Understanding the Immune Response to Two Different Meningitis Vaccines

The bacterium (germ) Neisseria meningitidis causes meningitis and blood poisoning. N meningitidis is classified into different serogroups (types), based on its outer polysaccharide (carbohydrate) capsule. Serogroups A,B,C,W \& Y are responsible for the vast majority of meningococcal disease worldwide. Older vaccines against types A,C,W \& Y contain part of the polysaccharide capsule of the germ. However, these polysaccharide vaccines do not provide long-term protection against disease and are less effective in young children, the group most at risk of meningococcal disease. Newer "conjugate" ACWY vaccines attach a polysaccharide to a protein carrier - these provoke a good response in young children and can provide long-term protection. White blood cells called B cells produce antibodies, which are the main components of protection against meningococcal disease. Although many studies have investigated the immune response to these vaccines in different age groups by measuring specific antibodies, there is limited information about the B cells underlying such an immune response. Several different subsets (populations) of B cells exist in the blood. Previous studies by the investigators group suggest that different numbers of B cells are produced in response to each vaccine type. However, little is understood about which subset of B cell is important for antibody production in response to these polysaccharide or conjugate vaccines. This study aims to provide detailed information on the immune response to meningococcal vaccines by investigating the appearance of B cells and their subsets in the blood after vaccination with the polysaccharide and conjugate vaccines. These observations will help us understand how polysaccharide and conjugate vaccines stimulate the immune system in different ways. This knowledge will help in the development of new vaccines that are effective across all age groups. The investigators aim to recruit 20 adults aged 30-70 from Oxfordshire. T