A cross-reactive neisserial antigen encoded by the NMB0035 locus shows high sequence conservation but variable surface accessibility

1 Departamento de Microbiología y Parasitología, Facultad de Farmacia, Campus Sur, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain 2 Centro Nacional de Microbiología, Instituto de Salud Carlos III, Ctra. Majadahonda-Pozuelo Km2, 28220 Majadahonda, Madrid, Spain 3 Laboratory for Vaccine Research, Netherlands Vaccine Institute, PO Box 457, 3720 AL Bilthoven, The Netherlands Correspondence Carlos M. Ferreirós mpcfytc{at}usc.es Received 19 January 2007 Accepted 13 September 2007 The meningococcal NMB0035 locus encodes a 47 kDa outer-membrane protein that is highly conserved antigenically, and is able to induce antibodies during infection and bactericidal responses in vitro . This study analysed the surface exposure of this protein using specific antibodies in flow cytometry assays and determined its nucleotide sequence in 33 Neisseria strains. Genomic analyses revealed no significant differences in the nucleotide or amino acid sequences, but flow cytometry showed that surface accessibility was highly variable among the strains. These results suggest that masking by and/or association with lipo-oligosaccharides or other membrane molecules can be crucial for antigen accessibility, which must be thoroughly analysed in new vaccine candidates. Abbreviations: LOS, lipo-oligosaccharide; OMP, outer-membrane protein; OMV, outer-membrane vesicle. The GenBank/EMBL/DDBJ accession numbers for the p47 gene sequences reported in this paper are DQ788636–DQ788662 ( N. meningitidis strains) and DQ788663–DQ788666 ( N. lactamica strains).