Radioimmunoassays that demonstrate type-specific and group-specific antigenic reactivities for the major internal structural protein of murine mammary tumor viruses.

The 28,000-dalton (p28) major structural polypeptide of the mouse mammary tumor virus (MMTV) was isolated and used to develop a highly sensitive and specific radioimmunoassay. Under conditions of limiting antibody in competitive binding assays, as little as 50 pg of purified p28, as well as disrupted MMTV virions and mammary tumor extracts, competed specifically with 125I-labeled MMTV p28. The p28 polypeptide was further shown to contain both group-specific and type-specific antigenic determinants, thus also allowing for further differentiation of various MMTV strains.