Comparison of the biological effects of anemia inducing and polycythemia inducing Friend virus complex.

The comparison of the biological effects of FVP and FVA showed that leukemogenesis appears to be delayed in FVA infected mice as compared to FVP infected animals after injection of comparable quantities of virus as measured in spleen focus forming units. In addition, no CFU-EI, characteristic for FVP induced leukemia, were found in leukemic spleen or bone marrow of FVA infected mice. Since it was possible to distinguish both viruses by their different host ranges, which are helper virus determined, it is suggested that the observed differences, especially the lack of CFU-EI in FVA infected mice, might be due to differences in the helper virus component of the FV complex.