Studies on receptors of animal lentiviruses

动物体内存在多种慢病毒，包括猫免疫缺陷病毒（FIV）和猴免疫缺陷病毒（SIV），感染动物可出现免疫缺陷综合征、脑炎和血液系统疾病等各种症状。为了了解慢病毒感染动物的发病机制，研究病毒包膜与病毒受体之间的相互作用是很重要的。今年，我们开展了FIV env基因异质性和病毒致病潜力分析的研究。首先，采用巢式PCR方法从一只脑炎猫的大脑、淋巴结和骨髓中扩增出FIV env基因（V3-V6区），并测定了这些克隆的核苷酸序列。从这些组织中获得的15个病毒克隆由一个统一的病毒群体组成，表明在这种情况下，来自单个克隆的病毒传播。值得注意的是，该病例的毒株（JN-BR1）与此前日本分离株（TM2毒株）序列相似性较低，但与Petaluma毒株非常接近，具有神经致病性。其次，FIV env基因同样从表现出骨髓抑制的猫的相同组织中扩增出来。该病例组织的16个克隆在氨基酸序列上的遗传异质性高达11.1%。由于16个克隆中有5个在V3和V5区域含有帧内停止密码子，因此它们被认为是复制缺陷并与发病机制有关。虽然TM2毒株已被证明属于B亚型，但本病例的病毒毒株（PTH-BM3毒株）被发现属于a亚型，其中包括几种致病性fiv。

There are a number of lentiviruses including feline immunodeficiency virus (FIV) and simian immunodeficiency virus (SIV) in animals, and various symptoms such as immunodeficiency syndrome, encephalitis and hematological disorders are recognized in the infected animals. To understand the pathogenesis by lentiviurs infection in animals, it is important to examine the interaction between virus envelope and virus receptor. In this year, our study was carried out to analyze the heterogeneity of FIV env gene and the pathogenic potential of the viruses. First, FIV env genes (V3-V6 region) were amplified by nested PCR from the cerebrum, lymph node and bone marrow of a cat with encephalitis, and the nucleotide sequences of these clones were determined. Fifteen viral clones obtained from these tissues were composed of a uniform viral population, indicating that viruses from a single clone were spread in this case. It was noteworthy that the virus strain from this case (JN-BR1 strain) showed a low sequence similarity with a previous Japanese isolate (TM2 strain), but was very close to Petaluma strain showing a neuropathogenicity. Second, FIV env genes were similarly amplified from the same tissues of a cat showing myelosupression. Marked genetic heterogeneity as high as 11.1% in their amino acid sequences was observed among the 16 clones from the tissues of this case. Since 5 of the 16 clones contained in-frame stop codons in the V3 and V5 regions, they were considered to be replication-defective and associated with the pathogenesis. Although the TM2 strain has been shown to belong to the subtype B,the virus strain from this case (PTH-BM3 strain) was found to be a member of subtype A which includes several pathogenic FIVs.