Chimeric Capsid Proteins Impact Transduction Efficiency of Haploid Adeno-Associated Virus Vectors

Abstract

Our previous studies have demonstrated that haploid AAV vectors made from capsids of two different serotypes induced high transduction and prevented serotype-specific antibody binding. In this study, we explored the transduction efficiency of several haploid viruses, which were made from the VP1/VP2 of one serotype and VP3 of another compatible serotype. After systemic injection of 2 × 1010 vg of AAV vectors into mice, the haploid AAV vectors, composed of VP1/VP2 from serotypes 8 or 9, and VP3 from AAV2, displayed a two to seven-fold increase in liver transduction compared with those of parental AAV2 vectors. Furthermore, a chimeric AAV2/8 VP1/VP2 with N-terminus of VP1/VP2 from AAV2 and C-terminus (VP3 domain) from AAV8 was constructed, and produced the haploid vector 28m-2VP3 with AAV2 VP3. The haploid 28m-2VP3 vector showed a five-fold higher transduction than that of the vectors composed solely of AAV2 VPs. Remarkably, the 28m-2VP3 vectors also induced a significant increase in transgene expression compared to the vectors composed of AAV8 VP1/VP2 with AAV2 VP3. The results suggest that the difference in the VP1/VP2 N-terminal region between AAV2 and AAV8 may allow better “communication” between the VP1/VP2 N-terminus of AAV2 with its cognate VP3. Similarly, the haploid vectors, VP1/VP2 from serotypes 8 or 9 and VP3 from AAV3, achieved higher transductions in multiple tissue types beyond typical tropism compared with those of AAV3 vectors. Consistently, higher vector genome copy numbers were detected in these tissues, indicating that an incorporation of non-cognate VP1/VP2 might influence the cellular tropism of the haploid vectors. However, there was no significant difference or even decreased transductions when compared with those of parental AAV8 or AAV9 vectors. In summary, these studies provide insight into current development strategies of AAV vectors that can increase AAV transduction across multiple tissues.

AAV vectors: The Rubik’s cube of human gene therapy

“…Chai et al. 177 explored the transduction efficiency of several haploid viruses, which were made from the VP1/VP2 of one serotype and VP3 of another compatible serotype. The haploid AAV vectors, composed of VP1/VP2 from serotypes 8 or 9, and VP3 from AAV2, displayed an increased liver transduction compared with those of AAV2 vectors, while those with VP1/VP2 from serotypes 8 or 9 and VP3 from AAV3 achieved higher transductions in multiple tissue types compared with those of AAV3 vectors.…”

Adeno-Associated Virus (AAV) Gene Delivery: Dissecting Molecular Interactions upon Cell Entry

“…AAV capsid monomers from different plasmid sources can also form “mosaic” rAAV particles with altered transduction efficiency. Mosaic rAAV are typically avoided for current gene therapy approaches [ 96 ], but researchers continue to identify mosaic AAV capsids with unique biochemical and transduction properties [ 97 , 98 , 99 , 100 , 101 ].…”

Bound Protein- and Peptide-Based Strategies for Adeno-Associated Virus Vector-Mediated Gene Therapy: Where Do We Stand Now?

“…28 Moreover, we recently demonstrated that polyploid rAAV vectors, generated from the cotransfection of AAV helper plasmids of different serotypes or mutants, are able to enhance AAV transduction in the liver and muscle and escape the pre-existing Nabs. 28,29 Since polyploid vectors contain subunits from different AAV capsids, they potentially acquire advantages from parental serotypes or mutants for enhanced AAV transduction. Additional approaches without capsid modification involve proteins and peptides, which have attracted considerable attention for a wide range of applications in the fields of gene therapy and biotechnology.…”