Centro de Biotecnologia, Instituto Butantan, Av. Vital Brasil 1500, 05503-900 São Paulo, São Paulo, Brazil.
Parasitol Res. 2011 Jan;108(1):123-35. doi: 10.1007/s00436-010-2045-1. Epub 2010 Sep 18.
Schistosomiasis affects more than 200 million people worldwide; another 600 million are at risk of infection. The schistosomulum stage is believed to be the target of protective immunity in the attenuated cercaria vaccine model. In an attempt to identify genes up-regulated in the schistosomulum stage in relation to cercaria, we explored the Schistosoma mansoni transcriptome by looking at the relative frequency of reads in EST libraries from both stages. The 400 genes potentially up-regulated in schistosomula were analyzed as to their Gene Ontology categorization, and we have focused on those encoding-predicted proteins with no similarity to proteins of other organisms, assuming they could be parasite-specific proteins important for survival in the host. Up-regulation in schistosomulum relative to cercaria was validated with real-time reverse transcription polymerase chain reaction (RT-PCR) for five out of nine selected genes (56%). We tested their protective potential in mice through immunization with DNA vaccines followed by a parasite challenge. Worm burden reductions of 16-17% were observed for one of them, indicating its protective potential. Our results demonstrate the value and caveats of using stage-associated frequency of ESTs as an indication of differential expression coupled to DNA vaccine screening in the identification of novel proteins to be further investigated as potential vaccine candidates.
血吸虫病影响全球超过 2 亿人；另有 6 亿人面临感染风险。减毒尾蚴疫苗模型认为，曼氏血吸虫的童虫期是保护性免疫的靶标。为了确定与尾蚴相关的童虫期上调的基因，我们通过比较两个阶段的 EST 文库中读取的相对频率，探索了曼氏血吸虫转录组。对 400 个可能在童虫期上调的基因进行了基因本体论分类分析，并集中研究了那些编码无相似性预测蛋白的基因，假设它们可能是寄生虫特有的、对在宿主中生存重要的蛋白。对 9 个选定基因中的 5 个（56%）进行了实时逆转录聚合酶链反应（RT-PCR）验证，以验证其在童虫期相对于尾蚴的上调。通过 DNA 疫苗免疫接种和寄生虫挑战，我们测试了它们在小鼠中的保护潜力。其中一个基因的虫体负荷减少了 16-17%，表明其具有保护潜力。我们的结果证明了使用 EST 的阶段相关频率作为差异表达的指示，并结合 DNA 疫苗筛选，用于鉴定新的蛋白质作为进一步研究的潜在疫苗候选物的价值和局限性。
