Rapid in vivo assay for Friend polycythemia virus

An assay for the Friend polycythemia virus (FVP) was developed based on the capacity of plasma from FVP infected animals to increase greatly the splenic uptake of ⁵⁹Fe as early as 3 days after infection in fasted BALB/c mice. The authors' experiments supported the following conclusions. The increase in splenic ⁵⁹Fe uptake represented a proportional increase in hemoglobin synthesis. The ⁵⁹Fe response was not due to the presence of erythropoietin in the FVP plasma or to the induction by FVP of endogenous erythropoietin production. The ⁵⁹Fe assay correlated well with the spleen focus forming assay. The assay had applicability in monitoring FVP purification procedures and studying physicochemical properties of FVP.