Incorporation of CypA versus CypB seems to be virus-specific: CypA-CD147 interaction enables SARS-CoV and HIV-1 infection (73, 87), while CypB-CD147 interaction has been shown to facilitate infection of measles virus (88), and in both cases, virus infectivity is hindered by cyclosporin A treatment (87, 88). Here, PPIB is linked to HIV-1 infection.