The DNA from 17 lymphoid tumors induced by bovine leukemia virus (BLV) was digested with the restriction endonuclease EcoRI. Filter hybridization analysis using radioactive probes specific for the BLV genome showed that all tumors contained at least one or a portion of one provirus. Bovine leukemia virus (BLV), an exogenous retrovirus of cattle (1, 2), induces B lymphocyte neoplasms (called enzootic bovine leukosis, EBL) after long latent periods (3). BLV does not contain any host cellular sequences and does not appear so far to bear genes directly inducing transformation. It follows that leukemogenesis by bovine leukemia virus might be due to (i) initiation of transcription of a cellular gene from a viral promoter as found in avian leukosis virus (ALV)-induced lymphoid leukosis (4); (ii) position effect of the provirus with, as a consequence, enhancement of expression of neighboring cellular information or extinction of previously expressed normal DNA; (iii) expression of viral information. The present study is aimed at characterizing the BLV provirus in tumor cell DNA and at providing some insight into the molecular events that lead to tumor development. MATERIALS AND METHODSBovine Tissues and Cells. Bovine material was collected from field cases of enzootic bovine leukosis in Belgium (animals 12, 15, 82, 950, 2586, and 2587), France (animals 53, 56, 104,106, 108, and 120), Japan (animals 119, 1345, 1347, and 1351, and the USA (animals 79-2, 3156, 3168, 3202, and 3261). Circulating leukocytes'ordymphoid tumors, kept at -70°C, were used as sources of DNA or RNA. Leukocytes from a normal animal (animal 94) were used as a source of control DNA and RNA.Molecular Cloning of DNA Fragments. The isolation of the 9.2-kilobase (kb) Sac I fragment containing all the BLV information has been described (2). EcoRI tumor DNA fragments containing the right viral long terminal repeat (LTR) together with flanking cellular sequences of various lengths (see Fig. 2) were cloned in Charon 21A A phage (5) essentially as described by Maniatis et al. (6). The National Institutes of Health guidelines for recombinant DNA research were followed during the entire procedure.

No abstract

In recent years, a neuroimmunomodulatory role for 1,25-dihydroxyvitamine D(3) [1,25(OH)(2)D(3)] has emerged. Microglial cells present a potential target for the effects of this hormone in the brain. This study focuses on the effect of 1,25(OH)(2)D(3) on the expression and production of inflammatory cytokines and nitric oxide (NO) by the EOC13 microglial cell line. The presence of the vitamin D3 receptor in microglia was demonstrated by RT-PCR. 1,25(OH)(2)D(3) inhibited the production of tumor necrosis factor-alpha, interleukin-6, and NO by stimulated microglia in a concentration-related fashion. The production of transforming growth factor-beta1 (TGF-beta1), an anti-inflammatory cytokine, was not modified in the presence of 1,25(OH)(2)D(3), indicating that the effects of 1,25(OH)(2)D(3) may not involve TGF-beta1 regulation. These results show that 1,25(OH)(2)D(3) has direct anti-inflammatory properties on microglia. It further supports the hypothesis that 1,25(OH)(2)D(3) could be involved in the maintenance of the brain homeostasis and may have a therapeutic potential in inflammatory pathologies of the central nervous system.

The nucleotide sequences of the env genes of seven bovine leukemia viruses and the encoded peptide sequence were compared, with the objective of (i) determining the genetic distance separating bovine leukemia virus isolates from different geographical regions, (ii) identifying particular amino acids that contribute to the sequential and conformational epitopes, and (iii) relating such epitopes to their projected position in a threedimensional model of the structure of the gp5l surface glycoprotein. Two bovine leukemia virus subgroups were clearly identified, a Japanese-American subgroup represented by strains XBLV-1, VdM, and FLK-BLV and a European subgroup by strains T15-2, LB285, and LBS9. It was possible to identify amino acids that were important in determining three of the epitopes (F, G, and H) recognized by neutralizing monoclonal and polyclonal antibodies. On the model, these epitopes were adjacent and located on the exposed region of the molecule. Amino acid sequences contributing to a fourth cryptic epitope were identified; as predicted by the model, they lay on the opposite side to the neutralizable epitopes in a region involved in glycoprotein subunit association. The fact that this region is not normally exposed on the virion surface provides further evidence for the validity of the model.