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.