Abstract: Expression conditions of human immunodeficiency virus type 2 external glycoprotein gp105 in the recombinant Pichia Pastoris strain were optimized via orthogonal test of some factors such as the rate of aeration, the inductive duration, the initial pHand the concentration of methanol. The results from tests of between-subjects effects showed that the most important parameter for efficient expression of gp105 in recombinant Pichia Pastoris strain is adequate aeration during methanol induction, and the optimum inductive condition for gp105 expression was: more than 80% aeration, 3 days for induction, th einitial pHof 6.0-7.0, the final methanol concentration of 1.0%-1.5%. With this condition, the expressed gp105 was secreted into fermentation broth and reached a ield of 30%, approximately 200 mg/L. Expressed gp105 was isolated and purified by sating out and Sephadex G-100 chromatography and the yield of gp105 was 40%. gp105 was purified to electrophoretic purity and its pIwas about 5.0 by SDS-PAGEand isoelectrofocusing. Its N-terminal amino acid was arginine by Dansyl-Cl and the result indicated that expressed gp105 was secreted and cleavaged correctly. The results from ELISAdemonstrated that the purifiec gp105 showed good reactiongenicity and antigenic specificity.

Key words: Human immunodeficiency virus type 2(HIV-2>), External glycoprotein gp105, Purification