Partial Nucleotide Sequencing and Molecular Evolution of Epidemic Causing Dengue 2 Strains

Abstract

To study the genetic variability and to detect evolutionary changes and movement of dengue 2 (DEN-2) strains, nucleotide sequencing of the envelope protein gene and the nonstructural protein 1 gene junction was performed for 9 isolates from the 1996 Delhi epidemic and 1 isolate from the 1967 Delhi epidemic. The epidemic strains had a divergence of 10%-11% from the 1967 strains, but were quite similar to DEN-2 isolates from Seychelles, Somalia, and Torres Strait. In addition, the sequence data were compared to the prototype DEN-2 strain, New Guinea C, and other published DEN-2 sequences from different parts of the world. The phylogenetic analysis by the Molecular Evolutionary Genetics Analysis program suggests that the 1996 Delhi isolates of DEN-2 were genotype IV. The 1967 isolate was similar to a 1957 isolate of DEN-2, P9-122, from India, and was classified as genotype V. This study indicates that earlier DEN-2 strains of genotype V have been replaced by genotype IV.

Molecular epidemiology and evolutionary analysis of dengue virus type 2, circulating in Delhi, India

“…This is further supported by increased mean divergence (3.86 %) of currently circulating Delhi isolates (KT717968-90), to the Seychelles strain (L10048). As in DENV-2 isolates from 1996 outbreak, 3.5 % mean divergence to this strain (L10048) was recorded [2].…”

“…Nearly after a decade, DENV-2 reemerged as predominant serotype during the outbreak in 2013 [6]. The emergence of DENV-2 is an alarming signal for public health, as this serotype has been associated with major DF and DHF outbreaks [2,[6][7][8]. Based on genomic Electronic supplementary material The online version of this article…”

“…During last two decades, Delhi, the national capital has emerged as one of the ''badly hit'' city by dengue. The city witnessed its first major dengue hemorrhagic fever (DHF) outbreak in 1996 [2]. Dengue virus type 2 (DENV-2) was confirmed as main etiological agent for this outbreak.…”

“…During the outbreak of DHF in 1996 in Delhi, predominance of Cosmopolitan genotype (genotype IV) was reported. Vigilance over the years recorded its continued circulation in the following years [2,8]. However, with emergence of DENV-3 in 2003, a downward shift in predominance of DENV-2 occurred, and its spread narrowed to sporadic cases [3][4][5]14].…”

“…The E protein, a major antigenic determinant, consists of three domains (I, II and III) and plays important role in virulence, receptor binding and fusion during the entry of virus particle [15]. Partial nucleotide sequence of E gene is widely used to infer the phylogeny of DENV [2,6].…”