title: Prediction and characterization of helper T-cell epitopes from pneumococcal surface adhesin A.
abstract: Pneumococcal surface adhesin A (PsaA) is a multifunctional lipoprotein known to bind nasopharyngeal epithelial cells, and is significantly involved in bacterial adherence and virulence. Identification of PsaA peptides that optimally bind human leucocyte antigen (HLA) and elicit a potent immune response would be of great importance to vaccine development. However, this is hindered by the multitude of HLA polymorphisms in humans. To identify the conserved immunodominant epitopes, we used an experimental dataset of 28 PsaA synthetic peptides and in silico methods to predict specific peptide-binding to HLA and murine MHC class II molecules. We also characterized spleen and cervical lymph node (CLN) -derived T helper (Th) lymphocyte cytokine responses to these peptides after Streptococcus pneumoniae strain EF3030 challenge in mice. Individual, yet overlapping, peptides 15 amino acids in length revealed residues of PsaA that consistently caused the highest interferon-γ, interleukin-2 (IL-2), IL-5 and IL-17 responses and proliferation as well as moderate IL-10 and IL-4 responses by ex vivo re-stimulated splenic and CLN CD4⁺ T cells isolated from S. pneumoniae strain EF3030-challenged F1 (B6 × BALB/c) mice. In silico analysis revealed that peptides from PsaA may interact with a broad range of HLA-DP, -DQ and -DR alleles, due in part to regions lacking β-turns and asparagine endopeptidase sites. These data suggest that Th cell peptides (7, 19, 20, 22, 23 and 24) screened for secondary structures and MHC class II peptide-binding affinities can elicit T helper cytokine and proliferative responses to PsaA peptides.
authors.affiliation: Department of Microbiology, Biochemistry, & Immunology, Morehouse School of Medicine, Atlanta, GA, USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Singh
authors.forename: Pranav
authors.initials: P
authors.lastname: Gupta
authors.forename: Praveen K
authors.initials: PK
authors.lastname: Sharma
authors.forename: Edwin W
authors.initials: EW
authors.lastname: Ades
authors.forename: Susan K
authors.initials: SK
authors.lastname: Hollingshead
authors.forename: Shailesh
authors.initials: S
authors.lastname: Singh
authors.forename: James W
authors.initials: JW
authors.lastname: Lillard
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation; D018920:Coculture Techniques; D018604:Epitope Mapping; D018984:Epitopes, T-Lymphocyte; D061252:Feeder Cells; D005260:Female; D006680:HLA Antigens / Q000276:immunology / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism; D006801:Humans; D016056:Immunodominant Epitopes; D007371:Interferon-gamma / Q000378:metabolism; D007378:Interleukins / Q000378:metabolism; D008198:Lymph Nodes / Q000276:immunology / Q000382:microbiology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011008:Pneumococcal Infections / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013154:Spleen / Q000276:immunology / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000276:immunology* / Q000378:metabolism; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D018984:Epitopes, T-Lymphocyte; D006680:HLA Antigens; D000949:Histocompatibility Antigens Class II; D016056:Immunodominant Epitopes; D007378:Interleukins; C051592:pneumococcal surface protein A; D007371:Interferon-gamma
keywords: MHC; Streptococcus pneumoniae; T helper type 1/2 cytokine; peptide vaccine