Lessons from outbreaks of infection
Update on Meningitis UK funded study
Meningitis UK is funding a study led by Professor John Heckels at the University of Southampton, which aims to identify potential vaccine candidates, for a cross protective vaccine against meningococcal group B disease. It uses a unique resource of sera collected following colonisation and infection in a group of students and using highly refined investigatory techniques.
The sera that are being used were taken from individuals before and then after they became carriers of the bacteria, together with cultures of the meningococcal strains taken from their nasopharynx (back of the nose and throat). This was obtained from undergraduate students at the University of Southampton during two previous meningococcal carriage studies. This is an extremely valuable resource which can be used to identify which antigens (molecules that can stimulate an immune response) are associated with the production of protective immunity as these would be attractive candidates for the production of a vaccine.
During the first year of the study the researchers used the paired sera taken from individuals before and then after they have been colonised by serogroup B meningococci and measured the ability of this sera to kill meningococci. In each case, after colonisation, the individual's sera showed a much greater ability to kill the meningococcal strain that colonised their nasopharynx. Importantly, the sera could also kill other meningococcal strains. The sera which showed the greatest increase in ability to kill additional strains were selected for detailed study of the immune response.
How was this done? The bacteria were dissolved and the constituent proteins were then subjected to a technique called 2D immunoblotting, in which the proteins were separated by applying an electric current on a slab of gel, producing separate spots for each of the many proteins present. The gel was then reacted with the individual's serum before and after colonisation. Of particular interest are those spots which reacted with the serum after, but not before, the individual had been colonised and developed the ability to kill meningococci, as these result from proteins that induce the protective (ie killing) antibodies. In this way the researchers could identify 27 discrete spots associated with development of protective immunity. They are now identifying the proteins present in each spot using the technique of mass spectrometry, in which the proteins are broken into small fragments and identified by comparison with the database of all known meningococcal proteins.
This is the first use of 2D immunoblotting to analyse the development of natural immunity to meningococci in humans. The list of protein antigens that has been generated included some already well known protein antigens (eg PorA) which validates the techniques used but also, importantly, new potential vaccine candidates which are associated with the development of cross-reactive immunity to serogroup B meningococcal infection.
Having identified the protective proteins the team will next be able to use techniques they have already developed to isolate the genes which are responsible for the proteins of interest, transfer these to a harmless bacterium and produce the proteins in sufficient quantity to test their potential as vaccines designed to prevent all group B meningococcal infections.
This important work was presented at the International Pathogenic Neisseria Conference in Rotterdam in September 2008 and a manuscript is being prepared for publication.
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