VIRAL VECTORS EXPRESSING IMMUNOREGULATORY CYTOKINES TO TREAT INFLAMMATORY BOWEL-DISEASE

Inflammatory bowel disease (IBD) is characterised by altered immunoreg ulation and augmented synthesis of nitric oxide. The purpose of this s tudy was to determine the effects of exogenous IL-4, introduced by a r ecombinant human type 5 adenovirus (Ad5) vector, on the tissue injury associated with an experimental model of colonic immune activation and inflammation. Colitis was induced in rats by the intrarectal admirati on of trinitrobenzene sulfonic acid (TNB) dissolved in 50% ethanol, an d control rats received saline via the same route. 1h later all rats w ere randomised into two groups. The first group was injected intraperi toneally (ip) with 3.0 x 10(6) plaque forming units (PFUs) of Ad5 tran sfected with murine interleukin-4 (Ad5IL-4) and the second group was i njected ip with the same amount of Ad5 expressing the Escherichia coli Lac Z gene (Ad5LacZ). One-half of the colitic and controls rats were injected again with 3.0 x 10(6) PFUs of Ad5IL-4 or Ad5LacZ on day 3 of the 6-d study. When introduced once or twice via the peritoneal route into control rats Ad5LacZ was localised to the serosal lining of the peritoneal cavity, the diaphragm and liver on day 6. One or two inject ions of Ad5IL-4 into rats also produced measurable levels of circulati ng IL-4. TNB-colitis in both Ad5LacZ-treated groups was associated wit h pronounced elevations in serum IFN-gamma, and mucosal ulceration of the distal colon. Myeloperoxidase and inducible nitric oxide synthase II (NOS II) synthetic activity were also increased by 30- and fivefold , respectively, above control levels in the distal colon. However, two injections of AD5IL-4 into colitic rats caused the overexpression of IL-4, and significantly inhibited tissue damage, serum and colon IFN-g amma levels and myeloperoxidase activity in the distal colon. In addit ion, NOS II gene expression and NOS II nitric oxide synthesis was sign ificantly inhibited. No therapeutic effect was observed in rats inject ed once with AD5IL-4. Thus, IL-4, introduced by Ad5, is therapeutic du ring acute inflammation in the rat colon. The therapeutic effect of IL -4 was associated with an inhibition of inducible nitric oxide express ion and a reduction in nitric oxide synthesis.