LAUSR

Chikungunya is a mosquito-borne disease that causes periodic but explosive epidemics of acute disease throughout the tropical world. Vaccine development against chikungunya virus (CHIKV) has been hampered by the inability to conduct efficacy trials due to the unpredictability of CHIKV outbreaks. Therefore, immune correlates are being explored to gain inference into vaccine-induced protection. Current study is an in-depth serological characterization of Fab and Fc-mediated antibody responses in selected Phase 2 clinical trial participants following immunization with the recombinant measles-vectored CHIKV vaccine, MV-CHIK. Antibody comparisons were conducted between participants who received prime versus prime-boost vaccine regimens. MV-CHIK vaccination elicited potent Fab-mediated antibodies (such as CHIKV-specific IgG, neutralization and avidity), including dominant IgG3 responses which translated into strong antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). At 1-month, prime-boost immunization lead to significantly greater responses in every measured Fab and Fc antibody parameter. Interestingly, prime-boost-elicited antibodies decreased rapidly over time, until at 6-months both vaccine regimens displayed similar antibody profiles. Nonetheless, antibody avidity and ADCP remained significantly greater following boost immunization. Our observations suggest that a prime-boost administration of MV-CHIK will be more appropriate for CHIKV-endemic regions, while a prime only regimen may be sufficient for travel purposes or outbreak situations.