CCR5 and infection: To explore whether stable expression of A3Z2Z3-M can impact spreading infection, human HOS.CD4.CCR5 cells expressing either wild-type or mutated A3Z2Z3 were established (Fig. 8e, Additional file 1: Fig. S6) and infected by HIV-1 expressing FIV Vif (HIV-1vifFIV) [36].