牡蛎疱疹病毒致病性差异的遗传学基础

Ostreid herpesvirus 1 (OsHV-1) has been associated with mass mortalities of cultured bivalves such as Zhikong scallops (Chlamys farreria) and Pacific oysters (Crassostrea gigas) around the world since 1990s. Primary studies indicated that strain differentiation has occurred in OsHV-1 populations associated with the variation of its epidemiologic features such as virulence, but little is known about the underlying genetic basis and evolutionary mechanisms. Currently, only a few studies concerned about strain differentiations of the virus depending primarily on a single genetic locus, and thus blamed for low resolution. In view of this problem, the proposed project will firstly complete the genome sequences of OsHV-1 variants with typical epidemiological features. Then a high-resolution genotyping system covering multiple genetic loci will be established by comparing and analyzing of the genomic sequences of different variants of OsHV-1. And the strain differentiation status of OsHV-1 infected bivalve mollusks in China will be analyzed with the established genotyping system. Finally, the correlation between the genetic variations of OsHV-1 and its pathogenic features such as disease outbreaks and mortalities will be determined, and employed to decode the genetic basis underlying pathogenic divergence of OsHV-1.

牡蛎疱疹病毒（Ostreid herpesvirus 1，OsHV-1）自上世纪90年代以来，在全球范围内引起养殖栉孔扇贝和长牡蛎等双壳贝类的大规模死亡。初步研究表明，OsHV-1近年来发生了明显的株系分化，并伴随着其致病力等流行病学特征的改变。然而，目前对导致这些变化的遗传学基础及其演化机制所知甚少；个别研究OsHV-1株系分化的工作主要建立在单一分子标记上，存在分辨力不足的缺陷。鉴于此，本课题首先拟对流行病学特征具代表性的OsHV-1变异株进行全基因组测序。然后基于不同变异株全基因组比对结果，筛选分子标记位点，建立OsHV-1高分辨力株系鉴定与分型系统；并利用该系统对历年来感染我国贝类的OsHV-1株系分化情况进行分析。最后，结合贝类发病和死亡等流行病学调查数据，对OsHV-1基因变异特征与其致病性特征进行关联分析，揭示OsHV-1致病性发生变异的遗传学基础，推测其分子演化机制。

牡蛎疱疹病毒(Ostreid herpesvirus 1, OsHV-1)是引起双壳贝类疱疹病毒病的病原，该病毒自1991年首次报道以来，在全球多个国家传播、流行，范围覆盖亚洲、欧洲、美洲及大洋洲多个国家，给双壳贝类养殖业造成无可估量的经济损失。该病毒1997年以及2012年OsHV-1及其变异珠分别引起我国北方海区养殖栉孔扇贝（Chlamys farreri）和魁蚶（Scapharca broughtonii）的大规模死亡。我们通过本项目，建立了一套基于长片段PCR技术的贝类疱疹病毒基因组高通量测序方法，并利用该方法完成了6个OsHV-1变异珠和1株Haliotid herpesvirus 1 (HaHV-1) 的基因组测序；利用本项目获取和已发布的贝类疱疹病毒基因组序列进行系统发育分析，我们发现OsHV-1株系分化主要受宿主范围而非地理隔离影响。推测HaHV-1 1999年起源于福建地区，2003年传到台湾，2005年随鲍饲料传到澳大利亚。基于不同变异株基因组序列比对结果，构建了OsHV-1基因分型系统，并应用于感染我国贝类OsHV-1的株系分化研究；发现感染我国贝类的OsHV-1发生了较大的变异。对OsHV-1重要变异珠魁蚶株（OsHV-1-SB）的致病性、基因组序列及其相关性进行初步研究；基于不同变异株基因组序列比对结果，筛选到一个高度保守位点，并据此建立了可检测OsHV-1不同变异株的PCR方法。

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