Stabilization of aerosolized IFN-γ by liposomes

Aerosolized IFN-gamma is very unstable. We have improved the stability of IFN-gamma in the jet nebulizer by adding small liposomes. Aerosolized IFN-gamma was recovered in PBS solution by bubbling and its concentration was determined. After nebulization for 30 min, aerosolized IFN-gamma, was detected only 0.4 +/- 0.2% of the initial amount in the PBS solution and 3.1 +/- 0.7% in the reservoir. On the other hand, the addition of small liposomes (HSPC/DSPG = 10/1 (molar ratio), 45 +/- 24 nm) in the nebulizer increased the stability of IFN-gamma, 27.2 +/- 4.7% of the initial amount in the PBS solution and 25.7 +/- 12.6% in the reservoir. The present study also examined the effects of composition and concentration of liposomes on the stabilization of aerosolized IFN-gamma. Liposome prepared from distearoyl phosphatidylcholine (DSPC) or hydrogenated soy phosphatidylcholine (HSPC) was very effective for stabilization of aerosolized IFN-gamma (DSPC/DPPG = 10/1, HSPC/DSPG = 10/1). HSPC/DSPG liposome was efficient at the concentration higher than 12.5 mu mols/ml for the stabilization of 5 x 10(5) JRU/ml of IFN-gamma. In considering the mechanism of this stabilization, the results of gel filtration chromatography suggest that IFN-gamma is inactivated by polymerization or aggregation in nebulization, while the inactivation is suppressed by liposomes due to their adsorption to IFN-gamma. (C) 1999 Elsevier Science B.V. All rights reserved.