[Reoccurrence of histomonosis in turkey breeder farm].

Histomonosis is a severe disease caused by the protozoan parasite Histomonas (H.) meleagridis, which can lead to high losses in turkeys. The present report describes the reoccurrence of histomonosis in a turkey breeder farm.

Establishment of a new bovine leukosis virus producing cell line.

Due to the prevalence of different bovine leukosis virus (BLV) species in the cattle population in Europe, problems may arise in the serological diagnosis of BLV infections. In addition, earlier investigations demonstrated that contamination of the BLV antigen-producing cell culture systems by bovine viral diarrhea virus (BVDV) may give rise to misinterpretation of serological test results after BVDV vaccination of cattle. By co-cultivation of peripheral leukocytes of a BLV-infected cow with a permanent sheep kidney cell line, a new BLV-producing cell line named PO714 was established.

Effects of hydrogen peroxide on bovine leukemia virus expression.

Several activators of bovine leukemia virus (BLV) expression, including lipopolysaccharides, phorbol esters and calcium ionophores, are known to generate reactive oxygen species (ROS). Therefore the influence of H2O2 on BLV expression in two BLV producing cell lines was investigated. The effect of H2O2 on BLV expression is apparently dose-dependent.

Identification of different BLV provirus isolates by PCR, RFLPA and DNA sequencing.

A first attempt for the investigation of molecular epidemiology of BLV was carried out. PCR amplicons of a part of the env gene of BLV isolated from 309 cattle of different geographical origin were compared with known BLV env sequences. Using RFLPA most of the PCR products can be assigned to the Australian, the Japanese or the Belgian subgroup.

Involvement of intracellular Ca2+ in the regulation of bovine leukemia virus expression.

The calcium ionophore A23187, which was used to increase the intracellular calcium concentration ([Ca2+]i), was analyzed for effects on bovine leukemia virus (BLV) expression in two BLV infected cell lines. To clarify the role of intracellular free calcium in this response, [Ca2+]i was measured during ionophore treatment with the fluorescent calcium indicator Fura-2. Elevation of intracellular calcium under these conditions caused an enhancement of BLV gp51 and p24 synthesis as well as an activation of the BLV long terminal repeat (LTR) in a dose-dependent manner.