Preformulation study of highly purified inactivated polio vaccine, serotype 3

To improve the effectiveness of the polio vaccination campaign, improvements in the thermal stability of the vaccine are being investigated. Here, inactivated polio vaccine, serotype 3 (IPV3) was characterized via a number of biophysical techniques. The size was characterized by transmission electronic microscopy and light scattering. The capsid protein conformation was evaluated by intrinsic fluorescence and circular dichroism (CD), and the D-antigen content by enzyme-linked immunosorbent assay (ELISA). The pH thermal stability of IPV3 (pH 3.0-8.0; 10°C-87.5°C) was evaluated by fluorescence, CD, and static light scattering. The transition temperatures reflect the responses, respectively, of tertiary structure, secondary structure, and size to applied thermal stress. The data were summarized as empirical phase diagrams, and the most stable conditions were found to be pH 7.0 with temperature lower than 40°C. CD detected a higher transition temperature for capsid protein than that for RNA. The effects of certain excipients on IPV3 thermal stability and antigen content were evaluated. The results of their effects, based on intrinsic fluorescence and ELISA, were in good agreement, suggesting the feasibility of applying intrinsic fluorescence as a high-throughput tool for formulation development. The study improves the understanding of IPV3 thermal stability, and provides a starting point for future formulation development of IPV3 and other serotypes.