猪圆环病毒引发的断奶仔猪多系统衰竭综合征致病机理

断奶仔猪多系统衰竭综合征于1997年首次在加拿大西部发现,随后许多国家报道了本病的存在和发生,相继证实该病是由圆环病毒科(Circoviridae)猪圆环病毒2型(Porcinecircovirus 2,PCV-2)引起的。PMWS典型特征是全身性淋巴肿大。病毒感染后引发机体免疫抑制,可继发多种病原混合感染。经证实,PCV2感染对胸腺淋巴细胞的损伤在PMWS致病机理中发挥主导作用,巨噬细胞和树突状细胞浆内PCV-2检出率较高,但至今还不清楚哪些细胞亚群最先被PCV-2感染并提供了病毒复制的场所。PCV-2与细小病毒一样,需要依赖细胞生长S周期合成的聚合酶复制。许多研究者试图通过加强抗原刺激以提高进入S周期细胞数,却很难提高病毒在细胞培养中的增殖量。文章着重阐述PCV-2感染引发PMWS的致病机理以及未来需要开拓的研究方向。

Pathogenesis of Postweaning Multisystemic Wasting Syndrome Caused by Porcine circovirus

Postweaning multisystemic wasting syndrome(PMWS) was a disease of pigs first recognised in North America in 1997 and subsequently reported worldwide.It is caused by Porcine circovirus 2(PCV-2),a member of the family Circoviridae.The most consistent feature of PMWS is the generalized Lymphadenectasis.Secondary infections with mult-organisms are common for the immunesuppression caused by the virus.There is evidence that the destruction of thymic lymphocytes has a central role in the pathogenesis of PMWS.There is a high detection rate of virus in matrophages and dentritic cells.It remains unknown which cells are primarily infected and are permissive for the replication of PCV2.Macrophages and dendritic cells commonly contain virus in their cytoplasm but may not be the primary source of the large amounts of virus found in tissues of diseased pigs.There is evidence that PCV-2,like mammalian parvoviruses,requires cells in the S phase of the cell cycle for replication.It is difficult to reproduce PMWS experimentally although some protocols have been developed which involve antigenic stimulation with other agents that presumably increase the number of permissive cells entering S phase of the cell cycle.In addition to reviewing the literature on the pathagenesis of PMWS caused by PCV-2,attempts are made to identify key unresolved areas that should be the focus of future research.