APOBEC3B and infection: To ask whether human A3B can restrict MmuPV1, 100,000 A3B-expressing or control primary murine keratinocytes were infected with a log10 gradient of MmuPV1 viral genome equivalents (104 to 108 VGE), which helped to ensure low (<1) to high (>>1) multiplicity of infection (MOI; experimental workflow in Fig. 2A).