Cellular distribution of bovine leukemia virus proteins gp51SU, Pr72(env),and Pr66(gag-pro) in persistently infected cells

Monoclonal antibodies (mAbs) against bovine leukemia virus (BLV) mature pro teins and precursors were used to map the localization of these proteins in persistently infected non-lymphocytic cell lines using immunofluorescence assay (IFA) and immuno-electron microscopy. IFA staining was observed in th e basolateral surface of live FLK-BLV cells. When using a mAb against Pr66( gag-pro), mottled pinpoint fluorescence was seen in the cell surface of pol arized cells, but no reaction was observed in cells undergoing mitosis. How ever, a mAb against Pr72(env) stained only mitotic cells and cellular fragm ents. Additionally, in these dividing cells, this envelope (Env) precursor polyprotein was not evenly distributed but concentrated predominantly in on ly one daughter cell. To the best of our knowledge, this observation has no t been reported previously, either for BLV or for other retroviruses. The r esults of immunogold electron microscopy confirmed the specificity of the m Abs in the intracellular level. In infected cells, Pr72(env) and gp51SU wer e seen in proximity at the plasma membrane in incipient budding sites. Addi tionally, the mAb against Pr72(env) also reacted with Env precursor polypro teins in the mitochondria of BLV-bat(2) ultrathin sections. These mAbs may be used as a tool for mapping virus excretion sites in the cell surface of naturally or in vitro infected cells in the different stages of the cell cy cle. (C) 2001 Elsevier Science BN. All rights reserved.