Thursday, 17 May 2012

Hope for a new meningococcal B vaccine

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Vaccine babyA larger phase three study is likely to start by the end of 2012 to finalise human testing before the vaccine can be made available to the public. Image: iStockA PERTH-based paediatrician has led an international collaboration to develop a highly anticipated meningococcal serogroup B vaccine, broadly protective against a variety of strains.

The study, published in The Lancet Infectious Diseases, involved a phase two clinical trial which showed robust immune responsiveness to a safe and well tolerated new vaccine.

Meningococcal disease is caused by an invasion of meningococci bacteria in the bloodstream, which can lead to infections in the membrane around the brain and spine (meningitis) and in the blood (septicaemia).

This serious condition is known to progress rapidly and can be fatal within 24 to 48 hours.

UWA School of Paediatrics and Child Health Associate Professor Peter Richmond says the study focused on adolescents and young children, who are most at risk.

“In WA almost all cases of meningococcal disease are now due to serogroup B [bacteria],”Dr. Richmond says. 

“This study specifically identifies one of these risk groups.”

Healthy teenagers from 25 locations in Australia and Europe participated in the randomised placebo-controlled clinical study.

Previous attempts to develop a meningococcal B vaccine have been successful but the applications have been limited.

“They have [only] worked against the strain they were developed from,” Dr. Richmond says.

“Here in Australia we have a number of circulating endemic [serogroup B] strains, so we need a vaccine that can provide a broader protection against other group B strains as well.”

The new approach uses a recombinant factor H-binding protein, which counteracts the protection that bacterial factor H offers against human complement deposition on bacteria—our main method of killing invasive bacteria.

To survive within the human body, bacteria cannot do without this anti-complement regulator, which appears highly conserved across different strains.

Meningococcal vaccines against other serogroup strains are of the more common polysaccharide conjugate type of vaccines.

“The problem with meningococcal B has been that the meningococcal B polysaccharide mimics a neural cell adhesion molecule expressed in the foetal and infant brain.”   The alternative has been an engineered protein-based vaccine, which is significantly different from a whole bacteria approach to immunogenicity. 

“There is clearly no chance of getting meningitis from this vaccine,” Dr. Richmond says.

“This has really been quite a breakthrough.”

Dr. Richmond believes there is potential for vaccines against all types of meningococcal disease in a few years time.

A larger phase three study is likely to start by the end of 2012 to finalise human testing before the vaccine can be made available to the public.

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