Department of Biology, Loyola University Chicago, 1032 W Sheridan Rd, Chicago, IL 60660, USA.
Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD, 20814, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, 6720A Rockledge Drive, Suite 100, Bethesda, USA.
Vaccine. 2023 May 16;41(21):3367-3379. doi: 10.1016/j.vaccine.2023.04.042. Epub 2023 Apr 24.
Recent work demonstrating that asymptomatic carriers of P. falciparum parasites make up a large part of the infectious reservoir highlights the need for an effective malaria vaccine. Given the historical challenges of vaccine development, multiple parasite stages have been targeted, including the sexual stages required for transmission. Using flow cytometry to efficiently screen for P. falciparum gamete/zygote surface reactivity, we identified 82 antibodies that bound live P. falciparum gametes/zygotes. Ten antibodies had significant transmission-reducing activity (TRA) in a standard membrane feeding assay and were subcloned along with 9 nonTRA antibodies as comparators. After subcloning, only eight of the monoclonals obtained have significant TRA. These eight TRA mAbs do not recognize epitopes present in any of the current recombinant transmission-blocking vaccine candidates, Pfs230D1M, Pfs48/45.6C, Pf47 D2 and rPfs25. One TRA mAb immunoprecipitates two surface antigens, Pfs47 and Pfs230, that are expressed by both gametocytes and gametes/zygotes. These two proteins have not previously been reported to associate and the recognition of both by a single TRA mAb suggests the Pfs47/Pfs230 complex is a new vaccine target. In total, Pfs230 was the dominant target antigen, with five of the eight TRA mAbs and 8 of 11 nonTRA gamete/zygote surface reactive mAbs interacting with Pfs230. Of the three remaining TRA mAbs, two recognized non-reduced, parasite-produced Pfs25 and one bound non-reduced, parasite-produced Pfs48/45. None of the TRA mAbs bound protein on an immunoblot of reduced gamete/zygote extract and two TRA mAbs were immunoblot negative, indicating none of the new TRA epitopes are linear. The identification of eight new TRA mAbs that bind epitopes not included in any of the constructs currently under advancement as transmission-blocking vaccine candidates may provide new targets worthy of further study.
最近的研究表明，无症状的恶性疟原虫寄生虫携带者构成了大部分感染源，这凸显了开发有效疟疾疫苗的必要性。鉴于疫苗开发的历史挑战，已经针对多个寄生虫阶段进行了靶向研究，包括传播所需的有性阶段。我们使用流式细胞术来有效地筛选恶性疟原虫配子/合子表面反应性，鉴定出 82 种与活恶性疟原虫配子/合子结合的抗体。10 种抗体在标准膜饲养试验中具有显著的传播减少活性（TRA），并与 9 种非 TRA 抗体一起作为对照进行亚克隆。亚克隆后，只有获得的 8 种单克隆抗体具有显著的 TRA。这 8 种 TRA mAb 不识别当前任何重组传播阻断疫苗候选物（Pfs230D1M、Pfs48/45.6C、Pf47 D2 和 rPfs25）中存在的表位。一种 TRA mAb 免疫沉淀两种表面抗原，Pfs47 和 Pfs230，这两种抗原均由配子和配子/合子表达。这两种蛋白质以前没有被报道过存在关联，并且单一 TRA mAb 同时识别这两种蛋白质表明 Pfs47/Pfs230 复合物是一个新的疫苗靶标。总的来说，Pfs230 是主要的靶抗原，其中 8 种 TRA mAb 中有 5 种和 11 种非 TRA 配子/合子表面反应性 mAb 与 Pfs230 相互作用。剩下的 3 种 TRA mAb 中有 2 种识别未还原的寄生虫产生的 Pfs25，1 种识别未还原的寄生虫产生的 Pfs48/45。TRA mAb 均未结合还原配子/合子提取物的免疫印迹上的蛋白，有 2 种 TRA mAb 免疫印迹为阴性，这表明没有新的 TRA 表位是线性的。鉴定出 8 种新的 TRA mAb，它们结合的表位不包含当前任何作为传播阻断疫苗候选物的构建体，这可能提供了值得进一步研究的新的靶标。
