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Challenging settled opinions in classic foot-and-mouth disease vaccine preparation
Abstract:
In a previous study we challenged the generally accepted opinion that inactivation of FMDV by formaldehyde (FA) is an (unsafe) non-linear process. Our data showed that under proper conditions inactivation will be linear without "tailing-off". For more than forty years two other fixed beliefs existed with respect to FMD vaccine preparation: Virus must first be adsorbed to Al(OH)3-gel before being inactivated. Concentrations of formaldehyde are critical and must be within a very narrow range. Until recently the prescription of adsorption of the virus prior to inactivation made proper control of inactivation kinetics impossible. However, by eluting the virus from the gel by caesium chloride density centrifugation, the kinetics of inactivation can be studied. For adsorbed and non-adsorbed virus, identical inactivation curves were found. Antigenicity was found to be of identical "quality" for adsorbed and non-adsorbed virus. The second dogma was challenged by inactivating non-adsorbed virus with FA-concentrations of up to 6 times the one originally prescribed. In parallel inactivation was performed with acetyl-ethylene-immine (AEI). The antigen was purified after inactivation. Antigen yields after purification were systematically lower at high FA-concentrations, however, antigenicity seemed only slightly changed by the treatments: In an immunosorbent (ELISA) assay using a panel of 22 monoclonal antibodies (McAb) only few McAb's reacted differently with FA-treated antigen if compared with AEI-treated or fresh (A10) FMDV. The FA-treatment induced decreases, as well as increases in reactivities. The AEI-treated virus reacted almost identically to non-treated 146S particles.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
This study challenges FMD vaccine preparation dogmas, showing formaldehyde inactivation is linear and virus adsorption to Al(OH)3-gel is unnecessary for antigenicity, optimizing vaccine safety and efficacy.
Area of Science:
- Veterinary Virology
- Vaccine Development
- Biophysical Chemistry
Background:
- Traditional Foot-and-Mouth Disease Virus (FMDV) vaccine preparation involves inactivating the virus after adsorption to aluminum hydroxide (Al(OH)3) gel.
- Established protocols dictate narrow formaldehyde (FA) concentration ranges and suggest non-linear inactivation kinetics.
Purpose of the Study:
- To challenge the long-held beliefs regarding FMDV inactivation linearity and the necessity of pre-inactivation virus adsorption to Al(OH)3-gel.
- To investigate the impact of formaldehyde concentration and adsorption on FMDV inactivation kinetics and antigenicity.
Main Methods:
- Elution of FMDV from Al(OH)3-gel using cesium chloride density centrifugation to enable kinetic studies.
- Inactivation of adsorbed and non-adsorbed FMDV using varying formaldehyde concentrations and acetyl-ethylene-immine (AEI).
- Antigenicity assessment of purified FMDV using ELISA with monoclonal antibodies.
Main Results:
- Identical linear inactivation curves were observed for both adsorbed and non-adsorbed FMDV.
- Antigenicity quality remained consistent regardless of adsorption status.
- High formaldehyde concentrations reduced antigen yield but minimally impacted antigenicity as assessed by monoclonal antibody reactivity.
Conclusions:
- FMDV inactivation by formaldehyde can be a linear process under optimized conditions, debunking previous assumptions of non-linearity.
- Adsorption of FMDV to Al(OH)3-gel prior to inactivation is not essential for maintaining antigen quality.
- Current FMD vaccine preparation protocols may be revised to improve efficiency and control.