Genetic diversity of bovine lentivirus distributed in south Asian countrirs

为了了解牛慢病毒（BIV）的遗传多样性，我们对北海道牛的BIV感染进行了血清学调查，发现10%的反应阳性。从血清阳性动物中分离出3只BIV，从阳性动物的外周血淋巴细胞中提取DNA样本，采用巢式pcr检测BIV前病毒DNA，检测部分pol基因。扩增出一个298 bp的BIV前病毒DNA特异性pol区片段。日本BIV野株扩增片段的核苷酸序列与美国分离株R-29具有99%的同源性。采用巢式PCR扩增日本BIV分离株env基因的C2、V1、V2和C3区。与美国R-29分离株相比，3株分离株的env基因在V1区有几个碱基替换，在V2区有缺失。在柬埔寨，采集了544头牛和43头水牛的样本，牛和水牛的BIV血清阳性率分别为26%和17%。从血清阳性动物中获得5种乙肝病毒原病毒。与美国和日本BIV相比，pol区核苷酸序列高度保守。相比之下，柬埔寨BIV田间分离株的环境区域似乎小于美国分离株。在柬埔寨分离株的V2区观察到核苷酸取代改变氨基酸序列。在赞比亚共获得262份牛血清样本，血清阳性率为11.4%。采用巢式PCR法获得4株乙型肝炎病毒原病毒。这些原病毒的pol区核苷酸序列与美国和日本分离株高度同源（超过97%）。

To understand the genetic diversity of bovine lentivirus (BIV), we have examined serological survey of BIV infection in cattle in Hokkaido and found 10% of positive reactors. From the seropositive animals, 3 BIV were isolated and DNA samples were obtained from peripheral blood lymphocytes of these positive animals for the detection of BIV proviral DNA by nested-PCR to detect a part of the pol gene. A 298-bp pol region fragment specific to BIV proviral DNA was amplified. Nucleotide sequences of the amplified fragments from Japanese BIV field isolates had 99% homology with American isolate, R-29. Amplification of the C2, V1, V2 and C3 regions of the env gene of Japanese BIV isolates were carried out by nested PCR. All 3 isolates seemed to be smaller, several base substitutions were observed in the V1 region and deletions were found in the V2 region of the env gene when compared to that of American R-29 isolate.In Cambodia, samples from 544 cattle and 43 water buffalo were obtained and BIV seropositive rate were 26% in cattle and 17% in water buffalo. Five BIV proviruses were obtained from seropositive animals. Nucleotide sequence of pol region was highly conserved when compared to that of American and Japanese BIV. In contrast, env region of Cambodian BIV field isolates seemed to be smaller than those of American isolates. Nucleotide substitutions which alter amino acid sequences were observed in the V2 region of Cambodian isolates.Total 262 serum samples were obtained from cattle in Zambia and seropositive rate was 11.4%. Four BIV proviruses were obtained by nested PCR. Nucleotide sequences of pol region of these proviruses were highly homologous (over 97%) to that of American and Japanese isolates.