Imajoh Masayuki, Hirayama Takeshi, Oshima Syun-ichirou
Laboratory of Cell Structure and Function, Division of Marine Bioresource Science, Graduate School of Kuroshio Science, Kochi University, Nankoku Kochi 783-8502, Japan.
Fish Shellfish Immunol. 2005 Feb;18(2):163-77. doi: 10.1016/j.fsi.2004.07.002.
Infectious pancreatic necrosis virus (IPNV), a member of the genus Aquabirnavirus and family Birnaviridae, is an unenveloped icosahedral virus with two segments of double-stranded RNA. IPNV causes acute infection in salmonid fry and fingerlings with high mortality. However, this mortality is low as the age increases and survivors become IPNV-carrier fish. In this study, IPNV persistent infection was established in rainbow trout with no clinical signs or mortality. TUNEL staining and immunohistochemistry showed that IPNV antigen-positive cells did not have an apoptotic nucleus in almost all tissue sections and leucocyte smears, indicating that apoptosis was not induced in IPNV antigen-positive cells. The IPNV genome detected by in situ RT-PCR was more frequent than detection of the IPNV antigen by immunohistochemistry in the kidney, spleen, and liver. This result implies that the successive replication would not occur in many IPNV-infected cells. Further, apoptotic cells were predominant in the tissue sections where the signal-positive cells were frequently detected. Therefore, the presence of apoptosis in this study might be associated with host defense mechanisms, which eliminates IPNV-infected cells by the recognition of IPNV genome at the early stage of infection.
传染性胰腺坏死病毒（IPNV）是水生双RNA病毒属和双RNA病毒科的成员，是一种无包膜的二十面体病毒，含有两段双链RNA。IPNV可导致鲑科鱼苗和鱼种发生急性感染，死亡率很高。然而，随着年龄增长，死亡率会降低，幸存者会成为携带IPNV的鱼。在本研究中，在虹鳟鱼中建立了IPNV持续感染，且无临床症状或死亡情况。TUNEL染色和免疫组织化学显示，在几乎所有组织切片和白细胞涂片中，IPNV抗原阳性细胞都没有凋亡核，这表明IPNV抗原阳性细胞未被诱导凋亡。在肾脏、脾脏和肝脏中，原位RT-PCR检测到的IPNV基因组比免疫组织化学检测到的IPNV抗原更频繁。这一结果表明，在许多受IPNV感染的细胞中不会发生连续复制。此外，在频繁检测到信号阳性细胞的组织切片中，凋亡细胞占主导地位。因此，本研究中凋亡的存在可能与宿主防御机制有关，宿主防御机制通过在感染早期识别IPNV基因组来清除受IPNV感染的细胞。
