Serological evidence for antigenic differences between the Mason-Pfizer monkey virus (MPMV) and an MPMV-like virus (PMFV) detected in a malignant permanent human cell line

Suppression of human lymphocyte mitogen response by retroviruses of type D. II. Non-activity of Mason-Pfizer monkey virus versus activity of human cell line derived virus PMFV

In contrast to the human cell line derived type D retrovirus PMFV, the Mason-Pfizer monkey virus (MPMV) does not suppress the mitogen response of normal human lymphocytes. Both viruses have been propagated on the same cell lines and purified by the same methods. MPMV did not contain a factor able to abolish PMFV-induced suppression of the mitogen response. Neither could MPMV suppress the mitogen response of lymphocytes from rhesus monkeys or baboons. PMFV however inhibited their reactivity.

Further evidence from tryptic peptide analysis for heterogeneity among type D retroviruses

Tryptic peptide analyses were performed on the major internal structural proteins of type D retroviruses isolated originally from subhuman primate species (MPMV, SMRV, LV) and from permanent human cell lines (HeLaV, HEp-2V, PMFV). The p25 peptide maps of MPMV, LV, PMFV and HEp-2V were very similar but showed a striking dissimilarity to the p25 map of HeLaV and the p35 map of SMRV. All type D viruses included in this study could be distinguished by peptide maps of at least two of their three low-molecular-weight proteins p10, p12 and p15. These studies further demonstrate the heterogeneity among type D retroviruses.

Type D retroviruses from human cells do not contain a minor glycoprotein shared by old world monkey type D viruses

The protein patterns of type D retroviruses isolated either from permanent human cells (HeLa virus, HeLa V, and HEp-2 virus, HEp-2V) or from spectacled langur (langur virus, LV), an Old World monkey, were investigated using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Labeling with 14C-amino acids and 3H-glucosamine revealed for each of these isolates five polypeptides with molecular weights of 10,000, 12,000, 15,000, 25,000 and about 68,000 and identified the 68,000 D-protein as a glycoprotein. An additional glycoprotein with a molecular weight of 20,000 (gp20) was resolved in LV similarly as in previous studies with Mason-Pfizer monkey virus. However, in accordance with our recent analysis of a third type D isolate from human cells (PMFV), gp20 was not detectable in both HeLaV and HEp-2V regardless of the cell line in which they were grown. Thus, it appears that the type D virus isolates from human cells are slightly distinct from the presently known type D retroviruses of Old World monkeys. The relevance of this finding to the origin of the human isolates, however, remains to be shown.

The protein pattern of PMF virus, a type-D retrovirus from malignant permanent human cell lines

The protein pattern of a type-D retrovirus (PMFV) isolated from and propagated in human cell lines has been investigated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Staining with Coomassie blue and labeling with 14C-leucine/14C-lysine revealed five viral polypeptides with molecular weights of 10,000, 12,000, 15,000, 25,000, and 68,000. The 68,000 D-protein was shown to be a glycoprotein by incorporation of 3H-glucosamine and the 15,000 D-protein was identified as a phosphoprotein. By comparing PMFV with the closely related Mason-Pfizer monkey virus (MPMV) in co-electrophoresis experiments no clear difference was detected in viral 14C-leucine/14C-lysine profiles. The viruses differ, however, with respect to their glycoprotein patterns. A glycoprotein corresponding to the gp20 of MPMV has not been detected in PMFV irrespective of the cell line used for propagation of viruses.