Ferritin-conjugated plant lectins of varying saccharide specificities were used to characterize oligosaccharides present on the surface of mouse mammary tumor virus (MMTV) produced in cells of mammary tumors of mice of C3H/He/Tex, A/Dm, and RIII/Dm strains. Mouse mammary tumor (MMT) cells grown on discs of FEP Teflon were labeled in situ with ferritin conjugates of concanavalin A specific for α-d-gluco- and α-d-mannopyranosyl residues, wheat germ agglutinin specific for 2-acetamido-2-deoxy-d-glucopyranosyl residues, and Ricinus communis agglutinin I specific for d-galactopyranosyl residues. Electron microscopic examination revealed quantitative differences in binding of ferritin conjugates of wheat germ agglutinin and concanavalin A to C3H/He/Tex, A/Dm, and RIII/Dm MMTV. No strain-related differences in labeling of MMTV by ferritin conjugated R. communis agglutinin I were observed. Statistical analysis of labeling by ferritin-conjugated wheat germ agglutinin (Fer-WGA) indicated that there was a dense, uniform distribution of Fer-WGA on all 3 strains of MMT cells. However, plasma membranes of C3H/He/Tex and A/Dm MMT cells were unlabeled or only weakly labeled by Fer-WGA at virus budding sites. No major antigenic differences between C3H/He/Tex and RIII/Dm or A/Dm strain MMTV could be detected by immunoelectron microscopy. These results suggest the existence of strain-related variations in MMTV envelope oligosaccharide determinants and also indicate that virus-specific oligosaccharide determinants are present in cellular plasma membranes in the early stages of virus assembly.
This research was supported in part by Grants CA 16672, CA 16789, and RR5511-14, Allotment IN54, and Contract N01-CP-43370 from the National Cancer Institute, NIH, USPHS.