Assessment of the antigenic structure of tick-borne encephalitis virus by the use of synthetic peptides.

The feasibility of using synthetic peptides for the identification of individual monoclonal antibody (MAb)-defined epitopes was assessed on the basis of a structural model of the tick-borne encephalitis (TBE) virus envelope glycoprotein E. For this purpose a series of 19 synthetic peptides was prepared, covering most of the E protein sequence. Each of the peptides was tested by ELISA for reactivity with 19 protein E-specific MAbs raised against TBE virus strain Neudoerfl. Specific reactivity was observed with three MAbs and two peptides (representing amino acids 1 to 22 and 221 to 240, respectively), thus providing new information on the location of the corresponding epitopes. Specificity was confirmed in a competition ELISA by the ability of the peptides to block MAb binding to TBE virus antigen. However, in contrast to the other MAbs, these peptide-reactive MAbs were not blocked by native virus particles in the competition ELISA, indicating that they do not recognize the native conformation of the E protein. These three MAbs also showed increased reactivity with denatured forms of the virus in a dot blot assay. Additionally, they reacted only in ELISA systems in which the virus was directly coated to the solid phase and thereby presumably partially denatured, but not when a capture antibody was used, which preserves the native antigen conformation. We have thus identified two classes of MAbs, those which recognize the native form and those which recognize the denatured form of protein E. The latter may be useful for the analysis of sites probably involved in protein folding and oligomerization.