An Analysis of the Antibody Response against West Nile Virus E Protein Purified by SDS-PAGE Indicates that This Protein Does Not Contain Sequential Epitopes for Efficient Induction of Neutralizing Antibodies

The large envelope (E) protein of flaviviruses is the viral surface protein that contains neutralizing epitopes. We have analysed the E protein of the West Nile (WN) flavivirus for neutralizing epitopes generated from linear segments of the protein; if effective, these might allow the synthesis of peptides uitable for vaccination. For this study we used the E protein and defined fragments thereof as antigens in rabbits. The sera thus obtained, containing antibodies to E protein as shown by Western blot analyses, were tested for neutralizing activity by the plaque reduction neutralization test. If the E protein used as antigen was reduced (the native E protein contains ix disulphide bridges) and denatured the resulting antibodies did not consistently demonstrate n utralizing activity. These results how that the E protein of WN virus does not contain a linear segment hat is able to induce neutralizing antibodies efficiently. Studies using denatured E protein fragments containing subsets of the intact disulphide bridges showed that the local covalent primary structure of the protein involved in each of the six bridges was also insufficient for inducing the synthesis of neutralizing antibodies. The complete E protein, with all six disulphid