Host soluble factors that regulate the synthesis of the major core protein of the Bovine Leukemia Virus (BLV) in a naturally-infected neoplastic B-cell line

GUTIERREZ SE; CERIANI MC; JULIARENA M; FERRER JF

VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY

ELSEVIER SCIENCE BV

Año: 2009 vol. 131 p. 246 - 258

0165-2427

Bovine leukemia virus (BLV) is a B-cell tropic Deltaretrovirus that induces a lifelonginfection and causes a fatal lymphosarcoma in less than 10% of the infected cattle. BLV isusually present in its host in a transcriptional repressed state but becomes de-repressed afew hours after the infected lymphocytes are cultured in vitro. In the present study we haveexamined the effect of soluble host factors and various substances on the synthesis of themajor BLV protein (p24) in a permanent culture (cell line NBC-10) of neoplastic Blymphocytesderived from BLV-infected cattle. Certain batches of fetal calf serum (FCS)and bovine platelet lysates (PLy) induced a rapid and drastic increase of the synthesis ofBLVp24 in the NBC-10 cells. Neutralization experiments with specific antibodiesdemonstrated that the transforming growth factor-b (TGF-b) was responsible for thestimulatory activity of FCS and PLy on the synthesis of BLVp24 in the NBC-10 cells.Recombinant TGF-b also stimulated the synthesis of BLVp24 in cultures of peripheralblood mononuclear cells (PBMCs) obtained from BLV-infected cattle. Mitogens, phorbolmyristate-acetate and prostaglandin E2, previously shown to stimulate the expression ofBLV in cultures of PBMC, did not induce the synthesis of BLVp24 in cultures of NBC-10 cells.Plasma, serum and milk from BLV-negative cattle inhibited the synthesis of BLVp24induced by FCS, PLy or TGF-b in the NBC-10 cells. The blocking activity was found in thewhey and the b-casein fractions of bovine milk. The relevance of these findings withregard to the previously reported plasma factor (PBB) with blocking activity on theexpression of BLV in short-term PBMC cultures is discussed. Based on the informationobtained in the present study we have standardized a reproducible and rapid assay systemfor the identification of factors that regulate the synthesis of BLVp24 in naturally infectedneoplastic B cells.