Objective

Melittin and its derivatives have been characterized to establish effective gene delivery systems. Their capability of facilitating endosomal release enhances the nanoparticles-based gene delivery. Nevertheless, little investigation has been conducted to explore its potential application in the context of viral vectors.

Methods

Various melittin-derived peptides were inserted into the loop VIII of the capsid proteins of recombinant adeno-associated virus vectors. These vectors carrying either gfp or fluc genes were subjected to qPCR assays and transduction assays of HEK293T cells to investigate the efficiency of vector production and gene delivery. In addition, the ability of a specific p5RHH-rAAV vector to deliver genes was examined through in vitro transduction of different cultured cells and in vivo tail vein administration to C57BL/6 mice. Finally, the intricate details of the vector-mediated transduction mechanisms were revealed by specific pharmacological inhibitors of every stage of the rAAV2 intracellular life cycle.

Results

A total of 76 melittin-related peptides were compiled from existing literature. Among them, cMA2, Melt13, p5RHH and aAR3 were found to significantly enhance the gene delivery efficiency of rAAV2 vectors. The p5RHH-rAAV2 vectors efficiently transduced not only rAAV-potent cell lines but also cell lines previously considered resistant to rAAV. Mechanistically, bafilomycin A1, a vacuolar endosome acidification inhibitor, completely inhibited the transgene expression mediated by the p5RHH-rAAV2 vectors. Most importantly, p5RHH-rAAV8 vectors also demonstrated increased hepatic transduction in vivo in C57BL/6 mice.

Conclusion

The incorporation of melittin analogues into the rAAV capsids results in a significant improvement in rAAV-mediated transgene expression. While further modifications remain an area of interest, our studies have substantially broadened the pharmacological prospects of melittin in the context of viral vector-mediated gene delivery.

Key words: Melittin, Recombinant adeno-associated virus, Capsid engineering, Transduction efficiency