Direct synovial gene transfer with retroviral vectors in rat adjuvant arthritis.

OBJECTIVE

To evaluate the feasibility of direct in vivo gene transfer in an animal model of arthritis using a retroviral vector.

METHODS

The timing and dose of retroviral vector was examined using very high titer retroviral vector (> or = 10(9) CFU) in rat adjuvant arthritis. Retroviral vector expressing beta-galactosidase (beta-gal) or vehicle alone was injected into the right ankle of rats with adjuvant arthritis. Ankles were injected either on Day 7 (pre-arthritis), Day 10 (early arthritis), Day 15 (accelerating arthritis), or Day 28 (chronic arthritis) after adjuvant immunization. Joints were harvested 3 days later and extracts were assayed for beta-gal activity.

RESULTS

Synovial beta-gal expression was minimal in the Day 7 group and elevated in the Day 10, Day 15, and Day 28 groups. Gene transfer with retroviral vector did not exacerbate the local inflammatory response. Minimal or no beta-gal expression was observed in the contralateral uninjected paw or in the spleen, lung, liver, and kidneys. Frozen sections of retroviral vector injected joints were stained with X-gal and revealed transduced cells in the lining and superficial sublining layers. To determine the longevity of gene expression, ankle joints were injected with vector on Day 15 post-adjuvant, harvested, and assayed for beta-gal activity for up to 49 days after injection. Expression of the enzyme peaked from Day 3 to 7 and was still readily detected up to 49 days after retrovirus infection.

CONCLUSION

This is the first report of successful direct in vivo gene transfer in the rat adjuvant arthritis model using a retroviral vector. Appropriate timing of administration and very high titer retroviral vector preparations are key determinants of adequate gene transduction.