Naked Sendai virus vector tacking all of the envelope-related genes: reduced cytopathogenicity and immunogenicity

Background Sendai virus (SeV) is a new class of cytoplasmic RNA vector that is free from genotoxicity that infects and multiplies in most mammalian cells, and directs high-level transgene expression. We improved the vector by deleting all of the envelope-related genes from the SeV genome and thus reducing its immunogenicity. Methods The matrix (M), fusion (F) and hemagglutinin-neuraminidase (HN) genes-deleted SeV vector (SeV/Delta M Delta F Delta HN) was recovered in a newly established packaging cell line. Then, the generated SeV/Delta M Delta F Delta HN vector was characterised by comparing with single gene-deleted type SeV vectors. Results This SeV/Delta M Delta F Delta HN vector carrying the green fluorescent protein gene in place of the envelope-related genes could be propagated to a titer of more than 10(8) cell infectious units/ml. This vector showed an efficient transduction capability in vitro and in vivo, and the cytopathic effect and induction of neutralizing antibody in vivo were greatly reduced compared with those of single gene-deleted type SeV vectors. No activity of neutralizing antibody or anti-HN antibody was seen when SeV/Delta M Delta F Delta HN was transduced ex vivo. Additional introduction of amino acid mutations that had been identified from SeV strains causing persistent infections was also effective for the reduction of cytopathic effects. Conclusions The deletion of genes from the SeV genome and the additional mutation are very effective for reducing both the immunogenic and cytopathic reactions to the SeV vector. These modifications are expected to improve the safety and broaden the range of clinical applications of this new class of cytoplasmic RNA vector. Copyright (c) 2006 John Wiley & Sons, Ltd.