Development of dengue virus complex-specific IgG immunoassay, with high sensitivity, using envelope domain III variants

Purpose: Flaviviruses, particularly dengue virus (DENV) and zika virus (ZIKV), share antigenic similarities and induce cross-reactive antibodies that diminishes the utility of antibody detection immunoassays. Flavivirus envelope domain III (EDIII), a species-specific domain, can be used for specific detection of antibodies but with poor sensitivity. Objective of this study was to develop a sensitive EDIII-based immunoassay, for specific detection of anti-DENV IgGs, suitable for surveillance purpose. Methods & Materials: Recombinant EDIIIs, from four DENV serotypes and ZIKV, were produced in yeast P. pastoris. Whereas MBP-fused EDIIIs were produced in E. coli. For DENV IgG immunoassays, mixture of EDIIIs from four DENV serotypes were used. Direct immobilization of EDIIIs on polystyrene wells and immobilization of biotinylated-EDIIIs on streptavidin wells was done to establish several versions of time-resolved fluorescence immunoassays (FIAs). Performance of different FIAs was assessed using sera from pediatric and adult population. Full envelope (ecto-domain) based FIAs, and commercial Panbio dengue IgG ELISA were run in parallel. Results: Comparative analysis of different EDIII-based IgG FIAs revealed that the direct immobilization strategy is least sensitive [17.56% (95%CI: 11.99-24.97%) in pediatric and 40.74% (95%CI: 30.70-51.62%) in adult population]. On the contrary, immobilization of tagged EDIII enhances the sensitivity to 54.96% (CI 95%: 46.42-63.22%) in pediatric and 53.09% (CI 95%: 42.33-63.57%) in adult population for MBP-EDIII on polystyrene surface and 85.50% (CI 95%: 78.46-90.51%) in pediatric and 82.72% (CI 95%: 73.05-89.42%) in the adult population for biotinylated-EDIII on streptavidin surface. Almost all the DENV IgG positive samples (93.89% from pediatric and 98.77% from adult subjects) cross-reacted with ZIKV-envelope-based FIA. However, the cross-reactivity of DENV IgG positive samples with biotinylated-ZIKV-EDIII-based FIA was only 3.82% in pediatric and 9.87% in the adult population. Conclusion: The developed biotinylated-EDIII-based immunoassay can be used to detect anti-DENV IgGs, devoid of major cross-reactivity, in a sensitive manner. Therefore, this assay will be highly useful for the sero-surveillance purpose.