In addition, we recently obtained unpublished results showing that the expression of the Nef, Vif, Vpu, and Vpr viral auxiliary proteins, known to counteract SERINC (serine incorporator), APOBEC3 (apolipoprotein B mRNA editing enzyme polypeptide-like 3), BST-2 (bone marrow stromal antigen 2), and other restriction factors did not affect the cell-to-cell spreading to macrophages from infected CD4+ T cells, suggesting that this cell–cell fusion mode for HIV-1 infection of macrophages may also bypass these restrictions factors (SB and MW, unpublished results). This evidence concerns the gene CD4 and HIV-1 infection.