PPIA and infection: Given the well-established antiretroviral activity of TRIM5α ([1] and reviewed in [19]–[23]), the ability of CypA to interact with the CA proteins of several lentiviruses [24], and the capacity of TRIMCyp to block replication of HIV-1, SIVagm and FIV [9],[10],[14], it is possible that fixation of the CypA insertion in the Aotus lineage was driven by positive selection in the face of infection by an unknown lentiviral pathogen.