The eradication of enzootic bovine leucosis in a large farm population.

In the years 1992 to 2002 the ID and ELISA systemic serological examinations of infected cows from a large farm brought advantageous results. A total of 468 cows from three farms from Opole province were examined. In the years 1997 to 2002 there were four times more positive serological results obtained than in the years 1992 to 1996. The elimination of BLV infected animals from farms and watering of serologically negative calves with milk substitute feed were very useful methods. In the year 2002 the control of all cattle gave negative ELISA results based on anti-gp51 monoclonal antibodies. The farm demonstrated BLV-free status after 10 years as a result of regular laboratory testing and successful elimination of all positive animals.

The improvement of monitoring methods of cattle infection with bovine leukemia virus (BLV).

This study demonstrates the usefulness of PLA and nested-PCR methods for the detection of cattle infection with enzootic bovine leukemia virus. Serological control with PLA was by 1.7% more sensitive than reference ELISA examination. Both the DNA of env-BLV gene in NCR, V-NCR, FLK and in recombinated AG clone cells, as well as in the whole blood and in blood isolated leukocytes of dairy cattle, were detected with the nested-PCR.

Protection of cattle against bovine leukemia virus (BLV) infection could be attained by DNA vaccination.

The bovine leukemia virus (BLV) envelope gene encoding extracellular glycoprotein gp51 and transmembrane glycoprotein gp30 was cloned into a vehicle expression vector under the human cytomegalovirus (CMV) intermediate early promoter. The intramuscular injection of this plasmid vector generated a cellular immune response. Seven out of ten cows vaccinated with the DNA construct resisted a drastic challenge (500 BLV-infected lymphocytes as an infectious dose).

Immune response and resistance to Rous sarcoma virus challenge of chickens immunized with cell-associated glycoproteins provided with a recombinant avian leukosis virus.

The Rous-associated virus 1 env gene, which encodes the envelope gp85 and gp37 glycoproteins, was isolated and inserted in place of the v-erbB oncogene into an avian erythroblastosis virus-based vector, carrying the neo resistance gene substituted for the v-erbA oncogene, to generate the pNEA recombinant vector. A helper-free virus stock of the pNEA vector was produced on an avian transcomplementing cell line and used to infect primary chicken embryo fibroblasts (CEFs) or quail QT6 cells. These infected cells, selected with G418 (CEF/NEA and QT6/NEA, respectively) were found to be resistant to superinfections with subgroup A retroviruses. The CEF/NEA preparations were used as a cell-associated antigen to inoculate adult chickens by the intravenous route compared with direct inoculations of NEA recombinant helper-free virus used as a cell-free antigen. Chickens injected with the cell-associated antigen (CEF/NEA) exhibited an immune response demonstrated by induction of high titers of neutralizing antibodies and were found to be protected against tumor production after Rous sarcoma virus A challenge. Conversely, no immune response and no protection against Rous sarcoma virus A challenge were observed in chickens directly inoculated with cell-free NEA recombinant virus or in sham-inoculated chickens.

Experimental infection of sheep with bovine leukemia virus (BLV).

Nine groups of sheep have been experimentally infected with different doses of BLV and by various routes. An immunological response of animals, as well as clinical symptoms of leukosis in the experimental sheep were investigated within several years or months. The animals inoculated with the virus showed appearance of BLV-antibodies in 94 per cent of cases, lymphocytosis in 47 per cent and clinical symptoms of the disease in 33 per cent. In conclusion, sheep have been demonstrated to be animals suitable for experimental study of leukosis.

[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.