PROJECT

Pan-India antigenic characterization of dengue viruses: early warning signal for a potential pandemic

March 2024 - March 2027

Objectives:

i. To study antigenic characteristics of dengue viruses circulating across India.
ii. To develop Spatio-temporal antigenic maps on real-time basis to indicate the antigenic evolution of dengue viruses across India
iii. To understand factors associated with the cause of variation: vector, environment or host.
iv. To study the effect of genomic diversity on the antigenic variation of dengue viruses by in-silico analysis and it’s correlation with wet lab validation.
v. To determine the impact of antigenic variation on the efficacy of potential vaccines and specific therapeutic intervention if one becomes available.

Study Overview:

Early detection of any outbreak with a rapid response is the key to combating an emerging viral disease before it turns into an epidemic. Vector-borne flaviviruses (especially Dengue, JE, Zika and WNV) have an epidemic potential given the endemicity of flaviviruses in India and their peculiar immunopathogenesis. Like all other RNA viruses, dengue virus undergoes frequent genetic changes resulting in multiple circulating genotypes, commonly referred to as quasispecies, within a serotype. These genetic differences may or may not translate into antigenic differences. If the former happens then that results in differential neutralization of circulating strains within a serotype by hyperimmune sera (either from vaccinated or infected individuals) that affects the manifestation of clinical disease and hence the clinical outcome. This study aims to undertake antigenic characterization of dengue virus on a rolling basis across India to identify substantial antigenic variations that translate into phenotypic differences.

Study Approach:

• Surveillance for dengue virus by commercial multiplex and monoplex conventional RT- PCR or qRT-PCR will be done on Pan-India basis to cover the length and breadth of India.
• All positive samples will be subjected to genome sequencing to determine the genetic variation and cluster the circulating strains within known genotypes.
• Standard bioinformatics tools will be applied for studying virus evolution and antigenic clades will be defined in-silico based on envelope (E) and pre-membrane (prM) protein sequences.
• From each distinct antigenic clade, representative samples will be selected and characterized by plaque reduction neutralization test using NHP serum raised against reference strains of each serotype. Based on the PRNT titers, real-time antigenic maps will be prepared to depict antigenic relatedness.

Expected Public Health Impact:

The study will develop a year-on-year antigenic monitoring of dengue virus to provide an early warning signal for a potential pandemic if a substantial antigenic variation is noticed.