Ruthenium red preserves glycoprotein peplomers of C-type retroviruses for transmission electron microscopy

Peplomers, the glycoprotein projections of the outer viral envelope, are distinctive for many viruses. Peplomers of retroviral C-type particles are fragile and are not preserved in standard preparations for transmission electron microscopy of thin sections, whereas the peplomers of B- and D- type retroviruses are usually preserved. Ruthenium red, extensively used in transmission electron microscopy to enhance the preservation of glycosylated proteins, was used in the preparation of three retrovirus-producing lymphoblastoid cell lines: murine SC-1 cells producing the C-type murine leukemia retrovirus LP-BM5 that causes immunodeficiency, human DG-75 cells producing a murine leukemia retrovirus, and human C5/MJ cells producing human T-cell lymphotropic virus type I (HTLV-I). Fixation of cells was carried out with ruthenium red present in the glutaraldehyde, osmium tetroxide, and the ethanol dehydration through the 70% ethanol step. The detailed structure of peplomers of these three different viruses was well preserved.