人工感染IBDV鸡法氏囊的电镜研究

ELECTRON MICROSCOPY OF BURSA OF FABRICIUS EXPERIMENTALLY INFECTED WITH INFECTIOUS BURSAL DISEASE VIRUS

通过透射电镜系统观察了人工感染传染性法氏囊病病毒（ＩＢＤＶ）后鸡法氏囊各类细胞的病理变化。感染后１２～２４ｈ，病毒粒子主要见于髓质淋巴细胞中，细胞中可见到大量纤维样病毒发生基质及无囊膜包围的大型病毒晶格，细胞核染色质浓缩，核中出现纤维样结构。感染后３６ｈ，淋巴细胞开始大量裂解死亡。无囊膜包围的病毒晶格也出现于髓质网状细胞中，被感染的网状细胞并不裂解，而表现出细胞凋亡的特征：染色质固缩呈颗粒块状，胞质浓缩，最终被巨噬细胞吞噬。病毒粒子同样大量出现于巨噬细胞、网状上皮细胞、粒细胞和扁平上皮细胞的吞噬囊泡中，但未出现病毒复制的特征。我们的结果显示法氏囊髓质部的未成熟淋巴细胞是ＩＢＤＶ的最适靶细胞，ＩＢＤＶ感染可引起法氏囊淋巴细胞的大量坏死，同时诱导髓质部网状细胞凋亡。

The sequential morphological events of the bursa of Fabricius were examined by transmission electron microscope in specific pathogen free chickens experimentally infected with infectious bursal disease virus(IBDV).By 12h post infection(PI),small number of virus particles,arranged in a crystalloid pattern but not surrounded by a membrane,were observed in the cytoplasm of a few lymphoid cells in the medulla of the follicles.The number of virus containing cells markedly increased at 24h PI,especially in the medulla.In the cytoplasm of infected lymphoid cells,large amount of fibrous structure appeared among which immature virus particles of lesser density were observed.With further process of the disease,the infected cells exhibited increased degenerative changes,including condensation of nuclelus,appearence of large amount of intranuclear filaments and eventually complete disintegration.Crystalline arrayed virus particles without a surrounding membrane were also detected in medullary reticulum cells,as well as small amount of fibre similar to that found in lymphocytes,indicating the multiplication of the virus.The infected reticulum cells,however,showed the character of apoptosis instead of necrosis,with extensive chromatin clumping and cytoplasmic condensation.IBDV induced apoptosis in the bursa of Fabricius may play a role in the pathogenesis of the disease.Virus particles were also found within phagocytic or autophagic vacuoles of macrophages,heterphils,reticular epithelial cells and flat corticomedullary epithelial cells,but no sign of virus replication was detected.