Comparative potency testing of diphtheria toxoid in guinea pigs and mice for in-house diphtheria-tetanus-pertussis and diphtheria-tetanus vaccines

Authors

• wanlop leeden, Department Medical Microbiology, Interdisciplinary Program, Graduate School, Chulalongkorn University, Bangkok, ThailandFollow
• Supanee Ummalukacholk, Vaccine and biological product Quality control section 2, Quality assurance 2 Department, The government pharmaceutical organization, Bangkok, Thailand
• Orawin Mangkhaladul, Vaccine and biological product Quality control section 2, Quality assurance 2 Department, The government pharmaceutical organization, Bangkok, ThailandFollow
• Eakachai Prompetchara, Department of Laboratory Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, ThailandFollow

Abstract

Background: Diphtheria remains endemic in parts of Thailand and continues to threaten unvaccinated populations. To strengthen vaccine self-sufficiency, the Government Pharmaceutical Organization has developed in-house diphtheria–tetanus–pertussis (DTP) and diphtheria– tetanus (dT) vaccines. Potency testing of diphtheria toxoid is traditionally performed in guinea pigs; however, limitations in animal availability, cost, and logistics have prompted evaluation of alternative models.
Objectives: To compare diphtheria toxoid potency estimates of in-houseproduced DTP and dT vaccines using guinea pigs and mice, followed by a Vero cell-based toxin neutralization assay, and to assess the suitability of mice as an alternative model for potency testing.
Materials and Methods: Three consecutive lots of DTP and dT vaccines were tested in guinea pigs and ICR mice. Animals were immunized with serial dilutions of in-house vaccines and reference diphtheria toxoid. Animal sera were analyzed by a Vero cell-based assay for the measurement of vaccine potency in the induction of neutralizing antibodies.
Results: All vaccine lots met the World Health Organization-specified potency criteria in both models. No statistically significant differences in diphtheria toxoid were observed between models. In detail, the potency of diphtheria toxoid in DTP ranged from 45.93 to 55.78 international units (IU)/single human dose (SHD) in guinea pigs and 42.66–46.76 IU/SHD in mice, P = 0.103. The potency of diphtheria toxoid in dT ranged from 4.12 to 4.73 IU/SHD in guinea pigs and 4.13–4.61 IU/SHD in mice, P = 0.227. All assays met the validity requirements.
Conclusion: Diphtheria toxoid potency results tested in guinea pigs and mice were comparable; the results demonstrated comparable potency estimates between mice and guinea pigs when tested with a Vero cell-based toxin neutralization assay. These findings provide preliminary evidence supporting the further use of the mouse model for diphtheria toxoid potency testing. This approach complies with the Replacement, Reduction, and Refinement principle and contributes to sustainable local vaccine quality assurance and self-sufficiency.

DOI

10.56808/3027-7922.3226

Recommended Citation

leeden, wanlop; Ummalukacholk, Supanee; Mangkhaladul, Orawin; and Prompetchara, Eakachai (2026) "Comparative potency testing of diphtheria toxoid in guinea pigs and mice for in-house diphtheria-tetanus-pertussis and diphtheria-tetanus vaccines," The Thai Journal of Pharmaceutical Sciences: Vol. 50: Iss. 3, Article 3.
DOI: https://doi.org/10.56808/3027-7922.3226
Available at: https://digital.car.chula.ac.th/tjps/vol50/iss3/3