(a, b) MJS cells expressing the indicated gRNAs were infected with VACV-WR expressing eGFP (m.o.i. 0.01), and harvested 2, 8 and 15 days post-infection (p.i.). Subsequently, the cells were analysed for eGFP expression (a) and viability (b) by flow cytometry. The cell counts for infected cells were compared to those for uninfected cells (set at 100 %). Cells expressing Cas9 vector only, or in combination with gRNAs targeting bovine β-2M (bB2M) or TAP2, served as infection controls. (c, d) MJS cells expressing the indicated gRNAs were infected with cowpox virus strain Brighton Red expressing RFP and eGFP using an m.o.i. of 0.01 (c) or 0.1 (d). Fluorescence was analysed by flow cytometry at 5, 8 and 15 days p.i.