P52
Control of bocavirus vector production by CRISPRa-VPR
S D Moreno-Velasquez(1) M Fritzenschaft(1) L Blaier(1) D Grimm(1)
1:University of Heidelberg, Department of Infectious Diseases, Section Viral Vector Technologies, Bioquant
Parvoviruses have been widely repurposed as safe, versatile, and efficient gene delivery vectors with adeno-associated virus (AAV) among the most important in the gene therapy field. Yet, concerns over transduction efficiency, immune activation and limited cargo size must be addressed. Bocavirus vectors (BoV) have emerged as a promising alternative to AAV due to their expanded cargo capacity (up to 6.3 kb) and stringent cell tropism that is particularly relevant for treatment of lung diseases. The production of recombinant AAV/Bocavirus vectors (rAAV/BoV) depends on the combination of diverse viral genes encoded in numerous plasmids. However, the use of transient plasmid transfections poses significant hurdles for large-scale production such as plasmid preparation, transfection efficiency and the inherently constitutive expression of cytotoxic viral genes. We envision the creation of a cell line, where all genes required for rAAV/BoV production are activated spatiotemporally. As initial proof-of-concept, we have modified the genome of the human bocavirus 1 (HBoV1) to be compatible with the CRISPR activation system (dCas9:VPR) for the controlled activation of capsid genes. The addition of a protospacer sequence downstream of the truncated HBoV1 p5 promoter allows for the tight control of the viral capsid gene by dCas9:VPR, resulting in 283-fold higher mRNA levels in HEK-293T cells. Furthermore, we adapted this novel system for large-scale rAAV/BoV production and measured a 1500-fold activation over the uninduced state, with vectors retaining their transduction potency. These findings pave the way for further reengineering of the rAAV/BoV genome to create a synthetic rAAV/BoV producer cell line.
