Efficacy of retroviral gene transfer into synovial fibroblasts is reduced by co-transduction with adenoviral vectors

Objective

Virus-based gene transfer is an elegant method to over-express molecules of choice and to analyze their effects on cartilage destruction in arthritis models. As combinations of different vector systems for delivery of two cartilage-protective genes may result in higher transduction efficacy, we compared double gene transfer, using adenoviral or retroviral vectors alone, to the combination of these two vectors.

Methods

RA synovial fibroblasts were transduced using IL-10- or IL-1ra-encoding MFG retrovirus (multiplicity of infection (MOI) of 50–200) and/or Ad5 adenovirus (MOI of 10–50). Double gene transduction was performed in vitro in a co-culture approach with (a) retroviral IL-10 and IL-1ra, (b) adenoviral IL-10 and IL-1ra, (c) adenoviral IL-10 and retroviral IL-1ra, (d) retroviral IL-10 and adenoviral IL-1ra. Cytokine production was measured by ELISA. Expression of proto-oncogenes and cytokines before and after gene transfer was analyzed using a combination of RNA arbitrarily primed PCR (RAP-PCR) and cDNA expression array to determine virus-mediated molecular effects.

Results

IL-1ra and IL-10 overexpression performed either with retroviral or with adenoviral vectors resulted in an enhanced synthesis of these cytokines. Cytokine expression was substantially higher in adenovirally transduced than in retrovirally transduced fibroblasts (IL-1ra 317 vs. 39 pg/ml; IL-10 221 vs. 44 pg/ml). Double gene transfer of a combination of retrovirus- and adenovirus-encoded genes resulted in a predominant expression of the gene encoded by the adenovirus even when the retroviral transduction was performed first. Virus-related effects on gene expression using LacZ or EGFP were higher in adenovirus- (4% of the proto-oncogenes and cytokines) than in retrovirus transduced fibroblasts (2%).

Conclusions

The results of the study demonstrate that combination of retro- and adenovirus-based vector systems for double gene transfer into RA synovial fibroblasts does not result in enhanced synthesis of the respective gene products but in suppression of the retroviral gene transfer. In addition, the experiments reveal that for human gene therapy the higher efficacy of adenovirus-based vectors needs to be outweighed against the lower effects on general alteration of gene expression when retrovirus-based vector systems are used.