Identification of three H-2K(d) restricted CTL epitopes of NS4A and NS4B protein from Yellow fever 17D vaccine.

In this study, 12 nonamers derived from the nonstructural protein NS4A and NS4B of a Chinese attenuated Yellow fever 17D (YF-17D) vaccine strain were screened for their ability to elicit a recall interferon-γ (IFN-γ) response from the splenocytes of BALB/c mice following DNA vaccination and a booster vaccination with recombinant vaccinia virus expressing NS4A or NS4B protein. Three peptides (amino acid residues S(106)YIMLIFFV from NS4A protein and V(43)YVGIVTML and L(174)YLLLALSL from NS4B protein) were identified as CD8(+) cytotoxic T lymphocyte (CTL) epitopes. These peptides elicited a response from a significant numbers of IFN-γ secreting cells compared with the other nonamers of NS4A and NS4B and compared to one irrelevant nonamer derived from infectious bronchitis virus (IBV) H52 strain. Bioinformatics analysis demonstrated that these three nonamers are H-2K(d)-restricted CTL epitopes. The multiple amino acid sequence alignments among different YFV NS4A, and NS4B sequences submitted to GenBank indicated that these three CTL epitopes are strongly conserved; this novel finding will potentially aid further studies on cellular immunity against YF virus and YFV-based expression vectors.