The infection–proliferation cycle of human immunodeficiency virus-1 (HIV-1) is constituted by different steps, including (i) membrane attachment (cell-free or cell-to-cell transmission); (ii) receptor (CD4 or CD5) and co-receptor (CXCR4 in T-cells and CCR5 in macrophages) binding; (iii) membrane fusion (triggered by proteins such as CXCR4, CCR5, CD3, LFA-1, α4β7, tallin); (iv) transport of viral capsid into the nucleus; (v) nuclear transport, integration, and transcription; (vi) viral protein synthesis; and (vii) novel viral particles budding [54]. This evidence concerns the gene CXCR4 and infection.