Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana.
Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, Legon, Accra, Ghana.
PLoS One. 2020 Feb 10;15(2):e0228177. doi: 10.1371/journal.pone.0228177. eCollection 2020.
Sterile protection against malaria, most likely mediated by parasite-specific CD8+ T cells, has been achieved by attenuated sporozoite vaccination of animals as well as malaria-naïve and malaria-exposed subjects. The circumsporozoite protein (CSP)-based vaccine, RTS,S, shows low efficacy partly due to limited CD8+ T cell induction, and inclusion of such epitopes could improve RTS,S. This study assessed 8-10mer CSP peptide epitopes, present in predicted or previously positive P. falciparum 3D7 CSP 15mer overlapping peptide pools, for their ability to induce CD8+ T cell IFN-γ responses in natural malaria-exposed subjects.
Cryopreserved PBMCs from nine HLA-typed subjects were stimulated with 23 8-10mer CSP peptides from the 3D7 parasite in IFN-ɣ ELISpot assays. The CD8+ T cell specificity of IFN-γ responses was confirmed in ELISpot assays using CD8+ T cell-enriched PBMC fractions after CD4+ cell depletion.
Ten of 23 peptide epitopes elicited responses in whole PBMCs from five of the nine subjects. Four peptides tested positive in CD8+ T cell-enriched PBMCs from two previously positive responders and one new subject. All four immunodominant peptides are restricted by globally common HLA supertypes (A02, A03, B07) and mapped to regions of the CSP antigen with limited or no reported polymorphism. Association of these peptide-specific responses with anti-malarial protection remains to be confirmed.
The relatively conserved nature of the four identified epitopes and their binding to globally common HLA supertypes makes them good candidates for inclusion in potential multi-epitope malaria vaccines.
通过对动物进行减毒孢子虫疫苗接种以及对无疟疾和有疟疾暴露史的受试者进行接种，已经实现了对疟疾的无菌保护，这种保护很可能是由寄生虫特异性 CD8+T 细胞介导的。基于环子孢子蛋白（CSP）的疫苗 RTS,S 的疗效较低，部分原因是 CD8+T 细胞的诱导有限，包含这些表位可以改善 RTS,S。本研究评估了预测或先前为阳性的 Pf3D7 CSP15mer 重叠肽池中存在的 8-10 个 CSP 肽表位，以评估其在天然疟疾暴露的受试者中诱导 CD8+T 细胞 IFN-γ 反应的能力。
用 IFN-γ ELISpot 试验对来自 9 个 HLA 定型的受试者的冷冻保存的 PBMCs 进行了 23 个 3D7 寄生虫的 8-10 个 CSP 肽刺激。在 CD4+细胞耗竭后，使用 CD8+T 细胞富集的 PBMC 分数在 ELISpot 试验中证实了 IFN-γ 反应的 CD8+T 细胞特异性。
23 个肽表位中有 10 个在来自 9 个受试者中的 5 个的全 PBMC 中产生了反应。在来自 2 个先前阳性应答者和 1 个新受试者的 CD8+T 细胞富集的 PBMC 中，4 个肽呈阳性。所有 4 个免疫优势肽都受到全球常见 HLA 超型（A02、A03、B07）的限制，并且映射到 CSP 抗原的区域，这些区域的多态性有限或没有报道。这些肽特异性反应与抗疟保护的关联仍有待证实。
所鉴定的 4 个表位的相对保守性质及其与全球常见 HLA 超型的结合，使它们成为潜在的多表位疟疾疫苗的良好候选物。
