Morales Jorge, Chiu Hsiling, Oo Thiri, Plaza Rosemary, Hoskins Sally, Govind Shubha
Biology Program, The Graduate School and University Center of The City University of New York, 365 Fifth Avenue, New York, NY 10016, USA.
J Insect Physiol. 2005 Feb;51(2):181-95. doi: 10.1016/j.jinsphys.2004.11.002.
Drosophila melanogaster larvae are attacked by virulent strains of parasitoid wasps. Females of Leptopilina heterotoma produce virus-like particles (VLPs) that efficiently destroy lamellocytes, a major larval immune effector cell type. We report here that L. victoriae, a closely related wasp species, also produces VLPs that trigger immune suppression responses in fly hosts. We compare the ability of immune suppression of the two parasitoids using a mutant host strain hopscotch(Tumorous-lethal) (hop(Tum-l)). hop(Tum-l) larvae have two defects of hematopoietic origin: overproliferation of hemocytes and constitutive encapsulation of self-tissue by lamellocytes. The encapsulation phenotype is suppressed weakly by L. victoriae and strongly by L. heterotoma. In vitro studies on hop(Tum-l) lamellocytes show that VLP-containing fluid from either wasp species induces lamellocyte lysis, but with different kinetics. Previously undocumented precursors of L. victoriae VLPs are synthesized in the long gland and are first visible within canals connecting secretory cells to the long gland lumen. VLP assembly occurs in the lumen. VLPs show multiple electron-dense projections surrounding a central core. Maturing particles appear segmented, singly or in arrays, embedded in the reservoir matrix. In sections, mature particles are pentagonal or hexagonal; the polygon vertices extending into spikes. Our results suggest that L. victoriae is likely to promote immune suppression by an active mechanism that is mediated by VLPs, similar to that used by L. heterotoma.
黑腹果蝇幼虫会受到寄生蜂毒性菌株的攻击。异角细蜂的雌性会产生病毒样颗粒（VLP），这些颗粒能有效破坏片层细胞，片层细胞是幼虫主要的免疫效应细胞类型。我们在此报告，一种近缘黄蜂物种维多利亚细蜂也会产生能在果蝇宿主中引发免疫抑制反应的VLP。我们使用突变宿主品系跳房子（肿瘤致死）（hop（Tum-l））来比较这两种寄生蜂的免疫抑制能力。hop（Tum-l）幼虫有两个造血起源的缺陷：血细胞过度增殖以及片层细胞对自身组织的组成性包囊。维多利亚细蜂对包囊表型的抑制作用较弱，而异角细蜂的抑制作用较强。对hop（Tum-l）片层细胞的体外研究表明，来自任何一种黄蜂的含VLP液体都会诱导片层细胞裂解，但动力学不同。此前未被记录的维多利亚细蜂VLP前体在长腺中合成，最初在连接分泌细胞与长腺管腔的管道内可见。VLP组装发生在管腔内。VLP显示出围绕中心核心的多个电子致密突起。成熟颗粒呈单个或成阵列的分段状，嵌入储存基质中。在切片中，成熟颗粒呈五边形或六边形；多边形顶点延伸成尖刺。我们的结果表明，维多利亚细蜂可能通过一种由VLP介导的主动机制促进免疫抑制，这与异角细蜂所使用的机制类似。
