Phylogenetic comparison of the DEN-2 Mexican isolate with other flaviviruses

Recent attention has focused on the geographic variation of dengue viruses, since major epidemies may follow introduction of a new virus strain into susceptible populations. We cloned and sequenced a very interesting Mexican isolate (200787/1983) which is antigenically unique by signature analysis with respect to all other dengue-2 topotype viruses. This strain is also unique in biological behavior (neurotropism) and is of epidemiological significance in Mexico. The dengue-2 Mexican isolate sequence information was compared with that of other flaviviruses, analyzing the branching structure of the phylogenetic tree reconstructed from the E gene amino acid sequences. The E glycoprotein, is target for neutralizing antibodies and T-cell responses, and defines the tropism and virulence of flaviviruses. In the phylogram, our strain was located in the position of greatest dissimilarity within serotype-2. Also, frequency analysis of amino acids revealed a very different signature pattern from that found in viral serotype-2.