IMMUNOPROTECTIVE DETERMINANTS IN FRIEND MURINE LEUKEMIA-VIRUS ENVELOPE PROTEIN

Several immunological epitopes are known to be located within the Frie nd murine leukemia virus (F-MULV) envelope protein, but their relative contributions to protection from Friend virus-induced disease are not known. To determine how expression of various immunological determina nts affected protection, mice were immunized with recombinant vaccinia viruses expressing different portions of the FMuLV envelope protein, and they were then challenged with a lethal dose of Friend virus compl ex. The disease parameters that were followed in the mice were early v iremia, early splenomegaly, and late splenomegaly. Both the N-terminal and C-terminal portions of the F-MuLV gp70 were found to protect agai nst late splenomegaly, the primary clinical sign associated with virus -induced erythroleukemia. However, neither region alone protected agai nst early splenomegaly and early viremia, indicating poor immunologica l control over early virus replication and spread through the spleen a nd blood. In contrast, mice immunized with a vaccine expressing the en tire F-MuLV envelope protein were protected against all three disease parameters. The results indicated that expression of multiple immunolo gical determinants including both T-helper and B cell epitopes was nec essary for full protection. (C) 1998 Academic Press.