经有效 TLR 佐剂配方制成的动合子和子孢子穿透蛋白（CelTOS）可诱导产生高亲和力抗体，从而抑制冈比亚按蚊感染疟原虫。

Cell-traversal protein for ookinetes and sporozoites (CelTOS) formulated with potent TLR adjuvants induces high-affinity antibodies that inhibit Plasmodium falciparum infection in Anopheles stephensi.

机构信息

Malaria and Vector Research Group (MVRG), Biotechnology Research Center (BRC), Pasteur Institute of Iran, Pasteur Avenue, P.O. Box 1316943551, Tehran, Iran.

出版信息

Malar J. 2019 Apr 24;18(1):146. doi: 10.1186/s12936-019-2773-3.

BACKGROUND

Plasmodium falciparum parasite is the most deadly species of human malaria, and the development of an effective vaccine that prevents P. falciparum infection and transmission is a key target for malarial elimination and eradication programmes. P. falciparum cell-traversal protein for ookinetes and sporozoites (PfCelTOS) is an advanced vaccine candidate. A comparative study was performed to characterize the immune responses in BALB/c mouse immunized with Escherichia coli-expressed recombinant PfCelTOS (rPfCelTOS) in toll-like receptor (TLR)-based adjuvants, CpG and Poly I:C alone or in combination (CpG + Poly I:C), followed by the assessment of transmission-reducing activity (TRA) of anti-rPfCelTOS antibodies obtained from different vaccine groups in Anopheles stephensi.

METHODS

The aim of the current work was achieved by head-to-head comparison of the vaccine groups using conventional and avidity enzyme-linked immunosorbent assay (ELISA), immunofluorescence test (IFAT), and standard membrane feeding assay (SMFA).

RESULTS

Comparing to rPfCelTOS alone, administration of rPfCelTOS with two distinct TLR-based adjuvants in vaccine mouse groups showed a significant increase in responses (antibody level, IgG subclass analysis, avidity, and Th1 cytokines) and was able to induce reasonable transmission-reducing activity. Also, comparable functional activity of anti-rPfCelTOS antibodies was found in group that received antigen in either CpG or Poly I:C (69.9%/20% and 73.5%/24.4%, respectively, reductions in intensity/prevalence). However, the vaccine group receiving rPfCelTOS in combination with CpG + Poly I:C showed a significant induction in antibody titers and inhibitory antibodies in oocysts development (78.3%/19.6% reductions in intensity/prevalence) in An. stephensi.

CONCLUSIONS

A key finding in this investigation is that rPfCelTOS administered alone in BALB/c mouse is poorly immunogenic, with relatively low IgG level, avidity, inhibitory antibodies, and mixed Th1/Th2 responses. However, immunological characteristic (IgG level, cytophilic IgG2a and IgG2b, avidity, and Th1 cytokines) and TRA of anti-rPfCelTOS significantly enhanced in the presence of co-administration of TLR-based adjuvants, confirming that targeting TLRs would be an effective means for the enhancement of inducing TRA against rPfCelTOS.

背景

恶性疟原虫是最致命的人类疟疾寄生虫，开发一种有效预防恶性疟原虫感染和传播的疫苗是消除和消灭疟疾规划的关键目标。恶性疟原虫卵母细胞和孢子虫穿透蛋白（PfCelTOS）是一种先进的疫苗候选物。进行了一项比较研究，以表征用大肠杆菌表达的重组 PfCelTOS（rPfCelTOS）在 Toll 样受体（TLR）佐剂、CpG 和 Poly I:C 单独或联合（CpG+Poly I:C）免疫的 BALB/c 小鼠中的免疫反应，然后评估来自不同疫苗组的抗 rPfCelTOS 抗体在按蚊中的传播减少活性（TRA）。

方法

本工作通过对常规和亲和酶联免疫吸附试验（ELISA）、免疫荧光试验（IFAT）和标准膜喂养试验（SMFA）的疫苗组进行头对头比较来实现目标。

结果

与单独使用 rPfCelTOS 相比，rPfCelTOS 与两种不同的 TLR 佐剂联合使用的疫苗组显示出显著增加的反应（抗体水平、IgG 亚类分析、亲和性和 Th1 细胞因子），并能够诱导合理的传播减少活性。此外，在接受 CpG 或 Poly I:C 中抗原的两组中发现抗 rPfCelTOS 抗体具有相当的功能活性（分别减少强度/流行率 69.9%/20%和 73.5%/24.4%）。然而，rPfCelTOS 与 CpG+Poly I:C 联合使用的疫苗组在按蚊的卵囊中发育中显著诱导了抗体滴度和抑制性抗体（强度/流行率分别降低 78.3%/19.6%）。

结论

本研究的一个关键发现是，单独在 BALB/c 小鼠中给予 rPfCelTOS 免疫原性差，IgG 水平、亲和性、抑制性抗体和混合 Th1/Th2 反应相对较低。然而，在 TLR 佐剂联合给药的情况下，抗 rPfCelTOS 的免疫特征（IgG 水平、嗜细胞性 IgG2a 和 IgG2b、亲和性和 Th1 细胞因子）和 TRA 显著增强，证实靶向 TLR 是增强诱导抗 rPfCelTOS TRA 的有效手段。