1. State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, National Institute of Diagnostics and Vaccine Development in Infectious Diseases.School of Public Health, Xiamen University, Xiamen, Fujian, 361102, China;
2. School of Public Health, Xiamen University, Xiamen, Fujian, 361102, China;
3. School of Life Science, Xiamen University, Xiamen, Fujian, 361102, China;
4. Xiamen Innovax Biotech Company, Xiamen, Fujian, 361005, China
Funds:
This work was funded by the National Natural Science Foundation of China (Grant Nos.: 81993149041, and U1705283), the National Science and Technology Major Project, China (Project No.: 2018ZX09303005-002), Fujian Health Education Joint Research Project, China (Project No.: 2019-WJ-05) and Xiamen Science and Technology Major Project, China (Project No.: 3502Z20193010). We are grateful to Mr. Yibin Zhu, Mrs. Yue Zhang, Mr. Zhenqin Chen, Mr. Qingbing Zheng, and Mr. Yang Huang for their technical assistance.
Thimerosal has been widely used as a preservative in drug and vaccine products for decades. Due to the strong propensity to modify thiols in proteins, conformational changes could occur due to covalent bond formation between ethylmercury (a degradant of thimerosal) and thiols. Such a conformational change could lead to partial or even complete loss of desirable protein function. This study aims to investigate the effects of thimerosal on the capsid stability and antigenicity of recombinant human papillomavirus (HPV) 18 virus-like particles (VLPs). Dramatic destabilization of the recombinant viral capsid upon thimerosal treatment was observed. Such a negative effect on the thermal stability of VLPs preserved with thimerosal was shown to be dependent on the thimerosal concentration. Two highly neutralizing antibodies, 13H12 and 3C3, were found to be the most sensitive to thimerosal treatment. The kinetics of antigenicity loss, when monitored with 13H12 or 3C3 as probes, yielded two distinctly different sets of kinetic parameters, while the data from both monoclonal antibodies (mAbs) followed a biphasic exponential decay model. The potential effect of thimerosal on protein function, particularly for thiol-containing proteinaceous active components, needs to be comprehensively characterized during formulation development when a preservative is necessary.
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