Two monoclonal antibody neutralization resistant (MAb(R)) variants of the yellow fever (YF) 17D-204 vaccine virus strain were selected using YF type-specific MAb B39. These B39(R) variants were compared with the variant virus selected by Lobigs et al. using a second YF-type specific MAb (2E10) which mapped to amino acid position 71/72 in the envelope (E) protein. Neutralization assays with a panel of MAbs suggested that these two YF-type-specific epitopes are located in two discrete regions of the folded E protein. Each of the B39(R) variants had a single nucleotide mutation which encoded an amino acid substitution at either position E-155 or E-158. Thus, YF type-specific epitopes map to both domain I (B39) and II (2E10) of the YF virus E protein. The B39 defined epitope represents the first flavivirus neutralizing epitope localized to this region of domain I of the E protein.
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