Effect of glycosylation inhibitors on expression of HA-tagged mCAT-1 in M. dunni cells Because the resistance of NIH 3T3 cells to Spl574 infection is comparable to the resistance of M. dunni cells to MoMLV, we treated NIH 3T3 cells with 5 different glycosylation inhibitors before Spl574 infection (Table 4 ). All 5 inhibitors significantly reduced resistance to Spl574 replication, but inhibition of N-glycosylation did not affect the XC titer of other ecotropic viruses in NIH 3T3 cells, as shown for MoMLV. Resistance of SC-1 cells to Spl574 [1] is similarly relieved by glycosylation inhibitors (data not shown).