Characterisation of Neisseria meningitidis from a virulence and immunogenic perspective that includes variations in novel vaccine antigens

Sammanfattning: Neisseria meningitidis, also referred to as meningococcus, is a Gram-negative diplococcal bacterium best known as an important cause of meningitis and septicaemia worldwide. Meningococcal disease is a rare but life-threatening illness that may progress to death despite optimal medical care including appropriate antibiotic therapy. Case fatality remains high and survivors may suffer from significant sequelae because of impaired circulation and/or damages to the central nervous system. Prevention through vaccination remains a most effective approach to control disease. The main problem, however, is the absence of an effective vaccine against disease caused by a broad spectrum of group B isolates.Understanding how the meningococcus can be both a common commensal and a devastating human pathogen is a major task for researchers in the area of meningococcal disease. In paper I, we investigated and described the characteristics of fatal meningococcal isolates and compared these with non-fatal invasive meningococcal isolates. The diversity was high within the isolates from both patient groups. Group Y, serotypes 14 and 15 and genosubtypes P1.7,16-29,35 and P1.5-1,10-4,36-2 were more common in fatal cases as were being elderly and female.The second major task in the area of meningococcal disease is to develop a group B vaccine. Six genes encoding antigens identified as promising vaccine candidates were examined in papers II & III. Based on our results, the prevalence of these genes and their sequence variation have the potential to constitute a meningococcal vaccine of broad range that also cover group B isolates in Sweden and other countries with a similar distribution of disease causing meningococci.In paper IV, we investigated the levels of IgG antibodies in serum directed against fHbp and NadA, two of the antigens included in papers II & III. Overall, the immune response to fHbp seems to be higher than the immune response to NadA, with a clear rise of anti-fHbp in the young adult groups (20-29 years).