Enhancing immunogenicity: Evaluating the polio antigen immune response in hexavalent vaccine formulations

Hexavalent vaccines simplify childhood immunization by combining antigens against six diseases in a single formulation; however, the immunogenicity of each component must be evaluated. This study assessed poliovirus-specific immunoglobulin G (IgG) responses elicited by candidate hexavalent vaccines containing different doses of Sabin strain-derived inactivated poliovirus vaccine (sIPV). A preclinical study was conducted using 40 Wistar rats allocated to five groups: hexavalent vaccine containing low-, medium-, or high-dose sIPV; pentavalent vaccine combined with sIPV; or adjuvant control. Each group comprised four male and four female rats. The animals received primary immunization at week 0 and booster doses at weeks 4 and 8. Serotype-specific IgG titers were measured at weeks 0, 4, 8, and 12 using indirect enzyme-linked immunosorbent assay. Antibody responses were analyzed using repeated-measures analysis of variance. Titers against poliovirus serotypes 1, 2, and 3 were negligible at baseline and remained low at week 4. Marked responses were observed in all vaccinated groups at week 8, followed by lower titers at week 12. Significant between-group differences were detected at weeks 8 and 12 for serotype 1 (p<0.001 and p=0.010), serotype 2 (both p<0.001), and serotype 3 (both p=0.010). However, no consistent dose–response pattern was observed across serotypes, time points, or sexes. All animals survived and gained body weight during follow-up. The candidate hexavalent formulations elicited marked poliovirus-specific binding-IgG responses, supporting further preclinical evaluation using validated serological and serotype-specific neutralization assays.