Systemic production of IL-12 by naked DNA mediated gene transfer: toxicity and attenuation of transgene expression in vivo

J Gene Med. 2001 Jul-Aug;3(4):384-93. doi: 10.1002/jgm.201.

Abstract

Background: IL-12 is a potent antitumor cytokine for cancer gene therapy. Previously, we demonstrated that single systemic administration of naked DNA (encoding IL-12) could serve as a good model for in vivo evaluation of the antitumor effect of a candidate gene (unpublished data). In the present study, we propose that this gene delivery method could be a very useful model for in vivo evaluation of the toxicity of a given therapeutic gene (using IL-12 as an example). By comparing the toxicities and the effects of initial IL-12 administration on subsequent transgene expression, both IL-12 gene delivery and recombinant murine IL-12 protein (rmIL-12) administration showed similar toxicity profiles.

Methods: Naked DNA encoding murine IL-12 (mIL-12) was delivered into mice by systemic administration. Toxicity profiles of mice treated with DNA or rmIL-12 were compared.

Results: Systemic administration of naked DNA encoding mIL-12 resulted in very similar toxicity as rmIL-12 with respect to liver enzyme, hematological and immunological profiles. Repeated injection of mIL-12 gene did not recover a high level of mIL-12 production as the first injection. Moreover, initial mIL-12 administration resulted in inhibition of subsequent reporter gene expression with both viral and non-viral promoters (CMV, human alpha-antitrypsin or chicken beta-actin promoter). This transgene inhibition effect was entirely mediated by IFN-gamma as the transgene expression was fully recovered in IFN-gamma knockout mice.

Conclusions: Systemic IL-12 therapy, with either a protein or gene therapy approach, resulted in comparable liver and systemic toxicities. Refractoriness of mIL-12 production by subsequent administration of mIL-12 gene was observed. The transgene attenuation effect of IL-12 pre-dosing (either by IL-12 or rmIL-12), mediated by IFN-gamma, provided important insights for the design of IL-12 combination gene therapy and the improvement of gene vectors for IL-12 therapy. The present results show that simple injection of naked DNA could serve as a good model for in vivo evaluation of the toxicity of a candidate therapeutic gene.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cytomegalovirus / genetics
  • Hematocrit
  • Interleukin-12 / genetics*
  • Interleukin-12 / toxicity
  • Leukocytes / drug effects
  • Liver / drug effects
  • Liver / pathology
  • Liver / physiopathology*
  • Liver Function Tests
  • Mice
  • Mice, Transgenic
  • Plasmids
  • Promoter Regions, Genetic
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / toxicity
  • alpha 1-Antitrypsin / genetics

Substances

  • Recombinant Fusion Proteins
  • alpha 1-Antitrypsin
  • Interleukin-12