ERVW-1 and Splenomegaly: While the immunization of mice with the reduced dose of F-MuLV Env- and Gag-encoding vectors alone did not result in significant protection against initial splenomegaly, co-administration of adenoviral vectors encoding IFNα2, IFNα4, IFNα6 or IFNα9, but not IFNα1, IFNα5 or IFNβ, resulted in significant reduction of FV-induced splenomegaly (P < 0.05; shown in Figure 1A and 1B for days 14 and 17 post-challenge (p.c.)).