title: Tandem use of PCR and synthetic peptides to map helper T-cell epitopes on 27-kDa sexual stage antigen of Plasmodium falciparum.
abstract: Monoclonal antibodies recognizing two overlapping linear epitopes (amino acid residues 10 to 25) on the 27-kDa sexual stage antigen of Plasmodium falciparum (Pfg 27) effectively reduce the infectivity of the parasites to mosquitoes. Although malaria transmission-blocking immunity is largely antibody-mediated, T cells play critical roles in the regulation of antibody-secreting B cells. In order to facilitate the development of a malaria transmission-blocking subunit vaccine, studies were undertaken to map epitopes on Pfg 27 recognized by T-helper lymphocytes. Pfg27-specific T-cell hybridoma clones were produced from rPfg27-immunized BALB/c (H-2d) and C57BL/6 (H-2b) mice, and used in studies to map antigenic determinants using PCR-generated Pfg27 gene fragments expressed in E. coli and synthetic peptides based on the Pfg27 sequence. We identified and mapped five distinct T-cell epitopes that are recognized by major histocompatibility complex (MHC) class II-restricted T-cell hybridoma clones. A single peptide (21 residues) was shown to contain two tandem or partially overlapping epitopes recognized by T-cell hybridomas in the context of I-Ad and I-Ab, respectively. Synthetic peptides representing epitopes recognized by T-cell hybridoma clones elicited strong IgG responses in immunized mice, suggesting that T-cells of the helper phenotype were stimulated in vivo by these peptides. These studies represent the first detailed T-cell epitope analysis of a malaria sexual-stage antigen.
authors.affiliation: Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD, USA.
authors.forename: G K
authors.initials: GK
authors.lastname: Koski
authors.forename: I N
authors.initials: IN
authors.lastname: Ploton
authors.forename: R
authors.initials: R
authors.lastname: Viscidi
authors.forename: N
authors.initials: N
authors.lastname: Kumar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000918:Antibody Specificity; D000953:Antigens, Protozoan / Q000276:immunology*; D002999:Clone Cells; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping / Q000379:methods*; D006825:Hybridomas; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D010963:Plasmodium falciparum / Q000276:immunology*; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D010455:Peptides; D015800:Protozoan Proteins; C069962:Pfg25-27 protein, Plasmodium falciparum