Because obtaining an infectious titer via plaque assay as an experimental measure was not possible for mutants 204/5 and 142, luciferase activity was measured 24h following Vero cell infection with VEEV TC-83 nsP3 mutants expressing luciferase, using undiluted viral stocks or 1:1 diluted viral stocks to ensure cells were infected with at least some mutant virions (Figure 3E). Here, SH2D3C is linked to infection.