title: NadA diversity and carriage in Neisseria meningitidis.
abstract: NadA is a novel vaccine candidate recently identified in Neisseria meningitidis and involved in adhesion to host tissues. The nadA gene has been found in approximately 50% of the strains isolated from patients and in three of the four hypervirulent lineages of non-serogroup A strains. Here we investigated the presence of the nadA gene in 154 meningococcal strains isolated from healthy people (carrier strains). Only 25 (16.2%) of the 154 carrier isolates harbored the nadA gene. The commensal species Neisseria lactamica was also found not to have the nadA gene. Eighteen of the carrier strains belonged to the ET-5 and ET-37 hypervirulent clusters, indicating that only the 5.1% of the genuine carrier population actually harbored nadA (7 of 136 strains). Five of the seven strains harbored a novel allele of the nadA gene that was designated nadA4. The NadA4 protein was present on the bacterial surface as heat-stable high-molecular-weight oligomers. Antibodies against the recombinant NadA4 protein were bactericidal against homologous strains, whereas the activity against other NadA alleles was weak. In conclusion, the nadA gene segregates differently in the population of strains isolated from healthy individuals and in the population of strains isolated from patients. The presence of NadA can therefore be used as a tool to study the dynamics of meningococcal infections and understand why this bacterium, which is mostly a commensal, can become a severe pathogen.
authors.affiliation: IRIS, Chiron Vaccines, via Fiorentina 1, 53100 Siena, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Comanducci
authors.forename: Stefania
authors.initials: S
authors.lastname: Bambini
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Caugant
authors.forename: Marirosa
authors.initials: M
authors.lastname: Mora
authors.forename: Brunella
authors.initials: B
authors.lastname: Brunelli
authors.forename: Barbara
authors.initials: B
authors.lastname: Capecchi
authors.forename: Laura
authors.initials: L
authors.lastname: Ciucchi
authors.forename: Rino
authors.initials: R
authors.lastname: Rappuoli
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Pizza
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D004847:Epithelial Cells / Q000276:immunology; D005260:Female; D006801:Humans; D022401:Meningococcal Vaccines / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000235:genetics / Q000276:immunology*
chemical_list: D000906:Antibodies; D000942:Antigens, Bacterial; D022401:Meningococcal Vaccines