The Onchocerca volvulus cysteine proteinase inhibitor, Ov-CPI-2, is a target of protective antibody response that increases with age.
The Onchocerca volvulus cysteine proteinase inhibitor, Ov-CPI-2, is a target of protective antibody response that increases with age.
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DOI：
10.1371/journal.pntd.0000800
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发表时间：
2010-08-24
影响因子：
3.8
通讯作者：
Lustigman S
中科院分区：
文献类型：
--
作者：
Cho-Ngwa F;Liu J;Lustigman S
尽管付出了巨大的努力，针对盘尾丝虫感染的合适疫苗仍然难以找到。在此，我们报告了使用分子工具来识别和表征可能与盘尾丝虫病伴随免疫的发展相关的盘旋盘丝虫抗原。使用来自可能已产生这种免疫力的慢性感染患者的血清库筛选了第三阶段幼虫 (L3) 和蜕皮 L3 (mL3) 盘旋丝虫阶段特异性 cDNA 文库。分离出的 87 个免疫反应克隆被分为 20 种不同的蛋白质，其中 12 种之前已被克隆和/或表征，4 种已被证明在小型盘旋丝虫动物模型中具有保护作用。其中之一，盘曲霉素 (Ov-CPI-2)，一种先前鉴定的盘旋丝虫半胱氨酸蛋白酶抑制剂，总体而言，是 L3 和 mL3 cDNA 文库中免疫血清识别的最丰富的克隆。为了进一步表征其与保护性免疫的关系，我们测量了生活在喀麦隆高流行地区的推定免疫 (PI) 和感染 (INF) 个体对抗原的 IgG 亚类和 IgE 类特异性反应。两组对抗原的 IgG3 和 IgE 反应相似，但 INF 的 IgG1 和 IgG4 反应显着高于 PI 个体 (p<0.05)。在INF组中，IgG3水平随着感染者年龄的增长而显着增加（r = 0.241；p<0.01）。无论年龄如何，INF 中的 IgG1 反应都很高。值得注意的是，在抗 Ov-CPI-2 单特异性人抗体和幼稚中性粒细胞存在的情况下体外培养 L3 几乎完全抑制了 L3 向 L4 的蜕皮以及对幼虫的细胞毒性。这些结果增加了对盘尾丝虫病保护性免疫的了解，并支持抗 Ov-CPI-2 IgG1 和/或 IgG3 亲细胞抗体可能参与 PI 和 INF 保护性免疫的发展。结果进一步支持将 Ov-CPI-2 作为抗 L3 疫苗的主要靶点的考虑。盘尾丝虫病是一种慢性且高度衰弱的人类疾病，由盘尾丝虫引起。这种蠕虫可以在人体内存活15年以上。该疾病主要影响皮肤和眼睛，是全球第二大导致失明的传染性原因。目前没有疫苗可以预防这种感染。现有药物可以短期缓解症状，但无法治愈感染。为了预防感染，需要针对第三阶段感染性幼虫 L3 或发育中的幼虫的疫苗。这些阶段被证明是生活在盘尾丝虫病流行地区的个体产生的保护性免疫的目标。一种类型的保护性免疫已被证明会随着年龄的增长而发展，称为伴随免疫。在本研究中，我们鉴定了许多可能与这种免疫的发展有关的幼虫抗原。这些抗原中最突出的是 Ov-CPI-2，也称为盘曲霉素，此前已被证明是一种有前途的候选疫苗。该抗原被进一步表征并证实可能也是随着年龄增长而在感染个体中产生的免疫保护的目标，被称为伴随免疫。
Despite considerable efforts, a suitable vaccine against Onchocerca volvulus infection has remained elusive. Herein, we report on the use of molecular tools to identify and characterize O. volvulus antigens that are possibly associated with the development of concomitant immunity in onchocerciasis. Third-stage larvae (L3) and molting L3 (mL3) O. volvulus stage-specific cDNA libraries were screened with a pool of sera from chronically infected patients who had likely developed such immunity. The 87 immunoreactive clones isolated were grouped into 20 distinct proteins of which 12 had already been cloned and/or characterized before and 4 had been proven to be protective in a small O. volvulus animal model. One of these, onchocystatin (Ov-CPI-2), a previously characterized O. volvulus cysteine proteinase inhibitor was, overall, the most abundant clone recognized by the immune sera in both the L3 and mL3 cDNA libraries. To further characterize its association with protective immunity, we measured the IgG subclass and IgE class specific responses to the antigen in putatively immune (PI) and infected (INF) individuals living in a hyperendemic area in Cameroon. It appeared that both groups had similar IgG3 and IgE responses to the antigen, but the INF had significantly higher IgG1 and IgG4 responses than the PI individuals (p<0.05). In the INF group, the IgG3 levels increased significantly with the age of the infected individuals (r = 0.241; p<0.01). The IgG1 responses in the INF were high regardless of age. Notably, culturing L3 in vitro in the presence of anti-Ov-CPI-2 monospecific human antibodies and naïve neutrophils resulted in almost complete inhibition of molting of L3 to L4 and to cytotoxicity to the larvae. These results add to the knowledge of protective immunity in onchocerciasis and support the possible involvement of anti-Ov-CPI-2 IgG1 and/or IgG3 cytophilic antibodies in the development of protective immunity in the PI and the INF. The results further support the consideration of Ov-CPI-2 as a leading target for an anti-L3 vaccine. Onchocerciasis is a chronic and highly debilitating disease of humans caused by a worm called Onchocerca volvulus. This worm can live in the human body for over 15 years. The disease affects mainly the skin and eyes and is the second leading infectious cause of blindness worldwide. There is currently no vaccine to prevent the infection. Available drugs can give short-term relief but cannot cure the infection. To prevent infection, a vaccine against the third-stage infective larva, L3, or the developing larva is required. These stages were shown to be the targets of protective immunity that develops in individuals who live in onchocerciasis endemic regions. One type of protective immunity has been shown to develop with age and is called concomitant immunity. In the present study, we have identified a number of larval antigens that may be associated with the development of such immunity. The most prominent of these antigens was Ov-CPI-2, also called onchocystatin, which had previously been shown to be a promising vaccine candidate. This antigen was further characterized and confirmed to be possibly also a target of immune protection that develops in the infected individuals with age and is referred to as concomitant immunity.