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

Publisher Website
Google Scholar
Abstract
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 effetive, these might allow the synthesis of peptides suitable for vaccination. For this study we used the E protein and defined fragments there of 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 tests. If the E protein used as antigen was reduced (the native E protein contains six disulphide bridges) and denatured theb resulting antibodies did not consistently demonstrate neutralizing activity. These results show that the E protein of WN virus does not contain a linear segment that 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 disulphide bridges intact, purified by preparative SDS-PAGE under the condtions used in our experiments could, however, induce the synthesis of neutralizing antibodies in rabbits. These data indicate that at least one complex epitope which is able to induce neutralizing antibodies is not completely denatured or can be reformed to some extent if the complete E protein has been subjected to SDS-PAGE without prior destructuion of the disulphide bridges.