Nearly 20% of cultured shrimp die every year due to viral diseases. In this study, we evaluated the capacity of nanoparticulate RNA interference (RNAi) to down-regulate genes in Penaeus vannamei shrimp and protect shrimp against white spot syndrome virus (WSSV, i.e. white spot disease). Using a reporter target gene, Rab7, we show that the length of the administered dsRNA correlates with gene knockdown. We found that 250 bp-long dsRNA strands knocked down gene expression most effectively, followed by 125 and 70 bp-long strands. The 21 bp long strands did not downregulate the gene. We also show gene downregulation to be concentration dependent. Even at low RNA concentrations of 0.01 μg per gram-body-weight gene knockdown exceeded 80%. Knockdown levels were similar in multiple organs, including the gills, gut, hepato-pancreas, pleopods and muscle. Gene knockdown lasted for one month, after which gene expression recuperated. To protect the RNA molecules from enzymatic degradation, we complexed the RNA with the cationic polysaccharide chitosan, forming 90–200 nm particles that facilitated efficient RNAi in vivo. In a double-blinded viral challenge test, RNAi targeting viral-protein 28 (VP28) protected the shrimp against WSSV infection. Survival of animals treated with RNAi nanoparticles exceeded 95% compared to no survival in the untreated controls. Nanoparticulate RNAi is an effective modality for protecting against viral diseases.

中文翻译：

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抗病毒RNAi纳米颗粒可保护虾免受白斑病侵害

每年有近20％的养殖对虾因病毒性疾病而死亡。在这项研究中，我们评估了纳米颗粒RNA干扰（RNAi）下调对虾南美白对虾基因和保护虾免受白斑综合症病毒（WSSV，即WSSV）的能力。白斑病）。使用报道分子的靶基因，Rab7，我们证明了所给予的dsRNA的长度与基因敲低相关。我们发现250 bp长的dsRNA链最有效地敲低了基因表达，其次是125和70 bp长的链。21 bp的长链没有下调基因。我们还显示基因下调是浓度依赖性的。即使在每克体重0.01μg的低RNA浓度下，基因敲除也超过80％。在多个器官，包括腮，肠，肝胰腺，腹足和肌肉中，击倒水平相似。基因敲低持续了一个月，此后基因表达恢复了。为了保护RNA分子免于酶促降解，我们将RNA与阳离子多糖壳聚糖复合，形成90-200 nm的颗粒，从而促进了有效的RNAi。体内。在双盲病毒攻击试验中，靶向病毒蛋白28（VP28）的RNAi保护虾免受WSSV感染。与未经处理的对照组相比，无RNAi纳米粒子治疗的动物的存活率超过95％。纳米颗粒RNAi是预防病毒性疾病的有效方法。