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Rabies vaccine standardization: International Collaborative Study for the Characterization of the fifth International
J Lyng1, M W Bentzon, M Ferguson
1International Laboratory for Biological Standards, State Serum Institute, Copenhagen, Denmark.
Summary
A new rabies vaccine standard (PISRAV) was established to replace the exhausted International Standard for Rabies Vaccine. The PISRAV, derived from the Pitman Moore strain, was validated using immunogenicity and antigenicity assays.
Area of Science:
- Vaccinology
- Virology
- Immunology
Background:
- The International Standard for Rabies Vaccine stocks are depleted, necessitating a replacement.
- Rabies vaccines are crucial for human health, requiring reliable standardization.
Purpose of the Study:
- To establish a replacement for the International Standard for Rabies Vaccine.
- To compare the potency and stability of candidate rabies vaccines using various assay methods.
Main Methods:
- A collaborative study involving 14 participants compared three rabies vaccines against the existing International Standard.
- In vivo and in vitro assay methods were employed to assess immunogenicity and antigenicity.
- Heat stability of the proposed standard's glycoprotein and immunogenicity was evaluated.
Main Results:
- The proposed fifth International Standard (PISRAV), derived from the Pitman Moore strain, was established.
- PISRAV showed approximately twice the potency in immunogenicity assays compared to antigenicity assays relative to the International Standard.
- Vaccine immunogenicity was sensitive to heat, losing 66% potency after 245 days at +37°C, while glycoprotein remained stable.
Conclusions:
- The NIH protection test is recommended as the primary basis for rabies vaccine potency assay.
- Glycoprotein content does not consistently correlate with immunogenic potency across different vaccine types.
- PISRAV was established as the fifth International Standard for Rabies Vaccine with assigned potencies.