The retrovirus particles in human myeloma cells RPMI8226: morphological, biochemical, immunological and infective transmission studies.

The retrovirus designated RPMI8226V (isolated from human myeloma cells RPMI8226) has been characterized with respect to its morphological, biochemical and immunological properties as well as its propagation in various animal and human cells. The myeloma cells RPMI8226 produce intracytoplasmatic A-type particles and extracellular particles. The extracellular particles have been classified as immature particles with translucent core center, typical mammalian C-type virus particles and C-type particles with intermediate membrane. However, the budded particles in secondarily infected human neoplastic cells contained complete doughnut-shaped nucleoids. This type of budding is rather characteristic for B-type particles. The 3H-uridine labeled RPMI8226 viral particles have a buoyant density 1.17 g/ml in sucrose gradient containing high molecular weight RNA and the distribution of viral structural proteins in SDS-PAGE is characteristic for oncornaviruses. The internal structural proteins according to MW are ranged from 13 000 to 30 000 daltons. The virus contains a magnesium-dependent reverse transcriptase. The cellular homogenate and viral concentrate from RPMI8226 cultures do not react with antibodies against ALSV, MuLV, FeLV, RD114, MP-MV and SiSLV. The only reaction was scored with anti BLV antibodies. However, anti BLV serum inhibiting the reverse transcriptase activity of BLV to 60% does not cross-react with the reverse transcriptase of RPMI8226V. In contrast to BLV concentrates, neither XC nor KC cells show syncytia formation by RPMI8226V. The RPMI8226V replication is restricted to human tumor and normal human glia-like cells. The possible origin of the virus is discussed.