Young Adult
chemical_list: D015800:Protozoan Proteins; D007371:Interferon-gamma
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