EMERGENCE OF VIRUS ESCAPE MUTANTS AFTER IMMUNIZATION WITH EPITOPE VACCINE

BALB/c and C57BUL/6J mice were immunized with recombinant Vaccines con sisting of lymphocytic choriomeningitis virus CD8(+) T-lymphocyte epit opes and a carrier protein. During challenge infection with WE strain lymphocytic choriomeningitis virus, mutants with alterations in distin ct amino acid residues of the epitopic nonapeptides appeared and multi plied. Splenocytes from WE-infected BALB/c mice lysed cells coated wit h the WE-type epitope; lysis was considerably less effective when the epitopic nonapeptide with which the syngeneic cells had been sensitize d was the mutated form. Neither target was lysed by splenocytes from B AlB/c mice infected with the variant virus. Mutants were not detected in F-1 hybrid mice immunized with two viral epitopes that were restric ted by class I molecules of both parents.