Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.
PLoS Negl Trop Dis. 2019 Apr 22;13(4):e0007345. doi: 10.1371/journal.pntd.0007345. eCollection 2019 Apr.
Human hookworms (Necator americanus, Ancylostoma duodenale, and Ancylostoma ceylanicum) are intestinal blood-feeding parasites that infect ~500 million people worldwide and are among the leading causes of iron-deficiency anemia in the developing world. Drugs are useful against hookworm infections, but hookworms rapidly reinfect people, and the parasites can develop drug resistance. Therefore, having a hookworm vaccine would be of tremendous benefit.
METHODOLOGY/PRINCIPAL FINDINGS: We investigated the vaccine efficacy in outbred Syrian hamsters of three A. ceylanicum hookworm antigen candidates from two classes of proteins previously identified as promising vaccine candidates. These include two intestinally-enriched, putatively secreted cathepsin B cysteine proteases (AceyCP1, AceyCPL) and one small Kunitz-type protease inhibitor (AceySKPI3). Recombinant proteins were produced in Pichia pastoris, and adsorbed to Alhydrogel. Recombinant AceyCPL (rAceyCPL)/Alhydrogel and rAceySKPI3/Alhydrogel induced high serum immunoglobulin G (IgG) titers in 8/8 vaccinates, but were not protective. rAceyCP1/Alhydrogel induced intermediate serum IgG titers in ~60% of vaccinates in two different trials. rAceyCP1 serum IgG responders had highly significantly decreased hookworm burdens, fecal egg counts and clinical pathology compared to Alhydrogel controls and nonresponders. Protection was highly correlated with rAceyCP1 serum IgG titer. Antisera from rAceyCP1 serum IgG responders, but not nonresponders or rAceyCPL/Alhydrogel vaccinates, significantly reduced adult A. ceylanicum motility in vitro. Furthermore, rAceyCP1 serum IgG responders had canonical Th2-specific recall responses (IL4, IL5, IL13) in splenocytes stimulated ex vivo.
CONCLUSIONS/SIGNIFICANCE: These findings indicate that rAceyCP1 is a promising vaccine candidate and validates a genomic/transcriptomic approach to human hookworm vaccine discovery.
人类钩虫（Necator americanus、Ancylostoma duodenale 和 Ancylostoma ceylanicum）是寄生在肠道内吸食血液的寄生虫，全球约有 5 亿人感染此类寄生虫，是发展中国家缺铁性贫血的主要病因之一。药物对钩虫感染有一定疗效，但钩虫会迅速重新感染人体，且寄生虫可能产生耐药性。因此，开发钩虫疫苗将具有巨大的益处。
方法/主要发现：我们在叙利亚仓鼠这一近交系中，对先前鉴定出的两类有希望的候选疫苗蛋白中的三种 A. ceylanicum 钩虫抗原候选物进行了疫苗有效性研究。这些候选物包括两种肠内丰富的、推测分泌的组织蛋白酶 B 半胱氨酸蛋白酶（AceyCP1、AceyCPL）和一种小 Kunitz 型蛋白酶抑制剂（AceySKPI3）。重组蛋白在巴斯德毕赤酵母中表达，并与氢氧化铝凝胶吸附。重组 AceyCPL（rAceyCPL）/氢氧化铝凝胶和 rAceySKPI3/氢氧化铝凝胶在 8/8 名接种者中诱导出高血清免疫球蛋白 G（IgG）滴度，但没有保护作用。rAceyCP1/氢氧化铝凝胶在两项不同试验中约 60%的接种者中诱导出中等血清 IgG 滴度。rAceyCP1 血清 IgG 应答者的钩虫负荷、粪便卵计数和临床病理学与氢氧化铝对照组和非应答者相比显著降低。保护作用与 rAceyCP1 血清 IgG 滴度高度相关。rAceyCP1 血清 IgG 应答者的抗血清，但非应答者或 rAceyCPL/氢氧化铝凝胶接种者的抗血清，在体外显著降低了成年 A. ceylanicum 的运动性。此外，rAceyCP1 血清 IgG 应答者的脾细胞经体外刺激后具有典型的 Th2 特异性回忆反应（IL4、IL5、IL13）。
结论/意义：这些发现表明 rAceyCP1 是一种很有前途的疫苗候选物，并验证了一种基于基因组/转录组的人类钩虫疫苗发现方法。
