Liver-Specific Alpha 2 Interferon Gene Expression Results in Protection from Induced Hepatitis

Abstract

The current therapy for hepatitis B and C is based on systemic administration of recombinant human alpha interferon (r-hIFN-␣). However, systemic delivery of r-hIFN-␣ is associated with severe side effects, but more importantly, it is effective in only a small percentage of patients. In an effort to maximize IFN-␣ antiviral efficacy, we have explored the therapeutic potential of murine IFN-␣2 (mIFN␣2) selectively expressed in the liver. To this end, we have developed a helper-dependent adenovirus vector (HD) containing the mIFN-␣2 gene under the control of the liver-specific transthyretin promoter (HD-IFN). Comparison with a first-generation adenovirus carrying the same mIFN-␣2 expression cassette indicates that at certain HD-IFN doses, induction of antiviral genes can be achieved in the absence of detectable circulating mIFN-␣2. Challenge of injected mice with mouse hepatitis virus type 3 showed that HD-IFN provides high liver protection. Moreover, liver protection was also observed in acute nonviral liver inflammation hepatitis induced by concanavalin A at 1 month postinfection. These results hold promise for the development of a gene therapy treatment for chronic viral hepatitis based on liver-restricted expression of IFN-␣2.Interferon (IFN) was discovered by Isaac and Lindenmann in 1957 (18), and recently the U.S. Food and Drug Administration has approved recombinant human IFN-␣ (r-hIFN-␣) for the treatment of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. IFN-␣ acts on target cells to confer a state of resistance to viral infectivity at one or more stages of virus entry or replication. These biological effects require binding to the type I IFN receptor complex, which is composed of two subunits, ␣ and ␤ (12). Both subunits undergo rapid ligand-dependent tyrosine phosphorylation, and the ␣ subunit itself acts as a species-specific transducer for type I IFN action (7). At least 30 genes are known to be transcriptionally induced by type I IFNs, including 2Ј,5Ј-oligoadenylate synthetase (2Ј5ЈOAS), the double-stranded RNA-activated protein kinase, and the IFN-I response factor I (8, 10). 2Ј5ЈOAS is important for antiviral response, and its activity is required by cells to activate the endonuclease RNase L, which degrades RNA (31).The currently available treatment for HCV with r-hIFN-␣ results in clearance of the virus in only 20% of patients. However, recent clinical trials have shown that a combination of r-hIFN-␣ and the antiviral drug ribavirin can increase the percentage of recovery up to 40% (9, 30). Although these results appear to be very promising, systemic injection of r-hIFN-␣ is associated with severe side effects, which worsen in combination with ribavirin, causing the withdrawal of 20% of patients from therapy.It is not clear why r-hIFN-␣ treatment is effective in only a minority of patients. One possible explanation has been postulated on the basis of association of specific HCV genotype and lack of sustained response. HCV proteins may block IFN-␣-induced antiviral polypeptides, t...

An improved helper-dependent adenoviral vector allows persistent gene expression after intramuscular delivery and overcomes preexisting immunity to adenovirus

“…delivery in both naïve small laboratory animals (8,9,11,16) and nonhuman primates (10). This important property, together with the observation that their systemic inoculation does not cause significant liver damage and toxicity (8,9,23,24), makes HD vectors the best available Ad vectors for somatic gene transfer, opening up possibilities for their future clinical use. However, systemic inoculation of Ad vectors in a clinical setting might be rendered inefficient by the presence of circulating neutralizing antibodies to the same or cross-reactive serotype as a consequence of a natural infection.…”

Gutless adenovirus: last-generation adenovirus for gene therapy

“…[80][81][82] Therapeutic genes carried by gutless vectors have been administered to the liver of mouse models for different diseases, such as hemophilia A and B, 83,84 obesity, 66 familial hypercholesterolemia, 81,85-87 ornithine transcarbamylase deficiency, 88 diabetes 89 and chronic viral hepatitis. 90,91 Therapeutic levels of most proteins have been documented for a long-term duration. In some cases the antibody response against a nonendogenous transgene led to a significant decrease in the circulating levels of the therapeutic protein.…”

“…However, when the transgene expression was driven by a liver-specific promoter, the immune response was lower, efficacy of the therapeutic protein increased and secondary effects derived from systemic circulation of the therapeutic protein were undetectable. 90,92 The encouraging results obtained in rodents had promoted the preclinical studies in larger animal models. This is the case for hemophilia A and B dogs, 72,83 which resulted in minimal acute liver toxicity and transient expression of the transgene allowing for partial or complete correction of hemophilia.…”

Genetic vaccines against Ep‐CAM break tolerance to self in a limited subset of subjects: Initial identification of predictive biomarkers

“…Ad vectors were constructed as described [30]. A tumor cell line expressing hEp-CAM was obtained using pV1J-Ep-CAM-Zeo, which contains the zeocyn-selectable marker.…”