Performance of Affinity-Improved DARPin Targeting HIV Capsid Domain in Interference of Viral Progeny Production.

Previously, a designed ankyrin repeat protein, Ank1D4, was generated for intracellular targeting of the HIV-1 capsid domain. The efficiency was satisfactory in interfering with the HIV assembly process. Consequently, improved Ank1D4 binding affinity was introduced by substituting tyrosine (Y) for serine (S) at position 45. However, the intracellular anti-HIV-1 activity of Ank1D4-S45Y has not yet been validated. In this study, the performance of Ank1D4 and Ank1D4-S45Y in inhibiting wild-type HIV-1 and HIV-1 maturation inhibitor-resistant replication in SupT1 cells was evaluated. HIV-1 p24 and viral load assays were used to verify the biological activity of Ank1D4 and Ank1D4-S45Y as assembly inhibitors. In addition, retardation of syncytium formation in infected SupT1 cells was observed. Of note, the defense mechanism of both ankyrins did not induce the mutation of target amino acids in the capsid domain. The present data show that the potency of Ank1D4-S45Y was superior to Ank1D4 in interrupting either HIV-1 wild-type or the HIV maturation inhibitor-resistant strain.