The purification of a gs antigen of the murine mammary tumor virus and its quantitation by radioimmunoassay.

A method using Concanavalin (ConA) affinity chromatography has been developed for the purification of the mouse mammary tumor virus (MuMTV) gs antigens (gp52) and (p27). The procedure combines ConA chromatography and DEAE cellulose fractionation to yield the gs antigens in both high yield and sufficient purity for use in radioimmunoassay (RIA). The gp52 obtained has been iodinated with the [¹²⁵I]Bolton-Hunter reagent, chromatographed on Sephadex G-100, and utilized in the development of a blocking radio immunoassay (RIA). The sensitivity of this assay (0.5–1.0 ng) is superior to that achieved with whole particle assays. The procedures used for the isolation and iodination of the gp52 avoid the technical problem of incomplete displacement of [¹²⁵I]gp52 by native viral antigen. The resulting RIA provides a sensitive, reliable tool for studying the expression of the gp52 antigen and its relationship to the onset and progression of murine breast cancer.