Prohibition of occurrence of viral diseases in the silkworm reared with artificial diet

本课题的一系列研究从化学物质、生理条件、不同营养条件和环境调控等方面对家蚕病毒感染的机理进行了新的认识。结果表明：(1)建立了蚕幼期和全期人工饲粮饲养方法。这两种方法对家蚕病毒学的基础研究和应用研究具有重要意义。(2)为研究蚕种生物洁净室（BCR）饲养新体系，研制了一套微生物测定试剂盒。微生物在BCR中的分布规律得到了明确，但一旦引入/发生在BCR中的微生物被认为很难追踪和去除。(3)对densonnucleosis病毒-2 （DNV-2）感染的家蚕进行了高温处理，结果表明，高温处理后，DNV-2可翻译mrna的表达量明显增加。因此，这表明病毒病的条件可以由环境因素控制。(4)建立了细胞质多角体病毒易感细胞系。血清素和5-羟色氨酸被认为是促进中肠运动的因素，导致幼虫对病毒病的抵抗力增强。(5)人工饲料对DNV的敏感性比桑叶饲料高10倍。将感染DNV的小细胞在蜕皮时排入肠腔，位于中肠中部的再生细胞发育成新的上皮细胞进行生理修复。家蚕中肠细胞的再生能力主要与幼虫对DNV感染的抗性有关。(6)盐酸胍（GH）可抑制感染性乳头状瘤病毒（IFV）引起的感染性乳头状瘤的发生。利用无细胞转导系统，GH抑制了ifv感染的中肠中病毒特异性可翻译mrna和结构多肽的积累。因此，我们认为生长激素对IFV感染的主要作用之一是抑制病毒输入基因组RNA的翻译。(7)一般认为，人工饲料饲养的幼虫比桑叶饲养的幼虫更容易感染核型多角体病毒，这取决于肠道液中抗病毒活性较低。研究表明，肠道液中的蛋白酶活性与抗病毒活性密切相关，表明病毒通过中肠感染的易感性因饮食性质而异。少

The series of studies in this project presented the novel understandings on the mechanis of virus infection of the silkworm in which mod-ulation of the infection by chemicals, physiological conditions, diff-erent neutrient condition of diet, and environmental regulation were conducted. The following conclusions were obtained: (1) The rearing metho using artificial diet during young silkworm stage and whole stage had been established.The both rearing procedures of the silk- worm were very useful for the basic and applied studies of the Bombyx-virology. (2) For the study of new rearing system of the silkworm using a bioclean room (BCR), an assay kit for surveying micobes was developed. The distributing patterns of microbes in BCR were clarfied, but microbes once instroduced/ occuurred in a BCR was considered to be difficult with tracing and removing them. (3) A study on a densonucleosis virus-2 (DNV-2) infected silkworm treated with a high temperature showed that inhibition of an accumul … More ation of translatable mRNAs occurred after that treatment. Therefore, it is demomstrated that a condition of viral desease could be controlled by environmental factors. (4) Several cell lines susceptible for the cyto plasmic polyhedrosis virus were established. Serotnine and 5-hydroxytryptophane were recognized as promoting facters of midgut motility resulting that resistance of larvae against viral disease increased. (5) DNV susceptibility in larvae fed on artificial diets were higher 10 times comparison with that in those fed on mulberry leaves. The DNV infected-midget cells were discharged into the gut lumen at molting and regenerative cell located midi of the midgut developed into new epithelial cells for the physiological repair.The regenerative ability of the midgut cells is mainly concerned with the resistance of the silkworm larvae to the infection of DNV. (6) Guanidine hydrochloride (GH) had been demonstrated to supress the incidence of infectious flacherie caused by infectious flacherie virus (IFV). Using a cell-free trasnaltion system, it was clarified that GH inhibits the accumulation of virus-specific translatable mRNAs and structural polypeptides in the IFV-infected midgut. Therefore, it was suggested that one of the primary function of GH action on the IFV infection is the inhibition of translation of input genomic RNA of the virus. (7) It is generally said that larvae reared on artificial diet were more susceptible to a nuclear-polyhedrosis virus than those reared on mulberry leaves, depending on lower antiviral activity in the gut juice. The study indicated that the protease activity in gut juice was highly concerned with the antiviral activity, suggesting difference susceptibility of virus infection through midgut depending on nature of diets. Less