Anti-adenovirus immune responses in rats are enhanced by interleukin 4 but not interleukin 10 produced by recombinant adenovirus.

Recombinant adenoviruses can be used for in vivo gene transfer with great efficiency. However, the duration of transgene expression and the possibility of readministering the virus are severely limited by the host anti-adenovirus immune response, which is controlled mainly by cytokine networks. Adenoviruses encoding IL-4 (AdIL-4) or IL-10 (AdIL-10) were administered to rats through the portal vein and the anti-adenovirus immune response was studied. As compared with administering adenoviruses without transgene (Addl324) or with the lacZ gene (AdlacZ), AdIL-4, but not AdIL-10, resulted in a significant increase in leukocytes in the liver, with a predominance of macrophages that peaked on days 7 and 14 after gene transfer and gradually returned to normal by day 28. AdIL-4 induced a significant increase in both neutralizing and ELISA-detected anti-adenovirus antibodies, whereas AdIL-10 caused an increase in ELISA-detected antibodies alone. Anti-adenovirus antibodies were predominantly of Th1-dependent immunoglobulin subclasses in rats receiving Addl324, AdlacZ, or AdIL-10, whereas animals receiving AdIL-4 showed a predominance of Th2-dependent immunoglobulin subclasses. Type 1 (IFN-gamma) and type 2 (IL-5) cytokines were increased only in livers from rats receiving AdIL-4. Rats receiving AdIL-4 showed increased anti-adenovirus cytotoxic T lymphocyte activity and CD8+ cell depletion prevented leukocyte infiltration in the liver. These results show that IL-4 increases local and systemic immune responses against recombinant adenoviruses.

Adenovirus-mediated gene transfer in rat liver of interleukin 4 but not interleukin 10 produces severe acute hepatitis.

Several immune responses are either limited to or concentrated in a given organ. Cytokines produced during ongoing immune responses have organ-localized effects that can be only partially mimicked upon their systemic delivery. Recombinant adenoviruses are efficient vectors to induce transient organ-localized cytokine expression. This allows in vivo analysis of the effects of cytokines produced spatially and temporally in a manner comparable to that observed during immune responses. The authors generated recombinant adenovirus for rat IL-4 (AdIL-4) and IL-10 (AdIL-10) to analyse the in vivo effects of these two important immunoregulatory molecules after gene transfer in the liver. It was first established that AdIL-4 and AdIL-10 were able to direct the production of biologically active cytokines by different rat cell types in vitro. Intraportal injection of doses of up to 10(10) pfu of AdIL-10 or control non-coding recombinant adenovirus were well tolerated, and hepatic histology showed only mild alterations. Conversely, animals receiving more than 2.5 x 10(9) pfu of AdIL-4 showed dose-dependent mortality, with clinical signs of hepatic dysfunction. Liver histology in animals receiving 2.5 x 10(9) pfu of AdIL-4 showed severe acute hepatitis with maximal lesions between day 7 and 14 and almost complete normalization by day 28 after gene transfer. The leukocyte infiltrate was composed primarily of mononuclear cells, but eosinophils and mast cells were significantly increased as compared to control animals. Hepatic function was also altered in animals that received AdIL-4, with kinetics similar to that of histological lesions. Our study describes a model for investigating cytokine function in vivo through liver-localized transgene expression mediated by adenoviral vectors and demonstrates that liver production of IL-4 but not IL-10 results in acute severe hepatitis.