Development and evaluation of baculovirus-expressed Chikungunya virus E1 envelope proteins for serodiagnosis of Chikungunya infection

- The diagnostics potential of recombinant baculoviruses carrying wild-type or mutant E1 envelope protein genes of Chikungunya virus were determined by developing IgG captured GAC-ELISAs.
- Both recombinant proteins were strongly reactive toward anti-CHIKV IgG and showed almost no cross-reactivity with anti-Dengue and flavivirus antibodies.
- These GAC-ELISAs were also able to detect the persistence of antibodies up to 6-months after the disease onset.
- These GAC-ELISAs will be a valuable tool not only to facilitate the clinical management, but also to advance disease-surveillance systems.

Population-based serosurveillance studies provide critical estimates on community-level immunity and the potential for future outbreaks. Currently, serological assays, such as IgG enzyme-linked immunosorbent assays (ELISAs) and indirect immunofluorescence tests (IIFT) based on the inactivated whole virus are used to determine past Chikungunya virus (CHIKV) infection. However, these commercially available tests have variable sensitivities. To develop and evaluate recombinant based CHIKV-specific IgG antibody capture ELISAs (GAC-ELISAs), baculoviruses carrying wild-type (E1-A226, named WT) or mutant (E1-A226V, named MUT) E1 envelope protein genes of CHIKV were generated. The seroreactivity of recombinant CHIKV WT and MUT envelope proteins were determined using residual blood, collected from CHIKV-confirmed patients. The sensitivities of both recombinant CHIKV envelope proteins were 83.0% as measured by GAC-ELISAs. The specificities of both recombinant proteins were 87.8%. These GAC-ELISAs were also able to detect the persistence of anti-CHIKV IgG antibodies up to 6 months after the disease onset, together with rise in sensitivities with increasing time. These results suggest that the baculovirus purified recombinant CHIKV envelope proteins react with anti-CHIKV IgG antibodies and may be useful in population-based seroprevalence surveys. In addition, these GAC-ELISAs offer good diagnostic value to determine the recent/past CHIKV infection status in non-endemic populations.