Radioimmunoassay of murine leukemia virus p30 using Staphylococcus aureus as immunoadsorbent.

A competition radioimmunoassay for murine leukemia virus p30 has been developed. Serial dilutions of the unknown in wells of microtiter plates are incubated with 125I-labeled p30 and goat antiserum specific for p30. Bound p30 is then removed by an immunoadsorbent specific for goat immunoglobulin, prepared from S. aureus. An internal standard of 51Cr is used to correct for volumetric errors, the amount of the labeled p30 precipitated being calculated from the 125I/51 Cr ratio of the supernatant. The assay is rapid, being completed within 2 h, precise, having a coefficient of variation less than 1%, and sensitive, being capable of detecting p30 concentrations as low as 2 ng/ml in a volume of 0.02 ml. It has been used to measure p30 levels in a series of MCA-induced fibrosarcomas of BALB/c mice.