Newly Developed Sendai Virus Vector for Retinal Gene Transfer: Reduction of Innate Immune Response Due to Deletion of All Envelop-Related Genes

Abstract

Purpose:: Recombinant Sendai virus vector (rSeV) is a new class of cytoplasmic RNA vector that has shown high gene transduction efficiency in various organs, including retinal tissue. This vector system is free from genotoxicity, an advantageous feature with regard to human gene therapy; however the related immune response are important issue to be overcome in some clinical applications. We recently developed a novel rSeV vector deleted all envelop-related genes (rSeV/dFdMdHN), and here assessed host immune responses following retinal gene transfer by rSeV/dFdMdHN.

Methods:: rSeV/dFdMdHN or F-gene deleted the first generation SeV (rSeV/dF) encoding the green fluorescent protein or luciferase was used in this study. Vector solution was injected into subretinal space of adult Wistar rats or C57BL/6 mice. The transgene expression and histopathological findings were assessed at various time points. Immunological assessments including the expression of proinflammatory cytokines, NK-cell activity, as well as SeV-specific cytotoxic lymphocytes (CTLs) and antibodies have been performed following vector injection.

Results:: rSeV/dFdMdHN showed high gene transfer efficiency into the retinal pigment epithelium (RPE) at the equivalent level to that was seen in use of rSeV/dF. In the early phase, up-regulation of pro-inflammatory cytokines, local infiltration of inflammatory cells and the tissue damage, that were prominently seen in rSeV/dF injection, was significantly diminished in use of rSeV/dFdMdHN. NK-cell cytotoxicity was also decreased, indicating the dramatic reduction of innate immune response. In the later phase, however, CTL activity and anti-SeV antibodies were similarly induced even in use of rSeV/dFdMdHN, resulted in the transient transgene expression in both vector types.

Conclusions:: Our investigations demonstrated that the expression of envelop proteins of SeV play a major role in the induction of innate immune response, and deletion of envelop-related genes dramatically reduce the vector-induced retinal damage. These findings may extend its clinical availability for ocular gene transfer; however further studies are called for regulating the acquired immune response against SeV in order to utilize this vector system.

Keywords: gene transfer/gene therapy • retina • immunomodulation/immunoregulation