Nonviral gene therapy by electrotransfer of hTNF-α soluble receptor variants: application to the treatment of collagen arthritis

Objectives

Electrotransfer (ET) was used to administer transgenes encoding three hTNF-α soluble receptor-I variants. Electrotransfer parameters and therapeutic effect in collagen-induced arthritis (CIA) in mice were studied.

Methods

Plasmids pCOR(hTNFRIs)1, pCORhTNFRIs/mIgG1, pCOR(hTNFRIs)2, encoding a monomeric, a chimeric or a dimeric form of hTNFRI, respectively, were used. Electrotransfer was performed by plasmids injection and electric pulses in muscle. hTNFRIs concentrations were determined by ELISA. PCR was performed on genomic DNA from various mouse organs to detect the plasmid. CIA was induced by immunization of DBA/1 mice with collagen II in adjuvant.

Results

ET of the three plasmids (1–15 μg) allowed hTNFRI production in sera and muscle after 10 days. This expression was dependent on the dose of plasmid. Local expression in the muscle lasted for at least 6 months. Systemic expression in the serum was detectable right from 1 μg for the hTNFRIs/mIgG1 form. It lasted for at least 6 months for the hTNFRIs/mIgG1 form, whereas expression was shorter for the two other forms (3 weeks). No plasmid DNA was found in the organs distant from the injected muscle (liver, spleen, kidney, gonads, heart, lung brain and distant muscle). ET of 50 μg pCOR/sTNFRI/IgG1 plasmid at the onset of clinical disease induced a clear-cut decrease in clinical signs of arthritis. The dimeric form was also efficient (P = 0.0378) although the effect was weaker than with the fusion protein. The monomeric form had no effect on arthritides.

Conclusion

Intramuscular ET of plasmids encoding the three forms of hTNFRIs leads to a long-term secretion of hTNFRIs in vivo. CIA is efficiently inhibited when ET of plasmids encoding either the chimera or the dimeric hTNFRIs was performed at the onset of the disease.