Serine protease inhibitors (serpins) are a broadly distributed protease superfamily in various organisms, which participate in the negative regulation of melanization in insects. Our pervious study demonstrated that induced melanization by Heliothis virescens ascovirus 3h is helpful for HvAV-3h viral replication. In this study, the serpin-2.1 like gene from Spodoptera exigua (Seserpin-2.1 like) which is a specific serpin after HvAV-3h infection was identified. Seserpin-2.1 like has the typical characteristics of serpin proteins family. Seserpin-2.1 like widely distributed in various tissues (including hemolymph, fat body, midgut, cuticle and head), and expressed at a higher level in fat body, hemolymph and head. At different developmental stages, it tends to express at eggs and 5th instar larvae. Seserpin-2.1 like shows special phenomenon for HvAV-3h infection. On the one hand, the transcription level of Seserpin-2.1 like in hemolymph was significantly upregulated after HvAV-3h compared to other immune challenges Gram-positive bacteria (Bacillus thuringiensis), Gram-negative bacteria (Escherichia coli), and Baculovirus (Autographa californica nucleopolyhedrovirus). On the other hand, its expression disappeared during 72 to 120 h post infection. In summary, our results suggest that Seserpin-2.1 like may be involved in innate immunity of S. exigua after infection with HvAV-3h. And HvAV-3h may inhibit the expression of Seserpin-2.1 like to promote the melanization of host larvae for viral replication.

丝氨酸蛋白酶抑制剂（serpins）是各种生物中广泛分布的蛋白酶超家族，它们参与昆虫黑色素的负调控。我们以前的研究表明，由Heliosthis virescens杆状病毒3h诱导的黑色素化有助于HvAV-3h病毒复制。在这项研究中，来自斜纹夜蛾的Serpin-2.1相似基因（Seserpin-2.1相似）是一种特定的Serpin在鉴定出HvAV-3h感染后。Seserpin-2.1类似物具有serpin蛋白家族的典型特征。Seserpin-2.1广泛分布于各种组织（包括淋巴，脂肪，中肠，表皮和头部），并在脂肪，淋巴和头部中以较高的水平表达。在不同的发育阶段，它倾向于在卵和五龄幼虫中表达。像Seserpin-2.1一样显示HvAV-3h感染的特殊现象。一方面，与其他免疫攻击革兰氏阳性细菌（苏云金芽孢杆菌），革兰氏阴性细菌（大肠杆菌）和杆状病毒（杆状病毒）相比，HvAV-3h后血淋巴中Seserpin-2.1的转录水平显着上调。加利福尼亚州的Autographa californica核多角体病毒）。另一方面，其表达在感染后72至120小时内消失。总之，我们的研究结果表明，Seserpin-2.1等可能在先天免疫参与甜菜夜蛾感染HvAV-后3h。HvAV-3h可能抑制Seserpin-2.1的表达，从而促进宿主幼虫的黑色素化，从而促进病毒复制。