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BIV感染进行了血清学调查，发现10%的阳性反应者。从血清学阳性动物中分离出3只BIV，并从这些阳性动物的外周血淋巴细胞中获得DNA样品，通过巢式PCR检测BIV前病毒DNA，以检测pol基因的一部分。扩增出BIV前病毒DNA特异性的298 bp pol区片段。日本BIV野毒株与美国分离株R-29的核苷酸序列同源性为99%。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株毒株的env基因V1区有多个碱基替换，V2区有缺失。在柬埔寨共采集牛544头，布法罗43头，牛BIV血清阳性率为26%，布法罗为17%。从血清阳性动物中获得5种BIV前病毒。pol区的核苷酸序列与美国和日本的BIV相比高度保守。相反，柬埔寨BIV田间分离株的env区域似乎小于美国分离株。柬埔寨分离株V2区存在核苷酸替换，改变了氨基酸序列。赞比亚牛血清262份，阳性率为11.4%。用巢式PCR方法获得4株BIV前病毒。这些前病毒pol区核苷酸序列与美国和日本分离株高度同源（97%以上）。

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.