Department of Pathogenic Biology and Immunology, School of Medicine, Yangzhou University, Yangzhou, 225009, People's Republic of China.
National Health Commission Key Laboratory of Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory On Parasite and Vector Control Technology, Jiangsu Provincial Medical Key Laboratory, Jiangsu Institute of Parasitic Diseases, Wuxi, 214064, People's Republic of China.
Parasit Vectors. 2023 Aug 8;16(1):269. doi: 10.1186/s13071-023-05897-9.
Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease has been underestimated. Plasmodium ovale curtisi Duffy binding protein domain region II (PocDBP-RII) is an essential ligand for reticulocyte recognition and host cell invasion by P. ovale curtisi. However, the genomic variation, antigenicity and immunogenicity of PocDBP-RII remain major knowledge gaps.
A total of 93 P. ovale curtisi samples were collected from migrant workers who returned to China from 17 countries in Africa between 2012 and 2016. The genetic polymorphism, natural selection and copy number variation (CNV) were investigated by sequencing and real-time PCR. The antigenicity and immunogenicity of the recombinant PocDBP-RII (rPocDBP-RII) protein were further examined, and the humoral and cellular responses of immunized mice were assessed using protein microarrays and flow cytometry.
Efficiently expressed and purified rPocDBP-RII (39 kDa) was successfully used as an antigen for immunization in mice. The haplotype diversity (Hd) of PocDBP-RII gene was 0.105, and the nucleotide diversity index (π) was 0.00011. No increased copy number was found among the collected isolates of P. ovale curtisi. Furthermore, rPocDBP-RII induced persistent antigen-specific antibody production with a serum IgG antibody titer of 1: 16,000. IFN-γ-producing T cells, rather than IL-10-producing cells, were activated in response to the stimulation of rPocDBP-RII. Compared to PBS-immunized mice (negative control), there was a higher percentage of CD4CD44CD62L T cells (effector memory T cells) and CD8CD44CD62L T cells (central memory T cells) in rPocDBP-RII‑immunized mice.
PocDBP-RII sequences were highly conserved in clinical isolates of P. ovale curtisi. rPocDBP-RII protein could mediate protective blood-stage immunity through IFN-γ-producing CD4 and CD8 T cells and memory T cells, in addition to inducing specific antibodies. Our results suggested that rPocDBP-RII protein has potential as a vaccine candidate to provide assessment and guidance for malaria control and elimination activities.
卵形疟原虫感染分布广泛，但研究较少，因此疾病负担被低估。卵形疟原虫 curtisi 杜菲结合蛋白结构域 II（PocDBP-RII）是卵形疟原虫 curtisi 识别网织红细胞和入侵宿主细胞的必需配体。然而，PocDBP-RII 的基因组变异、抗原性和免疫原性仍是主要的知识空白。
2012 年至 2016 年期间，从从 17 个非洲国家返回中国的移民工人中采集了 93 株卵形疟原虫 curtisi 样本。通过测序和实时 PCR 研究遗传多态性、自然选择和拷贝数变异（CNV）。进一步检测了重组 PocDBP-RII（rPocDBP-RII）蛋白的抗原性和免疫原性，并使用蛋白质微阵列和流式细胞术评估了免疫小鼠的体液和细胞反应。
成功表达和纯化了 39 kDa 的 rPocDBP-RII，可作为小鼠免疫的抗原。PocDBP-RII 基因的单倍型多样性（Hd）为 0.105，核苷酸多样性指数（π）为 0.00011。未发现采集的卵形疟原虫 curtisi 分离株的拷贝数增加。此外，rPocDBP-RII 诱导了持续的抗原特异性抗体产生，血清 IgG 抗体滴度为 1:16000。IFN-γ产生的 T 细胞，而不是 IL-10 产生的细胞，对 rPocDBP-RII 的刺激产生反应。与 PBS 免疫的小鼠（阴性对照）相比，rPocDBP-RII 免疫的小鼠中 CD4CD44CD62L T 细胞（效应记忆 T 细胞）和 CD8CD44CD62L T 细胞（中央记忆 T 细胞）的比例更高。
卵形疟原虫 curtisi 临床分离株的 PocDBP-RII 序列高度保守。rPocDBP-RII 蛋白可通过 IFN-γ产生的 CD4 和 CD8 T 细胞和记忆 T 细胞介导保护性的血期免疫，同时诱导特异性抗体。我们的结果表明，rPocDBP-RII 蛋白具有作为疫苗候选物的潜力，可为疟疾控制和消除活动提供评估和指导。
