Diphtheria
Our group carries out control testing to ensure the quality and safety of diphtheria vaccines and antitoxins, and develops biological standards. This work is underpinned by research that focuses on:
- assay development
- formulation and stability of biological standards
- evaluating novel vaccine antigens, adjuvants and delivery systems
Diphtheria is an acute, potentially fatal, infectious disease caused by toxigenic strains of Corynebacteria, primarily Corynebacterium diphtheriae. Diphtheria toxin – the most important virulence factor for disease-causing strains – is an exotoxin that inhibits cellular protein synthesis, resulting in cell death.
Vaccination and treatment
Diphtheria is well controlled by immunisation – although there can still be significant outbreaks where there is insufficient vaccination coverage. Diphtheria vaccine, produced by chemical inactivation of the purified diphtheria toxin (to produce toxoid), is a key component of combined vaccines used in routine immunisation programmes worldwide.
Diphtheria toxoid is adsorbed onto an adjuvant such as aluminium hydroxide or aluminium phosphate to increase antigenicity, and is used alone – or more commonly with other antigens – in combined vaccines. These combined vaccines may contain antigens against tetanus, pertussis, polio, Haemophilus influenzae type b and Hepatitis B virus.
Regular booster vaccination with diphtheria toxoid is recommended to maintain protective levels of circulating diphtheria antitoxin. Diphtheria antitoxin – produced by hyperimmunising horses with diphtheria toxoid/toxin – is given to patients with suspected cases of diphtheria.
Standardisation
NIBSC is responsible for developing, producing and characterising biological reference materials used for standardising diphtheria vaccines, antitoxins and related products or intermediates. We maintain a portfolio of diphtheria standards, including toxoids, toxins and antitoxins that are used to standardise:
- vaccine and antitoxin potency tests
- assays to measure diphtheria antigen content and purity
- serological assays for titration of immune sera
We design and coordinate international collaborative studies to characterise and calibrate new and replacement International Standards. We also work closely with formulation scientists at NIBSC to optimise formulations to successfully freeze-dry diphtheria standards.
Control testing
NIBSC carries out scientific testing for diphtheria vaccines as part of its role as a National Control Laboratory. We also perform testing as part of the World Health Organisation (WHO) Prequalification Programme for vaccines. We have wide experience in testing diphtheria vaccines, antitoxins and related intermediates and can perform assays for:
- vaccine potency (serological models)
- antitoxin potency (toxin neutralisation test)
- identity (immunodiffusion and ELISA methods)
- antigen content and degree of adsorption (ELISA)
- toxicity (including the VERO cell assay for diphtheria toxin)
Research and development
We have wide experience in developing and validating methods used in controlling and standardising diphtheria vaccines, antitoxins and related intermediates. We focus on methods that can be used to refine, reduce or replace animal testing – known as the 3Rs – and have developed an in vitro assay to monitor consistent production of diphtheria vaccines.
We worked closely with the European Directorate for the Quality of Medicines and Healthcare (EDQM) and the European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) to design and coordinate international collaborative studies to validate a modified potency test for diphtheria vaccine based on the use of a serological model to replace the direct challenge model. Other research areas include novel diphtheria antigens and delivery systems.
Our scientists collaborate with many UK, European and Global expert groups as part of different grant-funded consortia, currently including:
VAC2VAC – a wide-ranging collaborative research project funded by IMI2 which aims to develop and validate quality testing approaches for both human and veterinary vaccines using non-animal methods.
Contact us by emailing bacvac@mhra.gov.uk for information about control testing, standardisation or potential research collaboration.