Expression of Virus Structural Proteins on Murine Cell Surfaces in Association with the Production of Murine Leukaemia Virus

Abstract

SUMMARYWe have used a quantitative radiolabelled antibody procedure to measure the amount of certain virus structural antigens on the surface of BALB/c RAG cells producing endogenous B-tropic type C virus. RAG cells expressed group specificities of MuLV p3o on their cell surface but did not express gp7o group specificities. However, type specificities of gp7o were expressed on BALB/c cell lines infected with Moloney leukaemia virus. The majority of p3o antigens detected on the RAG cell surface were removed by trypsin and their reappearance was prevented by cycloheximide, even in the presence of' conditioned medium' containing MuLV. Passive adsorption of exogenous MuLV p3o to the surface of virus negative BALB/c fibroblasts reached a maximum of 2o ~ of the protein detectable on virus producing RAG cells. These data support the hypothesis that much, but not all, of the surface p3o is expressed de novo on the cell membrane and not derived from passive adsorption of p3o released from shed virus or as a by-product of virus infection of a cell.

Bvr-1, a restriction locus of a type C RNA virus in the feline cellular genome: pleiotropic restriction of endogenous BALB virus in cat X mouse somatic cell hybrids.

“…The present studies demonstrate that a feline chromosomal gene, Bvr-1, exerts a trans-dominant restriction on the endogenous B-tropic virus produced by BALB/c tumor cells and also described in aged BALB/c mice (7)(8)(9)14). The time of action of Bvr-1 has been previously established as late in MuLV assembly since budding virions and viral structure proteins are detected in high amounts on restricted cell surfaces, but not in culture fluid pellets (13).…”

“…Type C Viral RNA-Dependent DNA Polymerase (RDDP) Assay. Type C virus activity was assayed by measuring particle associated RDDP or reverse transcriptase activity in tissue culture fluid of infected cells (14). Routine assays were performed with an rA.…”

“…The FL-74 parent is productively infected with FL-74 strain of FeLV. Neither of the parental species will support replication of the alternative parent's virus (Table II and * Criteria of type C virus production include: particulate RDDP activity in cell supernates, budding particles on examination in transmission electron microscopy, and viral antigens (p30, gp70) on infected cell surfaces (14,36). * FL-74 is a lymphoid suspension cell which was a selective parameter used in hybrid production (13,27,36).…”