NS 1 gene sequences from eight dengue-2 viruses and their evolutionary relationships with other dengue-2 viruses.

The nucleotide sequences of the NS 1 genes from five Thai and three Sri Lankan dengue-2 viruses were determined by sequencing the viral RNA using synthetic oligonucleotide primers. The results were shown to be similar to four published dengue-2 NS 1 sequences and the classification of these genes was compared with the one obtained for the envelope genes of the same viruses. The classification was similar and showed that the Thai isolates could be divided into two separate groups and that the Sri Lankan isolates were distinct. We found no correlation between disease severity, serological response (1 degree or 2 degrees), or year of isolation and various aspects of NS 1 protein sequence variation; and no particular amino acid changes were correlated with virulence. The sequences were combined with those published and classified elsewhere to provide a comprehensive E/NS 1 gene taxonomy of dengue-2 virus isolates.