MX2 and HIV-1 infection: Considering the ~12-fold block to HIV-1 infection, a comparatively modest decrease (~3.9-fold at peak levels) in the level of WT 2-LTR circles was observed in MxB-expressing cells using qPCR conditions that do not distinguish molecules that contain circle junction sequences from those that may arise from autointegration (Figure 4C, solid and dashed black lines).