Klintevall K, Ballagi-Pordány A, Näslund K, Belák S
Department of Virology, National Veterinary Institute, Uppsala, Sweden.
Vet Microbiol. 1994 Nov;42(2-3):191-204. doi: 10.1016/0378-1135(94)90018-3.
The early stage of bovine leukaemia virus (BLV) infection was studied in experimentally infected calves in order to assess the diagnostic applicability of a double polymerase chain reaction (PCR). In addition, the kinetics of infection and virus distribution were evaluated. To simulate the natural route of virus transmission, the calves were infected by transferring two different infectious doses of whole blood from a BLV infected cow. The establishment of infection was determined by the double PCR and syncytia formation assay and by indirect serological methods including indirect ELISA, gp51/p24 ELISA, agar gel immunodiffusion (AGID) and Western blotting. BLV antibodies were first detected in ELISA on post infection (p.i.) day 26. Close agreement was found between the results of the various indirect methods. BLV infection was first detected in peripheral blood lymphocytes (PBL) by the PCR on p.i. day 7. No animal became seropositive to BLV prior to direct detection of BLV infection by the PCR. At slaughter, urine and saliva specimens as well as various organs were collected from the calves and tested by the double PCR. Several of the organs yielded positive results: e.g. spleen, uterus, liver, kidney, abomasum, and lymph nodes. Nine out of eleven spleen suspensions were positive by the PCR, including the spleen from one calf, which otherwise remained negative in all tests throughout the experiment. This phenomenon indicates that an animal may be infected without detectable levels of BLV proviral DNA in PBLs and without circulating antibodies, further emphasizing the diagnostic importance of the PCR. The findings indicate that the PCR is the most rapid method for the early detection of BLV infection in cattle and a valuable tool for studying the tropism of the virus.
为了评估双重聚合酶链反应（PCR）的诊断适用性，对实验感染的犊牛进行了牛白血病病毒（BLV）感染早期阶段的研究。此外，还评估了感染动力学和病毒分布情况。为模拟病毒自然传播途径，通过从感染BLV的母牛转移两种不同感染剂量的全血来感染犊牛。通过双重PCR、多核巨细胞形成试验以及包括间接ELISA、gp51/p24 ELISA、琼脂凝胶免疫扩散（AGID）和蛋白质印迹法在内的间接血清学方法来确定感染的建立情况。在感染后（p.i.）第26天，ELISA首次检测到BLV抗体。发现各种间接方法的结果之间高度一致。在p.i.第7天，通过PCR首次在外周血淋巴细胞（PBL）中检测到BLV感染。在通过PCR直接检测到BLV感染之前，没有动物对BLV呈血清阳性。屠宰时，从犊牛收集尿液和唾液样本以及各种器官，并通过双重PCR进行检测。几个器官产生了阳性结果，例如脾脏、子宫、肝脏、肾脏、皱胃和淋巴结。11个脾脏悬液中有9个通过PCR呈阳性，其中包括一头犊牛的脾脏，该犊牛在整个实验的所有检测中其他方面均为阴性。这一现象表明，动物可能在PBL中没有可检测水平的BLV前病毒DNA且没有循环抗体的情况下被感染，进一步强调了PCR的诊断重要性。研究结果表明，PCR是早期检测牛BLV感染的最快速方法，也是研究病毒嗜性的有价值工具。
