Identification of an epitope on the dengue virus membrane (M) protein defined by cross-protective monoclonal antibodies: design of an improved epitope sequence based on common determinants present in both envelope (E and M) proteins.

The protective capacity of monoclonal antibodies (MAbs) generated to the dengue-2 virus envelope (E) and premembrane (prM) proteins was tested in vivo. Two anti-E MAbs, 2C5.1 and 4G2 and two anti-prM MAbs, 2A4.1 and 2H2 provided cross-protection against all four dengue virus serotypes. Overlapping sets of synthetic peptides spanning amino-acid sequence 301-401 (domain III) of the E protein and the entire prM protein were then used to locate their epitopes. The anti-E MAbs strongly reacted with the peptide sequence 349-GRLITVNPIVT-359 (E349-359) from domain III and the immunodominant epitope, 274-SGNLLFTGHL-283 (E274-283) from the hinge region between domains I and II. The anti-prM MAbs strongly reacted with the sequence, 40-PGFTVMAAIL-49 (M40-49) from the first membrane-spanning domain of the M protein. These anti-prM MAbs also reacted with peptides E274-283 and E349-359, while the anti-E MAbs reacted with a peptide sequence, 1-FHLTTRNGEP-10 from the prM protein and these cross-reactions with both proteins were confirmed using immunoblot assays. MAbs 2C5.1, 4G2 and 2H2 more strongly reacted with an MEH1 peptide GLFTPNLITI, which was designed as an antigenic hybrid between these E and prM peptide sequences, than with any of these natural peptide sequences. These peptide sequence will now be tested for their ability to generate cross-protective antibodies against each dengue virus serotype when delivered with appropriate T-helper epitopes.