Identification of the RPMI 8226 retrovirus and its dissemination as a significant contaminant of some widely used human and marmoset cell lines.

A retrovirus designated RPMI 8226V, isolated in 1973 from the human myeloma cell line RPMI 8226 has been characterized by competition radioimmunoassay (RIA) for the major viral structural protein and by nucleic acid hybridization analysis using cDNA of the virus. The virus is highly related to the squirrel monkey type D retrovirus, SMRV. In the homologous RIA using rabbit anti-RPMI 8226V and 125I-labelled p37 of RPMI 8226V, RPMI 8226V and SMRV exhibited competition of 81% and 73% respectively. Similarly, in the homologous system for SMRV p36, these viruses competed 98 and 100%. Reagents made from the type D retrovirus. Mason Pfizer Monkey Virus (MPMV), known to be related but distinct from SMRV, were used in assays designed to detect interspecies determinants of type D retroviruses. In assays using goat anti-MPMVp26 vs SMRV 125I-p36, RPMI 8226V, SMRV and MPMV competed to the same extent (93%). Hybridization analysis of RPMI 8226V cDNA showed significant homology to cellular RNA and DNA of mink, bat, and human cell infected with RPMI 8226V and to DNA or SMRV infected cells but not to uninfected cells or cells infected with other viruses. These results taken together clearly indicate that RPMI 8226V and SMRV are very closely related to each other. The finding of a type D retrovirus in this human myeloma cell line that had been used in EBV studies (the usual source of EBV being the marmoset cell line B95-8) prompted a survey of RPMI 8226V in some human and marmoset cell lines. The assays included the RIA for p36, nucleic acid hybridization using cDNA of RPMI 8226V, reverse transcriptase analysis and electron microscopy (EM). The results clearly show that in addition to RPMI 8226, human Burkitt lymphoma cells BJAB/B-95-8/K which were supertransformed by EBV from B-95-8/K marmoset cells as well as marmoset cell lines [(B-95-8/K and B-95-8/N) obtained from Stockholm and Uppsala, Sweden] were positive for the RPMI 8226V. Similar lines obtained elsewhere were negative. The results obtained clearly indicate that RPMI 8226V is a serious laboratory contamination in some widely used human cell lines. The possible impact of this viral contamination for some virological and cell biological studies is discussed.