Supporting data for "Giardia Secretome Highlights Secreted Tenascins as a Key Component of Pathogenesis"

Giardia is a protozoan parasite of public health relevance that causes gastroenteritis in a wide range of hosts. Two genetically distinct lineages (assemblages A and B) are responsible for the human disease. Although it is clear that differences in virulence occur, pathogenesis and virulence of Giardia remains poorly understood.
The genome of Giardia is believed to contain ORFs which could encode as many as 6,000 proteins. By successfully applying quantitative proteomic analyses to the whole parasite and to the supernatants derived from parasite culture of assemblages A and B, we confirm expression of ~1,600 proteins from each assemblage, the vast majority of which being common to both lineages. To look for signature enrichment of secreted proteins, we considered the ratio of proteins in the supernatant compared with the pellet which defined a small group of enriched proteins, putatively secreted at a steady state by cultured growing trophozoites of both assemblages. This secretome is enriched with proteins annotated to have N-terminal signal peptide. The most abundant secreted proteins include known virulence factors such as cathepsin B cysteine proteases and members of a Giardia superfamily of cysteine rich proteins which comprises VSPs, HCMPs and a new class of virulence factors, the Giardia tenascins. We demonstrate that physiological function of human enteric epithelial cells is disrupted by such soluble factors even in the absence of the trophozoites.
We are able to propose a straightforward model of Giardia pathogenesis incorporating key roles for the major Giardia derived soluble mediators.

贾第虫（Giardia）是一类具有公共卫生意义的原生动物寄生虫，可在多种宿主中引发胃肠炎。目前已知两种遗传分化的谱系（群A与群B）是导致人类感染发病的元凶。尽管已有研究明确其毒力存在差异，但贾第虫的致病机制与毒力特征仍有待深入阐明。
贾第虫的基因组被认为包含多达6000个可编码蛋白质的开放阅读框 (Open Reading Frame, ORF)。本研究通过对群A和群B的完整寄生虫及其培养上清液开展定量蛋白质组学分析，证实两个群各自约有1600种蛋白质得以表达，其中绝大多数为二者共有的保守蛋白。为探寻分泌蛋白的特征富集模式，我们以培养上清与寄生虫沉淀中的蛋白质丰度比值作为筛选依据，鉴定出一小部分富集蛋白，推测它们是两种群体外培养的增殖滋养体 (trophozoite) 在稳态下分泌的产物。该分泌组 (secretome) 富含带有N端信号肽的蛋白质，其中丰度最高的分泌蛋白包括已知的毒力因子，如组织蛋白酶B半胱氨酸蛋白酶，以及贾第虫富半胱氨酸蛋白超家族成员，该超家族包含变异表面蛋白 (Variant Surface Proteins, VSPs)、富半胱氨酸膜蛋白 (High Cysteine Membrane Proteins, HCMPs) 以及一类新型毒力因子——贾第虫腱生蛋白 (Giardia tenascins)。
研究证实，即使不依赖滋养体本身，这类可溶性因子即可破坏人类肠道上皮细胞的生理功能。
基于上述结果，我们提出了一个简洁的贾第虫致病模型，该模型明确了贾第虫来源的主要可溶性介质在致病过程中的关键作用。