牡蛎疱疹病毒对魁蚶的致病性

Pathogenicity of Ostreid herpesvirus-1 to Scapharca broughtonii

为探明牡蛎疱疹病毒（Os HV-1）对魁蚶的致病性,本研究使用发病魁蚶组织制作病毒悬液进行感染实验。感染实验分为空白组、阴性悬液注射组和病毒悬液注射组,并使用实时定量PCR法对感染后魁蚶体内病毒的时空分布进行检测。实验结果显示,空白组和阴性悬液组魁蚶感染后未检测到病毒粒子,病毒悬液注射组魁蚶经人工感染后,各部位病毒含量均呈先上升再下降随后又上升的趋势,最终达到10^6拷贝/ng DNA左右。通过电镜观察,在感染魁蚶的鳃、肝胰腺、外套膜中出现染色质边缘化甚至消失,细胞核肿胀、溶解,核仁消失,核膜扩张、不清晰,线粒体肿大,脊崩解,核糖体脱落等一系列细胞病理变化。在其细胞核和细胞质中均能发现大量直径为90～110 nm球形病毒粒子,该病毒粒子具囊膜,囊膜内可见均匀高电子密度的核衣壳,与自然发病魁蚶负染电镜中的病毒粒子形态相同。研究结果表明,Os HV-1可以感染魁蚶并与魁蚶大规模死亡有直接相关关系;魁蚶感染Os HV-1后机体产生应激反应,对Os HV-1有一定抑制作用,但其作用机制还有待进一步实验验证。

To better understand the pathogenesis of the Ostreid Herpesvirus-1（Os HV-1） to blood clam,experimental infection was conducted by injecting filtered tissue homogenate into the gastropod of each calm.Experimental clams were randomly allocated into 3 groups： blank control group, negative contral group, Os HV-1infected group. After the experiment, the temporal distribution patterns of Os HV-1 infection loads in six different tissues were assayed with quantitative PCR（q PCR）. No virus was detected in clams injected with sea water and the negative control tissue homogenate. While virus DNA were detected in animals injected with tissue homogenate prepared from naturally infected clams. The virus DNA loads in tissues fluctuated first, and then reached about 106 copies viral DNA per ng of total DNA. Pathological changes including lysed connective tissue, dilation of the digestive tubules, eosinophilic inclusion bodies, nuclear chromatin margination and pyknosis were found in affected animals. Transmission electron microscopy（TEM） revealed herpes-like viral particles within the connective tissue of the mantle. These viral particles were about 90-110 nm in diameter with an electron-dense nucleoid packaged in capsid, which resembled those found in naturally infected clams. Overall, this work demonstrated the pathogenesis of Os HV-1 to blood clams and closely associated with the mass mortality of them.Additionally, our work also indicated the stress reaction after injecting Os HV-1 might play a role in the suppression of Os HV-1 replication, while the mechanisms need to be further studied.