Rapid Cell Culture Assay Technique for Murine Leukaemia Viruses

INFECTION of susceptible mouse cells in culture with murine leukaemia viruses (MLV) does not cause any observable change in cellular morphology, even though continuous virus replication in these cells can often be demonstrated. Complement-fixation 1 and fluorescent antibody 2 techniques as well as interference 3 or potentiation 4 of focus formation by “defective” murine sarcoma viruses have all been used successfully to detect and to quantitate in vitro infection of mouse cell cultures with MLV. These techniques, however, are less than ideal because they involve special reagents and lengthy incubation, or because they are relatively insensitive, Klement et al. 5 have shown that the XC cell line 6 , derived from a rat tumour induced by the Prague strain of Rous sarcoma virus, undergoes syncytium formation when present in mixed cultures together with MLV-infected mouse cells. This phenomenon of mixed culture cytopathogenicity has been used to develop a plaque assay for murine leukaemia viruses in mouse cell cultures (unpublished observations of W. P. Rowe et al. ).