Study on the effect of solution conditions on heat induced-aggregation of human alpha interferon

ABSTRACT

A major problem in the formulation of therapeutic proteins is the irreversible protein aggregation. Recombinant human interferon alpha2b [rhIFN alpha 2b] has poor stability and undergoes physical degradation. The aim of this study was to investigate the effect of solution conditions on the heat-induced aggregation of rhIFN alpha 2b. The protein was incubated for 1 h at 40-70 [degree sign]C and for up to 240 h at 50 [degree sign]C and its aggregation tendency was then studied using optical density [at 350 nm], SE-HPLC, dynamic light scattering and SDS-PAGE methods. The effect of various pH [5, 6 and 7] and buffer concentrations [10, 55 and 100 mM] on the aggregation of protein following incubation at 50 [degree sign]C for 72 h was also evaluated. The results obtained for samples incubated at 50 [degree sign]C for up to 240 h showed that OD[350] and the amount of higher molecular weight aggregates [HMW] increased and the monomer content decreased significantly [p<0.05] as the incubation time increased. Following incubation at various temperatures, a significant increase in OD[350], drop in monomer content and increase in the amount of HMW aggregates were observed [p<0.05]. Data obtained from incubation of samples at 50 [degree sign]C for 72 h confirmed that regardless of the buffer concentration, the percentage of monomer at pH 6 was significantly higher than that at pH 7 and pH 5 [p<0.05]. At constant pH, although not significant, the same trend was observed when the buffer concentration increased to 100 mM. In conclusion, the change in solution conditions can influence the aggregation extent of rhIFN alpha 2b