Cathepsin B homologue at the interface between a parasitic nematode and its intermediate host
Cathepsin B homologue at the interface between a parasitic nematode and its intermediate host
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DOI：
10.1128/iai.74.2.1297-1304.2006
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发表时间：
2006-02-01
影响因子：
3.1
通讯作者：
Appleton, JA
中科院分区：
文献类型：
--
作者：
Duffy, MS;Cevasco, DK;Appleton, JA
细细副圆线虫是一种寄生线虫，会导致许多北美鹿科动物和家畜物种出现衰弱性神经系统疾病。我们从感染性幼虫 (D) 中产生了一个基于 PCR 的 cDNA 文库，以鉴定介导寄生的分子。显性 1,250 bp 扩增子编码组织蛋白酶 B 半胱氨酸蛋白酶的同源物。该序列在假定的活性位点中引入了 C29G 取代。针对重组形式产生的抗体在 L3 提取物（而非成虫提取物）的蛋白质印迹分析中检测到天然蛋白 (PtCPR-1)。免疫组织化学方法显示，PtCPR-1 的合成仅限于蜗牛中间宿主 (Triodopsis sp.) 内的幼虫阶段，早在蜗牛感染后 2 天 (dpi) 就开始合成。这种蛋白质存在于肠道和管腔内容物中，并随着时间的推移从幼虫中流失。同时进行的研究表明，幼虫从 1 dpi 开始就诱导了蜗牛的免疫反应。感染后立即形成一层层血细胞包裹幼虫，在慢性感染中寄生虫周围形成肉芽肿样结构。 L3 中 PtCPR-1 的丢失及其在宿主组织中的积累与肉芽肿结构的退化（90 至 105 dpi）同时发生。此时，蜗牛体内出现了完全发育的L3。我们的数据表明 PtCPR-1 参与了幼虫的发育，并可能参与了中间宿主 P. tenuis 的出现。出现的 L3 在干燥和寒冷胁迫下幸存下来，这表明它们可以在环境中保持传染性。促进出现的分子将促进 L3 的扩散并增加传播至最终宿主的可能性。
Parelaphostrongylus tenuis is a parasitic nematode that causes a debilitating neurologic disease in many North American cervids and domestic livestock species. We produced a PCR-based cDNA library from infective larvae (D) in order to identify molecules that mediate parasitism. A dominant 1,250-bp amplicon encoded a homologue of cathepsin B cysteine proteases. The sequence incorporated a C29G substitution in the putative active site. Antibodies generated against a recombinant form detected the native protein (PtCPR-1) in Western blot assays of L3, but not adult worm, extracts. Immunohistochemical methods revealed that PtCPR-1 synthesis was restricted to larval stages within the snail intermediate host (Triodopsis sp.), beginning as early as 2 days postinfection (dpi) of snails. The protein was present in the intestine and luminal contents and was lost from larvae over time. Concurrent studies showed that larvae induced an immune response in snails beginning at 1 dpi. Layers of hemocytes encapsulated larvae immediately after infection, and granuloma-like structures formed around parasites in chronic infections. Loss of PtCPR-1 from L3 and its accumulation in host tissues coincided with degeneration of granuloma architecture 90 to 105 dpi. Fully developed L3 emerged from the snail at this time. Our data implicate PtCPR-1 in larval development and possibly in the emergence of P. tenuis from the intermediate host. Emerged L3 survived desiccation and cold stress, suggesting that they could remain infectious in the environment. Molecules promoting emergence would facilitate dispersal of L3 and increase the likelihood of transmission to definitive hosts.