Abstract
Recombinant adeno-associated virus (rAAV) has emerged as one of the best gene delivery vectors for human gene therapy in vivo. However, the clinical efficacy of rAAV gene therapy is often hindered by the host immune response against its transgene products. Endoplasmic reticulum aminopeptidase 1 (ERAP1) is specialised to process peptides presented by class I molecules of major histocompatibility complex. Therefore, we hypothesise that modulation of the ERAP1 activity in rAAV transduced cells may be favoured to evade immune response against transgene products. In this study, we incorporated either miRNA-UL112-5p or ERAP1 shRNA into rAAV vectors expressing full-length ovalbumin (OVA) as a model antigen, and evaluated their effects for antigen presentation, cellular and humour immune response induced by OVA expression. The results indicated that silencing ERAP1 using miR-UL112-5p or ERAP1 shRNA did not affect the expression of OVA in cells, but inhibited the processing and presentation of OVA antigen peptide SIINFEKL in antigen presenting cells (APCs). Moreover, the rAAV vector co-expressing ERAP1 shRNA maintains stable and high expression of OVA in vivo, while simultaneously suppressing the humoral immunity of OVA. In addition, experimental results demonstrated that rAAV vectors incorporated ERAP1 shRNA efficiently repress costimulatory signals in dendritic cells (DCs), significantly attenuated the cytotoxic T-cell response, allowed for sustained transgene expression and reduced clearance of transduced muscle cells in mice. Moreover, our study suggested that the incorporation of miRNA-UL112-5p or ERAP1 shRNA into rAAV vectors effectively reduced transgene products induced immune response. The proposed method may potentially be applied in clinics to deliver therapeutic proteins safely and efficiently.