Validation of Promoters and Codon Optimization on CRISPR/Cas9-Engineered Jurkat Cells Stably Expressing αRep4E3 for Interfering with HIV-1 Replication.

Persistent and efficient therapeutic protein expression in the specific target cell is a significant concern in gene therapy. The controllable integration site, suitable promoter, and proper codon usage influence the effectiveness of the therapeutic outcome. Previously, we developed a non-immunoglobulin scaffold, alpha repeat protein (αRep4E3), as an HIV-1 RNA packaging interference system in SupT1 cells using the lentiviral gene transfer. Although the success of anti-HIV-1 activity was evidenced, the integration site is uncontrollable and may not be practical for clinical translation. In this study, we use the CRISPR/Cas9 gene editing technology to precisely knock-in αRep4E3 genes into the adeno-associated virus integration site 1 (AAVS1) safe harbor locus of the target cells. We compare the αRep4E3 expression under the regulation of three different promoters, including cytomegalovirus (CMV), human elongation factor-1 alpha (EF1α), and ubiquitin C (UbC) promoters with and without codon optimization in HEK293T cells. The results demonstrated that the EF1α promoter with codon-optimized αRep4E3mCherry showed higher protein expression than other promoters with non-optimized codons. We then performed a proof-of-concept study by knocking in the αRep4E3mCherry gene at the AAVS1 locus of the Jurkat cells. The results showed that the αRep4E3mCherry-expressing Jurkat cells exhibited anti-HIV-1 activities against HIV-1NL4-3 strain as evidenced by decreased capsid (p24) protein levels and viral genome copies as compared to the untransfected Jurkat control cells. Altogether, our study demonstrates that the αRep4E3 could interfere with the viral RNA packaging and suggests that the αRep4E3 scaffold protein could be a promising anti-viral molecule that offers a functional cure for people living with HIV-1.