Citation

Interferon (IFN) is a cytokine and classified into three types, namely, type I IFNs such as IFN-α and IFN-β,
type II IFNs such as IFN-γ, and type III IFNs such as IFN-λs (IFN-λ1 [interleukin {IL}-29], IFN-λ2 [IL-28A], and
IFN-λ3 [IL-28B]) [1]. Each IFN possesses cytostatic, antiviral, and immunomodulatory effects and has been used
in the treatment of patients with cancer, viral hepatitis, and multiple sclerosis (MS) for a long time. However,
there are two concerns in IFN therapy, i.e. short half-life of IFN protein in the body [2] and side effects associated
with biological activity of IFN.
To overcome above two concerns, gene delivery is a promising approach to achieve continuous supply of
IFN based on sustained transgene expression with reduced side effects associated with IFN by modification of
IFN. Gene transfer technique has attempted from late 20th [3]. Both viral vector and nonviral vector such as
plasmid DNA vector have been commonly utilized as gene transfer vectors. However, viral vector has concerns
regarding immune response, mutation in genome, and so on. Therefore, I utilized plasmid DNA vector for a
continuous supply of modified IFNs because the use of plasmid DNA vector hardly evoke those concerns. In this
thesis, I aimed to develop a promising IFN gene therapy strategy by plasmid DNA vector design for the treatment
of refractory diseases.
In Chapter I, I aimed to develop a long-term expression system of IFN-β, type I IFN, using plasmid DNA
vector. The long-term expression vector of IFN-γ, type II IFN, has been constructed by using CpG vector without
CpG motif, which suppress transgene expression [4]. In contrast, the development of the long-term expression
vector of IFN-β has not yet been achieved. Therefore, initially, I attempted to develop a novel plasmid DNA
vector for long-term expression vector of IFN-β and to apply to cancer gene therapy.
In Chapter II, antiviral effect of three types of IFNs using long-term expression vector of each IFN,
developed in Chapter I, against antiviral drug-resistant hepatitis C (HCV) infection was investigated. Human
hepatocyte-transplanted chimeric mice were infected with antiviral drug resistant HCV and administered
long-term expression vector of each IFN for comparison of antiviral effect of IFNs.
In Chapter III, I investigated whether continuous supply of IFN-β by using long-term expression vector and
design of IFN-β fusion proteins was effective to treat MS. In general, repeated administration of IFN-β is required
to reduce the relapse of MS and prevent MS progression. In Chapter III Section 1, the therapeutic effect of single
administration of the long-term expression vector of IFN-β constructed in Chapter I into MS model mice was
evaluated. In Chapter III Section 2, IFN-β fusion proteins were designed to improve the therapeutic effects and to
reduce side effects of IFN-β. Therapeutic and side effects in MS model mice were compared between IFN-β and
IFN-β fusion proteins.