Spleen Focus-Forming Viruses

**Definition:** Strains of MURINE LEUKEMIA VIRUS that are replication-defective and rapidly transforming. The envelope gene plays an essential role in initiating erythroleukemia (LEUKEMIA, ERYTHROBLASTIC, ACUTE), manifested by splenic foci, SPLENOMEGALY, and POLYCYTHEMIA. Spleen focus-forming viruses are generated by recombination with endogenous retroviral sequences.

**Tree numbers:** - B04.613.807.375.525.850 - B04.820.650.375.525.850

**Synonyms:** - SFFV