The patient sera analyzed by IB were only from patients that had been laboratory confirmed for MenA meningitis (42) and for whom the serum from at least one phase had been collected. control sera, whereas anti-NadA IgG levels were significantly higher in acute-phase sera than in controls. The IgG antibody levels against LOS and NadA correlated moderately but significantly with serum bactericidal activity against MenA strains. Future studies on immune response during MenA Octanoic acid disease should take into account the high levels of anti-MenA polysaccharide IgG commonly found in the population and seek to clarify the role of antibodies against subcapsular antigens in protection against MenA disease. In the meningitis belt of sub-Saharan Africa (30), the incidence rate of meningococcal disease is usually higher Octanoic acid than in any other region of the world. In this area, epidemics of meningococcal disease can sweep through several countries T during the same year, and large epidemics occur roughly every 8 to 12 years (21). Historically, most of the cases are caused by bacteria harboring the capsular polysaccharide of serogroup A. In the last two decades, most serogroup A meningococci have belonged to the genetic lineage subgroup III, as determined by multilocus enzyme electrophoresis (1, 10). Most subgroup III strains belonged to sequence type 5 (ST-5) or ST-7, as determined by multilocus sequence typing (38). While ST-5 strains dominated from 1989 to the mid-1990s, ST-7 strains have since then replaced them in the area (38). In Ethiopia, which lies in the easternmost part of the meningitis belt, the replacement of ST-5 by ST-7 strains occurred between 1995 and 2000 (42). Both of these STs express the same PorA and PorB porins (P1.20,9 and P3.4/21, respectively). However, we recently showed that Ethiopian ST-5 and ST-7 strains Octanoic acid differed from each other at several loci associated with outer membrane antigens, changes that could be relevant for clonal replacement (42). Since such replacements may be related to immunological selection pressure, it is of interest to determine which antigens induce an antibody response following disease. The antibody response against meningococcal antigens following disease caused by serogroup A meningococci has been the subject of several studies (2, 6, 7, 28, 40, 49). The advent of whole-genome sequencing and improved protein characterization techniques have resulted in the identification of numerous novel meningococcal proteins (3, 32), but the naturally acquired human immunity against these antigens is usually less explored. Outer membrane vesicle (OMV)-based vaccines provide protection against serogroup B meningococcal (MenB) disease in humans (4, 48) and are able to induce bactericidal and opsonophagocytic antibodies against serogroup A meningococcal (MenA) strains in mice (39, 41). Therefore, generation of antibodies against outer membrane proteins or lipooligosaccharide (LOS) might be an alternative option to provide protection against meningococcal disease in the meningitis belt. Exploring the specificity of the non-polysaccharide antibody responses following MenA disease may thus contribute to vaccine development. A study of meningococcal meningitis in Ethiopian patients was performed in 2002 and 2003 (40, 42). Besides Octanoic acid characterization of the etiology, another major objective was to characterize the kinetics, functional activity, and specificity of the capsular and subcapsular antibody responses following MenA disease caused by subgroup III ST-7 meningococci in Ethiopia. We have previously reported the serum bactericidal activities and the immunoglobulin G (IgG) responses against MenA polysaccharide (APS) and OMVs in Ethiopian patient and control sera (40). We then confirmed that there was a significant anti-MenA background immunity in the Ethiopian population, as shown by a high proportion of both acute patient sera and controls with a putatively protective titer in the serum bactericidal activity (SBA) assay. We also found that MenA meningitis could induce bactericidal IgGs in nearly all of the patients. The IgG responses were directed both against APS and against subcapsular antigens. Besides showing a strong association between anti-APS IgG concentration and SBA titers, the results also indicated that this IgGs against subcapsular antigens could have a role in providing protection against MenA disease. To characterize the specificity of the subcapsular antibody response associated with the putative protection induced by MenA meningitis, the Ethiopian patient and control sera were therefore in the present study analyzed by immunoblotting (IB) and by enzyme-linked immunosorbent assay (ELISA) against LOS and the proteins NadA and NspA. The latter three antigens were selected for analyses for their ability to induce bactericidal antibodies and their potential as future vaccine components. (Part of this study was presented at the 15th International Pathogenic Conference in Cairns, Australia, September 2006.) MATERIALS AND METHODS Patients. Ninety-five suspected cases of meningitis.
