An enzyme-linked immunosorbent assay to detect alkali-soluble spore surface antigens of strains of Nosema bombycis (Microspora: Nosematidae)

Abstract

Spore surface antigens of strains of Nosema bombycis were extracted with alkaline solutions and used in an indirect enzyme-linked immunosorbent assay. Treatment of N. bombycis spores with 0.1 n potassium carbonate or potassium hydroxide solution at 27°C for 30 min was sufficient for the extraction of the antigens. Usually, 10 8 spores of N. bombycis liberated ca. 30 μg spore surface proteins. The indirect enzyme-linked immunosorbent assay detected as little as 60 ng of spore surface proteins (ca. 2000 spore-equivalent antigen). The alkali-soluble spore surface antigens of N. bombycis contained a specific antigen and were stable under storage at −20°C for more than 1 year. The serological assay separated the Nosema isolates pathogenic to the silkworm into three groups.