Orphan G protein-coupled receptor shown to be a coreceptor for simian and human immunodeficiency virus (SIV and HIV) strains. As long as apelin is an endogenous ligand for the APJ receptor, inhibitory effects of apelin peptides on HIV infection have been found to display that apelin peptides inhibit the entry of some HIV-1 and HIV-2 strains into NP-2/CD4 cells expressing APJ. Strong inhibitory efficiency