GP(33-41), a 9-aa-long peptide, is the optimal sequence of the GP1 epitope of lymphocytic choriomeningitis virus, and can upregulate H-2Db molecules at the RMA-S (Db Kb) cell surface with a SC50 of 344 nM. GP(33-41) Epitope is a strong agonist of CD8 T cells from P14 TCR-transgenic mice.