适应性免疫被认为是脊椎动物特有的免疫防御体系。有颌类脊椎动物的适应性免疫以免疫球蛋白和T细胞受体为基础，而无颌类脊椎动物是以可变淋巴细胞受体（VLR）为基础。自七鳃鳗VLR被首次报道以来，在棘皮动物和头索动物中也相继发现VLR类似基因，使得该基因的起源和进化问题备受关注。然而，目前仍缺少VLR基因起源和进化的有力证据，也未能清楚解析其在无脊椎动物免疫系统中的功能。申请人前期从对虾转录组中发现与七鳃鳗VLR基因具有较高相似性的转录本，其表达特征暗示着其与对虾的免疫相关。本项目拟全面解析对虾VLR类似基因（LvVLR-like）的结构特征，阐明不同病原刺激产生LvVLR-like基因转录本的多样性及其功能活性，探讨其与已报道的对虾“免疫记忆”现象的关系，明确其表达调控机制。相关研究成果不但可丰富无脊椎动物免疫学的基础理论，为对虾的病害防治提供指导，而且也可为VLR基因的起源和进化提供重要依据。

Adaptive immunity is regarded as the specific immune defense system in vertebrates. The adaptive immunity in jawed vertebrates depends on the immunoglobulins and T cell receptors, while it relies on diverse variable lymphocyte receptors (VLRs) in jawless vertebrates. Since the first report of VLR genes in lamprey, VLR like genes were then identified in echinoderm and cephalochordate, which had brought the issues of the origin and evolution of VLR gene into high focus. However, there is no strong evidence to elucidate the origin and evolution of VLR gene yet. The functions of VLR like genes in the immune system of invertebrates are not clear till present. Recently, we isolated a VLR-like gene transcript (LvVLR-like) from the transcriptome of Litopenaeus vannamei. The amino acid sequences encoded by LvVLR-like gene shared a high similarity to the lamprey VLR and the expression patterns of LvVLR-like gene indicated its possible involvement in the shrimp immunity. The present study will comprehensively elucidate the gene structure of LvVLR-like gene. The diversity of LvVLR-like gene transcripts and their functions in shrimp after infection by various pathogens will be studied. The relationship between LvVLR-like gene and the reported phenomenon of “immunological memory” in penaeid shrimp will be explored. The regulatory mechanism of LvVLR-like gene expression will be defined. The data will not only enrich our knowledge on the immunity of invertebrates to provide theoretical guidance for disease control of penaeid shrimp, but also give more information for clarifying the origin and evolution mechanism of VLR gene.