As has been shown in the previous paragraph, the interaction of gp120 with the cell surface CD4 receptor and coreceptor CCR5 or CXCR4 triggers a series of cellular signals that support viral infection, while the HIV-1 gp41 can also interact with cell surface proteins to activate cell signals that regulate both viral infection and host cell functions. This evidence concerns the gene CXCR4 and viral infectious disease.