CXCR4 and infection: Unlike wild-type HIV-1, infection with Vpu-S52,56D and Vpu-S52,56N viruses did not result in a significant loss of PEX2, PEX7, PEX11B, or PEX13 in HeLa-CD4/CXCR4/CCR5 cells, macrophages, or T cells (Fig. 4).