Model relating cell-cell fusogenicity, viral homeostasis, and A3G antiviral activity.

The upper panel depicts a vif-null scenario with frequent syncytia and disrupted viral homeostasis characterized by less Gag-Pol packaging, slower reverse transcription, and a high susceptibility to A3G-mediated restriction. The lower panel depicts an adapted virus scenario with few syncytia and restored viral homeostasis including more Gag-Pol packaging, higher rates of reverse transcription, and resistance to A3G-mediated restriction. Individual cells are depicted with one nucleus, and fused cells with four nuclei. For simplicity, individual cells are shown producing particles with 4 units of RT and 2 units of A3G, whereas the syncytium is shown producing particles with 50% less RT (2 units) with the same amount of A3G (2 units). See text for additional explanation.