Use of nucleotide sequencing of the genomic cDNA fragments of the capsid/premembrane junction region for molecular epidemiology of dengue type 2 viruses

The recent emergence of dengue hemorrhagic fever/dengue shock syndrome (DHF/ DSS) in India has been a source of concern. In the present study a quantitative comparison of 406 nucleotide long sequence from the capsid-premembrane junction region (C-PrM) of 9 dengue virus type 2 (DEN-2) isolates from Delhi with 10 DEN-2 isolates from diverse geographic areas provided sufficient information for estimating genetic relationships. The data indicated that the 1996 epidemic of DHF in Delhi was caused by genotype IV strains of DEN-2. This genotype, perhaps, displaced genotype V strains of DEN-2, which was circulating genotype in 1967. The period during which this displacement had occurred is not clear from the present study. Nonetheless, similar experience in four countries in Latin America and in Sri Lanka suggest that the introduction of new genotypes of DEN-2 displacing the circulating genotype may be associated with the appearance of DHF/DSS. More work is required to elucidate this hypothesis. Transitions at nucleotide positions 406 and 431 resulted in amino acid substitutions near (aa position 104, methionine --> valine) and at the hinge region (aa position 112, valine --> alanine) of C-PrM, respectively in all/most genotypes of group III and IV DEN-2 viruses analysed. Most of these virus strains have been isolated from DHF/DSS outbreaks. Significance of this observation is discussed. The data presented in this study suggest the utility of C-PrM sequence analysis for molecular epidemiology of dengue viruses.