MX1 and infection: We monitored the replication of VSV at the single-cell level (by immunofluorescence for VSV N) in cultures transiently transfected with a GFP-MxA construct and then with VSV at moi >10 pfu/cell followed by fixation 4 or 5 h after infection which is near the peak of VSV N expression in infected cells [13,52,53].