Identification of minimal human MHC-restricted CD8+ T-cell epitopes within the Plasmodium falciparum circumsporozoite protein (CSP)

Malaria Journal

Research

Yohan Kim¹  Bjoern Peters¹  Alessandro Sette¹  Denise L Doolan²  Harini Ganeshan³  Fouzia Farooq³  Michael R Hollingdale³  Jo Glenna Banania³  Jun Huang³  Martha Sedegah³  Esteban Abot³  Maria Belmonte³  Cindy Tamminga³  Shannon McGrath³  Thomas L Richie³  Eileen Villasante³  Lorraine Soisson⁴  Carter Diggs⁴ 

[1] La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA;Queensland Institute of Medical Research, Brisbane, Queensland, Australia;US Military Malaria Vaccine Program, Naval Medical Research Center, Walter Reed Army Institute of Research, Silver Spring, MD, USA;USAID, Washington, DC, USA;

关键词: Malaria;    Vaccine;    Circumsporozoite protein;    ELISpot;    Flow cytometry;    NetMHC;    Epitope mapping;    Class I restriction;    Localization;   

DOI  :  10.1186/1475-2875-12-185

 received in 2013-03-02, accepted in 2013-05-23,  发布年份 2013

来源: Springer

【 摘 要 】

BackgroundPlasmodium falciparum circumsporozoite protein (CSP) is a leading malaria vaccine candidate antigen, known to elicit protective antibody responses in humans (RTS,S vaccine). Recently, a DNA prime / adenovirus (Ad) vector boost vaccine encoding CSP and a second P. falciparum antigen, apical membrane antigen-1, also elicited sterile protection, but in this case associated with interferon gamma ELISpot and CD8+ T cell but not antibody responses. The finding that CSP delivered by an appropriate vaccine platform likely elicits protective cell-mediated immunity provided a rationale for identifying class I-restricted epitopes within this leading vaccine candidate antigen.MethodsLimited samples of peripheral blood mononuclear cells from clinical trials of the Ad vaccine were used to identify CD8+ T cell epitopes within pools of overlapping 15mer peptides spanning portions of CSP that stimulated recall responses. Computerized algorithms (NetMHC) predicted 17 minimal class I-restricted 9-10mer epitopes within fifteen 15mers positive in ELISpot assay using PBMC from 10 HLA-matched study subjects. Four additional epitopes were subsequently predicted using NetMHC, matched to other study subjects without initial 15mer ELISpot screening. Nine of the putative epitopes were synthesized and tested by ELISpot assay, and six of these nine were further tested for CD8+ T cell responses by ELISpot CD4+ and CD8+ T cell-depletion and flow cytometry assays for evidence of CD8+ T cell dependence.ResultsEach of the nine putative epitopes, all sequence-conserved, recalled responses from HLA-matched CSP-immunized research subjects. Four shorter sequences contained within these sequences were identified using NetMHC predictions and may have contributed to recall responses. Five (9-10mer) epitopes were confirmed to be targets of CD8+ T cell responses using ELISpot depletion and ICS assays. Two 9mers among these nine epitopes were each restricted by two HLA supertypes (A01/B07; A01A24/A24) and one 9mer was restricted by three HLA supertypes (A01A24/A24/B27) indicating that some CSP class I-restricted epitopes, like DR epitopes, may be HLA-promiscuous.ConclusionsThis study identified nine and confirmed five novel class I epitopes restricted by six HLA supertypes, suggesting that an adenovirus-vectored CSP vaccine would be immunogenic and potentially protective in genetically diverse populations.

【 授权许可】

CC BY   
© Sedegah et al.; licensee BioMed Central Ltd. 2013