Researchers at the University of Leicester and the Meningococcal Reference Unit have developed a new approach to assess the effectiveness of the Men B vaccine, Bexsero, against different strains that cause meningococcal meningitis and septicaemia.
The approach is being assessed by Public Health England for its potential to routinely test all meningococcal disease cases.
The new approach allows direct testing of blood samples from patients with meningococcal disease to find out if the strain they are infected with might have been prevented by the vaccine. Currently, it is estimated that the vaccine offers protection against 73-88% of strains responsible for meningococcal disease in England and Wales.
The research was based on looking at one of the four antigens that make up the vaccine. More work is needed to look at the remaining three antigens.
Dr Chris Bayliss, from the University of Leicester's Department of Genetics and Genome Biology, said: “This new research fills a gap in current testing capabilities that determine whether a disease-causing meningococcal strain is expected to be covered by the vaccine.
“We are currently unable to obtain and grow live bacteria from up to half of patients to determine whether the vaccine might have prevented the type of meningococcal disease they have, often because treatment with antibiotics has already killed them. There is a need for new tests to identify and measure the amount of antigen by obtaining meningococcal DNA directly from patient samples.”
Bexsero is a vaccine that helps protect against group B meningococcal disease (MenB), developed by GSK. It was introduced into the UK infant immunisation schedule in September 2015 and has been shown to be highly effective in preventing MenB disease in vaccinated infants.
One of the protective components of Bexsero is an antigen called factor H binding protein (fHbp). Infants vaccinated with MenB vaccines produce antibodies against this protein, so that if they are exposed to meningococcal bacteria that possess this protein, these antibodies will kill the bacteria.
“We are very encouraged by the results of the study, though measuring the attribution of only one antigen, fHbp, alone, without taking the effect of the other three components of Bexsero into consideration, may underestimate its protective effect,” said Dr Rafik Bekkat-Berkani, Global Medical Affairs Lead from GSK.
In a study published in the academic journal PLOS ONE, funded by Meningitis Research Foundation (MRF), the researchers show how a combination of DNA sequences and statistical testing can be used to measure the amounts of fHbp present in disease-causing meningococcal bacteria.
Researchers and Mathematicians at the University of Leicester studied more than 2000 disease causing meningococcal isolates to measure how much antigen each strain produces.
They used the results to categorise each strain into three classes: ‘covered’; ‘not covered’; and ‘at risk’. The ‘not covered’ groups included the ~12% of strains that will not be covered by the vaccine while the ‘at risk’ groups contains strains that are more likely to cause illness in vaccinated individuals.
Dr Bayliss said: “Detailed molecular analyses of clinical samples are essential for understanding how efficient the new vaccines against meningococcal disease are at protecting people against different meningococcal strains.
“This novel approach has the potential to help measure the effectiveness of Bexsero more accurately. The detailed information collected on the fHbp protein could be important in helping to improve the next generation of MenB vaccines,” explained Dr Bayliss.
