Detection of the bovine leukaemia virus by the polymerase chain reaction.

The polymerase-chain reaction was applied for detection of provirus DNA of the bovine leukaemia virus (BLV). A short fragment of 292 bp including region R and U5 LTR 5' of BLV was amplified, and the optimum parameters of amplification of this fragment were established. Electrophoresis revealed the presence of the 292 bp fragment from the leucocytes of four out of six cows showing a positive serological response to BLV antigens. Application of the polymerase-chain reaction in diagnosis of bovine leukaemia is suggested.

Molecular cloning of provirus DNA from bovine leukaemia lymphocytes and its application as a probe for diagnostic purpose.

The provirus DNA isolated from lymphocytes of a cow infected with the bovine leukaemia virus (BLV; positive immunodiffusion test), was subjected to molecular cloning and identified by comparing with the 32P-labelled provirus cDNA isolated in Belgium. Hybridization revealed a clone containing 8.5 kb DNA fragment of the BLV provirus. The probe based on the "Polish fragment" of leukaemia virus was tested on 10 cows with a positive serological response. The presence of provirus DNA in the cellular genome of lymphocytes was confirmed.

[Obtaining specific antigens of enzootic bovine leukemia virus]. / Uzyskanie swoistych antygenów wirusa enzootycznej bialaczki bydla.

The authors presented two methods of producing BLV antigens which had been proved and are utilized now at the Veterinary Institute in Pulawy. One of them is based on cultivation of blood leukocytes from leukotic cattle and on extraction of antigenic material with ethyl ether. The second method consists in obtaining antigenic proteins from a monolayer FLK-BLV culture by means of ammonium sulphate precipitation. The preparations obtained according to the above techniques showed specific serological properties and correspond with foreign standards.

Protein concentrations and immunosuppressive properties of serum in chickens experimentally infected with avian tumor viruses.

Sera from chickens affected by Marek's disease or developing Rous sarcoma were investigated. There were changes in the protein fractions, and the amount of alpha and beta fractions was consistently increased. At the same time, immunosuppressive factors were found to inhibit the number of plaque-forming cells in the spleen of mice immunized with sheep red blood cells.

Studies on specific antigen content in different fractions of preparations from BLV-producing cell cultures.

Different protein fractions of BLV-antigens were examined with serological and chemical methods. The fractions of ether resistant and dual antigens were obtained by means of QAE-50A Sephadex chromatography and the fractions of gp-antigen were collected in the course of the affinity chromatography on Concanavalin A-Sepharose. All protein fractions examined by means of polyacrylamide gels electrophoresis occurred to be heterogenous. Some of them showed positive RID or GID reactions with sera of cattle or sheep affected with leukosis. By means of thinlayer chromatography on Sephadex, there were estimated following molecular weights of proteins in the serologically positive fractions: 12.500, 67.000, 70.000 and 150.000.

Chemical characteristics of chalones isolated from bovine spleen.

Isolation of spleen chalones from the postmicrosomal supernatant is described. Two glycoprotein fractions homogeneous on polyacrylamide-gel electrophoresis were obtained. In the biological test on mice, the preparation of 38 000 mol. wt. inhibited mitosis in spleen cells, and the low-molecular fraction (2100 mol. wt.) in thymus cells, showing respectively the properties of chalones B and T.