EYRAplex platform for quantification of viral antigen-specific IgG responses.

Quantification of antigen-specific antibodies is fundamental to studies of infection, vaccination, and humoral immunity. Conventional serological assays typically measure responses to a single antigen and require relatively large sample volumes, whereas multiplex platforms enable simultaneous analysis of multiple analytes while conserving sample material. Here, we describe the use of EYRAplex as a bead-based multiplex platform to quantify antigen-specific IgG responses against multiple viral antigens. The major structural envelope proteins from three flaviviruses, tick-borne encephalitis virus, Japanese encephalitis virus, and yellow fever virus, were coupled to color-coded magnetic beads and used to measure IgG responses in longitudinal serum samples from vaccinated individuals. Assay performance was optimized by evaluating antigen coupling densities and serum dilutions, and analytical sensitivity was assessed using flavivirus-specific monoclonal antibodies. The assay reliably quantified the magnitude and kinetics of vaccine-induced antibody responses and distinguished type-specific from cross-reactive antibodies across flavivirus antigens. These findings demonstrate that EYRAplex provides a robust, scalable, and versatile multiplex platform for quantifying antigen-specific IgG responses in human samples.