870 FRIEND MINK CELL FOCUS - INDUCING VIRUS - LIKE gp 70 Membrane

Multiple host genes have been shown to influence the course of erythroleukemia induced by Friend virus (FV) 1 (1). Two H-2-associated genes and a non-H-2-1inked gene are required for recovery from FV leukemia (2, 3). The non-H-2-1inked gene, Rfv-3, appears to influence the production of anti-FV antibody independent of the H-2 genotype (3). Although mice of the Rfv-3 r/~ genotype produce high levels of antiFV antibody, they fail to recover from FV-induced leukemia unless the appropriate H-2-associated genes are present (3). Thus, FV leukemia cells continue to proliferate even in the presence of anti-FV antibody, possibly because of their resistance to antibody-complement-mediated lysis (4). Furthermore, FV leukemic spleen cells late in the disease express decreased amounts of FV cell surface antigens and release less infectious virus than leukemic spleen cells early in the course of the disease (5). The low levels of FV cell surface antigens and infectious virus observed in mice with antiFV antibody were found to be reversible after transfer of leukemic spleen cells into nonimmune animals (5). Therefore, anti-FV antibody appeared to play a role in altering the expression of viral antigens and infectious virus release in these cells. To examine further this phenomenon, we studied the expression of individual FVencoded proteins in FV leukemic spleen cells at various times in the course of the disease. Our results indicated that the presence of anti-FV antibody late in the disease was associated with a decreased expression of Friend helper virus (F-MuLV)-encoded intracellular and cell surface proteins, whereas the expression of the replicationdefective spleen focus-forming virus (SFFV)-encoded proteins appeared to be minimally altered. This selective loss of F-MuLV proteins appeared to correlate with the specficity of the mouse anti-FV antibody that was found to recognize F-MuLV but not SFFV-specific proteins. In addition, we have also demonstrated a new gp70