Division of Infectious Diseases, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
Int J Nanomedicine. 2023 Jun 8;18:3087-3107. doi: 10.2147/IJN.S406314. eCollection 2023.
Malaria is a devastating infectious illness caused by protozoan parasites. The circumsporozoite protein (CSP) on sporozoites binds heparan sulfate proteoglycan (HSPG) receptors for liver invasion, a critical step for prophylactic and therapeutic interventions.
In this study, we characterized the αTSR domain that covers region III and the thrombospondin type-I repeat (TSR) of the CSP using various biochemical, glycobiological, bioengineering, and immunological approaches.
We found for the first time that the αTSR bound heparan sulfate (HS) glycans through support by a fused protein, indicating that the αTSR is a key functional domain and thus a vaccine target. When the αTSR was fused to the S domain of norovirus VP1, the fusion protein self-assembled into uniform S-αTSR nanoparticles. Three-dimensional structure reconstruction revealed that each nanoparticle consists of an S nanoparticle core and 60 surface displayed αTSR antigens. The nanoparticle displayed αTSRs retained the binding function to HS glycans, indicating that they maintained authentic conformations. Both tagged and tag-free S-αTSR nanoparticles were produced via the system at high yield by scalable approaches. They are highly immunogenic in mice, eliciting high titers of αTSR-specific antibody that bound specifically to the CSPs of sporozoites at high titer.
Our data demonstrated that the αTSR is an important functional domain of the CSP. The S-αTSR nanoparticle displaying multiple αTSR antigens is a promising vaccine candidate potentially against attachment and infection of parasites.
疟疾是一种由原生动物寄生虫引起的破坏性传染病。子孢子上的环子孢子蛋白（CSP）与硫酸乙酰肝素蛋白聚糖（HSPG）受体结合，这是肝脏入侵的关键步骤，也是预防和治疗干预的关键步骤。
在这项研究中，我们使用各种生化、糖生物学、生物工程和免疫学方法，对 CSP 的αTSR 结构域和包含 III 区和血栓反应蛋白型-I 重复（TSR）的区域进行了表征。
我们首次发现αTSR 通过融合蛋白与硫酸乙酰肝素（HS）糖结合，这表明αTSR 是一个关键的功能结构域，因此也是疫苗的靶标。当αTSR 融合到诺如病毒 VP1 的 S 结构域时，融合蛋白会自行组装成均匀的 S-αTSR 纳米颗粒。三维结构重建表明，每个纳米颗粒由一个 S 纳米颗粒核心和 60 个表面展示的αTSR 抗原组成。纳米颗粒展示的αTSR 保留了与 HS 糖结合的功能，表明它们保持了真实的构象。通过可扩展的方法，通过系统可以高效地生产标记和非标记的 S-αTSR 纳米颗粒。它们在小鼠中具有高度的免疫原性，可诱导产生高滴度的αTSR 特异性抗体，该抗体可与高滴度的子孢子 CSP 特异性结合。
我们的数据表明，αTSR 是 CSP 的一个重要功能结构域。展示多个αTSR 抗原的 S-αTSR 纳米颗粒是一种很有前途的疫苗候选物，可能对寄生虫的附着和感染具有预防作用。
